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

[DHT 845]

Oh come on: you can't be serious! This is a list of prejudices which are all overcome. Definitely! I bought a Class D amplifier after 4 decades of Class A/B and I had to overcome this prejudices too. After comparing it with different A/B amps (admittedly sighted though) I found none of my subjective concerns proven. The Amp is based on Hypex modules btw....

I talked the same when I had class D amp. It was great. Fantastic, clean etc. But I listened less ans less music with it. I am not prejudice.
When I find class D amp that I could live with longer time, I will buy it, they are cheap. I lately bought class AB solid state monos (DIY project) that I like more that most solid state amps, but I listen on triodes 90% of the time

 

[Geert]

Ok. pace and rhythm or PRAT factor is perceived speed or attack. There are big differences in that among amps. How it is possible? I will explain.
When amp has very high dumping factor it grips the speaker driver firmly, thus bass stops fast and do not go deeper due to inertia (opposite is loose bass, that may go deeper but the accelleration from "the deeper point" takes longer time). Class D is perceided as "fast" (but in fact the rhythm is the same of course, that is only the perception of the character of the bass).

Debunkt 45 years ago http://diyaudioprojects.com/Technic...ping-Factor-and-Damn-Nonsense-Floyd-Toole.pdf. And if you don't understand the technical aspects, most popular class D amplifiers have a higher damping factor than other types of amp's.

 

[DHT 845]

Except for the most part, that is not nearly as true as you may think it is except if you are comparing most transformer tube amplifiers with typical solid state amplifiers. The amplifier output impedance is just one part of the circuit. The dominating term in that circuit is voice coil resistance. Past a certain damping factor there is virtually no improvement in how fast the woofer stops. For a typical 8 ohm speaker, that comes at about 20 (hence the rule of thumb). Loose bass does not go deeper, there is just more of it, and at a slightly higher frequency.

That is not true, compare old Jeff Rowland amp with low damping factor to new Hegel amp with high damping factor and yoy will notice what is the point... Paradoxally low damping is more "musical". I know, that is "audiophile nonsense..."

 

[Inner Space]

Thank you for sharing your impressions -- don't take the skeptics around hear too seriously: they enjoy mocking and ridiculing subjective impressions.

Not really true. Subjective impressions are very valuable to all concerned. What matters is their source or derivation. If someone hears a difference between Amp A and Amp B in a controlled and unsighted test, then a verbal description of the two amps' perceived qualities and differences can be useful and meaningful. But not if the listening was sighted and subject to unconscious bias - too many uncontrolled variables, meaning that the subjective report likely wasn't about actual observed phenomena, and that its utility is hard to determine.

 

[SIY]

That is not true, compare old Jeff Rowland amp with low damping factor to new Hegel amp with high damping factor and yoy will notice what is the point... Paradoxally low damping is more "musical". I know, that is "audiophile nonsense..."

Uh huh.

 

[KSTR]

To me, controlled sighted and blinded listening tests, impressions, comparsions all have value. Proper blinded tests just have more significance. Therefore, thank you @MasterApex.

 

[Gregss]

Hello All,

Have a question for you. As those who are using the VTV Purifi Eigentakt amp seem to be using several different (supposedly different sounding) buffers for this power amp, which buffer was used in this test?

Assuming there are different sounding buffers, that would make a difference. FWIW.

Regards, Greg

 

[audio2design]

That is not true, compare old Jeff Rowland amp with low damping factor to new Hegel amp with high damping factor and yoy will notice what is the point... Paradoxally low damping is more "musical". I know, that is "audiophile nonsense..."

No it is true. Jeff Rowland amps always had a pretty high damping factor. The Hegel is not going to control the woofer any better, unless we perhaps cherry pick an old Jeff Rowland and a very low impedance speaker, i.e. multiple parallel 4 ohms. Unless you tested on exactly the same speaker in the same room, any comparison is moot. Now low damping factor amps are not more musical. Some people may prefer that sound, some may not. On some typically older speakers, with low damping factor you can impact the frequency response enough that in particular rooms, the result may be more even bass, but you could just as well in another room with another set of speakers have less even bass.

 

[Rottmannash]

Hello All,

Have a question for you. As those who are using the VTV Purifi Eigentakt amp seem to be using several different (supposedly different sounding) buffers for this power amp, which buffer was used in this test?

Assuming there are different sounding buffers, that would make a difference. FWIW.

Regards, Greg

I'm using the stock buffer.

 

[pma]

Remember Rs of the woofer voice coil, usually close to rated impedance (4 - 8 ohm). DF of 10 - 1000 thus makes not much difference re "bass control", which is just another myth. The only difference is that high DF means less FR modulation due to complex impedance of the speaker.

 

[KSTR]

That is not true, compare old Jeff Rowland amp with low damping factor to new Hegel amp with high damping factor and yoy will notice what is the point... Paradoxally low damping is more "musical". I know, that is "audiophile nonsense..."

