Little Dot I+

General Information

The Little Dot I+ is a hybrid transistor-vacuum tube headphone amplifier, which combines the smooth, musical sound of tubes with the high output current of transistors. The vacuum tube stage is run in Class-A, the MC33078 operational amplifier (socketed) provides voltage amplification, and BD139/BD140 transistors serve as output buffers. The Little Dot I+ is specifically designed and optimized for driving low impedance headphones that require high current to perform to their full potential. Depending on how the switches are configured, three different families of vacuum tubes can be used (EF95, EF92, and 408A). With two gain settings and DIP switches for vacuum tube rolling, the Little Dot I+ offers versatility in a tiny footprint!

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New Head-Fier
Pros: drives 64 ohms with ease, can tube roll, adds warmth, amazing value
Cons: not portable, need to open up to change settings
I ordered the Little Dot I+ through Massdrop and got about 30% off the regular price.  I skipped the stock tubes because I heard poor reviews about them and instead opted for the 6CQ6 which are supposed to add a fair bit of warmth.  The warmth is definitely noticeable which is great for my AKG Q701 headphones which are pretty sterile (yet accurate).  They help a lot with the tapering of the bass for these headphones.
Paid $102.99 from Massdrop including the upgraded tubes.  I should have bought two!
I have them set to the high gain setting and have listening impressions for the following outputs with the 6CQ6 tubes:
HeadphonesHeadphones Plugged Into:Device Plugged Into:Sound Impression
Q701Macbook Headphone Jack (directly)N/Atinny sounding.  Can't drive the low end, I'm guessing about half the decibels for sound below 200hz compared to the sound in the 500hz range.  Sound in the 1000hz and up range comes through clear (almost too much of it)
Q701Little Dot I+Macbook Pro Headphone JackMore linear sound.  The bass is nice and warm and there's still detail in the mids & highs.  Very large upgrade!  Well worth it!
Q701Dragonfly Black 1.4Macbook Pro USBMore linear compared to directly in the headphone jack.  Bass is a little reduced compared to the little dot I+ in the headphone jack.  Sounds "cool" but linear.  Resonance is very clear compared to the little dot I+.  Extremely spatial sound.  Makes "concert hall" recordings sound awesome (ie:  live music, classical)
Q701Little Dot I+Dragonfly Black 1.4 (Into macbook pro USB)Not much of a difference from the Little Dot I+ plugged directly into the headphone jack. Makes it clear that the MAC DAC is not that bad the computer is more limited as a headphone amp.  Lose a bit of resonance detail but save $100-150 by cutting out the additional device.
The instructions detail how to change the jumpers & dip switches but don't give instructions on how to open it up.  Only need to remove lower screws on front & back plates, no other screws.  Tubes are cool enough to touch but unit itself is almost too hot to touch after an hour of use.  Hissing & crackling goes away after an hour of use.
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Headphoneus Supremus
Pros: Perfect tubey sound for low-imp cans; Cheap; Extreme SQ scalability with opamps and tubes;
Cons: NOT that easy to change tube family; NOT that easy to change gain level;
First, a few words about me. I would consider myself a semi-audiophile, as I have written a few reviews in details, I understand audiophilespeak and I have gone through plenty of equipments searching for the most analogue sound possible. 
For those who were looking for a structured review, this one won’t be like that. I already did a review for the LD I+ that way but it was in Vietnamese, my mother tounge. The only reason I’m doing another review for the I+ is because I’ve just received the Burson V5 SS opamp and it takes the I+ to a level I never thought this cheap Chinese amp could reach. If you want my assessment on SQ of the Little Dot I+ w/ Burson V5 SS opamp combo, please skip a few dozens paragraphs.
Also, all apologies for any mistake I’m going to make, as I’m not a native English speaker.
A long journey
I’ve heard of tube amps since I had my first true headphones – SR60i and Sennheiser HD448. However, at that moment, amps and DACs still costed a lot and tube amp was way out of my reach as an engineering student. I had an iBasso D2, but the improvement over my HP Envy laptop’s lineout was minimal.
