[HeadphoneAddict]

UPDATE 7/5/08 - Ranking is at the bottom of POst #2:

I rolled my updates into the initial review post, so I can provide one direct link to the entire review.

UPDATE 12/15/08 - CANNOT FIT MY NUFORCE ICON REVIEW BELOW INTO THE FIRST POST, EXCEEDING 100000 CHARACTER LIMIT - ALL FUTURE REVIEWS WILL BE POSTED IN THIS SECOND POST OF THE ORIGINAL THREAD, AND LINKED FROM THE FIRST POST:






HEADPHONES USED: Westone 3, Klipsch Image X10, Denon C700, Nuforce NE-7M, ATH-ESW10JPN, APS V3 cabled HD600, APS V3 cabled RS-1, APS V3 cabled markl Woodied Denon D2000, and APS V3 cabled Edition 9.

MUSIC USED: Michael Knowles "Bink Audio Test CD", Nils Lofgren "Acoustic Live", Arne Domnerus "Antiphone Blues" and "Jazz at the Pawnshop", Infected Mushroom "B.P. Empire", Tord Gustavsen Trio "Being There", Pat Metheny "Day Trip", Tsuyoshi Yamamoto "Autumn in Seattle" and "Smooth Jazz Festival", B.B. King and Eric Clapton "Riding With the King", Shelby Lynn "Just a Little Lovin'", Nora Jones "Not Too Late", Arvo Part "Tabula Rasa", Jack Johnson "Sleep Through the Static" and "In Between Dreams", Elaine Elias "Something for You", Gary Karr "Super Double-bass", Guinea Pig "Kool Cats", Christopher Hogwood "Handel Messiah", Pink Floyd "DSOT", The Beatles "Love", Beck "Sea Change", Diana Krall "Girl in the Other Room", Coldplay "Viva La Vida", and Skillet "Comatose".

The Nuforce Icon Mobile is a $99 entry level portable USB DAC/Amp, which has more of a flat form factor that is amenable to being stacked under an iPod without adding too much size to the overall package. It is about the same width and depth as the iBasso D2 Boa, but almost half as tall/thick, so you can almost stack two Icon Mobile on top of each other to achieve the thickness of one D2 Boa. When plugged into the Macbook's USB port the DAC shows up as a "C-Media USB Headphone Set". The Nuforce has some unique features including two headphone out jacks which switch on the power when a headphone plug is inserted, with the jack closer the center being a special jack that works with 4-conductor headsets with stereo headphones and a built-in microphone, like the Nuforce NE-7M iPhone IEM (or other iPhone IEM). This allows the NE-7M to be used as a headset with telephony applications, instant messaging and Skype, and probably for gaming as well. I have not been able to test this telephony feature, but the mic did show up in my Mac's Audio MIDI setup application as the left channel only microphone. The analog input is on the same end of the amp as the two outputs (we'll call it the top end), and all three jacks are slightly recessed by about 0.5 mm along one edge of the amp.

All my portable headphones worked fine with the slightly recessed jacks, but my full size APS V3 cabled headphones needed an adapter because the 1/8" Neutrik plugs on my APS cables are too wide and would hit the lip of the case around the jacks. Nuforce has informed me that they are already planning to make changes to the case to allow a wider variety of headphone plugs to fit, and they will make it available to early buyers who have problems - but they are not sure yet if it will be possible to use the wider Neutrik 1/8" plugs used by APS, while I know the smaller Neutrik plugs from Qables.com already fit. On one side there is a USB jack for charging and the USB DAC input, a recessed gain switch that cannot not be accidentally changed, and a rotary volume knob. The volume knob is of fairly decent quality, and in low gain it is easily usable with high sensitivity IEM at very low volumes, with channel imbalance only at the very lowest volumes. The amp is totally silent in high gain with the USB music paused and volume turned all the way up.

To my ears the Nuforce does benefit noticeably from burn-in. When it was right out of the box it struck me as just a little dull and bland when compared to the iBasso D2 boa, and I feared that I would be disappointed with it in the end. I left it running for 6-7 hours and came back to it and the sound was already starting to clean up some. So I left it running via USB with music 24/7 but with a 1 hour break each day, and went back to listen for about an hour each night at 24 hour intervals. By 24-36 hours it was sounding good enough to actually recommend it to others, by 55-60 hours I was posting that it sounded a little forward but was sounding similar to my Meier Headsix which I like more than the D2 Boa. At that time I noted that it was also less edgy than the Vivid V1 but not as powerful. By 80 hours it was becoming more transparent and detailed, and sounded good with all my portable headphones including ATH-ESW10, Westone 3, Image X10, NE-7M and even the Denon C700. By that time I was finding that it is one of those amps that actually makes the C700 smoother and less harsh in the highs, while controlling the bass - one of the things I like about the Headsix and Predator when driving the Denon C700 (sometimes I think the C700 was tuned to sound best right out of the headphone jack of the 5.5G iPod video and 2G Nano). Between 180-200 hours the soundstage had finished opening up. I continued burn-in via USB through 210 hours and then switched to analog input for the remainder of burn-in. I did my once a day listening until it had 230-240 hours on it and felt it seemed to be done changing by 180-200 hours. I did not listen for the last 60-70 hours of burn-in until time to start the review after 300 hours on 12/14.

During burn-in I was able to determine that the Nuforce amp was above the iBasso D2 Boa and Vivid V1 in most areas of performance and sound (but not all areas), but still below the top tier amps like Pico, Predator and D3 Python. I have not reviewed the Practical Devices XM5 yet, but I am fairly sure it will be among the top tier amps based on the limited listening I have done during burn-in. I do not have the 2MOVE or D2 Viper to compare to in this review, but if I did I would guess it would fall below the 2MOVE or rolled-opamp Viper but above the Stock D2 Viper. So, since I had so many headphones to listen with most of my comparisons were with the D2 Boa and V1 to properly discern the ranking. Although I did also do comparisons with the top amps as well, I just did not spend as much time with them.

For the first part of my dedicated listening for the review I decided to start with my full size headphones (HD600, RS-1, D2000, Edition 9) since I had already done a fair bit of listening with my portable headphones and IEM during burn-in, and was already enjoying the amp with them. Typically the Nuforce could be turned up all the way to 100% volume with HD600 without clipping. And, it would play to decent volumes at that setting but not more than mildly or moderately loud - max volume of the Nuforce Icon Mobile was still about 2-3 db below D2 Boa, which could be turned to about 3:30 o'clock before clipping in high gain (max is 4:30). On the other hand, unlike with the HD600, the Nuforce could drive the Grado RS-1 and Denon D2000 at max volume MUCH much louder than I would ever care to listen to music. Typically I could sweep the side scrolling rotary volume knob 4 times to go from from zero volume to 100% volume. With the Nuforce in high gain with anything other than HD600 I would normally listen with the volume rotated up only 1/2 of the way to max. With the volume turned 3/4 of the way up it was quite loud with RS-1 and D2000, and full volume was uncomfortable and likely damaging. With RS-1 there was some clipping starting to creep in as I got very close to max volume at the end of the dial with the RS-1, but it was more of a soft clipping with less dynamics and some fuzzyness to the sound. The clipping was even better/softer with the D2000 at max volume, and with some material it was not even there. I could never explore the upper volume limits with my IEM without worsening my chronic tinnitus, so I didn't try. Suffice it to say the Nuforce will go loud enough with any of my IEM. So, to summarize, the Pico, D3, V1, Micro Stack and XM5 are all more powerful with HD600 than the D2 Boa which slightly edged out the Nuforce, but with any portable earphone or low impedance full size headphone the Nuforce has plenty of power to go around.

With the Nuforce the bass is fairly strong with all the low impedance phones, but with HD600 pushed to high volumes the bass was not quite as good as the D2 Boa, especially as the volumes would get closer to max output. Bass with infected mushroom and HD600 was stronger at normal volumes but not impressive like with the lower impedance phones. It was only a problem with HD600 in which I found the bass pulling back or thinning out when the amp is pushed hard (similar to the Meier Headfive desktop amp when pushed hard with Grados). So like the D2 Boa, the Nuforce was not optimal with high impedance phones, although it still drives the HD600 better than the headphone out of my Macbook. Better portable amps from my review to drive the HD600 better include the Pico and Vivid V1 or D3 Python or XM5 as the most powerful, followed by the Predator and D2 Boa, and then the Nuforce. However, with lower impedance headphones like my portable headphones and RS-1, D2000 and Edition 9, the Nuforce really came into it's element and it became more dynamic and powerful sounding. The D2000 and Edition 9 are very enjoyable with the Nuforce, and the bass is powerful enough to tickle my eardrums and damage my hearing if I wish, passing up the RS-1's bass by a noticeable margin too (unless I switch to flat pads). With test tones on the HD600 the Nuforce sounded strong to 31Hz, and was maybe 3-4db down at 25Hz but then rolled off below that. But I found that the 20-25Hz notes were stronger with the low impedance phones than with the 300 ohm HD600, and the NE-7M actually went deeper than most of my full size headphones (16Hz). The Pico, Predator, D3 Python and XM5 all had more powerful and present or pervasive bass, but you wouldn't know the Nuforce is lacking anything but for the comparison with the top tier amps. It's all relative, as listening to the Nuforce on its own merits did not make me wish for bass boost or anything like that. Bass was fairly well controlled as well, although pushing the amp to it's limits at the highest volumes the IEM, D2000 or Edition 9 the bass was just starting to get a little loose. Only with the HD600 did it start to fade at higher volume levels. The ESW10 bass was lighter and more along the lines of the RS-1 (ESW10 is kinda like a closed RS-1) and just a little more reserved with the Nuforce than with the top tier amps. This is not a bass-thin amp, it's just that some others have more bass punch. But, pair it with the Westone 3, NE-7M with Complys tips, D2000 or Edition 9 and the bass is rocking.

