[Chops]

Here are the three amps in question...

Modded 708B (Mundorf 100+100uF x 2 output caps; Hovland 0.22uF x 2 coupling caps; ALPS 100k Blue Velvet)

BONE Stock Little Dot II ++

BONE Stock Little Dot Micro +

My AKG K701 cans with 650+ hours (probably more) and counting

And the entire family photo...

Source:
My stock Sony DVP-NS755V DVD/SACD player has two sets of 2-channel analog outputs as well as the 5.1 analog outputs. I have the 5.1 outputs configured to 2.0 stereo fullrange output only. I had both my 708B and the LD II ++ connected via identical pairs of Cardas Crosslink 1 interconnects from both pairs of 2-channel outputs. The LDM+ was connected via an Acoustic Research 1/8" phono to RCA cable to the 2.0 output. I used a Behringer ECM8000 calibration mic along with TrueRTA to match the outputs of all three amps. I played a large range of music that consisted of everything from classical to jazz to blues to pop to gothic to new age; good recordings, great recordings, bad recordings, SACDs. You name it, I tried to play it.

So now about the sound.

LDM+:
I'll start off by saying that the LDM+ is a very good sounding little amp for the price. As of right now, it has well over 500+ hours on it and it is giving the other two amps a run for their money! Bass is tight and punchy, and fairly extended. Midrange is full, but can get a little "sharp" sounding when pushed. Treble is detailed, extended and clear. It's pretty much what others have said, "wire with gain". The amp really doesn't draw any attention to itself, which is a good thing. The only thing I have to say is that it doesn't have a huge soundstage. It's there, but don't expect to hear things much outside the ear cups. This is NOT bad performance considering that this is a little portable, battery-powered amp with a cellphone audio chip as the amplifier, and pushing the tough AKG K701's. It's not bad at all.

LD II ++:
Next up is the LD II ++. This amp is definately nice, and has that traditional "tube" sound. It also has a low amount of hours on it, most likely less than 50 hours, and still has the original tubes. With that in mind, this amp is slightly rolled off on the top, has a slightly thick bass that's a little "soft" around the edges, and a midrange that's pushed a tad bit forward, but still warm. The bass is there, and it's deep, and it has more OOMPH than the LDM+, but it doesn't have that sharp attack and/or kick that should be there. As I said, the midrange seems pushed just a tad forward, but it's still smooth and warm. The treble is extended and crisp, but is a little further back in the mix, giving the amp a warmer tone on the top end. The soundstage is tricky. It's not noticable with everything, you have to listen for it, and it's usually heard with the quieter details of the music, more like the ambience of buried instruments. The only thing I don't care for with this amp is the way it gets red hot after being on for an hour or more. I mean, ridiculously hot to the point of not being able to touch any part of the unit, except for the volume knob. I know Little Dot claims that this is normal for this amp to run warm, but holy cow! What the heck is creating all that heat?!?! It's definately not the tubes since they are outside the chassis.

708B:
Lastly, the modded Xiang Sheng 708B. A big thanks to dcheming, zer061zer0 and drarthurwells on the Xiansheng 708B headphone tube amp thread, for documenting their findings, tweaks and mods performed to this amp, I have been able to improve on my amp as well, thanks to these guys.

The changes are as listed:
1) NOS RCA 6DJ8 output tubes - 2
2) NOS Russian Military 6N3P driver tube - 1
3) 68k - 2W bleeder resistor - 1
4) Mundorf M-Lytic HV 100+100uF (200uF total per cap) - 450V output capacitors - 2
5) Hovland Musicap 0.22uF - 400V coupling capacitors - 2
6) ALPS Blue Velvet 100k Potentiometer - 1

Stock internals with new components to the side

Everything installed...

Now for the sound of this amp.

Before:
When I first got the 708B, it didn't impress me that much, if at all. It didn't sound much different than the LDM+. In fact, the only major improvement was that the treble was a smidge smoother and the bass a smidge stronger than that of the LDM+, but the midrange was a little rough around the edges, which I found odd for a tube amp. One other thing I noticed with the stock 708B is that it would run out of steam rather quickly with the K701's. I was constantly getting some distortion at higher levels, but these "higher levels" were considerably lower than what I was pushing with the LDM+.

After some Tube Rollin':
I then got the NOS driver and output tubes in the mail from drarthurwells. These made a rather healthy improvement in overall sound and performance. For one thing, the distortion was gone! The bass became punchier and tighter, the midrange cleaned up quite a bit and I was able to hear more detail throughout the entire range. Everything else pretty much stayed the same.

After the Mods:
And then after getting and installing the caps and volume pot, and letting the new components run in for 60 hours straight, things have really improved. Granted, they aren't huge improvements, but they are there and quite noticable when you switch between the three amps. The bass extends deeper than ever before, and deeper than the other amps. The bass has tightened up more, has more punch and overall more power and slam. The midrange has cleaned up so much that it sounds really good now, moved up a row or two and has opened up considerably. There's more life in the midrange, making for a more "real" sound. The treble is still extended plenty, but the quality of it has improved a lot. It's still crisp and precise, but now it's also refined, providing a cleaner and higher class sound. The soundstage still isn't overly huge, but it is larger than it was, and larger than either one of the other amps by a decent margin. There's more "air" to the entire sound now.