Hell, the O2 ODAC didn’t even pop up on the scene back then!
One of the first photos I took on the I+.
Fast forward to the time when Little Dot, Hifiman and a few other lesser known brands like Little Bear, Nobsound, [insert random Chinese brand here] have taken the price of tube amp to under $200, I decided to join head-fi after too many years as a lurker. The I+ was the first product recommended to me by a head-fier: @JoeDoe told me that the I+ and Grados “are a match made in heaven”.
As a Grado fanboy then (and now), that was all I need to hear.
My journey with the I+ is not an easy one. I got it from an audiophile shop in Hanoi (my home city) for around 125 USD, which is much more expensive than what you can get it for right now on Massdrop. The version I bought was the Valvo EF92 one, which honestly, sucked. I didn’t like the stock sound one bit. It sounded like a cheap Fiio amp with no tangible benefits to speak of, almost everything was rolled off and artificial.
3 months later, when I’ve traveled cross countries at least 3 times, one of the Valvos stopped working for no reason.
I’m thankful it did.
It’s a tube amp with a lot of jumpers
The Little Dot after I replaced the stock tubes.
The natural things to do was to look up the Little Dot thread on head-fi to see what tube was the best. Thanks to the very helpful post by @Dept_of_Alchemy, I decided to go for the Mullards CV4010, which was readily available in Singapore.
But here comes the biggest obstacle: in order to use the EF95 tubes, I had to remove some jumpers inside the amp. I have to admit I wasn’t too pleased with this. LD should have devised some easy way to change tube family so that we non-hardware guys wont’ feel a tiny bit scared when we do. Like, they could have created a mechanism to remove the jumpers from outside the chassis.
Anyway, it is sounds much more difficult and scary than it actually is. I only have to remove 4 screws (2 on the front plate, 2 on the back plate) to open up the amp. The instruction was clear; this little amp has gone through some variations and the location of the jumpers have changed but the denotation have not. As long as you follow the instruction, there should be no problem.
Once you have removed the bottom-panel, the Little Dot I+'s board is fairly straight forward (the red thingy sticking out is Burson V5 SS's opamp)
It really sucks that a lot of functionalities are hidden inside the chasis. If you want to switch from low-gain to high-gain, you’ll have to change some jumpers as well. If you want to roll op-amp, well the location is on the board. It would be great if LD could use an extender to connect the op-amp slot on the I+ to some place on the outside of the chasis, but they didn’t do that.
Here’s where another caveat of the LD I+ shows up: the screws are somewhat of bad quality. One of mine almost got stuck as the (+) shape on the head got messed up by the screwdriver.
Don’t get disappointed just yet. The LD I+ cost less than $100, and as far as I know, all Chinese products will trade off some build quality factors for sound quality. Here’s when the “sound quality” part kicks in.
A cheap, boring I+ that can be good and great and awesome
My jaws dropped when I first heard the Mullards. I have heard of the “analogue tube sound” but this was the first time I have actually experience it. Vocals was rich and intimate for The Carpenters, bass was visceral for my favorite Alternative Rock bands, Muse and Garbage. And yet the soundstage was much more open, layering was much better than my most favorite discrete amp, nwAVguy’s Objective 2.
It didn’t take long for me to join the tube race. Once again, it’s head-fi that provide the guidelines and in 3 months I’ve bought the GE JAN 5654W, Voskhod 6zh1p-ev and Siemens 5654W to “complement” my I+. Since then I’ve bought RTC 5654RT, another pair of Voshkhods (which, unlike the previous pair, do not have notches), Brimar CV850 and EI Yugoslavia 6hm5. Trust me, any of these bad boys won’t disappoint you, except for the Voskhods that don’t have notches and Rocket logo.
But in between those 2 waves of tubes are a big revelation. One certain day it occurred to me that the famed opa2107ap cost less than a pizza and decided to have it delivered to my place in Singapore. Took 3 weeks for it to arrive, I never understood why but was thankful that it did.
My collection of tubes.
