This is a basic newbie question.
I have never designed an amplifier. I have read books on audio amplifier design by Randy Slone, Doug Self and Bob Cordell, and done some DIY circuit building, designed some PCBs from existing schematics.
Now for my question. Twenty years ago, Randy Slone and Doug Self used to design amplifiers whose THD went from 0.003% at 1KHz to perhaps 0.05% at 20KHz. These were considered top of their lines. I'm focusing only on SS Class B here.
Now I am seeing discrete Class B amps routinely getting into triple-zero THD territory. The DIYaudio Wolverine. The Benchmark AHB2. The Topping B100/B200. And others. How are they able to do this?
I am aware of composite amplifiers which use a precision opamp in the feedback loop of a larger Class B amp. Neurochrome and Kaltecs.com do this. But both of these designers have done it only with chip amps. The Wolverine does not use an opamp in the feedback path. And I am told that it's damn hard to design a composite amp which does not oscillate, so I'm assuming that this approach is usable with a lot of effort with chip amps but unviable with a classic three-stage discrete design. I have heard the term TMC. What is it? I am aware of Miller compensation capacitors from Randy Slone's books, and he hesitated to use a CRC pi filter for stability concerns, he'd usually use just a single capacitor. Is the TMC I hear about fundamentally different from the stuff he explained? I am also aware that regulated supply rails for the input and VAS stages of an amp may deliver some improvements in performance, though I haven't seen it being used by Slone or Self, no idea why. Does this help?
So my question is basically: what are all the techniques modern designers are using to get to triple-zero territory? They are using parts which do not seem to be very exotic or unique, nor are their designs so narrow that we get a very unique set of circumstances which give us the magic. What changed in 20 years? Is this achieved by obsessing over details (like using an optical connection from front panel power switch to the rear, instead of an electrical cable, to keep mains hum out, or like feeding the supply rails of the actual amp with the output of a regulated massive power supply, like I'm told Halcro does), or by advances in topology and semiconductor parts quality?
(I am aware that my question is more an expression of my ignorance and misunderstanding than a simple search for some facts. I am hoping for some patient answers from some of you which will complete my education and clear my misunderstandings.)
My question is only about Class B SS amps.
I have never designed an amplifier. I have read books on audio amplifier design by Randy Slone, Doug Self and Bob Cordell, and done some DIY circuit building, designed some PCBs from existing schematics.
Now for my question. Twenty years ago, Randy Slone and Doug Self used to design amplifiers whose THD went from 0.003% at 1KHz to perhaps 0.05% at 20KHz. These were considered top of their lines. I'm focusing only on SS Class B here.
Now I am seeing discrete Class B amps routinely getting into triple-zero THD territory. The DIYaudio Wolverine. The Benchmark AHB2. The Topping B100/B200. And others. How are they able to do this?
I am aware of composite amplifiers which use a precision opamp in the feedback loop of a larger Class B amp. Neurochrome and Kaltecs.com do this. But both of these designers have done it only with chip amps. The Wolverine does not use an opamp in the feedback path. And I am told that it's damn hard to design a composite amp which does not oscillate, so I'm assuming that this approach is usable with a lot of effort with chip amps but unviable with a classic three-stage discrete design. I have heard the term TMC. What is it? I am aware of Miller compensation capacitors from Randy Slone's books, and he hesitated to use a CRC pi filter for stability concerns, he'd usually use just a single capacitor. Is the TMC I hear about fundamentally different from the stuff he explained? I am also aware that regulated supply rails for the input and VAS stages of an amp may deliver some improvements in performance, though I haven't seen it being used by Slone or Self, no idea why. Does this help?
So my question is basically: what are all the techniques modern designers are using to get to triple-zero territory? They are using parts which do not seem to be very exotic or unique, nor are their designs so narrow that we get a very unique set of circumstances which give us the magic. What changed in 20 years? Is this achieved by obsessing over details (like using an optical connection from front panel power switch to the rear, instead of an electrical cable, to keep mains hum out, or like feeding the supply rails of the actual amp with the output of a regulated massive power supply, like I'm told Halcro does), or by advances in topology and semiconductor parts quality?
(I am aware that my question is more an expression of my ignorance and misunderstanding than a simple search for some facts. I am hoping for some patient answers from some of you which will complete my education and clear my misunderstandings.)
My question is only about Class B SS amps.
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