Final thought...
If I had to place these amps (all in stock form), in order from most preferred (1) to least preferred (3), I'd have to put the 708B at the bottom (3) mainly because of the distortion issue. It was fine if you like listening at lower than "normal" volume levels. Yeah, I know, what's normal, right? But even at the lower volumes, it still had that somewhat harsh midrange to contend with. In the middle (2), I'd place the LD II ++. Again, it's a nice little amp, but for my tastes, the bass and treble is a bit too mushy and soft for me. The midrange is great, even if it is pushed a little forward. But that HEAT! On top (1), I'd have to say the LDM+ takes it. It's that whole "wire with gain" thing again. Nothing is thrown in your face with this amp, and it seems to do just about everything right, minus the lack of a wide soundstage. But to be completely fair, all three of these amps have very similar soundstage width, and even their overall sound is somewhat similar. In stock form and with the right recording, it would probably be hard to tell which one was which, especially between the LDM+ and 708B. The LD II ++ gives itself away with the softer top end more than anything else.

However, with the mods done to the 708B, it would now be placed on top. Yeah, I probably went overboard going with $40+ worth of Mundorf and $20+ worth of Hovland caps, but apparently it paid off. The funny thing is I'm not even finished yet! I still have the input caps to upgrade, several pairs of resisitors to upgrade, and some signal wiring to upgrade. Who knows, maybe even beef up the power supply caps with something a little bigger. Only time will tell.

So there you have it. Yeah, it's probably not the greatest comparison review out there, but it at least gets the general idea across. Plus I am willing to answer any questions anyone might have about specific areas of these amps. Just ask and I'll try my best to answer them the best that I can.

 

[cotdt]

very interesting! have you tried more hi-end amps?

 

[Chops]

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif very interesting! have you tried more hi-end amps?

I did several years ago, but with Senn HD580 and HD600 cans. The amps were the Headroom Cosmic, Cosmic Ref, MAX, and Carry SLi 80. So to mention them in this thread really wouldn't apply, I think. Plus, it's hard to comment on sound from memory, especially over a several year period.

 

[Bob A (SD)]

Chops,

Kudos for the comparison. I appreciate the honesty in giving high marks to the LDM+ against the more costly tubed amps. Too often folks get their gray matter in a twist subconsciously convinced that the more costly must be better.

I still have the original amp Tyll introduced and I bought new in '93. I agree with what John Atkinson said about it in his Stereophile review: http://stereophile.com/headphones/530/ When I take out the crossfeed processing and filters, and match the gain I find it virtually impossible to differentiate between the 14 year old $399 Headroom Supreme (20k Sennheiser version, shown in my avatar with the Senns and the Philips CDP) and the half year old $59 LDM+ when driving my HD-580s. No question that in terms of portability the diminutive LDM+ tromps my old brick (especially if I'm resorting to the 4 D-cell accessory pack). But the surprise for me is how well it compared to the old original Headroom benchmark. It certainly confirms how far things have come in that decade plus.

 

[tbonner1]

It takes courage to top rate the LDM+ around here, but I think the LDM+ is underated and a nice little amp for the money.

I was underwhelmed by the stock 708 and noted the distortion issue driving even IEMs like the Altec IM716.

Thanks for the review.

 

[drarthurwells]

The 708 B is bad with the stock Chinese tubes but excellent for the low cost with better tubes.

 

[Mikesul]

thanks for the informative review. I have been puzzled by the differing opinions about this amp. Your experiences with mods explains some of those differences.

 

[penguindude]

Interesting review. Nonetheless, I'd have to disagree with you on the fact that LDM+ is better than ld2++. Although ldm+ changes the sound less and therefore gives a "cleaner" amplification than ld2++, the fact that it doesnt bring out the full capability of my hd595 is a no no for me. Also, many with full-size phones have reported that the ldm+ sort of "does nothing to the sound," but its interesting to see your side of the story.

 

[Bob A (SD)]

Quote:

Originally Posted by penguindude /img/forum/go_quote.gif Interesting review. Nonetheless, I'd have to disagree with you on the fact that LDM+ is better than ld2++. Although ldm+ changes the sound less and therefore gives a "cleaner" amplification than ld2++, the fact that it doesnt bring out the full capability of my hd595 is a no no for me. Also, many with full-size phones have reported that the ldm+ sort of "does nothing to the sound," but its interesting to see your side of the story.

Penguindude,

Interesting that you cite those who seemingly complain that the LDM+ "does nothing to the sound" as an inferred negative. For literally decades the definition of good amplification in audiophile circles was "straight wire with gain."