Upon plugging in this opamp I can see that the stock opamp was really really congested and boring. In restrospective the opa2107 had its trebles rolled off a lot, but that’s only because I’ve tried other opamps. The first time I listened to my favorite music on it, I felt like the sound stage expanded twice or thrice (do native speakers even use this word now?). The bass was even more prominent, but in a good way, not the Beats-by-Dre way.
The I+ sounded like a true tube amp. And I didn’t buy any tube amp worrying that it wouldn’t pair well with my low-impedance Grados. 
However, I must bring to your attention the point that tube rolling would be more effective than opamp rolling on the I+ if a change in sound is what you are after. My wife, who enjoys every single pair of headphones I bring home (in other words, is not an audiophile), could easily tell when I change the tubes from Voskhods to EI Yugos, yet barely tell the difference between the MUSES8820 and MUSES8920.
Oh and the MUSES 8820 and MUSES 8920 were both gifted from a very talented friend of mine who made a lot of DIY stuffs. These two can be considered BOTH a huge improvement AND a letdown from the opa2107. Improvements: better trebles, cleaner, much more clarity and soundstage. Letdown: it takes a lot of tubey-ness from my Liddle Tot.
While the 8920 was more analogue-sounding than the 8820, both made my O2 + Little Dot + SR325e too hot in the trebles, even with my warmest tubes, the Mullards and RTC. With one of these two plugged in, the difference between Siemens and Mullards or Mullards and Voskhods got drastically less noticeable. I appreciate the clarity, but taking away the tubey-ness is too much.
Enters the Burson Audio Supreme Sound Opamp V5.
The Burson V5 SS is huge compared to monolithic opamps.
The *real* review
Disclaimer: The V5 unit was received from Burson Audio for review purpose. My review remains objective. There's no reason not to, as before receiving the V5 I've already have a lot of opamps for enjoyment.
When I received the V5 SS from Burson, I was a bit surprised. It was too big. When I plugged in the V5 I can’t close the chassis of the LD. Which explains why my I+ is pant-less like in all these photos. If only I had taken the extender, this wouldn’t be a problem. My I+ has been like this for more than a week, and I’m too lazy to go around Hanoi looking for an opamp extender.
But if it works, it ain’t stupid. And it sounds great!
First, my gear: iFi iDAC2 (with iPurifier2) as input for the LD I+. On the headphones side I’ve got Grado SR325e, AKG K7xx, ATH-AD2000 and Fostex THX00.
The EI Yugoslavia 6hm5 tubes flare up each time I turn on the amp!
Due to the V5 SS being too big, my I+ has had to stay pant-less for a couple of weeks.
I'm sorry for my untidy desk.
Let’s go into details.
Little Dot I+, Burson V5 SS with: RTC 5643 tubes & Fostex THX00
Lady Fostex, everyone!
Quite similar to their brothers Mullards, RTC tubes are warm and the THX00 is quite V-shaped with surprisingly large soundstage for a closed back, pleather-pad model, even though its mid-range is rich and more in-your-face than its brethren, the famed THX900.
So with the THX900’s quite prominent bass and the V5 SS tend to lean on the warmer side, I first tried my I+ with a pair of GE JAN 5654, perhaps the most lean of my tubes in the hope for a more neutral sound. The result was a neutral sound, as expected, however it was also a bit drier than what I’d like.
So I plugged in my beloved RTCs and BAM, the THX00 shows its true color. Bass rumbles like no other headphones in this review, rolling as deep as Adele on 21. I never thought I’d enjoy Adele this much on a closed-back, but I was wrong.  Mid-range is rich, not too smooth but not too grained either; trebles is crisp yet never harsh. I have seen too much closed-back over-ears and IEMs amps up their treble in exchange for an (artificially) big soundstage, but the THX00 is nothing like that. It all sounds just... natural, as if it were still 1971 and you are At Fillmore East. If you like electric guitars, the I+ V5 and THX900 is just perfect. This is the kind of perfect combination between the ranges so that anyone’s guitar riffs will sound right, be it The Allman Brothers, Eric “Slowhand” Clapton, Alice in Chains or, if you’re really into it, Devin Townsend.
