Benchmark AHB2 / Class D Purifi Eigentakt / Mark Levinson 333 - Listening impression & Conclusion

[Lord Victor]

No, I don't think it's a mental disorder by any means. Normal human brains, and most people aren't really aware of how powerful a liar is that hunk of goosh in our crania.

Agreed - I think it’s important to label/recognise ‘subjective’ experience here, vs more controlled comparison. So long as that’s clarified I don’t see the issue in such conversations - even if some might find them pointless.

If separate people have similar experiences, I think it’s valid conversation to have or as an offset for potentially doing properly rigorous voltage matched blind comparisons.
That’s certainly my intention if I get my hands on a Purifi again. Because for all we know, we might legitimately hear a difference, simply due to a difference in gain - plenty of power amps vary by sometimes several dB, which can give a genuine impression of one being dull, until properly matched.
I’ve matched most sounds identical. But I can’t speak to these ones since I haven’t personally tested them… never even tried a 606.

Though arguably given the attitude towards such conversations about subjective experiences, this is probably not the right forum for such discussions…

 

[JohnM-73]

Interesting comments about gain. I wonder of this is partially a factor here. I do recall with the Purifi, I kept turning up the volume to try and get more ‘life’ out of it. With the 606, I could happily listen at lower levels. Perhaps the more perfect an amplifier is, the better it sounds reproducing music at (roughly) the kinds of levels the music was played at during recording (assuming real world instruments here!). Perhaps I should just stop fretting about the reason(s) and just continue to enjoy my 606 though Life’s too short.

 

[SIY]

Interesting comments about gain. I wonder of this is partially a factor here. I do recall with the Purifi, I kept turning up the volume to try and get more ‘life’ out of it. With the 606, I could happily listen at lower levels. Perhaps the more perfect an amplifier is, the better it sounds reproducing music at (roughly) the kinds of levels the music was played at during recording (assuming real world instruments here!). Perhaps I should just stop fretting about the reason(s) and just continue to enjoy my 606 though Life’s too short.

Gain may very well be the driving factor here. If you have to turn it up more for the same volume, your brain will almost surely say, "Worse dynamics" or something like that, at least mine does.

If you're happy with your amp, why even think about changing it? Life is indeed too short.

 

[anmpr1]

Because there was nothing obviously wrong, yet music failed to hold my attention. That’s never happened before on music I love. I wanted to keep this amp, as I adored the smaller form factor...

True story follows. YMMV

When spring arrives I usually retire my tube amps because I don't need the x-tra room heat. I packed my 2 Dyna mono amps (and tube pre), substituting an AHB2/DAC3-HGC, which I moved out of my 'main' system. My first impression was, "This sounds weak, anemic, and frankly, not very good, compared to the Dynaco.

The next day I listened, and the Benchmark gear sounded much better than the Dyna. More open, authoritative lows, and generally more beef. What an improvement!

My main system? In that I went 'against the grain'. For the Benchmark, I substituted a ten or twelve watt/channel, little 6V6GT/6LS7 push pull 'integrated' amp from Shenzhen. My loudspeakers are on the sensitive side, so I don't require a lot of milliwatts. The tube amp sounded weak, anemic, and frankly, not very good, compared to the Benchmark.

The next day I listened, and the little tube amp sounded first rate.

My conclusions? First, it's easy to fool oneself in these sorts of things. Next, I concluded that I had all the qualities to become a Stereophile reviewer.

 

[rdenney]

Interesting comments about gain. I wonder of this is partially a factor here. I do recall with the Purifi, I kept turning up the volume to try and get more ‘life’ out of it. With the 606, I could happily listen at lower levels. Perhaps the more perfect an amplifier is, the better it sounds reproducing music at (roughly) the kinds of levels the music was played at during recording (assuming real world instruments here!). Perhaps I should just stop fretting about the reason(s) and just continue to enjoy my 606 though Life’s too short.

Understanding the reasons for things is the path to enlightenment. Then you are in control of your preferences rather than being pushed to and fro by what they seem to be on any given day.

The Purifi has lower voltage gain than many traditional amps. So you do have to turn up the preamp more. If the preamp lacks sufficient voltage capability, you may push it into clipping, or you may never reach full amp power. That is not the amp’s fault; it is the amp’s requirement, usually easily fulfilled by preamps that either pass through sources that have sufficient output of their own or that provide some line-stage gain for those that don’t.

My old analog source devices drive line-level output as defined before the digital era: 1 VRMS at peak output. CD players pushed that standard up to 2 VRMS. That is a 6 dB difference—even the earliest digital sources need 6 dB less gain than, say, a tuner of the era, to achieve the same listening level.

