Pass ACA Class A Power Amplifier Review

[VeerK]

Unfortunately or fortunately, experienced listener can hear differences in hi-end system that we can't measure with equipment.
Quality hi-fi system behaves like telescope, and expose every detail, component signature, timbre and soundstage.
In audio ears can sometimes see better than eyes.
I have feeling that some of members here don't have much experience in listening , they just measure.

Here’s a thought experiment for you: if you say you hear a difference between two amps, why would I believe you? Why should I trust what you say you hear?

 

[amirm]

I have feeling that some of members here don't have much experience in listening , they just measure.

I am professionally trained as a listener. In my last job, we conducted a large scale fidelity test of lossy compression to CD with our audiophile community at the company. Not one could find differences that our trained listeners could easily do so (including myself).

Audiophiles have very poor ability to detect complex/non-linear distortions. The ACA amp is a good example. An amp that distorts and yet people say it sounds good? Clearly they are not able to hear the distortions or they would run for the hills!

If Audiophiles were great listeners, 90% of the junk that is sold out there will disappear.

 

[Observer]

I need your evidence first.
1, dacs that measure the same
2, amps that measure the same
3, proof that you hear difference between any pair of the devices in 1 or 2 (properly designed and executed blind tests)
Then I can try to answer.

You can easy find two Dacs who measure about the same, and try listen on quality hi-end system. I am pretty sure you will hear difference.

 

[Frank Dernie]

Unfortunately or fortunately, experienced listener can hear differences in hi-end system that we can't measure with equipment.
Quality hi-fi system behaves like telescope, and expose every detail, component signature, timbre and soundstage.
In audio ears can sometimes see better than eyes.
I have feeling that some of members here don't have much experience in listening , they just measure.

The problem with many enthusiasts is they listen with their eyes.
I have never come across anybody who can hear a difference between kit that measures the same in a proper level matched blind (ie they don't know which they are listening to) comparison.
If there is a measured difference you may be able to hear it, you may not.
If there isn't you may imagine you can hear it, if you make a poorly controlled comparison.
I thought I could for years but I found I can not when properly tested.

I spent a lot of time and money over 40 years before finding this.

 

[amirm]

I have feeling that some of members here don't have much experience in listening , they just measure.

Adding on, our experience is in knowing our perception of audio and how it is easily fooled by non-sound factors. Here is a story I have told before.

I was teaching equalization of sound in a room. I would create a filter based on measurements, turn it on and off and ask them if they could hear the effect. As I went on, I got to one filter where my two sons gave me a blank look when I asked them if they could hear the difference. I look on my computer and realized my mouse had moved so when I was clicking, nothing was changing as far as filter setting! But I was "hearing" a difference clear as a day.

This is what I meant about knowing the real answer behind a change before you trust any audiophile. In above, it could be proven that I was not really changing anything yet thought I was. An audiophile saying this and that sounds great with no way to know the real answer is of no value. We know that when we test such people, they fail much easier tests as I mentioned. So it reasons that we ignore what they say.

 

[amirm]

You can easy find two Dacs who measure about the same, and try listen on quality hi-end system. I am pretty sure you will hear difference.

Give us an example that you heard and how. Don't predict what we will do after just telling us we only measure.

 

[Frank Dernie]

You can easy find two Dacs who measure about the same, and try listen on quality hi-end system. I am pretty sure you will hear difference.

I compared 4 DACs from £1000 to £15,000 on a £200,000 system and the differences I thought i heard disappeared when they were compared with the levels matched to within 0.1 dB and my daughter changed the channel so i didn't know which I was listening to.
This was 10 years ago.

 

[Observer]

I am professionally trained as a listener. In my last job, we conducted a large scale fidelity test of lossy compression to CD with our audiophile community at the company. Not one could find differences that our trained listeners could easily do so (including myself).

Audiophiles have very poor ability to detect complex/non-linear distortions. The ACA amp is a good example. An amp that distorts and yet people say it sounds good? Clearly they are not able to hear the distortions or they would run for the hills!

If Audiophiles were great listeners, 90% of the junk that is sold out there will disappear.

You are so skilled that you try ACA in review with Sounus Faber, it may look like beginners mistake.

 

[LTig]

Unfortunately or fortunately, experienced listener can hear differences in hi-end system that we can't measure with equipment.

Unfortunately the results of scientific research say just the opposite. Floyd Toole wrote in his book Sound Reproduction (3rd Ed) that the group of audio reviewers performed at 20% where selected and trained professionals reached over 90% (see figure 3.9 on page 40).