The problem with this that the change from the different damping factor must be the only variable, therefore the correspondening inevitable change in frequency response must be factored out (by a precision compensating EQ). Otherwise the different FR alone was likely the dominating factor for the perceived change, that is, you just don't know. And level matching is paramount, as usual.

 

[boXem]

The damping factor has an effect on the FR due to the "losses" in the output impedance it represents.
Not a question of "grip" or whatever, but when more than 1 dB is lost at low frequencies due to a poor output impedance, one can't just ignore it.
Not all class D amplifiers have a low output impedance BTW.

 

[stren]

Surely if there's an actual audible difference it would show up in frequency, step response and distortion measurements at various power levels in the room itself? That would be interesting data to back up any blind measurements. You would think if you can hear it, that a microphone could measure it.

 

[paulraphael]

However this is no proof. Only one more anecdotal story so our party may happily continue .

I don't know about "proof," but I see Dan Clark's many years of challenging people to amplifier AB/X tests as pretty persuasive evidence. After more than 2000 tests, not one person took home the $10,000 prize.

The requirements were stringent. They included level-matching, limiting loudness according to the lower-powered amp, running each amp in its linear range (no more than 2%THD), and eq'ing out any baked in frequency-response non-linearity (often just by adding a cheap capacitor to one amp's speaker leads). Also, the test had to be on commercially released music (test subject's choice ... no test tones allowed). And there was some limitation on what speakers could be used—no electrostatics, if I recall).

But considering that no one could pass this test, even comparing a Radio Shack receiver against a Macintosh tube amp, I remain skeptical of any Class-D vs. Class-Whatever claims, unless the test is conducted with similar rigor.

 

[mocenigo]

Thank you for sharing your impressions -- don't take the skeptics around hear too seriously: they enjoy mocking and ridiculing subjective impressions.

I do not take it personally. Some folks here just refuse to even consider anything if they have never read a paper about it. The alleged facts (?) about distortion and scene size I have heard from amp designers and apparently it is a quite common lore in the field. Yes, there should be papers documenting proper experiments to confirm or confute these assertions. Sadly, in this field this is rarely done. I was a bit puzzled when I saw people here drooling at the idea Bruno Putzeys would answer their questions and the same people even refusing to consider that hysteresis distortion may be a fact because they are not aware of ABX experiments (of course, in a different thread, assuming that Putzeys won't read ;-) )

 

[mocenigo]

Surely if there's an actual audible difference it would show up in frequency, step response and distortion measurements at various power levels in the room itself? That would be interesting data to back up any blind measurements. You would think if you can hear it, that a microphone could measure it.

Well, for one I believe that if its can be heard, it can be measured. Some people believe that there are things that are heard and cannot be measured – I would rather say that maybe we need to do different measurements, but everything audible is most likely measurable with current technology (and I say "most likely" only because I do not like claims with absolute certainty).

 

[mocenigo]

However this is no proof. Only one more anecdotal story so our party may happily continue .

Of course it is no proof. But Alan Shaw is not a complete idiot in the field...

 

[mocenigo]

That is not true, compare old Jeff Rowland amp with low damping factor to new Hegel amp with high damping factor and yoy will notice what is the point... Paradoxally low damping is more "musical". I know, that is "audiophile nonsense..."

No, it is not complete nonsense. It is nonsense to use a phrase like "more musical", but a more bouncy bass can be preferred by some - it makes up a bit for limited low extension. I just happen to like it extended and very, veeeery controlled (and that's why I use active ripoles in my speakers: https://ibb.co/album/1MRHsv?sort=date_desc&page=1)

 

[pierre]

I do not take it personally. Some folks here just refuse to even consider anything if they have never read a paper about it. The alleged facts (?) about distortion and scene size I have heard from amp designers and apparently it is a quite common lore in the field. Yes, there should be papers documenting proper experiments to confirm or confute these assertions. Sadly, in this field this is rarely done. I was a bit puzzled when I saw people here drooling at the idea Bruno Putzeys would answer their questions and the same people even refusing to consider that hysteresis distortion may be a fact because they are not aware of ABX experiments (of course, in a different thread, assuming that Putzeys won't read ;-) )

did you read #74? Best case there are very little differences between amplifiers. The likely explanation is that differences are not audible. Then X or Y came and tell they hear obvious differences between amps but they don’t have a methodology to reduce bias. Then X or Y have a hard time to convince rational people.

I have never been able to hear a difference between my accuphase and my crown. And I can tell you, I really wanted the accuphase to sound better.

 

[Wes]

Correct...that is what we did.
Hard to tell AHB2 vs 333, very easy to identify Purifi on songs G-I.

Thanks for your postings.

Just to clarify, was the Purifi tested blind vs. both amps?

How many replicates? and outcome?

Were the levels matched with a vollt meter at the speaker terminals?