My Hypex-powered amp needs 2.4 VRMS to be driven to full power. The active line stage in my preamp, when engaged, provides far more output than that, and thus requires only the bottom portion of the volume control’s range. When its line stage amp is switched out, the volume control has to be much higher to produce the same listening level. When I switch in the line stage, suddenly everything “comes to life”. Sure it does! It’s 10 or 12 dB louder at the same volume setting. Comparing the sound with and without requires real effort not to fool myself as a result of that difference in level. Read, when I leave the line stage bypassed and crank it up to the same loudness, it sounds great, if I don’t run out of the volume-control knob’s range first.

I have tape players that only put out 400 mV at 0 VU on the tape. Without the line stage amplification, I can only drive my power amp to a fraction of its output.

Gain management is important. There’s a reason good preamps of the past provided active line amplification, even if modern DACs that put out 4 VRMS at 0 dB (digital) don’t need it.

Or, maybe your old amp has a bit of the old loudness control effect baked into it. Hitting the loudness button always seemed to “bring to life” the sound at low listening levels.

Rick “knowing what and why is the whole point of ASR” Denney

 

[dlaloum]

Until recently I did not have the opportunity to have multiple amps and speakers.
With my older speakers, I could not tell the sound quality / presentation differences with these amplifiers.

However, with current 802D3 speakers , the amps under comparison are audibly distinguishable (amps were not driven to clipping, just engaging SPL level varies from 80-97dB SPL at 10ft distance).

It makes me wonder whether we have standard for highly resolving speakers ?
So when someone says he/she could not hear the difference, does he/she have resolving speakers to resolve the sonic differences?

My Onkyo 876 AVR (165W@8ohm into 2 ch) sounded well nigh indistinguishable from my Quad 606 - both into my Quad ESL63, and Quad ESL989.

When I later replaced the Quad ESL's with a set of Gallo Reference 3.2's - the 876 sounded marginally worse than the 606... but the difference was consistent... albeit minor.

A set of Crown XLS2500's counter-intuitively sound better than the Quad 606 into the Gallo's

My interpretation of this... all decent amps sound alike when they are not under stress... if your speaker pushes the amp to one of its limits, it will start to misbehave / distort - each amp distorts slightly differently, so they sound different.

The Gallo's drop down to circa 2 ohm in the high frequencies (tweeter) .... if the amps can't provide the current needed for those highs, then you get distortion throughout the frequency range... The XLS2500 is rated for 1200W@2ohm. the Quad is rated to be "stable" at 2 ohm, but would be lucky to put 80W? out at that impedance (maybe less). And the Onkyo 876, wasn't rated for speakers under 4 ohm.

Into Quad ESL's the 3 amps sound identical, into Gallo's they clearly sound different - both speakers are highly revealing - but it is not about how good the speaker is, rather it is about whether the amps are pushed out of their optimal performance envelope, into zones of performance where distortion starts to become audible - once the distortion becomes audible, the amp with the least distortion is the best amp - regardless of how good or bad they are in other ways. Distortion is far far more audible, than any form of detail, imaging, soundstage, etc.... - and most of those latter aspects can be adjusted with judicious and light handed EQ.

 

[dlaloum]

That's likely a distinct possibility. Or there's something else present that the average human can't hear per-se, but can detect. It really bugged me - still does - as I wanted to keep the Purifi and retire the Quad 606. Wish I had the funds to buy another, and get somebody to help set up a true DBT, AND a longer listening test too as an extra data point. I remain convinced that some 'traits' only manifest themselves after listening for a while. As you say, human brains are funny.

My long term listening with a pair of 606's (biamping... not that biamping seemed to make a difference) vs Crown XLS2500... ended up in favor of the Crowns - but only for these speakers.

The 606's are such a great amp - and I have used them with a range of different speakers with fantastic results - just these ones, wanted more current (at a guess) than the quads could provide.

I wouldn't be giving away my 606's (and I havn't) - although, I admit to being fascinated by the AHB2's - which is basically a more sophisticated, modern version of the Quad / Peter Walker current dumping design... - but also $$

 

[dlaloum]

Gain may very well be the driving factor here. If you have to turn it up more for the same volume, your brain will almost surely say, "Worse dynamics" or something like that, at least mine does.

If you're happy with your amp, why even think about changing it? Life is indeed too short.

Gain is relevant only on short term - "switch between" comparisons - if you are doing long term listening, swapping over every few weeks or months, then gain is meaningless.... but the overall sound can still be identifiably different.