Never thought I'd enjoy Pink Floyd this much on an closed-back like the THX00. Not actual Pink Floyd, but still.
That’s what my I+ V5 combo brings to the table, for guitar and everything else: Texture and details. Unlike the O2, there’s something about the way the bass and the trebles on my I+ and V5 THX00 decay that I can’t put into words. They all rumble/ring very nicely at the right place, resulting in an energetic sound that won’t overwhelm you with droning thickness or sibilance. Songs that are complex in the low-range like Sky Ferreria’s Boys suddenly has “bass resolution” where you can easily tell apart each instruments, each layer while they’re still flowing together. Steel-stringed guitar “pops” on the THX900 and you can air-bass after John Paul Jones or John Myung perfectly on these gears. It’s as if I feel their fingers move on the bass.
With the V5 SS installed, the I+ is easily king of soundstage among my entry-level amp/DACs. It just blows the O2, the C5D and the Class A amp section on my iFi iDAC2 away. Even the m9XX is no match, though its DAC section is superior to virtually any other DAC under $1000 and also a good combination with my I+ V5.
But don’t put too much of your hope into the stock I+ as its op-amp is too mellow. The weakness is going to show clearly on warmer tubes like Mullards, Siemens and RTC, as the I+’s trebles and bass are both going to lose the “bite” that make my THX00 so exciting. My wife tells me that this sound is too “pinkie” for her liking, because yep it’s soft and squishy. On the other hand, MUSES8820 has this bite, but as I have mentioned since the start, it lessens the “tubey-ness” on my I+. Thankfully the Burson V5 SS is here to help.
Little Dot I+, Burson V5 SS with: Mullard CV4010 8100 tubes and AKG K7XX
The biggest challenge that I threw at the I+ V5.
One thing I notice only after pulling the trigger on the THX00 is that while the impedance is quite low (25 ohms), the sensitivity is rather low (94 db/mW). Anyway, it has provided easy to drive these Fostex. My limited audio knowledge tells me it must be thanks to the V5 SS, which does the heavy-lifting in this hybrid amp (please correct me if I'm wrong). Next up is something much more challenging: AKG K7XX. Don’t let its impedance of just 62 Ohm and sensitivity of 105 db/V fool you: like all of its sibling K701, K702, Q701 and K712, the K7XX requires large current, large voltage and is definitely one of the hardest-to-drive mid-fi headphones.
The result is extremely pleasing. My Dot I+, Little as it is, drives the K7XX with full authority! I never had to experience the thin lifeless bass that plagued my previous experience with Fiio's E11K. Thanks to the V5 I++ and my beloved, expensive Mullards, the K7XX's bass extends enough for you to feel like nothing is cut from the song. That said, the K7XX's bass actually rolls off quite a lot.
The I+ V5 Mullards and K7XX combo does lean towards the warm side, but this is a AKG after all. Thankfully the typical AKG harshness that I dreaded so much on the K701 is no where to be found thanks to the Mullards tubes and the Burson warmness so present on my V5 SS. Treble here is not as crisps as I'd like but the level of detail is just enough to make things sound transparent. On Radiohead's No Surprise, you can say that the AKG's treble is smooth and very musical. This is something that 5 years ago I wouldn't dream of, having auditioned the K701, loving its midrange, huge soundstage and great detail retrieval but hating so much on its overall sibilant, artificial sound.
The I+ V5 k7xx combo is very kind towards beautifully recorded song.
Did I say I love the AKG midrange? Oh Sarah Brightman sounds so smooth and sad (so sad!) on A Winter Shade of Pale. The hardcore Prog fan in me cries out, but this is one cover that I prefer much more to the original. Sarah's voice sounds as if she's performing live, cutting through all the production that I suppose must be heavy on all Sarah Brightman's records.
Here's another Prog Rock cover: Don't Leave Me Now by Gregorian (originally by Supertramp). The intro section to this song is done so beautifully: piano is full but still clean, cello is bodied and thick. Overall the vocals in this song is very foward but it feels like you are standing in the middle of the choir. Oh and steel guitars sound very steely indeed, which is commendable as I supposed the V5 SS combined with Mullards tube may result in a soupy sound. This was thankfully not the case and while the vocals were forward, the airy icy coldness of the song is very much preserved to me.
