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Why do so many prefer the sound of "Class A" amplification vs. "linear" amps?

rsoffer

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I'm more curious, as I've never owned a class A amp and have never been able to A/B test them myself.

They point to the sound being more "open", "warmer", "dynamic", less "sterile".

For tube amps, it seems more reasonable there would be a difference. That extra distortion which colors the sound. For class A, are they essentially hearing less of the same phenomenon?




In the above videos, Mid-Fi guy goes into great detail listing out the differences between various solid state amps. Part of me finds it very hard to believe that he's simply imagining all of it. What do you guys think is going on there?

Josh Valour does a fairly unscientific A/B test of the A90 vs. A90D, but it's still a data point showing some audible differences.

What's going on here? Are so many audiophiles who spend time with this equipment on a daily basis simply imagining all of it?
 

levimax

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Unless they do a double blind level matched test it is meaningless. I built a DIY Class A amp to see what all the fuss was about... it was very expensive to build (big heatsinks, big PS Caps and PS Chokes) heated up the room and didn't put out much power (25 Watts). It sounded fine but when I compared it level matched to other amps I had it sounded the same. I ended up converting it to Class AB to get more power and less heat and it still sounds fine. At the end of the day Class A amps work fine but they really only have disadvantages compared to a well designed Class AB or Class D .... except maybe on a cold winter day.
 

Spkrdctr

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I commend him on trying. The problem is that he (the father) alternated every single time, never going out of his alternating order. He needed to pull it and re-plug it into the same one a few times to mix it up. The test is basically invalid as the father was helping and just didn't really know what to do except change it when his son told him too. Great attempt, it just needed a bit more to make it "in the home valid". I will not tear it apart but leave it as a botched attempt. But, if he does it again with some minimal advice from me (I try to be helpful) he will get the answer he seeks. He now thinks the results are fantastic and that as he stated, "he is not crazy". If I helped him doing maybe two or three things different he would have seen that he could not reliably tell the difference. Oh well.
 

fpitas

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Once upon a time class A was the go-to for horns, since AB amps had (and to a small extent, still do have) crossover distortion. A horn is about 20dB more sensitive than a cone speaker, so even normally inaudible crossover distortion can become audible. These days though, I'd just use class D.
 

Doodski

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Unless they do a double blind level matched test it is meaningless. I built a DIY Class A amp to see what all the fuss was about... it was very expensive to build (big heatsinks, big PS Caps and PS Chokes) heated up the room and didn't put out much power (25 Watts). It sounded fine but when I compared it level matched to other amps I had it sounded the same. I ended up converting it to Class AB to get more power and less heat and it still sounds fine. At the end of the day Class A amps work fine but they really only have disadvantages compared to a well designed Class AB or Class D .... except maybe on a cold winter day.
I've owned and operated 2 class A USA made amps. Both are the same amp but came in rack mount and standard width. Ratings are as follows. It does sound smoother and more musical.
z kba.png
 

DJNX

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The results on the second video would be interesting if the alternation from of A and B were random.
If he does that and still accurately identifies each amp, then he needs to upgrade to an ABX setup, to see if there is any preferability.
 

fpitas

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Lol... It has a AC muffin fan blowing out the rear across the heatsink. Surprisingly the amount of heat is not that high.
i stuck a couple quiet fans on top of my J2. I figure there's no reason to roast the power supply capacitors.
 

Jim Taylor

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Basically, people will hear what they expect they will hear, and not hear what they expect to not hear. It's called expectation bias. There are exceptions, but they are few and far between. So if they've been told, many times, that Class A is "better" or "smoother", that's what they will hear ............. until they face a rigorously controlled blind test.

Jim
 
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Astoneroad

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It says more about what is in their heads than what is actually coming out of the amp. People spend a lifetime studying a religion, doesn't make any of it true.
Amen to that.
 

GXAlan

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It’s rare to find a pure class B amp nowadays. With Class AB amps, you are running class A at low power anyways.

Take a look at my three generations of Marantz measurements as well as Amir’s PM-90 review which showed vanishly small differences.
 

Waxx

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Class A is basicly about harmonic distortion (profile) it generates, (the infamous warmth). For the rest they are inefficient and often way to expensive (because it's class A). What these lads are talking about, i don't know, it does not sound logic to me and it does not sound like they get it.
 

Doodski

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i stuck a couple quiet fans on top of my J2. I figure there's no reason to roast the power supply capacitors.
This fan layout has pros and cons and has stirred a bit of controversy in past postings.
2480726-77b9bcb6-kinergetics-research-kba-75-platinum-pure-class-a-power-amplifier-one-off-completely-restored.jpg

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2443696-7203ccf6-kinergetics-kba-75-for-parts.jpg
 

sarumbear

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Once upon a time class A was the go-to for horns, since AB amps had (and to a small extent, still do have) crossover distortion. A horn is about 20dB more sensitive than a cone speaker, so even normally inaudible crossover distortion can become audible. These days though, I'd just use class D.
The only reason there’s that letter A is in AB is to get rid of the crossover distortion that B has. Where do you measure that distortion on an AB amp?
 

NiagaraPete

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Slightly off topic. I have a Topping A30 Pro that at lower volumes runs class A. It gets really warm. At high volumes it run with just a touch of heat.
 

Doodski

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Where do you measure that distortion on an AB amp?
I searched and looked at high resolution at the zero volts crossover point and have not found it on a AB or A. Perhaps in a lab layout when testing a AB then crossover distortion might exist.
 
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rsoffer

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Class A is basicly about harmonic distortion (profile) it generates, (the infamous warmth). For the rest they are inefficient and often way to expensive (because it's class A). What these lads are talking about, i don't know, it does not sound logic to me and it does not sound like they get it.
This is somewhat what I suspect. More harmonic distortion = warmth or whatever else they're describing. But is this actually audible?
 
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