The Mids of the Nuforce tend to be more forward like the Meier Amps (Headsix and 2MOVE) or the Vivid V1. I have always felt that Pat Metheney "Day Trip" is recorded with a little too much energy in the mids with the electric guitar (granted that is the "star of the show"), so switching to the D2 Boa or other amps usually helps pull the guitar back a little. Still, this particular recording was listenable with the Nuforce, although it was much better if I was using the Westone 3, NE-7M, C700, D2000 or RS-1 with bowls than the HD600 or Edition 9 with it. With most music I appreciated the more forward mids of the Nuforce with the D2000, as I feel the D2000 are still slightly recessed in the mids despite the wood cups and earpad mods that I have done which also helped a bit. I haven't been using my RS-1 much lately, as I tend to prefer my stats and my modded D2000, Edition 9, or ESW10 more. The RS-1 did not sound bad with the Nuforce, but with bowl pads I sometimes (not always) felt there was a similar but less prominent upper mid coloration with Grados, like the Vivid V1 amp demonstrated earlier in the review. My other headphones did not have this issue with the mids, and I still preferred bowls with the Grados for their improvement in soundstage through the Nuforce. I would not rule out the Nuforce with Grados as it is still better than the V1 with them, and often better than the D2 Boa as well - where sometimes the D2 Boa's mids felt slightly sucked out with the RS-1 after listening to the RS-1 with the Nuforce for a while and got used to it. I still felt the top tier amps were warmer and richer in the mids than the Nuforce, D2 Boa or V1, and the D2 Boa sounds like an artificial warmth at times, with slightly boosted upper bass and lower mids. But what I liked most about the Nuforce mids was the clarity and very little coloration.

In general I felt that the forward mids of the Nuforce helped improve the audibility of the midrange detail, and music became more engaging than with the D2 Boa (similar to the Headsix and 2MOVE). This was one of the things that attracted me to the 2MOVE that I borrowed a while back. Female vocals like Shelby Lynn, Nora Jones, Elaine Elias and Jane Monheit don't have the bass bleed into the lower mids a little, like with the Boa, so they sound more open and natural most of the time (less boomy or boxy or close mic'd sounding). The D2 Boa with Westone 3 was the worst offender in that regard. Nora Jones's vocals in "Not Too Late" and on Herbie Hancock "The River" are more present and engaging with the Nuforce. With the Boa, Nora Jones and Jane Monheit's vocals do sound better than did Shelby Lynn or Diana Krall on the Boa, but I liked the Nuforce a little better with all of them. On Elaine Elias "Something for You" I got caught up in the music better, and forget that I am doing a review, so it seems little more involving as well. The Boa still acquitted itself well with Elaine Elias during the instrumental jazz parts, but lost the illusion when the vocals would come in.

I did enjoy pianos with the Nuforce, but the Nuforce maybe smoothes out the piano a little more than the other amps, making it more polite. Despite that, it still did a nice job with piano and guitar and vocals in B.B. King and Eric Clapton "Riding With the King". Nils Lofgren "Acoustic Live" was crisp and detailed and airy but not as spacious as the top tier amps listed above. And the Nuforce also seems good with unamplified acoustic guitar as well, like with Jack Johnson and Andy Mckee or Govi. In Tsuyoshi Yamamoto "Smooth Jazz Festival" during "Somewhere Over the Rainbow" the sax is more intimate and engaging with the Nuforce, but the Boa has little stronger bass response from the plucked string bass. However with the D2 Boa the sax sounds thinner in the middle and more upturned at the ends of the frequency spectrum. With Gary Karr "Super double bass" this issue on the D2 Boa also caused the bass fiddle to seem slightly more hollow or lacking than with the Nuforce, especially when listening with the D2000 but also with the HD600 and others. This recessed mids of the D2 Boa was still better than with the stock D2 Viper last time I compared them. These slightly tipped up ends of the frequency spectrum or the recessed mids (however you look at it) make the D2 Boa a little better for low volume listening with the HD600, but very quiet listening was among the few instances where I would grab the D2 Boa over the Nuforce. On the other hand, the Nuforce with D2000 was still better for low volume listening than D2 Boa with HD600.

Treble on the Nuforce is smooth but slightly recessed with a variety of headphones. With my D2000, Westone 3 and ESW10 the Nuforce does not accentuate sibilance that I usually hear in my Diana Krall "Girl in the Other Room" CD, which is my test CD for sibilance since it seems to be mastered with that in there. Switching to the Grado RS-1 I found there was less sibilance through the Nuforce than with my D2 Boa. The slightly laid back treble made the Nuforce amp more forgiving of some music. With the D2000 I actually listened to the entire Diana Krall CD with the Nuforce as I typed my review, without thinking about the sibilance. With Tord Gustavsen Trio's song Karmosin off the "Being There" CD, this is a good test of cymbals as they are lightly and hauntingly tapped during the intro drums and piano, and I did not feel there was a lack of treble as the ring of the cymbals would hang in the air properly with a nice slow decay.

I have rarely bothered to test high frequency extension, but decided to start doing that and tested all of the amps tonight, along with the Nuforce using Michael Knowles "Bink Audio Test CD". With treble test tones on the Nuforce I used the D2000 which for me have better treble extension than my HD600 or most IEM. There I found a problem - with the Nuforce while at 16Khz I was getting a strange harmonic at exactly 4Khz that was louder than the actual 16Khz tone. I've had this problem with another USB DAC amp before, but I cannot recall which one now (might have been the Lyrix or D1). This 4Khz artifact did not happen with the D2 Boa via USB which was still going strong at 16Khz, or with the Nuforce via analog input. With music I was unable to hear any artifacts like with the test tone. For me, 16Khz is the practical limit of my hearing as I can't hear the 20Khz tone unless I crank an amp like the D2 to 3:30 o'clock or 80-90% of max. While I could hear 20Khz with the D2 Boa at full volume, cranking the Nuforce volume at 20Khz was inaudible. Via analog input on the Nuforce the 20Khz test tone was still inaudible to me, although it was still barely audible if I plugged the headphones directly into the Macbook. The only other amps that would allow me hear the 20Khz test tone at high volume was the Pico and Predator, although I could hear it louder with the Pico. I found that in doing this test that the V1, XM5 and D3 were all quite noisy in the background at high volumes past 3 o'clock with the 20Khz test tone, so I could not hear the tone over the noise. The Nuforce had just a tiny bit of noise at max volume hooked up via USB, and the Pico and Predator were silent. The D2 Boa background noise was silent and allowed me to hear the 20Khz tone. After I accidentally hit my ears full volume with a 440Hz piano note, I could not do further testing of the highs until my ears recovered.

The Nuforce combines a forward soundstage with decent air and ambience, although like the 2MOVE it puts the listener in a more intimate position while making the venue seem a little smaller. With the D2 Boa and Arvo Part "Tabula Rasa" the image is a little more spread out and deeper but less precise than with the Nuforce. With Gary Karr "Super Double-bass" the imaging was similarly a little more focused and the bass fiddle more centered with Nuforce (almost like a slight hint of crossfeed), while with the same music on the D2 Boa the bass fiddle sounded a little more spread out and hard to pinpoint. Soundstage is obviously better with the HD600 and D2000 than Westone 3 or ESW10 and RS-1. But even with those headphones, when comparing the Nuforce soundstage to the Pico or D3 and Predator the Nuforce soundstage seems flatter and more 2D, with a wide but not as deep soundstage. Air and ambience with the Nuforce was about the same as my D2 Boa, but with the Boa placing the listener a little farther from the stage than Nuforce or Vivid Audio V1. Switching from the Nuforce to the Pico and D3 (or even Predator) it was clear that the top tier amps are more open and spacious, with more micro-detail and are even more rich sounding and engaging. The difference in sound between the Nuforce and the top three on hand (Predator, Pico and D3) is bigger than it is between Nuforce and D2 Boa or V1, confirming that the D2 Boa and Vivid V1 are it's main competitors in sound and price range. The Predator is in between the forwardness of the Nuforce/V1 and Pico/D3, but still maintains a better soundstage, warmth and richness. The degree of detail of the Nuforce DAC seems to be on par with the DAC in the 2MOVE and Predator, but below that of the Pico and iBasso D2/D3 amps. I have not reviewed the XM5 that is burning-in right now, so I really cannot comment on soundstage or micro-detail yet.

The last area I looked at was the RFI interference problems that have cropped up the past 2 months since I got an iPhone 3G. I found the D3 to be the most susceptible to iPhone BUZZ from 3-4 feet away, followed by the D2 Viper and the D2 Boa from 1-2 feet away, then the Predator/Pico/Nuforce which could be within 6-9" of the iPhone. With an EM blocking card from Quick Bridge Solutions - EM Shield for iPhone I can stack any of the amps under the iPhone except for the D3 Python which still needs to be 6-9" away. The only big problem I have run into is that "static discharge" makes the amp go nuts - so don't shuffle across the carpet and then touch the amp or headphones or laptop or all kinds of nasty noises will emanate from the headphones till you unplug the headphones to switch the amp off.

ADDENDUM: While the Nuforce via USB is slightly brighter and slightly more forward than the 3MOVE with slightly less bass, with analog input it does sound a little brighter and a little more forward and aggressive than with USB input. Keep that in mind when pairing with bright headphones. For example, I can use the Nuforce via USB just fine with Phonak Audeo IEM with black filters, but via analog input and grey filters it can be too bright.