I think this is the dream combo for the Progressive Rock/Space Rock/Classic Rock fan in me. The AKG K7XX is not a fast headphone, but it can handle complex guitar passage just fine. Riffs sound raspy and nuanced when needed. Most importantly, there's enough space to actually enjoy Pink Floyd and Porcupine Tree. The THX00's just pale in soundstage comparison with the K7XX, which is actually not surprising at all. This is AKG.
Unfortunately, having been spoiled by the Grace M9xx's crossfeed feature, I've come to the conclusion that the I+ V5 combo's imaging is not very good. It's still more wide than deep. Sylvania tubes might be the solution to this problem, but I'm not that ready to spend 50 bucks on a new pair yet.
Little Dot I+, Burson V5 SS with: GE JAN 5654W tubes and Grado SR325e
My beautiful, beautiful SR325e.
Next in line is my most favorite headphones of all time: Grado SR325e. So favorite that I've sold and bought it again for 3 times (if you also count the 325is, that's 6 times). The SR325e is perhaps one of the most Grado-ish of all Grados with crunchy bass, highly energetic trebles and sweet refined mids, even though the mid-range here can be considered a bit more neutral and less forward than its siblings RS1i or SR60e.
What would the I+ V5 brings to my 325e? First of all, with the right tube it retains all the thing I love the most about the 325 line: aggressive trebles and textured, forceful bass.
Take my reference Metal track for example: I Remain by Paradise Lost. Each guitar notes rings out really nice into the soundstage, each cymbal crash or snare beat can be felt with the satisfying "crunchie" that I've come to love from the 325 line. Most beautiful and addictive of all is the distorted guitar sound: one again, it's as if you can count each layer inside the riff. Think of the words that are often used to name those Metal subgenres. "Groove", "Grind(core)", "Industrial", "Thrash" etc. The riffs on my V5 I+ 325e combo are going to turn all those lousy names into reality.
The Burson V5 SS must play some role in bringing out the bass and the low-mid sections from my SR325e, as my old MUSES8820 reduced these to ...And Justice for All level. That was the reason why my GE JAN 5654W never got much love while the MUSES was driving my I+, but now with the V5 SS I can certainly enjoy the sparkly trebles and the slightly accented mids.
Beautiful Metal, anyone?
On the other hand, it's quite obvious to me that the V5SS gives a smoother, more laid-back sound than the 8820. No wonder my Siemens 5654W turns out to be too smooth, too laid-back to pair with the V5 SS on my I+. These tubes practically muffle everything from November Rain (Guns n' Roses) to Angels (Within Temptation).
It can be said that the level of smooth-ness and forward-ness determines which tubes pair well and which don't with my I+ V5. My Voskhods 6ZH1P-EV, while also belong to the "warmer" group, doesn't take the bites away from my SR325e. Or, my CV4010 would turn my Nightwish listening session into a bombastic cinematic experience that any Tarja Turunen fan should have the chance to enjoy. It's is with this combo that Over the Hills and Faraway fires its denied-for-10-years emotions into the oceanic soundstage.
Wait, what did I say? "Soundstage"? Yep that's right, with the I+ V5 now my SR325e actually has a big one! Ask any Grado fan (like me) about these Brooklyn handmade's weakness and the first word comes to mind should be soundstage. Thankfully the I+ V5 is here to help! Actually, my tubes and the Little Dot already opens the soundstage a bit in comparison to the benchmark O2 ODAC sound, but it's with the V5 SS that a Grado fan can experience the spacious feeling that, say, AKG K612 users are used to. Now instead of me sitting onstage with the guitarist, the bassist and the drummers, I can hear them playing onstage with me taking a comfortable sip in a middle-row seat. Sure, it does take a bit of intimacy away, but that's totally acceptable for someone who's not really into Jazz like me. It's interesting to hear the wife proclaim "Oh, it sounds really wide!", which she never said about any Grado before.
