I”m for a good part with Galen, but also with you (a little softer doesn’t mean „not absolutely beautiful“).
When I take my experience with the following higher end power amps of which I owned most:
Class A:
Threshold SA/2 monos, Pass Aleph 0 monos, Gryphon Antileon special prototype Stereo, Vitus prototype Stereo, Lamm 1.1 monos
Class AB:
Gryphon S100, Brinkmann monos, big Chord Stereo, big Boulder Stereo
I also perceived the big Class A amps (besides their noticable strengths against AB) as softer, with less good prat and less speed than the best AB amps I heard.
But I wouldn’t say that’s a characteristic of Class A generally, as the Treshold, the Pass Aleph as well as my Class A tube preamp go in the opposite direction.
Technically all watts are “equal” as a watt is a current through, or voltage dropped, across a resistive load. Thus Current squared x resistance or amps time volts at the load.
What is not equal, is the reactance magnitude angle across a load. This angle changes the “power” (watts again) factor to describe how efficient the load is at doing work. But a watt is indeed a watt as it cannot become a watt until the load is 100% resistive.
Yeah we were just having fun and seeing how dynamic the system would sound. We were only playing the “bangers” in our libraries (that’s what the kids call loud tracks with a wide frequency and dynamic range). None of us were even sitting down in the listening chairs, it was a much more informal, fun test. We did pull an AQ Dragon from one of the BHK 600s and had it plugged into a P20. It looked pretty ridiculous. All of us had ear to ear smiles. If tapping toes and big smiles is any indication of how it sounded, it sounded pretty damn good.
In reality though, nothing compared to them new BHK600s!
I am glad that this hasn’t changed since I went to college or worked in an Anti-Submarine Warfare research laboratory. Nothing like a 300,000 watt system to teach you how all this works.
I’m going for NO SOUND from the amp. Curious as it seems, we aren’t there yet.
I want to hear back to the source, and the better we do that the wider the variations of our sources as we don’t push or pull the sound to a specific corner. The key to a great stereo is the WIDTH of the source variation. No rose colored glasses! The hardest part of this is isolating errors and not offsetting error with just an opposite error. We all do that by accident or are forced into it as a better path forward doesn’t exist yet within a component. Thus, we try to neutralize error when that allows TWO errors to exist. YIKES!
Amps aren’t drastic in error but they do get in the way as stuff gets really good, you hear it! My amps change when they are warm. All of a sudden POP, stuff is great.
I just like to error on the solid / architectural sound verses pastel / impressionist side as most sources warm it up by default. New digital doesn’t need added warmth to be tolerable.
Curious, why does AB amps run well in the class A range not sound the same as class A full range designs in the exact same peak load? You’d think as long as we are inside class A part of AB, we’d hear a “like” sound unless we crank it up. The class A bias in AB is not the same as a true class A or it SHOULD duplicate the sound in my M40 HV amps. I can run these amps A or AB. But ALL AB amps fall into this pattern. They are class A under say 10 - 30 watts but don’t sound like classic A amps to my ear. Thoughts on that amp design guys?
The FR30 will play PLENTY load with 10 watts peak, too, so these aren’t immune from the A to AB switch or even stay in class A like most 87-90 db SPL rated speakers.
But it doesn’t really SAY specifically why, when we are in “A” mode with all the same parts it sounds different than a class A amp. The answer is hidden in the CURRENT delivery system where AB has an advantage;
It also is the least efficient of the Class A configurations, with an efficiency figure on the order of 20%, sometimes less. A limitation of single-ended Class A operation is that the peak output current is limited to the value of the bias current. By comparison, pushpull Class A can deliver twice the bias current as peak output in Class A, and generally much more than that in Class AB
This says we have a trade off, steady state signal distortion over dynamic current delivery properties. AB in class A can deliver more current. But we need to qualify that as the limitations CAN BE fixed with a heavy handed level of MORE bias in CLASS A.
This higher bias fix ups the price of the amp if it is class A, so few can enjoy this kind of design. There are other class A topologies too, as Nelson suggest, and he talked about the worst one to keep things simpler.
It seems that we can get a “fast” class A amp with good current delivery with a high bias AB design cheaper. I’m not sure I’m saying this 100% correct but it is the signal CURRENT differences and thus the sound as well as the bias current level lowering and changing the type of distortion.
I’d think AB amps harmonic distortion TYPE will change spots with output power, too. That first watt thing is true,
After re reading ( I haven’t read that paper in years), I can see your point.
Pass has lots of writings in the Support section of his website. Maybe we can find your answer there.
And as to Pass amps specifically, I wonder if they do sound different, Class A vs Class AB while both are within the bias range of Class A. I doubt that his A and AB designs are the same re number and type of input devices, etc.
Haha, it kind of stinks because I was the youngest in the company for about 3 years. Now we have someone working here that is a decade younger than me. I’m legacy at this point.
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