RANKING: Post #2 exceeds 100,000 characters with this obsolete ranking left in place - please see newer ranking below: In summary, this amp ranks in the middle of the pack, with better USB performance than D1 or Lyrix, but more colorations than those others in the amp section.


UPDATE 01/04/09 - XM5 USB DAC Amp by Practical Devices Corporation



I used my usual playlist of lossless songs and typical rotation of headphones with the XM5, and I really like the XM5 - the quality of sound it puts out deserves the $245-$325 that it sells for (depending on options like optional BUF634, or AD8397 kit, or Li rechargable vs Alkaline). Based on the sound, I assume this dual mono amp has to be a major upgrade from the XM4, not just an evolution. It comes stock with a pair of OPA134 opamps, which are single channel opamps, and it has a pair of buffer sockets for improved current output by using optional BUF634 chips, or another opamp like AD8397 in the buffers. It come standard with using a 9v alkaline battery (50 hours), and a charging circuit for rechargables is optional (40 hours).

And the number of features it has makes my head spin. I like the 1-3-6 hours timer for falling asleep to music, similar to my old Xin super macro III but more precise, the battery voltage display (# of LED flashes) comes in handy, and I've already dimmed the LED. Crossfeed as set by default has a more profound effect than Micro Amp and Meier, but it is adjustable from near full stereo all the way to mono - so I need to spend some time with that other than at the factory setting. It also has an input selector on back, 6dB bass and 3dB treble boost, high/lo gain, LED flashlight function and LED dimmer funtion, plus a 75 ohm P-to-S switch yet. It also comes with a USB cable, velcro dots, stick on feet, and an allen hex key to open it and roll opamps or swap out batteries. I was disappointed that it wont brush or whiten my teeth yet.

When I first received it I left it on 24/7 for burn-in and I got between 30-40 hours on the Li rechargable the first time around - it was still playing at 30 hours (6.5v) when I went to bed and when I woke up 10 hours later the battery was drained. At full charge the battery meter says it is 8.4 - 8.5 volts (varies), so it dropped about 1v per 15 hours. They claim battery life drops from 40 hours to 30 hours on rechargable with the extra BUF634 chips, but I think it may be good for up to 35 hours at normal low-medium volume levels. Louder volumes may result in it being drained by 30 hours. This still doubles the battery life vs D2 Viper and 30% more than Pico, but is about the same as D2 Boa - while still half what the Predator does, it also seems to have more output power than Predator. I gave the XM5 300 hours of burn-in, although it didn't really change much during that time. I suppose the recommended 8 hours is right.

I posted a couple of questions to Practical Devices, and the Q&A is below:

QUESTION: How much burn-in does it need?

REPLY: 8 hours.

QUESTION: Can any opamp be used as a buffer, or are the buffer sockets limited to buf634 only? I don't think others would be as good as the buf634.
REPLY: I'm going to define the following: "Semi-Standard Singlechannel OpAmp Pinout" ("SSSOAP") - which is what the OPA134 has, as well as a zillion other single-channel 8-pin opamp chips (pin2 = "opamp input-", pin3="opamp input+", pin4="negative supply", pin6=output, pin7="positive supply"). The BUF634 sockets on the XM5 can handle anything with a SSSOAP; any SSSOAP chip you stick in a buffer socket will be configured as a non-inverting follower (with Gain=1x, or 0 dB). So yes, you can put other chips in the buffer sockets - although I haven't tried this much, YMMV.

QUESTION: Do I need to do the copper bridge if I try the AD8397, or can the buf634 stay? I know the AD8397 is a very high output opamp and doesn't really need buffers, but we used LMH6655 in the iBasso D1 with AD8397 to smooth it out. I often don't like opening up an amp to roll opamps if the stock sound is good enough to make me happy, and I suspect this will sound good enough that I will feel lazy about rolling...\

REPLY: Yes, you can leave the BUF634s in when using the AD8397. But like you said the AD8397 already contains (very strong) output buffering, so having another set of buffers in series won't buy you much of anything. I've never actually tried this AD8397+BUF634 configuration myself; but if you uncover a great discovery, let me know.

I don't think I would like the AD8397 more than the current configuration as a dual mono, but I probably have to give it a try soon, along with the OPA627 and AD743. It doesn't seem to me to need much improvement right now though.

I first tried the XM5 with my IEM. The volume pot is very nice and allows minute adjustments at low volumes with minimal channel imbalance at the bottom range. I found it sounds great with my Livewires, SE530 in custom shell, IM716 at 33 ohm, NE-7M and Westone 3, which were the IEM that I started burn-in with, and the amp is a good match for these portable headphones. It even seems to improve the sound of my Denon C700 and makes them enjoyable again. With bass boost flipped on the amp is also very good with Nuforce NE-8. It was slightly bright with my Livewires and SE530 customs at first, but my brain adjusted to it pretty quickly and then it was fine.

I also tried the XM5 with my Freq Show triple driver customs which don't get much use since I got them, and SURPRISE, the XM5 is the first amp to really make the Freq Show sound very good. I don't know why, but they are a match made in heaven and I've been looking for something to make the Freq Show sound as good as my Livewires for months. Typically my Freq are not used much because I feel they lack treble extension and seem to emphasize a portion of the lower mids that makes pianos or other instruments resonate in my right ear canal like a "roaring crowd". Some amps make the "roaring" better or worse but never gone. Previously the modded D2 Viper and Pico were the champs with these IEM because they would improve the treble extension some and not exacerbate the "roar", but I don't have any problems at all with Freq out of the XM5 now either. I am excited about getting to know the Freq better now.

While I did not find any of my IEM that did not get along with the XM5, with my Macbook and a USB DAC I tend to gravitate towards full size headphones for reasons of comfort and less need for isolation, so I approached the full size cans later in my review, having nothing bad to say about it's performance with IEM. In a comparison I did early on in the process I started with the ATH-ESW10JPN as my first full size can. I found they were very good with the XM5, as well as Predator, Nuforce Icon Mobile - plus I threw in the TTVJ portable Millett hybrid as someone requested, using the Headstage USB DAC cable on my Macbook to make it a DAC/amp.

In a sense the TTVJ, 3MOVE and XM5 are similar to the Nuforce in it's forwardness and presentation - but the TTVJ and XM5 add to it with a wider soundstage, more powerful bass and presence, and a warmer richer more refined sound overall. Although there is no lack of treble or darkness, the Headstage DAC cable/TTVJ combo is also slightly less detailed than the Nuforce, XM5, 3MOVE or Predator - while with the iMod as the source their level of detail is closer. I still prefer the Millett combo a good bit more than the Nuforce, but it's a $450 amp + $40 DAC vs a $99 DAC amp combo, so it's more of an apples vs oranges kinda thing. However, the XM5 compared to the TTVJ (and Predator) is more similar in refinement, warmth and richness of the TTVJ and Predator than the Nuforce, but with smaller price than TTVJ or Predator, and a built-in DAC so it's better suited to traveling.

With the ESW10, the XM5 is almost a SS version of the TTVJ Millett's sound and power, but I can tell there is a slight difference in tonality. For those that want a more romantic euphonic or lush sound with ESW10 or Grados the TTVJ is excellent, but obviously there are SS amps like the XM5 that can come close, while doing it with more detail and battery life. The mids with the XM5 and ESW10 are simply delicious as well. Incidentally, with the ESW10 I am only using the XM5 or TTVJ at 10-11 o'clock on the volume knob (XM5 low gain, Predator medium gain at 12 o'clock). I could be happy with just the XM5 and ESW10 for a long time.

I then spent most of the Sunday before my Christmas vacation using the XM5 with Macbook and Denon D2000 (woodied re-cabled) and loving it. The bass was tight and well controlled with almost everything I listened to, with a few exceptions. I tried some new music and with Yo-Yo Ma "Sounds of Joy and Peace" song no. 2 with Diana Krall, the string bass was a little boomy and sloppy but it became much better with 75ohm switch set to on. Using the 75ohm switch is the only instance in which the D2000 needed the XM5 in high gain, and the only instance in which I did not think it controlled the bass well. This was more of a fault of the music rather than the amp's fault. The 75 ohm was useful to remedy this when I wouldn't have that option with other amps.

With female vocals like Nora Jones, Diana Krall, Elaine Elias, and Shelby Lynn the XM5 did not emphasize any portion of the vocals, making them sound natural. However, the D2000 mids are slightly recessed when A/B with Predator or 3MOVE, and are closer to the mids of the Pico. With the D2000 the more forward mids of the Predator and 3MOVE are more welcome. With more forward phones like ESW10JPN and HD600 the smooth mids of the XM5 can be better appreciated. The treble with D2000 was good, and not grating or etched, nor sibilant. With Bink Audio test CD from Michael Knowles I was able to hear the 20,000Hz tone with the volume turned up on the 3MOVE, but as stated in the previous Nuforce review I cannot hear it in the XM5 (yes to 16Khz without having to max the volume).

With my old standard, Tsuyoshi Yamamoto "Smooth Jazz Festival" Somewhere over the Rainbow, I found the saxophone with XM5 and D2000 to be just right with that combo of breathiness, chestiness and reediness in the right proportions. The string bass was crisp and well controlled as well. With "Misty" I did not find the piano strikes to be piercing at all, and the speed was good. With other jazz such as Elaine Elias "Something for You", and McCoy Tyner "New York Reunion, I could really get into the music and forget to work on the review, but switching to the Pico or Predator when I come out of my trance shows an little extra layer of detail and transparency in those amps, although the Pico is still not quite as euphonic as the XM5 and Predator (or TTVJ/3MOVE). It's easy to get caught up in the music with this amp as it is so musical, and one has to be reminded every once in a while that the sound can be even better (same thing happens when I switch from portable amps to my WA6 maxed or Single Power Square Wave XL).