That all said, the soundstage here is more wide than deep, and it's still not as 3D as what you'd have on a true crossfade amp/DAC. But don't be surprised if upgrading the stock opamp to the V5 SS feels like you just switched headphones.
The I+ V5 SR325e combo is not just a strong password but a Rockfan/Metalhead's dream come true.
Details have never been a strength of the SR325e in comparison to its higher-priced siblings in the RS, PS and GS lines, but at least on my I+ V5 there's no such thing as "I can hear this on the $700 RS1i but it's nowhere to be found on the SR325e". The quality of those details is another matter, but I think the Eagles diehard in me is quite pleased with what I got on Hell Freezes Over. And let's face a somewhat unpleasant truth: the LD I+ is a cheap tube amp, so in the stock configuration more often than not it would take away those micro details we crave rather than accent them up. The V5 opamp and more detail-oriented tubes like the GE JAN and the Voshkhods would help resolve that problem, though much cheaper opamp like the MUSES8820 and 8920 can also do that. Anyway, just take away the stock opamp and put into the I+ something of quality and you can enjoy nitpicking those details out of your favorite Indie tracks.
One thing I like the most about Grados is how easy it is to change the sound by changing the pads. This adds another dimension to the tune-ability of the whole sound signature. On songs where even the V5 SS cannot help the bass to be more prominent, I'd change to using the Sennheiser HD414 pads. Normally, this would result in a very unpleasant trade-off: the Grado soundstage, small as it is, would get reduced even more. Even Radiohead or Pink Floyd would become claustrophobic in that case. This is one more instance where the expansive V5 soundstage helps: it helps balance out the closeness that the Sennheiser pads bring, allowing me to enjoy the bass without any particular trade-offs.
All in all (for the SR325e), experiment all you can, but I think how much you'd like the V5 on your LD I+ really depends on what kind of tubes and what kind of headphones you're using. For me, the tube shouldn't be too laid back.
Little Dot I+, Burson V5 SS with: EI Yugoslavia 6hm5 and ATH-AD2000
Ah, the AD2000. The reason why this review get posted so late. Having bought this via Yahoo Auction in Japan, I had to wait for the famed Audio Technicas to return to Vietnam for 2 months. Is it worth it?
Hell yeah! As a big big Grado and Audio Technica fan I can see why a lot of people consider the AD2000 their endgame cans. The midrange in these classic are so desperate beautiful. Armed with articulate bass and sparkling trebles, the AD2000 are the ultimate headphones for any fan of great Vocals works.
The thing is, with the wrong amp, the AD2000 can sound annoyingly sibilant. For the I+, the wrong tubes and opamp can cause the same thing. Tubes defintely play a more important role here, as even with the V5 SS I had to go through all of my tubes to find that the EI Yugoslavia 6hm5 and the Voshkhods 6zh1p-ev helps my AD2000 reach its full potential.
How would I describe the voice of Karen Carpenter on this combo? Well, The Ultimate Carpenters Collection FLAC sound nothing like FLAC or anything digital. Everything is so natural and analog like, it's as if Karen is singing in front of me, not even via a mic and speakers! Many people complain about the AD2000 being too in-your-face, but perhaps the V5 SS and the 6hm5, which both have strengths in soundstage, help in my case. Even with Karen's sultry voice the AD2000 doesn't sound too claustrophobic for me and I can still pinpoint all the instruments in the background. Sometimes, high notes sound like they want to break out but always stopped at the right place. There's not too much bass and not much to say about bass, but I think for The Carpenters the bass from the AD2000 is just right. After all I'm standing in front of the band and NOT listening through any speakers that amplifies the bass.
That part when my taste in music is so good even Johnny Blaze agrees.
