Review and Measurements of Benchmark AHB2 Amp

[SIY]

I'm not disrespecting Scott but responding to posts which are apparently incomplete (or I'd be able to clearly discern where he's going... other than along the same path of tortured illogic that we've all seen before).

I'm sorry, but that is totally off base. It is absolutely legitimate to simultaneously believe that the AHB2 is a superb piece of engineering with remarkably good performance, but will likely not sound any different when blind-tested against amps with far worse measured performance.

If you feel that someone's answer to things isn't understandable, ask. Now, if after asking, you get inundated with nonsense, then it's legitimate to arrive at a negative conclusion.

 

[Thomas savage]

Is running massive server farms environmentally responsible?

The word ' farm ' makes it sound so..

 

[Thomas savage]

Try me, you'll lose. I thought this place was different.

Well iv enjoyed reading your contributions so thanks and welcome..

 

[PierreV]

I had zero idea who Scott was until it was explained, but it doesn't really matter... Is it a good attitude to immediately snipe at people coming here because one thinks, possibly wrongly, that a short sentence hints at some potential future disagreement??? And even if a disagreement actually comes, wouldn't it be better to see it as an opportunity to learn from the arguments developed in support of the opposing point of views?

 

[maty]

On an observational level, the AHB2 seems to resolve details ever so slightly better than the NAD. I am not certain of that though. On the other hand, in my system the bass is clearly more enjoyable with the NAD. I know, I know. “Both amps have great damping and handle impedance swings in an exemplary way, so your observation is BS...”

Maybe you need to try with something like this very great recording.

Just now, https://www.diyaudio.com/forums/music/6958-playing-listening-post5830694.html

Stanislaw Skrowaczewski, Minnesota Orchestra - Ravel - Daphnis Et Chloé - Ma Mère L'Oye - Valses Nobles Et Sentimentales (1975), SACD, MFSL 2005 remastered, US

Maurice Ravel / Stanislaw Skrowaczewski / Minnesota Orchestra - Daphnis Et Chloe - Ma Mere L'Oye - Valses Nobles Et Sentimentales (SACD, Album, Hybrid, Multichannel, Remastered, Limited Edition) | Discogs



DR Peak RMS Duration Track
--------------------------------------------------------------------------------
DR17 -1.12 dB -25.39 dB 13:36 01-Daphnis Et Chloé (Ballet) - Suite No. 1
DR17 -0.01 dB -23.81 dB 17:17 02-Daphnis Et Chloé (Ballet) - Interlude - Suite No. 2
DR19 -3.24 dB -29.52 dB 30:03 03-Ma Mère l'Oye
DR19 -0.16 dB -27.16 dB 17:52 04-Valse Nobles Et Sentimentales
--------------------------------------------------------------------------------

Number of tracks: 4
Official DR value: DR18


CD, 2005

https://www.amazon.com/Daphnis-Chloe.../dp/B0007XGPNQ

 

[GrimSurfer]

I'm sorry, but that is totally off base. It is absolutely legitimate to simultaneously believe that the AHB2 is a superb piece of engineering with remarkably good performance, but will likely not sound any different when blind-tested against amps with far worse measured performance.

If you feel that someone's answer to things isn't understandable, ask. Now, if after asking, you get inundated with nonsense, then it's legitimate to arrive at a negative conclusion.

Legitimate it may be but it's is also highly speculative... and a statement that has basis in belief but not Fact.

Let's just do away with measured performance then, because the theory that all amps sound alike is the prevailing view (which is utter nonsense once one factors in spl, load, phase changes, play time, etc.). Is that what you're saying? Hopefully not!

I understand what Scott has written but am not clairvoyant. He's leaving out a great deal... probably because the basis of what he is saying is rather thin (I'm being kind here). I'm hoping he offers something to prove me wrong but ATM it seems rather like a lot of the other nonsense and half truths that I hear from many in the industry.

Once again...

The thread is measurement of the AHB2. Amir's tests showed astonishingly good results, including a very low noise floor and low THD. Both of which are unquestionably preconditions for good sound. Agree/disagree?

 

[SIY]

Let's just do away with measured performance then, because the theory that all amps sound alike is the prevailing view...

By whom? Not any engineer I'm aware of. I think you have reified a straw man or forgotten the qualifiers (high input impedance, low output impedance, reasonably low distortion, not clipping, not oscillating, flat frequency response). One needs low enough noise and distortion to escape perception, but those have been widely achieved for decades. We're well past the point where new engineering in power amps results in sonic improvement.

The AHB2 is indeed a wonderful engineering achievement, and I wish I could afford one or two of them, but you (and I!) won't hear a difference between it and any other engineered power amp when used within their output limits. If you believe that you can, let's see some DBT results.

 

[scott wurcer]

I understand what Scott has written but am not clairvoyant.

Let's just write this off as a misunderstanding, nothing said at first bothered me at all BTW. I was interested at first in SY's crossover measurements and wondered if he could repeat THD alone at very low power, I was simply curious. There are other conventional class A/B amps with nested feedback and/or well known error correction techniques that have ppm levels of distortion at full power this only one measurement and just that a measurement. I have nothing to sell BTW and never have.