If the difference is sufficiently small - then we can be prone to various biases.... but sometimes the difference is clearly audible.

 

[SIY]

Gain is relevant only on short term - "switch between" comparisons - if you are doing long term listening, swapping over every few weeks or months, then gain is meaningless.... but the overall sound can still be identifiably different.

If the difference is sufficiently small - then we can be prone to various biases.... but sometimes the difference is clearly audible.

Evidence for that remarkable assertion?

 

[dlaloum]

Understanding the reasons for things is the path to enlightenment. Then you are in control of your preferences rather than being pushed to and fro by what they seem to be on any given day.

The Purifi has lower voltage gain than many traditional amps. So you do have to turn up the preamp more. If the preamp lacks sufficient voltage capability, you may push it into clipping, or you may never reach full amp power. That is not the amp’s fault; it is the amp’s requirement, usually easily fulfilled by preamps that either pass through sources that have sufficient output of their own or that provide some line-stage gain for those that don’t.

My old analog source devices drive line-level output as defined before the digital era: 1 VRMS at peak output. CD players pushed that standard up to 2 VRMS. That is a 6 dB difference—even the earliest digital sources need 6 dB less gain than, say, a tuner of the era, to achieve the same listening level.

My Hypex-powered amp needs 2.4 VRMS to be driven to full power. The active line stage in my preamp, when engaged, provides far more output than that, and thus requires only the bottom portion of the volume control’s range. When its line stage amp is switched out, the volume control has to be much higher to produce the same listening level. When I switch in the line stage, suddenly everything “comes to life”. Sure it does! It’s 10 or 12 dB louder at the same volume setting. Comparing the sound with and without requires real effort not to fool myself as a result of that difference in level. Read, when I leave the line stage bypassed and crank it up to the same loudness, it sounds great, if I don’t run out of the volume-control knob’s range first.

I have tape players that only put out 400 mV at 0 VU on the tape. Without the line stage amplification, I can only drive my power amp to a fraction of its output.

Gain management is important. There’s a reason good preamps of the past provided active line amplification, even if modern DACs that put out 4 VRMS at 0 dB (digital) don’t need it.

Or, maybe your old amp has a bit of the old loudness control effect baked into it. Hitting the loudness button always seemed to “bring to life” the sound at low listening levels.

Rick “knowing what and why is the whole point of ASR” Denney

The original 606 required a very low input voltage - maxing power at 500mV (!) - later 606-2's required a bit more at 700mV or so.... Hence I don't expect gain matching would be an issue?

 

[dlaloum]

Evidence for that remarkable assertion?

If you are sitting down listening to a component for a long time - then you adjust the volume according to the mood - the psycho-acoustic differences generated by 0.5db to 3db volume variations simply don't apply.

(gain mismatches could still cause a problem though, I admit... but the Quads require very little voltage to drive, so I would not expect that to be a problem)

 

[freemansteve]

My personal conclusion:

1. Class D amplifiers have improved a lot of the years but Class D Amps are still no match to good design Class AB Amp.in term of sound quality and dynamic handling

How was this statement even possible after trying one class-D amp and one set of speakers ?

I'm sorry, but there was no point reading beyond this assertion.

 

[Lord Victor]

Interesting comments about gain. I wonder of this is partially a factor here. I do recall with the Purifi, I kept turning up the volume to try and get more ‘life’ out of it. With the 606, I could happily listen at lower levels. Perhaps the more perfect an amplifier is, the better it sounds reproducing music at (roughly) the kinds of levels the music was played at during recording (assuming real world instruments here!). Perhaps I should just stop fretting about the reason(s) and just continue to enjoy my 606 though Life’s too short.

I sadly couldn’t find the 606’s gain to compare, but also yes, it’s quite likely a ‘perfect’ amp would be more prone to sounding boring at low levels vs one that hypothetically had some distortion causing a ‘loudness’-like effect (presuming that is possible and the case). Fx I suspect one of mine might have some treble artifacts/distortion going on, and all the rest of them sound basically the same. That deviation makes it sound more energetic/precise.
But that’s all guesswork.

The Purifi boards in raw form have very low gain, so it requires whoever made the input boards to compensate or it will sound quieter.

 

[dlaloum]

I sadly couldn’t find the 606’s gain to compare, but also yes, it’s quite likely a ‘perfect’ amp would be more prone to sounding boring at low levels vs one that hypothetically had some distortion causing a ‘loudness’-like effect (presuming that is possible and the case). Fx I suspect one of mine might have some treble artifacts/distortion going on, and all the rest of them sound basically the same. That deviation makes it sound more energetic/precise.
But that’s all guesswork.