With classical music like Arvo Part "Tabula Rasa" and D2000 I thought the XM5 was similar to the 3MOVE, coming in just behind the Predator but with Pico on top due to it's huge spacious soundstage. The XM5 DAC is nicely detailed and like the 3MOVE, but it seems with classical music that the XM5 puts you in the 2nd row of the auditorium venue vs the 3MOVE which puts you on the 1st row instead. This goes against my auditory memory where I would have said the MOVE puts you on the conductor's podium, but it's not as forward as I remembered after all (although with HD600 it is closer to the podium). Imaging and focus was good however, so instruments didn't seem to come from all over the auditorium like the D2 Boa. Soundstage is not as deep as the Pico or Predator, but was nice and wide like the 3MOVE.

I also found that one does NOT need high gain on XM5 for D2000, as it has plenty of driving power! With D2000 at good volume levels the XM5 is in low gain at 11 o'clock while the Predator is in medium gain at 11:00 o'clock for similar volumes, and TTVJ has a fixed gain and was at 11 o'clock. With HD600 the Predator is in medium gain at 3 o'clock to reach similar volumes, while the volume of XM5 is at 3 o'clock in low gain (or XM5 at 1 o'clock in high gain). The 3MOVE in high current mode and Pico in high gain are also at 1 o'clock like XM5 in high gain. Any of these amps can produce ear-drum tickling volume levels with D2000 and Edition 9. And speaking of Edition 9, the XM5 was just a little better with them than it was with the Denon, and I preferred it over the 3MOVE with these phones as it was closer to the Predator with them. Heaven on earth. I just don't do a lot of reviews with the Edition 9 because so few people have them or have heard them. I actually thought the XM5 was a little better controlled with them than the TTVJ which has a similar sound signature.

Moving on to the HD600 I started with some Nils Lofgren "Acoustic Life". The XM5 gives off a good feeling of spaciousness with a large venue musical program. With this music I still found the Predator most engaging and slightly more forward than XM5, but the 3MOVE is most forward of all and sometimes a better match for the D2000 than the HD600. With HD600 the XM5 soundstage size is somewhere between the Pico and Predator, and slightly larger or farther back than Predator and 3MOVE. But the XM5 is still not quite as spacious or smooth as Pico due to less micro-detail from the DAC and a slightly more forward sound than the Pico, making it closer to the soundstage of the Predator. Never was the soundstage lacking unless compared to my WA6 or Single Power desktop amps, but it is at least as good as my EF1. I also found the XM5 to put out more bass and volume than Predator with HD600, but it was also not as smooth as Predator either and was closer to the 3MOVE in that regard. In Tsuyoshi Yamamoto "Autumn in Seattle" song Misty, the XM5 with HD600 seems slightly withdrawn in the lower treble of the cymbals vs Predator, and piano had slightly less bite in the upper mids - both areas where the Predator seems to be a little more forward. With HD600 and the song "Misty" listed above, the XM5 is more transparent with clearer soundstage vs 3MOVE, but with the D2000 I preferred the 3MOVE for it's ability to bring out the D2000 midrange detail. With McCoy Tyner Quartet "New York Reunion", the XM5 gives a better sense of the venue than the 3MOVE. While the Pico is less forward and still more detailed and smoother sounding, it is sometimes less engaging than the XM5.

With the BUF634 it seems to drive the HD600 almost as well as the Pico in terms of impact and bass and control, with only slightly less volume when cranked up. With infected Mushroom max volume of Pico before clipping was at about 3 o'clock high gain, while XM5 at 1:30 - 2:00 o'clock was just below clipping and maybe 1-2db less volume than Pico before clipping (battery was down to 8v). This is already quite loud, but not painful. The 3MOVE at 4 o'clock before clipping was clearly 1-2db louder than the Pico, and able to just about match the V1 performance with HD600. Not only was the 3MOVE more powerful than Predator, Pico or XM5, it maintained a more balanced frequency response at extremely high volumes, like the V1. I should mention that these are not volumes I typically listen to music, and so this issue would almost never come up. With James Taylor "Steamroller Blues" off the greatest hits, the XM5 and Pico were able to come closer to the night club volumes than the Predator with HD600, making the Predator almost sound thin when pushed too hard The XM5 was still 1-2db behind the Pico, while the 3MOVE was again the clear leader in max dB with HD600 alongside the V1. This volume capability is program specific, as switching to the CD "Jazz at the Pawnshop" the XM5 was able at 3 o'clock to easily match the loud volume of the 3MOVE at 100% at 5 o'clock and get closer to live club volume levels with HD600. I was also impressed with the transparency of the XM5 with this particular CD as well.

I did some listening with my Grado RS-1 and most of my playlist, and the XM5 and Grado get along well. The Yo-Yo Ma song with Diana Krall that had some uncontrolled string-bass with the D2000 was better with the RS-1 and enjoyable. I tried the RS-1 with the Predator on this song but instead the mids became too forward vs the XM5. I just can't make heads nor tails of this song, as it always seems to have something wrong depending on the amp or headphone, but the RS-1 and XM5 finally got it right. The RS-1 with XM5 and rock like Coldplay Viva La Vida perform well, with minimal midrange congestion that I sometimes hear with modern rock when it gets a little busy. Sometimes I feel the RS-1 could use more bass with portable amps and I switch to flats, but then miss the bigger soundstage of the bowls; but with the XM5 I did not find the RS-1 lack bass. There are no warnings with using the XM5 with Grado, like I had with the V1 and Grados.

EXTRA SWITCHES and FEATURES:

Crossfeed: On FIM Audio Reference III - The Super Extended Resolution Sound Of TBM, Isao Suzuki Quartet, "My One And Only Love" has an excessively wide stage, with a guitar all the way to the left and string bass to far to the right. "I Can't Get Started" has the piano only on the left and string bass only on the right, and Mari Nakamoto "Georgia on my Mind" has string bass far left and jazz guitar far right - the XM5 crossfeed helps with the soundstage on these extreme left right spread recordings, although it is really only a stereo channel mix/blend control. The songs are almost unlistenable on headphones without this, being clearly designed for speakers. The XM5 makes the song listenable; nevertheless, I thought the 3MOVE crossfeed did an even better job, although subtle and not adjustable.

Imagine the soundstage stretched from one ear to the other, from 9 o'clock on the left to 3 o'clock on the right. In in the song "Georgia" mentioned above, the string bass in the intro is SO FAR to the left side that the right ear feels like it has noise canceling turned on, and you get that imaginary "pressure" on your right ear. Using the XM5 "crossfeed" simply compresses the width of the soundstage, bringing instruments closer and making it narrower but still spanning 9-3 while filing in the hole in the center. With the XM5 crossfeed the string bass moves in closer to the ear like 5 feet away, but stays at 9 o'clock. On the other hand, the 3MOVE crossfeed keeps a very wide soundstage but removes the sense of extreme left-right spread instruments just a bit. So, with the 3MOVE crossfeed turned on the string bass is still about 8 feet away but the image of the string bass moves from 9 o'clock to 10 o'clock and the "pressure" on the right ear is gone. This is certainly more speaker like to me.

DAC: The amp is better than the DAC, just like the Predator, and as an amp it rivals some desktop amps to a point. In my case I think the amp sounds warm. The XM5 reminds me of a tube hybrid like my TTVJ portable Millet. There are differences in their sound, but the Predator, XM5 and TTVJ portable Millett hybrid sound like they are from the same family; but while the XM5 and TTVJ could be brothers, the Predator is the cousin. Likewise, the Pico, D3 and D2 Viper with LM4562/LM6172 sound like they are in the same family. The Nuforce sounds like it is in the Meier Family with Headsix and 2MOVE.

I also think the DAC is on the level of the DAC in the Predator and 2MOVE and it's a little more detailed and spacious than Headstage Lyrix (or Headstage DAC cable). It is actually the same Japanese PCM2702E that comes in the 2MOVE and 3MOVE. The Nuforce and XM5 USB DAC seem to have a good level of detail as well, despite the lack of a high technology DAC circuit like a USB receiver chip > I2S > Wolfson WM8740, and are are at least as good as the 2MOVE and Predator DAC (i.e. better than Headstage DAC). However, using an iMod as source, or Micro DAC as DAC or Pico as DAC/Preamp to feed the XM5 does provide the upgrade in sound one expects. Yet the internal DAC is still better than the one built into my Macbook or iMac and I think it is pretty good vs headphone out of the Macbook or iPod.

Bass and Treble Boost The bass and treble boost are much cleaner than using the iPod EQ, and probably on the same level as the iTunes EQ - although sometimes the bass boost is too much and other times just right, depending on the headphone. For example - with Nuforce NE-8 the bass boost is just right, and also good with the RS-1 and MS-1, but with HD600 it is just a little more than I'd like but not too much, and with D2000 or Edition 9 it is ridiculous/useless being too much. The treble boost is more subtle, and probably would have used it with my Klipsch Image X10, stock SE530, SA-6 or q-JAYS, but otherwise I didn't really need it. I did enjoy it with my HD600 at times, to get just a little more sparkle out of them.

Gain: The amp in low gain using the USB DAC or iMod to feed it can drive anything from Livewires low impedance high sensitivity IEM to HD600, and like the 3MOVE and TTVJ portable Millett it could go without the gain switch. However, when I tried the iBasso D3 line out from the D3 DAC to feed the XM5 (ALO cryo silver x mini-mini) I found high gain to be quite useful, because the D3 doesn't put out a lot of voltage from line out (I guess it is direct from the DAC chip without opamps or buffering). Doing this, I found the D3 DAC to be more detailed and spacious, but the sound was less dynamic than feeding the XM5 from my Headroom Micro DAC which I like better.