 

[SIY]

Let's just write this off as a misunderstanding, nothing said at first bothered me at all BTW. I was interested at first in SY's crossover measurements and wondered if he could repeat THD alone at very low power, I was simply curious.

So far, everything I could measure at 200 mW with the amp I have is noise dominated.

 

[scott wurcer]

So far, everything I could measure at 200 mW with the amp I have is noise dominated.

Using the AP? I was just trying to rationalize John Atkinson's measurements where he said he was plotting THD only and showed a 15dB rise by 100mW. I'm afraid I would instrument this measurement with synchronous averaging to remove the noise.

 

[SIY]

Using the AP? I was just trying to rationalize John Atkinson's measurements where he said he was plotting THD only and showed a 15dB rise by 100mW. I'm afraid I would instrument this measurement with synchronous averaging to remove the noise.

Yes, the 525. Most of the noise won't average out in this case because it's mains frequency and harmonics. If you have an idea of how I can deal with that, I'd be appreciative. The THD part is low enough that I'm limited by the AP's generator (-115 dB third harmonic).

I have a 555 B-series on the way which will increase the sensitivity of my measurement.

 

[D700]

Is running massive server farms environmentally responsible?

Very much so

 

[DonH56]

I am sure there must be a way to drag this further off topic...

I guess it doesn't matter since most everyone agrees the amp is so %$@# good there's not much else to discuss. But I had to hunt a while to find the power cube post, just to have something to drool over during lunch (my turkey sandwich didn't cut it).

 

[garbulky]

Legitimate it may be but it's is also highly speculative... and a statement that has basis in belief but not Fact.

Let's just do away with measured performance then, because the theory that all amps sound alike is the prevailing view

From a general reading, I think most level matched DBT tests appear to show (in music listening) - A null result, no better than random chance. Though null results is not the same as
proof of no difference,, I am not aware of positive results proving difference in music listening.

There is an amp challenge that offers $10,000 since 2006 for anybody that can differentiate an amp with less than 2% (!!) THD from a different amp which AFAIK has not been succcessfully overcome. The requirements are tremendously low too - channel separation of 30 db etc.
http://tom-morrow-land.com/tests/ampchall/index.htm?i=1

As far as DBT testing goes, there's not been many positive results for music listening. Does that make sense to you? That most amps sound the same?

 

[KSTR]

Yes, the 525. Most of the noise won't average out in this case because it's mains frequency and harmonics. If you have an idea of how I can deal with that, I'd be appreciative. The THD part is low enough that I'm limited by the AP's generator (-115 dB third harmonic).

I have a 555 B-series on the way which will increase the sensitivity of my measurement.

The System Two series can do synced averaging of the notched DUT signal before FFT'ing by using a trigger source, routed from the generator. I would think the 5xx models can do that also.
While not as good as true sample synced averaging (with the signal on an exact bin frequency and no windowing) because of trigger jitter causing some signal loss at higher frequencies it still is helpful to reduce any uncorrelated stuff (noise and mains) by some 20dB at least.

 

[SIY]

The System Two series can do synced averaging of the notched DUT signal before FFT'ing by using a trigger source, routed from the generator. I would think the 5xx models can do that also.
While not as good as true sample synced averaging (with the signal on an exact bin frequency and no windowing) because of trigger jitter causing some signal loss at higher frequencies it still is helpful to reduce any uncorrelated stuff (noise and mains) by some 20dB at least.

Well, for the FFT, the harmonics are pretty easy to dig out. It's the time-domain signal I'm trying to get. I can try using the fundamental as a trigger and see if the mains noise averages out.

 

[KSTR]

Yep, since the FFT is working on a time signal the noise reduction is seen there as well.

 

[amirm]

Guys, let's drop it.

 

[zalive]

Now, why would we want to drop this fine amp?

 

[zalive]

I'd guess that the main reason for this somewhat complex power section of this amp is to make it as lightweight as possible - since manufacturer's strategy is direct sales, it's pretty important to keep the weight as low as possible - amps need to live through shipping process. In the end, it's the cost - packing cost and shipping cost. But manufacturing cost as well, since quality transformers are expensive. But I'm not convinced if classic transformer of a decent capacity would not be a yet better choice when it comes to sound quality.

OTOH feedforward is a commendable approach IMO. One wonders why it's not used more widely in amp designs, especially taking into account that this design approacvh is like 35-40 years old, or even more? And speaking of the concept which seems not to be the most liked one - the time domain - feedforward is pretty much the most sound approach, as it follows the signal path in the time domain, unlike any feedback - and I'm somehow confidend that low distortion of this amp greatly depends on feedforward design.

As for the time domain, at least few of the local audio designers are confident of its importance. Also, the one I talk to often is pretty confident of using subjective listening tests in evaluating the sound quality, even if it's not DBT. However he's a trained pro - such are usually trained to use their ears professionally while their eyes are being open, you know