The Purifi boards in raw form have very low gain, so it requires whoever made the input boards to compensate or it will sound quieter.

The V1 606 was 500mV for 140W out (from memory) where the V2 was 700mV for the same 140W out.

I presume the gain could be calculated accordingly (power out was rated at 8ohm)

 

[SIY]

If you are sitting down listening to a component for a long time - then you adjust the volume according to the mood - the psycho-acoustic differences generated by 0.5db to 3db volume variations simply don't apply.

(gain mismatches could still cause a problem though, I admit... but the Quads require very little voltage to drive, so I would not expect that to be a problem)

So no controls, no evidence. Just a special pleading claim.

 

[rdenney]

The V1 606 was 500mV for 140W out (from memory) where the V2 was 700mV for the same 140W out.

I presume the gain could be calculated accordingly (power out was rated at 8ohm)

~36 dB for the 606--much higher than amps currently on the market (except for some integrated amps, perhaps), which seem to top out at around 29 dB of gain (which is about where my B&K amps are). The Purifi is at 14 dB as I recall, but it depends on a "buffer" that provides gain between the source/preamp and the final amp. Most that I've seen are about 12 dB of gain for a total gain of around 26 dB. This is also about where the bigger nCore modules are. The Benchmark is switchable to one of three different gain settings.

Most active preamplifiers provide around 12 dB of gain, but passive line switches (the word "preamplifier" seems out of place there) are at unity gain, of course.

Plugging a DAC with 4 VRMS output into that Quad will have to be seriously attenuated to avoid overdriving the amp's input, it seems to me. The combination of active preamps and high-gain amplifiers means not much volume knob will be used. But the early 606 could apparently be driven to full power even with the tape players of the day that were rated at 400 mV at 0 VU, using passive line-stage switching.

The sound from a high-input-sensitivity amp will fairly jump out of the system as soon as one cracks the volume control off zero. That surely must make an impression and affect one's perception all by itself.

Rick "fun with logarithms" Denney

 

[Lord Victor]

~36 dB for the 606--much higher than amps currently on the market (except for some integrated amps, perhaps), which seem to top out at around 29 dB of gain (which is about where my B&K amps are). The Purifi is at 14 dB as I recall, but it depends on a "buffer" that provides gain between the source/preamp and the final amp. Most that I've seen are about 12 dB of gain for a total gain of around 26 dB. This is also about where the bigger nCore modules are. The Benchmark is switchable to one of three different gain settings.

Most active preamplifiers provide around 12 dB of gain, but passive line switches (the word "preamplifier" seems out of place there) are at unity gain, of course.

Plugging a DAC with 4 VRMS output into that Quad will have to be seriously attenuated to avoid overdriving the amp's input, it seems to me. The combination of active preamps and high-gain amplifiers means not much volume knob will be used. But the early 606 could apparently be driven to full power even with the tape players of the day that were rated at 400 mV at 0 VU, using passive line-stage switching.

The sound from a high-input-sensitivity amp will fairly jump out of the system as soon as one cracks the volume control off zero. That surely must make an impression and affect one's perception all by itself.

Rick "fun with logarithms" Denney

That might be the culprit then - or one of them. If the 606 is 36db, and the raw Purifi is 12.8db, or 14/27dB with the Eval input board, that would make the 606 sound much better in a direct AB with no voltage matching…

 

[freemansteve]

By and large, louder works better for me....

 

[JohnM-73]

That might be the culprit then - or one of them. If the 606 is 36db, and the raw Purifi is 12.8db, or 14/27dB with the Eval input board, that would make the 606 sound much better in a direct AB with no voltage matching…

Yes, and I need to make clear my listening was purely subjective, no level matching etc, just for my own enjoyment with no time scale limits to switch over amps. The Purifi was run from the balanced outputs of the Quad Artera CD/Pre at the time, which has adjustable output, which I’m pretty sure I dialied in to match the Purifi. Used the standard line outputs to feed my (mk.1 version, 0.5V input) Quad 606s. The 606s are band limited too, so perhaps I prefer that sound. Or perhaps the Purifi was justbrevealing that I wasn’t that taken by the Quad Artera’s DAC implemntation. Too many variables in hindsight, and not enough controls.

 

[pma]

Perhaps the more perfect an amplifier is, the better it sounds reproducing music at (roughly) the kinds of levels the music was played at during recording (assuming real world instruments here!).

Or there are some pitfalls that cannot be explained by primitive reasoning based on 1kHz SINAD.