Benchmark AHB2 amplifier - what to expect?

Neutrix connector IIRC - they are as close to gas-tight as you'll get (outside a lab)

BTW, were the comparisons above vs. the Rowland?

Randy, you mean my clumsy attempt to write review? Yes it was in comparison to Rowland 102, but it is likely not very useful, since Rowland 102 is based on old, first generation of Icepower modules. I can only say that AHB2 sounds wonderful to me and it is getting better in all respects every day, but again it means nothing taking into consideration my limited experience. Rowland was a good amp (I keep it for the second system), but AHB2 is outstanding.

I found interesting discussion on Audioasylum :
http://https//www.audioasylum.com/messages/amp/205426/review-benchmark-ahb2-with-avantgarde-speakers-what-a-disappointment

OP calls AHB2 a big disappointment in comparison to his SET amp, while in follow up discussion another person has completely different view. At one point John Siau, a lead engineer at Benchmark, explains why opinions can be so different.

I solved the problem with my remote. Receiving diode in DAC3 had one pin poorly soldered. This pin connects to ground plane that sinks a lot of heat. It looked like soldered by somebody who doesn’t have any experience (or is blind). I fixed it to avoid shipping it back and forth, but I would expect better from Benchmark. The problem is that almost everything else is SMT - a well controlled process, but hand soldering depends on the skill of a person. RCA was famous for cold solder joints in their TVs (I had one with two cold joints), because it was most likely assembled by cheap unskilled labor.

I appears that link above doesn't work, not to mention very long discussion.  Let me show quotes from original post and two responses.

OP:

I don't pretend to be a professional reviewer (in fact this is the first time I've been moved to review any equipment), so can't explain exactly the differences, but it was akin to listening to a live acoustic performance versus listening to music through loudspeakers. The difference was not slight - it was dramatic. There is no "tingle factor" and no goose-bumps when listening with the Benchmark. If anyone says that the Benchmark is more accurate - frankly I don't care - I listen to music with my ears, not an oscilloscope! It was dull and lifeless by comparison. If you listen to live music there's inevitably background noise (you're sharing the auditorium with other people) and the acoustics are possibly not as good as a recording studio, but despite all the drawbacks, live music is so much more exciting to listen to. Similarly with the valve amps, an evening listening to music is thoroughly enjoyable. With the Benchmark it was little better than loud background music. Furthermore, the inclination was to turn down the volume of the Benchmark and turn up the SETs - inaccuracies, slight background noise and all! Music should be a thrilling experience and the Benchmark sadly doesn't offer thrills.

Response1 (John Siau):

Peter,

This is John Siau, VP of Benchmark.

Thanks for taking the time to document your experience with the Benchmark AHB2.

The AHB2 is well suited to use with high-efficiency speakers. The low noise allows noise-free operation with very high efficiency speakers.

Of equal importance, the AHB2 virtually eliminates the zero-crossing distortion that is normally produced conventional Class AB push-pull output stages. This is especially important for high efficiency speakers because the amplifier will spend so much time in low power region where crossover distortion can become most audible. The AHB2 behaves like a Class-A amplifier in that it is free from this very objectionable form of distortion.

But the AHB2 isn't for everyone. If you prefer an amplifier that enhances your listening experience then the AHB2 is not for you.

Your SET amplifier is specifically intended to add the euphonic qualities produced by the single-ended tube topology. This specific character is produced by the unique non-linearities that are characteristic of single-ended tube topology. The SET topology provides significant coloring of the music in a way that many people enjoy. If this is what you prefer, then you will be very unhappy with most other power amplifiers.

The AHB2 and SET amplifiers are on the very opposite end of the spectrum. You are completely correct when you say that the difference is dramatic.

The AHB2 is a much different listening experience. In contrast to an SET amplifier, the AHB2 is designed to be virtually distortion-free. The output of the AHB2 will sound exactly like the input. The AHB2 will not enhance or improve what goes in.

Please understand that this is a mater of taste. Many people enjoy the coloration produced by SET amplifiers.

Amplifiers can fall into three categories:

1) Amplifiers that add nothing to the audio
2) Amplifiers that add musically-disturbing distortion
3) Amplifiers that add musically pleasing coloration

The AHB2 falls into category 1, your SET amplifier falls into category 3.

Technically "coloration" is distortion but I think the word "distortion" gives a completely misleading description of something that may actually enhance the sound.

Again, it comes down to a matter of preference.

Response 2:

My experience with the Benchmark AHB2 driving sensitive speakers is somewhat different. In my current setup with Benchmark DAC2 HGC/AHB2, I am driving a pair of Klipschorns with a 105 dB sensitivity so in that sense they would be comparable to the Avantgarde speakers.

In my 25 years of of experience with mostly tube amplifiers of all sorts, I have never come across a more emotionally involving amplifier than the AHB2. It is exactly because it doesn't "interpret" the music by adding coloration or any artificial sense of ambience or reverberation that it is so fascinating to listen to. The AHB2's ability to reproduce the timbre and texture of acoustic instruments is beyond anything I have experienced before - just listen to brass or woodwind! - and the precision with which it reveals the actual acoustic properties of the recording venue, whether it be a small café or a concert hall, is second to none. At least to my ears. I think what captured my attention from the very first instant was how honest and genuine the sound is. If it is in the recording, it is there, otherwise not.

This amplifier keeps me on the edge of my seat in excitement and anticipation even with recordings that I have known for years and not thought very highly of, so in my view it is the very antithesis of boring. I don't remember having ever been so moved by reproduced music as with this Benchmark combo. FYI, I almost exclusively listen to classical music and much of it in hi-rez, but I have to say that well-recorded CDs are also much more enjoyable and listenable now than before.

Karsten

I would like to add to the discussion regarding the strong reactions to the AHB2 and other amps. I find that audiophiles  (but never reviewers! LOL) present strong, hyperbolic statements in regards to components or systems that represent emotional reactions, rather than absolute conclusions to the value/sound of the gear. Readers should realize that and not react overly to someone's strong description, as it may not reflect the experience of every user. 

There is such a huge variance in listener preferences that one is bound to encounter strong negative and positive reactions to any given product. John Siau is cordial and correct in his analysis; the Benchmark products would be categorized imo more as "studio sound" rather than smoke-filled club sound. They do not editorialize, but neither did I find them to assault the ears. Many audiophiles seek what is imo a dullish, bloated, euphonic, but distorted sound and they consider that "real". Well, that depends on how much accuracy you want and how much tonal coloration/warmth. Of course, that varies with listener and system. 

Anyway, in my testing in the review I agree that the Benchmark products are neutral in a good way, not sterile. Are there more warm sounding components? Of course. But, often you have an expense associated with obtaining that warmth. I do not wish to give up either extreme definition or tonal richness, and obtaining both can be like balancing on a razor's edge. 

Finally�, don't forget, the speaker system has an overwhelming impact on the final result. It's not terribly convincing to declare a component warm, thin, tube-like or not, based on a listen with one speaker system. One may say, "... in my rig it sounded..." and be accurate, but this in no way captures the span of results possible. Try a product with dynamic, ESL and high efficiency speakers, a few amps and cables, then conclude. Most cannot, so any declaration based on one setup should be taken with a caveat, spoken or not.  

Kijanki,. Good stuff. I agree 100% with those quotes. I am firmly in the "I want to hear it accurately" camp.  Also low noise is exactly what one wants with HE speakers, all else aside.