Quality hi-fi system behaves like telescope, and expose every detail, component signature, timbre and soundstage.
In audio ears can sometimes see better than eyes.

The problem is that most audiophiles prefer to see with their eyes than to hear with their ears. Or why is there such a big fear of taking part in a DBT?

I have feeling that some of members here don't have much experience in listening , they just measure.

Arrogant BS. Always the last resort if arguments don't win. You don't know at all how often I (or others here) visit the opera, the ballett, classical, Rock and Jazz live concerts.

 

[VeerK]

I’d wager a guess that this is yet another troll poster, I wouldn’t continue to waste energy as they aren’t arguing in good faith and starting to lean into ad hominem attacks. Would be curious if all of these clowns are coming from the same circus...

 

[amirm]

You are so skilled that you try ACA in review with Sounus Faber, it may look like beginners mistake.

Did you read what I wrote?

So no, no mistake. I used a "high-end" speaker brand which you said was a requirement. A cheap mass market amplifier ran circles around this amplifier with the same amplifier.

If you were really into listening and enjoying music, you would avoid the ACA amp. It doesn't have much power and has a lot of distortion. If on the other hand, if you want to go by non-audio factors like who designed the circuit, then sure, carry one. We like the amplifier to work for us, not the other way around.

 

[JeffS7444]

I know the Covid lockdown is making people batty including myself but why do we have this discussion, in one form or another, over and over again. Should someone really be interested they would read all 24 pages of posts and decide if this forum was for them or not.

But he's gone through all this trouble to bring audio enlightenment to us, perhaps the least we could do is be suitably awed by the power of many year's worth of accumulated audiophile wisdom.

 

[amirm]

I’d wager a guess that this is yet another troll poster, I wouldn’t continue to waste energy as they aren’t arguing in good faith and starting to lean into ad hominem attacks. Would be curious if all of these clowns are coming from the same circus...

He is useful in keeping this thread fresh so when people search for this amp, they see our take on it so they are fully informed.

 

[VeerK]

He is useful in keeping this thread fresh so when people search for this amp, they see our take on it so they are fully informed.

I suppose so, when people google search the ACA they deserve to see the ASR info.

That being said, it is grating every time someone new shows up to grace us with the ethereal magic of audiophilia. Although, I guess this means that ASR has truly anchored itself in this industry, makes me happy seeing this since the earlier days

 

[amirm]

There must be a reason on reviewer (your) side for bad listening experience, maybe Topping dac have bad/low output level so you have no enough gain . Once I had Smsl dac , I had to put volume on 12 o'clock on my Verdi Cento (100w@ch) to hear something. Some chinese brands match output/impedance to their cheap amps , but usually don’t match well to “normal” amps . A guy with iPhone test ACA amp, and got good level &sound, here is link:

You want us to be impressed that an amplifier produced music? That is your standard of something being good? That you hear music in a youtube video from an amplifier?

His excitement is not about fidelity of said amp. He is excited and rightly so because he built it himself and it didn't smoke when he turned it on. In what way this is inconsistent with my review?

 

[MRC01]

Unfortunately, measurements do not support that assertion.

Neither does my tactile hand-o-meter measurement. Some class AB amps are biased high enough that both sides conduct up to several watts of output, consequently they draw considerable power and get warm when idle. I'm not saying this is the only way for an amp to perform well, but only that crossover distortion is not an issue with well engineered class AB amps.

 

[SIY]

Neither does my tactile hand-o-meter measurement. Some class AB amps are biased high enough that both sides conduct up to several watts of output, consequently they draw considerable power and get warm when idle. I'm not saying this is the only way for an amp to perform well, but only that crossover distortion is not an issue with well engineered class AB amps.

And as Self pointed out, "well engineered" means "optimum idle current," not "high idle current." And "optimal" is often pretty low.

 

[Observer]

I’d wager a guess that this is yet another troll poster, I wouldn’t continue to waste energy as they aren’t arguing in good faith and starting to lean into ad hominem attacks. Would be curious if all of these clowns are coming from the same circus...

For shure I am not from your “tedy bear” circus, I have 40 years experience in audio as hobbyst, listener and dealer. Your style where are you using “clowns” just to discredit people speak much about you - idiot.

 

[SIY]

dealer.

Bingo.

 

[Observer]

Bingo.

Yeah... l was dealer for headphone amps for a while. Is that illegal?