75 ohm P-S Switch: Kicking this in did drop the volume a bit, and the knob had to be turned up to accommodate the drop. This did clean up the bass on a couple of songs with the D2000 that had been mastered poorly. I did not like it with my Livewires (reportedly they do better with only 50 ohms) but it did help the KSC35 sound a little more refined.

Input Selector: The nice thing about the XM5 is that like the Predator you can keep your analog source and USB plugged into the amp at the same time, and manually switch between the two sources, while the other amps automatically switch to USB input when plugged into USB.

SUMMARY: Overall I find the sound to be a cross between the performance of the 3MOVE and Predator rather than Pico, due to the lesser DAC performance, while closer to the Pico in soundstage - an interesting combination. While I felt the D3 Python was closer to a Pico clone, I would not confuse the XM5 sound with the Pico. However, many times when I thought I was listening to the Predator or 3MOVE I then looked and saw that I was listening to the XM5, and visa versa. Like I said, they sound like cousins (with the TTVJ being the XM5's brother). However, switching to the Predator or 3MOVE made it clear that the amps don't sound the same, just related. With HD600 however, saxophones are different in tonality, but I can't put my finger on it exactly - it's almost like with the Sax on XM5 the high notes sound slightly closer than the low notes.

I previously guessed that from my memory of how the 2MOVE sounded that I would likely prefer this XM5 over the 2MOVE, but I didn't have Skylab's 2MOVE to compare to anymore. I felt this was probably going to be in the top 3 so far, right below the Pico and Predator. Well, I picked up a B-stock 3MOVE with some hours already on it and I did compare them, and I think they should be ranked similarly. Also, I still like the mids of the XM5 and 3MOVE a little more than the Pico, even if I like the Pico soundstage and micro-detail a little more. After playing with the 3MOVE and XM5 I am likely going to be selling my D3 Python soon after this review, since I can't deal with the RFI from NORAD behind my house and Buzz from my iPhone - otherwise the D3 is a great amp. The Nuforce Icon has me thinking about selling my D2 Boa as well, since I have too many portable amps again (after selling the D1, Lyrix, Caffeine and D2 Viper). But I don't plan to let the XM5 or 3MOVE go anywhere, and they will have to live in harmony with my Predator and Pico for a while.

RANKING: Please see newer ranking below, as the old ranking caused this post to exceed 100,000 characters and could not be saved. I placed the XM5 on a similar level with the 3MOVE, in the top tier.


Feb 22, 2009 UPDATE - iBasso D10 REVIEW AND REVISED RANKING:

The iBasso D10 is an evolutionary product that takes the best of what they have had to offer over the past year and a half, and all crammed into one little box. My first amp from them was the D1 back at the end of August 2007, which basically took the chipset of the Headroom Micro Stack (separate DAC and Amp) and put it all into one package at a fraction of the size. Yet it was still too big for true portable use. I enjoyed that amp and moved it to my bedside where I could use it as a DAC for my tube amp. And with new opamps it was a real contender, but only via optical (or coax) input and not as good via USB. With stock opamps the original D1 probably could be described as poor via analog input, although significantly improved with a set of AD743 or AD797 in the main amp (on a 2:1 adapter) with AD8397 or LMH6643 as buffers, and AD8656 or LT6234 in the DAC section. Because the Headroom Micro DAC has a much better sounding USB DAC, and better sounding line out, I traded my D1 for some electrostatic equipment and bought a Headroom to replace it. Something I regretted later because of the D1 high quality optical DAC and smaller size.

After the success of the D1 iBasso introduced the D2 Viper which was a limited run of 100 amps with socketed opamps so that the main opamp and ground channel opamp could be changed to tune the sound. It's main feature was an improved size and superior USB DAC section, using I2S between the USB receiver and DAC, and upgrading the DAC chip from the CS4398 to the Wolfson WM8740 (like the Pico). It shipped with an LT1364 in main amp and NE5532 in ground, and while it outperformed the stock D1 it didn't outperform the "rolled" D1. However, changing the opamps to LM6172 main and THS4032 ground turned it into a giant-killer, and opamp combos to mimic the Predator and the Pico were found as well. Co-developed at the same time as the D2 Viper was the D2 Boa that was meant to be the same amp but smaller, and it eliminated the socketed opamps due to size constraints. I have suspected that if not for the insistence of several head-fi members that the D2 Viper may have never made it to production, with the D2 Boa being the final product instead. While the Viper ran at 12v for only about 15 hours, the Boa runs on 5v for about 35-40 hours and could be charged by the USB Port. The sound was better than the stock D2 Viper, but not up to the level of the D2 Viper after it received new opamps.

The D3 was developed to fill the spot in sound quality left vacant by the discontinued D2 Viper, including the need for more power than the 5v in the Boa, and the ability to swap batteries by frequent travelers - it runs on 7.5v with 5xAAA replaceable batteries. The D3 sounds much better than the D2 Boa, but still not quite as good as the D2 Viper with the right opamps. A nice new feature was the ability to use it as a DAC with line-out only and no batteries needed, like the 2MOVE and 3MOVE when used as a DAC/amp without batteries. Unfortunately the D3 headphone out was still better than the line-out; but it could be used as a DAC preamp with good results, at the expense of using up the batteries. It's biggest problem to me was the susceptibility to RFI from the iPhone. Still, for 2/5 of the cost of a Pico or Predator it was a good bang for the buck if one wanted a DAC/amp with bigger soundstage and more detailed DAC than the 3MOVE, despite a less powerful and slightly less refined amp section.

In the meantime, for reasons unknown to me the D1 was discontinued after the D2 Boa was released, and that left a gap in the product line in my eyes. I was excited to hear that a new upgraded and smaller version of the D1 was being developed, and when it was released I ordered the same day it was up on the website. This is an amp that is only 1/2" longer than the D3 with the same height and width (and 1" longer than the D2), but manages to cram an additional Optical and Coax input along with the USB and analog input of the D3, plus a charging circuit that like the D2 Boa can be charged by the computer's USB port, while still retaining the line-out function of the D3 and it's Wolfson DAC. For all of us with current day macintosh computers, discontinued portable CD players with optical out, or discontinued iRiver H120 and H140 MP3 players with optical out could again have a small portable solution for DAC and amp.

In this photo you can see the D10 Cobra on the bottom is about 1/2" longer than the D3 Python sitting on it, which is about 1/2" longer than the D2 Boa sitting on it, which is about 2/3" longer than the Pico on the top. I will get some more pictures this weekend and post them.







Main Features (per iBasso website):

- PCM2906, converts USB into a S/PDIF signal
- CS8416, DA-receiver chip
- WM8740, D/A chip
- OP+BUF structure for amplification
- 2-Setting Gain Switch for impedance matching (+3/10dB)
- Dedicated MCU (Micro Controller Unit) to manager inputs, outputs, and functions.
- Flexible input and output compatibility. It has USB, optical, coaxial, stereo input, line out, and stereo output
- Works as a combo or a stand-alone AMP, DAC, USB soundcard
- Built-in rechargeable Li-polymer battery plays up to 30 hours (30 hrs for AMP, or 20hrs for combo)
- Measures 55*21*104mm, and weights 168g
- Comes with power adapter, leather pouch, optical cable, USB cable, warranty card, owner¡¯s manual, and opamp rolling kit. (includes AD8656*2, LMH6643*2, Dummy adapter*2)

As you know, the amplifier ranking can actually be a bit different depending on the headphones being used at the time, so I had to do detailed comparisons of multiple amps using multiple headphones and it takes longer and longer with the more amps and headphones I have. With the D10 included, I still have 10 of the 13 amps that have been reviewed! (minus Lyrix, D2 Viper and D1). I just can't listen to 7 or 8 headphones on 10 amps in quick succession in a way that I can remember the previous combination's sound, so I have to make some compromises.

So, I narrowed down the D10 comparisons to only vs the top tier amps where the D10 belongs, and I compared it only to the top 4 amps that don't sound alike and were the most enjoyable = Predator, Pico, 3MOVE and XM5. At one point late in the review I got a loaner Apogee Duet to dompare it to as well. I can skip most of the others from previous reviews for a variety of reasons: I know where the D3 stands vs the Pico (almost the same but slightly less) and where the Micro DAC/Amp stands (pretty much the same as Pico). I didn't need to do a side by side with D2 Boa, Vivid V1 or Nuforce which are below the top tier for reasons mentioned previously in my reviews.

I used my RS-1, D2000, HD600, Edition 9 and ESW10 as my full size phones, and I used my Westone 3 and ES3X plus Phonak Audeo as my IEM for the review. I first want to say that the D10 is a good match for any of these headphones, and there was not one that stood out as not getting along with it, even with the stock opamps that were installed. In addition to listening via USB, I found it was very good with my iMod portable (modded ipod), so unlike the D1 it is good out of the box with analog input while the D1 needed new opamps to sound good with analog inputs. And it was very competent via USB as well, but even better with optical as I discovered later. Anytime I did testing via optical I made sure my Macbook pro was set for 24/96 output, as several of the music files I used were native 24.96 files. Lastly, I also tried the DAC line-out and used it as a DAC/pre-amp via headphone-out vs Pico as a DAC/Pre-amp for my Woo GES/Stax O2 rig as well.