There appears to be two camps. One which continues to embrace the straight wire with gain approach as part of the bigger philosophy in which each component should minimize coloration contributed to the system and thus the music the system is reproducing. Others want specific characteristics to augment or offset issues with other components in their systems. To me that's plain wrong. Synergy to me is when components mesh well because they don't detract from others in the chain. And I have always looked at upgrades as providing the elimination of inhibitors which detract from the listening experience. Your comment about the LDM+ not bringing out the full capabilities of your HD595s to me equates with the need to offset something you're experiencing with your HD595s which the neutral LDM+ can't do. More of a can issue than amp....


The LDM+ excels because of its neutrality period. And that was what Chop was citing in his review.

 

[penguindude]

Quote:

Originally Posted by Bob A (SD) /img/forum/go_quote.gif Penguindude, Interesting that you cite those who seemingly complain that the LDM+ "does nothing to the sound" as an inferred negative. For literally decades the definition of good amplification in audiophile circles was "straight wire with gain." There appears to be two camps. One which continues to embrace the straight wire with gain approach as part of the bigger philosophy in which each component should minimize coloration contributed to the system and thus the music the system is reproducing. Others want specific characteristics to augment or offset issues with other components in their systems. To me that's plain wrong. Synergy to me is when components mesh well because they don't detract from others in the chain. And I have always looked at upgrades as providing the elimination of inhibitors which detract from the listening experience. Your comment about the LDM+ not bringing out the full capabilities of your HD595s to me equates with the need to offset something you're experiencing with your HD595s which the neutral LDM+ can't do. More of a can issue than amp.... The LDM+ excels because of its neutrality period. And that was what Chop was citing in his review.

Bob,

Interesting that you have brought out the 2 sides of ideas regarding amps. And yes, you're correct at the fact that I'm on the side which considers amping to be an addition to the chain that improves listening quality. I think a lot of people would agree that different amps would have different sound signature, and a lot of people here are on a hunt for one that matches well with their phones. For me, and most of those who are like me, we consider an amp that brings us the best listening quality from our cans to be a winner. I mean why else would you buy an amp anyway?

 

[Bob A (SD)]

Penguindude,

Oh I don't disagree in principle that when selecting a component such as an amplifier to add to our systems that personal criteria come into play.

My point rather was to object to why you originally you took issue with Chops citing the merits of the LDM+ over the LD II+. He presented a pretty objective sound analyses of the 3 amps and that the LDM+, while suffering from a somewhat restrictive soundstage, did everything else quite well. So well that, with minor qualifications, the LDM+ was viewed as the best of the three evaluated on its own merits. You disagreed primarily because of your perceived deficiencies vis-a-vis your HD595s. I certainly am not taking issue with your HD595 - LDM+ perceptions at all here.

What Chops post and yours provided was an opportunity to cite (1) Chops' evaluation as courageous for acknowledging the strengths of a very inexpensive little amp among more expensive units, and (2) your feedback as reflecting a different school of thought where interaction with other components is the primary evaluation / ranking criteria over inherent design execution strengths and weaknesses. When your post indicated that the lack of doability with your HD595s made the LDM+ a non-starter for your use, again no problem. You cited one of the LDM+ strengths as a reason to rank it as inferior to another amp. Converting your HD595 observation and others' comments about the lack of a sound signature to mean that the LDM+ must be inferior became a transference that I wanted to explore with you.

I'm reminded of discussions about phono cartridges where evaluations address the unit's inherent tonality, compliance, frequency response, tracking force, etc. Then apart from the cart itself discussions are had about the mass of suitable tonearms and pf/ohm loads of phono stages and what seems to work best. You can have a great neutral sounding cartridge sound like crap when mismatched. So too with a headphone amp. The LDM+ is a great bank-for-the-buck neutral sounding amp period. For you it is a mismatch with your HD595s for reasons discussed, but that in and of itself shouldn't invalidate Chops ranking. That was all I sought to clarify.

 

[Chops]

Calm down guys. Nothing here to get worked up over.

BTW, did a couple more mods over the weekend to the amp.

1) Tested my DVD/SACD player's RCA outputs for any DC. None found!...

SO...

2) Replaced the 0.1uF input capacitors with tinned 20awg OFC wire
3) Replaced the stock 24awg steel jumper with tinned 20awg OFC wire
4) Completely removed the garish and useless tube/reflector/LED crap
5) Placed the PS transformer on the nylon stand-offs from the window LEDs
6) Moved the Mundorf M-Lytic HV output capacitors up front in window
7) Removed the wiring for the preamp output RCAs
8) Removed the 0.22uF preamp output capacitors

 

[Jon L]

Nice work! Have you thought about doing some mods to some Darkvoices, especially the 337? I have a feeling the 337 can really be something else with some better parts..

http://www.head-fi.org/forums/showthread.php?t=221842

 

[Chops]

Quote:

Originally Posted by Jon L /img/forum/go_quote.gif Nice work! Have you thought about doing some mods to some Darkvoices, especially the 337? I have a feeling the 337 can really be something else with some better parts.. http://www.head-fi.org/forums/showthread.php?t=221842

Thanks!

If the opportunity ever came up, and I was sure that I was able to do it?... Sure, why not!

 

[Kipper]

how much were the parts so far? keep it up!!