Moving to other Vocals-focused music like Celine Dion and Whitney Houston, I'm really thankful that the AD2000 have such desperately beautifully mid-range and that the V5 SS and 6hm5/6zh1p-ev tubes are there to help smooth things out a bit. Male Vocals are no less natural and rich-sounding. Listening to Lionel Ritchie's Hello, Phil Collins's Against All Odds and Elton John's Sacrifice feels like I'm re-discovering these classics again, despite having learnt them by heart ever since I was a small boy (Thanks, Dad!). Sacrifice definitely shines out here, as there are a lot of times I'm pretty sure the Rocket Man's voice would cut my ears when he makes the "ss" sound, but thankfully he didn't.
That all said, the AD2000 will not always tolerate bad recordings. I tried Amy Winehouse's You Know I'm No Good from Apple Music and the artifacts just ruined the sound, no matter what tubes I tried. Also, the AD2000 sounds quite bad with bass-heavy songs. It's as if the beats try to get out but stopped in their track before they could do what they wanted do. Still, this could be the spoilt THX00 fan in me talking.
Home is where the tube amp is
Having auditioned some tube amps after buying the I+, I still think that this is the best amp for all the headphones that I've got, which always include some Audio Technicas and Grados. The V5 SS and my collection of tubes solidify that position of the I+.
Yes it can be said that in its stock form, the I+ sounds bad. But a lot of guys in the I+ thread have come to the realization that the I+ is actually a platform for improvement. There's tubes to roll, opamp to change, and if you're a DIYer, there's also the volume pot to replace. Even the fuse can be changed to improve the sound.
I have not replaced the volume pot yet, but I like my I+ in its current form. Rolling tubes is fun and changing the opamp to Burson V5 SS helps put the Little Dot into a whole new level. This is important, I don't intend to buy high-impedance cans in the future and there will always be some Audio Technicas and Grados in my line-up. In other words, there's no point for me to upgrade to some expensive "pure" tube amps. 
That alone ensures that I will stay with my I+ V5. This is the sound I have always wanted since I started this hobby: the most analog, open and natural sound possible for low-impedance cans. This is the best sound that I can have, not because I can't afford the Little Dot mk3 or Schiit Valhalla 2, but because I love my Grados so much I want to find the best amp for them. 
  1. Cheap
  2. Extreme SQ scalability
  3. Perfect tubey sound for low-imp cans
  1. NOT that easy to change tube family.
  2. NOT that easy to change gain level.
@16 Bit Bowser  sorry for taking this long to reply. It would pair well with the 598, yes. But the sound would be too slow if you like Rock or Metal. It's really good with Vocals though.
That said, the I+ does have room for better headphones, like the Audio Technica AD1000X.
@Rearwing sorry for taking so long. I'm not sure if the mk2 or the II+ does have an opamp. A quick google seems to indicate that it doesn't
Geat review! Thanks a lot! Probably the Burson "V5i SS" would be the better (more suitable) Dual Op-amp choice instead of the "V5 SS"? Did you listen to it meanwhile? Any idea what tubes could pair good with Sundara?


New Head-Fier
Pros: Very good sound, and takes a range of different tubes
Cons: Only 1 set of inputs
I have had this amp now for about 6 months, and I very much enjoy the sound. I didn't even bother with the stock tubes, they got tossed in favor of a matched pair of GE 5654's, and I have a matched pair of Voshkod 6ZH1P-EV tubes held in reserve. I tried them, but they were brighter than the GE's, so I went back to the GE's. I didn't dislike the Voshkod tubes, but I wanted something a bit warmer. I use them with a pair of Sennheiser HD-650 phones. Setting the jumpers for the correct impedance was simple enough.
It has an excellent sound stage using the GE 5654 tubes, and did with the Voshkod as well, just the Russian tubes were a bit too bright for my listening taste. Very good sound overall from the lows, through the mids and up into the highs. Heard things in various classical pieces I'd not heard before - my favorite recording is a 1959 recording of Nikolai Rimski-Korsakov's Sheherazade, Leonard Bernstein conducting the New York Philharmonic and released by Sony records.
All in all a fine little amp. I have a DarkVoice 336SE that stays home, and the LittleDot+ goes with me on trips. Worth the money and great sounding for a amp in the <$150.00 USD category.
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Which headphones are you using?
I know its Grado but which model?