With no burn-in at all and right out of the box, using the stock opamps, and listening via USB it sounded as good as my 600-700 hour D3 via USB in a side by side comparison (I stopped counting after 600 hours). At 55 hours (with optical) D10 had slightly grainy highs vs Pico, but was very detailed and spacious like the Pico. By about 215 hours it had become more refined sounding and I felt that the D10 fed via optical out of a Macbook ranked up there with the top DAC/amps like the Headamp Pico, RSA Predator, Meier 3MOVE and such. I had passed my 300 hour mark set for burn-in the morning of 2/9/09 and over the course of the review I have over 400 hours on the D10 now. The Majority of my review was done with the stock opamps. During the initial evaluation period, I was happy to discover that the D10 has very good channel balance at low volume knob positions with IEM, and it is dead silent when music is not playing and it is connected as a DAC/amp to the computer. There is no hiss with high sensitivity IEM like the Macbook headphone out, while high end DAC/amp like the Apogee Duet has a very slight hiss with my Westone ES3X customs and Livewires or SE530 customs.

I started my initial listening with USB via RS-1, D2000 and HD600, and first compared it to the Predator. Listening to the D10 and Predator Via USB, and going back and forth between them, I was unable to tell any significant differences in the sound signature other than the Predator has a little less power to drive the HD600, was less detailed, and the Predator's soundstage was flatter than the D10. This was a very long listening session and by the time I was done it was the middle of the night and I was tired, but in subsequent comparisons I felt the D10 was still up to the level of enjoyment that I get from the Predator. So, it seems the D10 sounds as good as the Predator to me but the D10 USB DAC is more detailed and spacious than the Predator.

I then compared the iBasso D10 optical input vs Predator USB input the next night, using the Phonak Audeo IEM with grey filters and silicone tips while listening to CD's ripped lossless into ALAC format. This particular IEM setup is a more demanding test in that the Phonak with grey filters and silicone tips can be ruthless in revealing details, and usually need the Complys foam tips to smooth out the treble which can sometimes be bright. I often find the grey filters are a little harsher sounding with the silicone tips (or can border on sibilant), and almost always use the large Complys tips (which I had to buy separately). I wanted to see if any of the amps were more forgiving of a demanding and detailed IEM, and to see how much more detail was available via optical instead of USB.

When I used the D10 via optical I could have 3 amps connected to the Macbook Pro at the same time with two via USB, allowing me to quickly switch between the amps. I rotated the Predator, Pico 3MOVE, and XM5 through the two USB ports, and then also listened to the D10 via USB again. With this particular IEM setup the Predator was slightly smoother in the highs than the D10 Optical, 3MOVE USB or XM5 USB. The Pico was also very smooth and refined, and with this particular IEM setup I have to say the Pico DAC/amp combo is tied with Predator for smoothness when the Phonak have the wrong combination of filters and tips. Going back to the usual Complys T130 foam tips I felt all the amps became smoother with improved bass, so that is really an IEM issue and I should not have been using the silicone tips in the 1st place. In this round of testing the D10 optical does seem to have more micro-detail than all but the Pico (with 16/44 music). It seems the D10 DAC ties with the Pico as the most detailed and spacious while being smooth at the same time (except in mismatched IEM tips and filters). This held true with listening with the Westone 3 and ES3X as well.

I then tried the D10 DAC to feed another portable amp, using line-out and headphone out. I plugged the D10 line-out into the Predator using a nice quality ALO 22g Cryo Silver X mini-mini and the D10 was connected to the Macbook via optical and USB, but I also left the Predator connected via USB. This way I was able to flip the front panel switch to switch between the built-in DAC or the D10 DAC while switching the computer at the same time. The D10 line-out volume level matches closely the Predator's USB DAC line level, so the volume of the amp did not change with changing the source. With 16bit/44khz lossless ripped CDs, the D10 line-out into the Predator sounded better as a source than the Predator using it's built-in USB DAC, which sounded slightly flatter and less lively, regardless of whether the D10 was used with optical or USB. Switching to the D10 headphone-out to drive the Predator woke up the sound a bit, similar to what I heard with the D3 line-out function previously - both the D3 and D10 DAC's line-out seem slightly less alive and vibrant than their headphone out when feeding the sound into another amplifier. This was confirmed when comparing the D10 line-out to several desktop DAC at a recent mini-meet, where I only used line-out instead of the headphone out (there were also issues of different interconnects and digital cables and inserting a pre-amp and listener fatigue and severe lack of time).

I then put on three different albums with higher quality 24/96 bit rates in lossless (Ryan Adams and the Cardinals, and Portico Quartet, and Arnie Somogyl's Ambulance) and listened again. The D10 optical DAC into the Predator was superior with more micro-detail and ambience and air between instruments, and while the Predator via USB sounded good the soundstage was flatter and smaller than with the D10 optical. This improvement was still there even when feeding the inferior D10 line out instead of headphone out into the Predator. The D10 handles native 24/96 files well, while the older D1 could not decode digital signals greater than 24/48 via optical (Mac audio midi setup was set for 24/96 via optical before launching iTunes). With the computer still set for optical out and using the D10 DAC, swapping the headphones from Predator over to the D10 (and unplugging the mini interconnect) switched the sound to the D10 headphone out, and resulted in very little change in the sound when the headphones were driven by the D10 instead of the Predator. Basically, the D10 via USB matches or exceeds the Predator's performance as a DAC/amp, and via optical it beats it in detail and resolution with 16/44 or 24/96 files.

I then did some comparisons with the Pico vs D10. In many songs such as with an Elaine Elias song "You and the Night and the Music", some of the cymbals strikes or other notes die out just a little faster with the Pico and there is more quiet or blackness between the notes than with the D10. It's like with the D10 optical I can hear a little "deeper" into the music and hear more of the quiet stuff going on in the background and between notes, and I don't mean noise floor but rather the decay of the instruments and echos hiding in there. This gives the illusion that the notes start and stop slightly faster with the Pico, making it sound a little snappier. I find that the D10 as a DAC/amp and the Pico (and Duet) have a larger sense of space and ambience than the Predator, 3MOVE or XM5 which don't use the Wolfson WM8740 DAC like these two.

Similar to my DAC test vs Predator, I also tried feeding the D10 as a DAC line-out (and headphone out) into the Pico, and compared it's DAC to the Pico's built-in DAC (removing the amp section from the equation). The D10 headphone out volume needed to be set at 3 o'clock in high gain to get the output volume to match the Pico USB DAC volume when flipping between them. When using D10 line-out the volume was much softer and while I listened to the Pico in low gain via it's built-in USB, when switching to D10 as the DAC with its line-out feeding Pico I had to switch the Pico to hi-gain to match the volume of the Pico's USB input. The D10 line out is softer and quieter than the internal USB DAC of the Pico, which was not the case with the Predator. I found The D10 optical and the Apogee Duet via firewire were both slightly more detailed with native 24/96 files than the Pico, but the differences were much less with 16/44 music (almost negligible). So, the optical D10 line-out when fed native 24/96 did pull away slightly from the Pico, where the USB makes the Mac down-sample the music to 16/44, and then the Pico has to up-sample it back up to 24/96. But otherwise, with 16/44 files the advantage was minimal if any.

As for other areas of the sound, the D10 as an amp sounds slightly warmer than the Pico, and after getting used to the sound via D10 as a headphone amp, switching to the Pico can sometimes sound slightly thinner - the same effect I experienced almost a year ago when I was comparing the Pico to the Predator. Sometimes I think the D10 sound falls between the Pico and Predator, but with having the resolution and space of the Pico. I feel the musical performance via the D10 as a complete package sounded a little fuller and "bigger" than the Pico, despite having a little less power than the Pico for the HD600. It could still get loud with HD600, but was optimal with RS-1, D2000, Edition 9, ESW10, and all my IEM. When not pushing the D10 amp to the max, the sound signature seems just a little closer to a desktop amp to me, like the Predator, although neither one has the power of a desktop amp (or even the power of the 3MOVE and Pico). With the RS-1, D2000 and Edition 9 the D10 volume can go extremely high. With HD600 it is about as powerful as the D3 and XM5, and more than the D2 Boa or Predator or Nuforce. But the Pico and V1 are still more powerful, and the 3MOVE is the king of power with the HD600 (in hi-output mode). I am still amazed at the volumes I can get with the 3MOVE and HD600.

I did another comparison (which I repeated on 2/14 with Sherwood), comparing the D10 and Pico as USB DACs feeding my Woo GES and listening with Stax O2 Mk1 and Mk2. This rig is where the Pico gets used the most. The D10 via optical and feeding the line-out signal into a Woo GES desktop amp was very close to the Pico doing the same, and at the meet Sherwood didn't even notice the very small drop in detail and space when I switched the D10 from optical to USB when he wasn't looking (went from D10 optical > Pico > D10 USB). I found that it is easier to hear the drop in sound quality switching the D10 from optical to USB when one is looking for it. Nevertheless, the D10 USB DAC is at least as good as the D3 USB DAC that was so close to (but slightly below) the Pico previously. At one point the D10 DAC line-out output wasn't high enough for the low-gain GES. So I switched the D10 to headphone out into the GES, like I must do with the Pico, and I noticed an improvement in dynamics and soundstage which I assumed was from the higher gain. Further testing shows this is a slight improvement in sound from headphone out vs line-out when the D10 is used to drive another amp.

I want to mention that at the same meet last weekend, where Sherwood and I compared the D10 vs Pico as a DAC feeding a full size amp, we also tried comparing D10 to several desktop DACs. That didn't turn out as well. We had 6 DACs connected to an NAD542 via an S/PDIF distribution center via Coax with a mish-mash of digital cables, and a variety of interconnects feeding the DACs outputs into a Presonus central Station, and then fed the output of the Presonus to 3 electrostatic amps with a variety of cables and listened with 5 electrostatic headphones. Now that I look at it, there was no way to get all 5 listeners hearing the same thing, nor could we put the DACs on a level playing field. The test showed the line-out is not as dynamic and spacious (5 out of 5 people agreed) as the 5 desktop DACs. But, I don't recall the D10 ever sounding that flat and "un-dynamic" before. So I had to wonder if we did something wrong because we had clearly earlier in the day shown the D10 to be a match for the Pico as a DAC/Pre-amp. I wonder if part of that DAC shoot-out result was due to the difference between line-out and headphone out, but still, when connected directly to the amp it is feeding, the D10 DAC line-out is pretty good.

And, as far as I can tell the D10 via USB is MUCH better than the USB in the older D1 was - the D1 USB feeding another amp was closer to the $40 Headstage DAC cable feeding another amp (although D1 USB sounded better when feeding its internal amp). I also find that the D10 optical input DAC is a little better sounding than the D1 optical was as I remember it, because this D10 DAC is closer to the Micro DAC and Pico than the D1 was. In general, listening to the D10 via optical is like like mixing the best traits of the Predator and the Pico together, and even via USB I enjoyed it as much as the Predator and Pico or Duet. I believe it tops the sound of the D3 Python and the D2 Viper with rolled opamps, and is the best DAC/amp that iBasso has put out so far.

As I have reported problems with RFI from the iPhone causing a GSM Buzz with other amps, I listened for that issue as well. Fortunately the D10 does not pick up radio stations from the towers behind my house like my D3, and the RFI "buzz" from iPhone is less than with the D3 as well (and more like the RFI with my D2 Boa = mild but livable). The D10 is also less sensitive to RFI with nothing plugged into the USB port on the back of the amp, and the iPhone Buzz responds well to changing the opamp to an AD8656 and using a Quick Bridge Solutions - EM Shield for iPhone EM blocking card.

The ability to change or "roll" opamps is a nice feature. The D10 comes stock with an AD4841-2 in the main amp socket, and a pair of AD708 in the buffer sockets (all dual channel opamps, not single). They also include a small case with two AD8656 opamps, two LMH6643 opamps, and two dummy opamps for bypassing the buffers. I also have a large supply of opamps from my time rolling opamps in the D1 and D2 Viper, so I tried a variety of opamps with the D10. There are several that sound good, including an AD8066 with the AD708 buffers, AD8397 with the buffers bypassed (using dummy opamps that are included), and AD8656 with bypassed buffers. The AD8656 and 8066 have nice large/spacious soundstages and refined sound, and the AD8656 still puts out a lot of power without any buffers and can get loud enough with HD600 at max volume knob setting, without any clipping. Using the AD8656 does get a little brighter with any buffer I tried, including 2x AD708, LMH6643 and AD8656. I had a third 8656 left from my D1 kit (it will blow if used in the main amp socket of the D1), but I didn't like it enough with three 8656 to use anything but the one 8656 by itself. I have not had a chance to try any of the other opamps with two 8656 as buffers. Using the buffers did seem to add just a little more volume to the 8656, but then the D10 would clip before the volume knob would hit 5 o'clock. So far my two preferred setups are the stock one, or the AD8656 with bypassed buffers. I only started rolling opamps on 2/21 and the AD8656 is what is in it now, for the final few hours of my review. I left the D10 connected to USB with the switch flipped to charge for 2 weeks, to see how it would do in a desktop rig where it is plugged in and on all the time. Tonight I unplugged the USB and left it running via optical with the AD8656 opamp and bypassed buffers to test battery life. I will report on this later, so that I can post this review now.

UPDATE OPAMP ROLLING: The TLE2141 class-A biased on a 2:1 with EL8201 buffers brings the D10 very close to the P-51 mustang, but with just a little less treble extension and presence. It also sounds very similar to the iBasso D4 with stock opamps, which sounds like a cross between the P-51 and Pico.

To me there seem to be three tiers of portable headphone amps (examples are ones I have heard):

1. The "Don't bother with this if you don't have to" group = E3 and Boostaroo (add power but subtracts from the sound, narrow soundstage, or rolled off frequency response, or all of the above).

2. The "Good bang for the buck but with compromises" group which are not good for everything, but great for some things = includes Travagans Colors, JSeaber Cmoy, Caffeine Pro, Vivid V1, Nuforce mobile, D2 Boa and Stock D1 or stock D2 Viper.

3. And the, "Wow, this is getting closer to a desktop amp" factor (usually in sound but not power). These have more presence and body to the sound and are more refined, and there are very few phones they don't work well with = includes Pico, Predator, 3MOVE, XM5, D2 Viper with rolled opamps, D1 rolled and D10 stock or rolled, Headsix, TTVJ, Micro Amp. The Lyrix Total is an odd one out because the Amp sounds like a top tier and the DAC is a middle tier. The D3 sits at the bottom of top tier, straddling the fence. The D10 now joins this top tier portable amp group, and I put it at the top of my list for now.

RANKING: Please see newer ranking below, as the old ranking caused this post to exceed 100,000 characters and could not be saved. I placed the D10 as #1, in the top tier, due to it's very detailed DAC, and sound which could mimic the Predator (stock) or a cross between Pico and P-51 with the opamps listed above..


Clarification D10 DAC COMPARISONS: In response to some questions about D10 line out vs headphone out - the D10 line-out is still quite good and my review and rankings are based on the performance of the line-out when applicable. As a USB DAC I felt that the line-out was better in comparisons to other portable USB DAC in all cases except for the Pico USB DAC being better and closer to the higher performance of the D10 optical; however, I noted that the headphone out was even better than line-out, and the optical on top of either output was even better than USB.

It gets confusing because I listened to the D10 with (1) it's own DAC and amp with USB and optical, and then listened to the (2) Predator and (3) Pico with their own DAC. And I also listened to Predator and Pico with them being feed by the D10 DAC with optical and USB, using both line-out and headphone out to feed the Predator and Pico. That's 12 combinations of DAC and amp!

D10 optical > D10 amp
D10 USB > D10 amp
Predator USB > Predator amp
D10 optical line-out > Predator amp
D10 optical headphone out > Predator amp
D10 USB line-out > Predator amp
D10 USB headphone out > Predator amp
Pico USB > Pico amp
D10 optical line-out > Pico amp
D10 optical Headphone out > Pico amp
D10 USB line-out > Pico amp
D10 USB headphone out > Pico amp

The only time the line-out did not compare favorably was in the comparison to several desktop DAC, in a shoot out that I think involved poor methodology - where the DACs didn't all use the same digital and analog cables between the source, or same preamp and power amp interconnects, and where all the listeners were using different headphones and amps, without being able to volume match the lower output of the D10, with too little time to really begin to appreciate the sound. If the D10 line out is too weak/low, it works very well as a DAC/preamp using the headphone out to feed a full size amp.

01/24/10 - IBASSO D4 - I WILL NOT BE ABLE TO FIT THE ENTIRE REVIEW HERE DUE TO THE 100,000 CHARACTER LIMIT, AND WILL POST LINKS INSTEAD.. See links below. I have more comments posted in many posts which I am trying to consolidate into one review post.





FIRST IMPRESSIONS - http://www.head-fi.org/forums/6146137-post932.html and http://www.head-fi.org/forums/6147003-post934.html
MINI-REVIEW D4 vs D10 and others, with opamp rolling - http://www.head-fi.org/forums/6264269-post962.html
More COMPARISONS - http://www.head-fi.org/forums/6274204-post972.html

In summary - the stock D4 sounds very much like the D10 with it's best opamps installed, with a slightly beter USB DAC that rivals the D10 optical DAC. The D4 with OPA1611A class-A biased opamps on a 2:1 adapter and stock buffers is even better, and actually closest to my favorite P-51 Mustang. I confirmed this as I did a comparison feeding the D4 line-out into the P-51 with an 18G Jumbo Cryo Silver X mini-mini. I can go back and forth between the D4's built-in DAC/Amp and the D4's DAC feeding the P-51 and I am quite happy with both, finding them to sound very similar.

I am leaving the D4 set up qith OPA1611 class-A as a "P-51 clone" for the time being. Right now the D4 with upgraded opamps is my top pick for portable USB DAC/amp combo, that can be powered by battery or laptop, although my biggest gripe is the sub 10 hour battery life. If battery life along with a high end DAC is important to you, then the D10 still makes more sense, as it is very close to a cross between the Pico and P-51 when the best opamps are installed (minus some treble extension and presence), and it runs for 24-38 hours depending on the opamps and DAC used. Any of the 8 amps in the top 5 spots would keep me happy as my only USB DAC amp, and picking one should be based on features and price.[/B]

RANKING: Note - I have edited the comments in the ranking below, to elaborate on what I thought about the DAC or amp. I did sell the D2 Viper a while back because it could sound like a Predator or a Pico, but was redundant with less battery life than the others. And I also traded the Pico off because I have a Pico DAC with a Pico Slim to be on the way soon, to pair with my Pico DAC. That combo may soon become my #1 ranked DAC amp combo, while not being an all-in-one, but also while being the most expensive. I slightly preferred the Slim over my P-51 with ES3X at CanJam. I still had access to the sold Pico for this D4 review, since my friend Blutarsky who has it is only a 30 minute drive away.

I have several ties in rank, and as I use the amps more over time my preferences may change; but The 8 amps in 1st - 5th place are all on a similarly high level of performance, and are very close to a tie for 1st. There is NOT a huge leap in sound moving from #5 to #1, but rather the rank is rather based on preference and which I prefer to use the most. I could almost make all the top 5 places tie for 1st, but I wont.

Although some have better DACs than others, and some have better amp sections than others, it may average out in the final sound signature and performance. Choosing one can be based on features, price, synergy with the headphones tested, where I could be just as happy with any of them as my only portable DAC/amp if I were reduced to one. In the past I had moved the 2MOVE ranking down because I couldn't remember how good it sounded, having not listened to one in months. Then I bought a 3MOVE which is a 2MOVE with an upgraded case, and I fixed my ranking. Those changes were noted in the older rankings that were recently deleted to make more room in this post. See additional comments included in the ranking below if you haven't read the entire reviews:

1. iBasso D4 - Almost a tie for 1st once the D10 opamps are upgraded, but once the D4 opamps are upgraded the amp section pulls slightly ahead again. Battery life not as good as D10, DAC performance seems to equal D10 optical and Pico to the best of my ability to hear them, where USB DAC is only slightly ahead of D10 via USB. Based on features, D10 should tie D4, but since I am not using optical or battery and like the sound a little more, I prefer the D4 purely as my main laptop DAC/amp. As a portable, I'd prefer the D10 for 3-4x more battery life and ability to use with my iRiver H140 and Sony PCDP as well. But, both are too big to be my only portable and I most often use the P-51 for that.
2. iBasso D10 Great sound that blends the performance of the Predator and Pico, with a USB DAC that falls between them and an optical DAC that exceeds theirs (in 24/96). Ability to roll opamps and tune the sound is great, and it has convenient charging via USB port. It has decent power for even HD600, but I could wish for more, and good low volume channel balance for IEM.
3. RSA Predator - Good bass and soundstage, more body, organic, full. Seems to do well with all my headphones, and not bad with any. Gobs of power with RS-1, D2000 and Edition 9 but could use a little more power with HD600 - very underpowered for AKG K240M 600 ohm. DAC is not as good as the Pico, but the sound of the amp makes up for it.
4. D2 Viper with rolled opamps - This has been sold and is discontinued. It's spot in ranking stays due to how it sounded in relation to Predator, Pico and 3MOVE. However, with the opamps that gave it the 17 hour battery life, the sound was similar to a Pico clone with a slightly less resolving DAC. At that point the Pico and others would move up to take it's rank. With LM6172/THS4032 it was more balanced, not too forward, with sweet/magical Saxophone, and almost mesmerizing like Predator. With my IEM I found it sounded better with the LM6172 and THS4032 swapped. This second opamp configuration was good with all my IEM, and not bad with my full size phones, except the RS-1 seem a bit bright and the Proline 2500 lacked fullness in the mids. With LTC6241HV/LMH6622 sounds like 98% of the Predator but with only 7 hour battery life. Later I discovered the LM4562 main/LM6172 ground, and this works very well for full size phones and IEM - very open and spacious and detailed, sounding closer to the Pico without losing too much warmth or rich tone. And battery life was bumped from 7 hours to 17 hours! DAC is more detailed and spacious than Predator or 3MOVE, but not quite as good as Pico's DAC. This is just how close all these amps really were, that with the right opamps I only prefer it to the Pico or 3MOVE by a hair.
5. PICO - Smooth and transparent without coloration, Great DAC. Won the bad mastering Diana Krall test, but nothing special with piano and sax like the others, too neutral as an amp - how is that possible, maybe not because there is something around 2Khz that is not right with RS-1. It really seems to shine with my re-cabled Denon D2000, Klipsch Image, Freq Show customs, but doesn't sound bad with anything but my Proline 2500). Over the past few months the Pico has really been growing on me, and it no longer seems to lack warmth with my RS-1 or other headphones (especially since I sold the PL2500). The DAC's space and ambience and soundstage still stand out as slightly superior to other USB DAC, as before, and it seems to do well with most IEM but not all. With the D10 and D4 the USB DAC performance gap is closing.
5. Headroom 2006 Micro Stack Portable - A twin to the Pico's sound as far as portable amps go, but better with piano. Too BIG and out of production, with crossfeed mids are richer/warmer but highs rolled off. With comparing the newer Pico DAC only to Micro DAC only with a full size amp, the Pico DAC has an edge in performance over the Micro DAC only. With the portable amps the edge seems to go away as resolution of the amps is less.
5. 2MOVE/3MOVE - Sweet mids and with saxophone, midbass hmmm - maybe a little boost, failed the bad mastering diana krall test, great detail and air, too large and heavy, sounds as good as Pico but it's a different sound, sometimes too forward, other times fills in a thinner headphone. NO iPhone Buzz. Auditory memory faded as I hadn't listened to the 2MOVE in months, so I bought a B-stock 3MOVE and found I do still enjoy it very much. Since I am liking open and spacious sound a little more now, the Pico moved up to tie the 3MOVE rather than move the 3MOVE down. I did add listening to the Westone 3 with this amp and they are fantastic together. 3MOVE is a better match for the D2000 and RS-1 than XM5, while I liked the XM5 more with HD600, Edition 9 and ESW10, even though 3MOVE had more power for HD600. Slightly more power for HD600 than Pico.
5. Practical Devices XM5 - Stock amp section better than D3 and rivals higher ranked amps, but DAC not as good as the D3 - so it evens out. With AD8065 opamp and BUF634 installed it's on the level of the 3MOVE. Gets along better with more of my headphones than D3 and with all of my IEM, and I am having no iPhone buzzing with it so far. A chameleon - many times it sounds like my Predator, and other times it sounds more like the 3MOVE, depending on my expectations. And the amp section really shines with iMod or an external DAC instead of the built-in DAC.
6. D3 Python - Very sensitive to RF interference from Cheyenne Mountain and NORAD. Had to sell. The sound is very close to the 3rd place amps, but not quite there. I like it very much, being only slightly less smooth in the upper mids with Grado than Pico, and very slightly less micro-detail in ambient cues and complex passages, dropped in rank because of RFI problems)
7. Nuforce Icon Mobile - More forward than D2 Boa and closer to Vivid V1 and 2MOVE in that regard, has good synergy with Westone 3, Klipsch X10, Nuforce NE-7M, Denon C700, ATH-ESW10, D2000, and Edition 9 - sounded nice with HD600 but a bit under powered with HD600 and not worth trying with 600 ohm AKG K240M. With RS-1 occasionally had a similar upper mids coloration like Vivid V1, and sometimes needed to switch to the flats to enjoy them more. So not first choice for Grado but would not avoid the amp because one owns Grados. Good midrange detail but not as full and rich sounding as the top tier amps above except with D2000, Edition 9 and Westone 3 which bring that to the table on their own.
7. D2 Boa - Sonic signature slightly warmer than the Pico, and between the D2 Viper with LM6172 in the main amp (warmer) vs THS4032 in the main amp and LM6172 in the ground (cooler). Timbre and tone was good, and lower mids were slightly forward and rich, and highs had slightly less extension than the D2 Viper or Pico and Predator (in that order). The sense of space with live performances was superior in the D2 Viper, Pico and Predator (in that order), and LESS with the Boa at 300 hours of burn-in. However, the Boa did open up and gain more air and ambience on the level of the other top ranked amps by 575 hours of burn-in. Listening to Diana Krall "Girl in the Other Room" (Temptation and other songs) seemed to indicate more of a low mids hump than the other amps, which also caused problems with Pianos and realism on that CD. The problems reproducing this particular CD remained after 575 hours of burn-in, however with other CD's like Jazz at the Pawnshop, Handel Messiah and Tsuyoshi Yamamoto the D2 Boa demonstrated improved transparency and realism with the extra burn-in. And with other music it seems the bass extension is slightly less than the others in the top ranks, but by 575 hours of burn-in (with my RS-1) the 16Hz audio tones on Binks Audio Test CD were clearly audible, and the volume of the 20Hz tone caught me by surprise, while 25Hz was a little disorienting! With over 800 hours the lower mids hump is less noticeable with female and male vocals now, but the middle mids and upper mids now seem to be more withdrawn instead.
8. D1 with rolled opamps - With AD797 main/LM6643 buffer/LT6234 DAC - powerful, punchy, energetic, alive. Not as bright as AD743/6643/6241 which excelled with Edition 9 and re-cabled HFI-780. The D2 Boa moved up a little with more burn-in, but it wasn't quite good enough to rise up to a 3rd place tie. So the modded D1 and everything else had to move down a slot. The D1 via USB isn't as nearly good as via optical, which is why it is not tied with the D2 Boa after the Boa improved with extended burn-in. With optical input it might beat the Boa easily.
9. Vivid Technology V1 - Very good synergy with HD600 and AKG K240M 600 ohm, nice and fun with Edition 9 and Klipsch Image X10. Acceptable with RS-1 IF switching to flats, but bowls are not recommended, and unacceptable with my Freq Show but not the amp's fault. DAC with slightly more micro-detal than stock D1 via USB or Headstage Lyrix, slightly less than either D2 Viper/Boa or the other higher up amps. The most forward of all the amps. Can be closer to the top with HD600 and Edition 9 or 2nd with K240M, but closer to last place with Grado RS-1 and bowls (and last with Freq Show).
10. D2 Viper stock - tied. Thin in the middle, neutral with good bass - it was sound signature and power but not level of detail that held it back with the stock opamps. Sounds good with Freq Show and most of my IEM, fairly good with HD600 and Edition 9 but lacks power. Not bad with RS-1 but can't properly drive AKG K240M 600 ohm. Sounds better with re-cabled modded ATH-AD900 than the Boa or V1.
10. Lyrix - tied. Good frequency balance, DAC lacking details and air vs the others, but decent. The amp is great with analog input and closer to top teir like D3.
11. D1 stock opamps - I put AD823/NE5532/AD8616 back in right before I shipped it back for the 2-3db channel imbalance, too edgy and bright and distant. Very close to 7th as a DAC/Amp because the DAC is so good it makes up for the frequency response issues. Clearly 8th if only using analog input. NOTE - my V1 opamps were from the initial run, and iBasso updated the opamps to V2 in November 07 to make it better than Lyrix.)

I should note that any of these amps are very pleasing sounding, but 5th place and up are almost a tie for 1st.