Comments on: Class A Tube Amps: Marketing Hype vs. Reality

By: Nick

Nick — Sat, 16 Mar 2019 23:28:17 +0000

I think quite a few electrical engineers might have a difference of opinion on this …

By: A false idiot

A false idiot — Wed, 01 Feb 2017 10:22:07 +0000

There are always some paranoid idiots on the internet who say that this or that amp company makes false claims or that class a or ab , or that ‘a tube in there’ is a ‘gimmick’. What they do not realize is that they look like the complete idiots they are, to people who know what they talk about.

By: groovimus

groovimus — Mon, 14 Nov 2016 16:04:55 +0000

Can an electrical engineer come on here and correct a few things? First of all do not tell an engineer what you are effectively saying – that if you bias a push-pull output stage one way it will be a “class A” and bias it another way it will be “class AB”. On way to prove it to you is for you to go look up class B and class AB in the textbooks and you will see that they are implemented with push-pull topology in tube designs, and with complementary/quasi-complementary topologies in solid state. All three of those topologies require a minimum of two output devices, and have a maximum theoretical efficiency of 78% excluding filament power.

A true class A amplifier design by contrast can be implemented with one output device, and so this proves that they are a completely different architecture and thus the issue is not one of “biasing”. They are maximum 50% efficient with transformer coupling, and 25% efficient with capacitive coupling.

Class A amplifiers add harmonic distortion at all integer harmonics in overdrive, and only even harmonics in sub-overdrive. Class A and AB amplifiers theoretically generate only odd harmonics with perfect device matching. So if the user thinks there is an advantage to using class A, the only difference would be the addition of even harmonics to the output signal over a class AB

By: Csaba

Csaba — Tue, 06 Sep 2016 09:16:49 +0000

“Tubes biased to operate in Class A/B produce more odd order harmonics. Generally, even order harmonics sound more pleasing than odd. That’s why Class A and Class A/B sound different. ”

?????

Not really….. Connecting harmonic distortion directly to classes is another myth….

By: Jerry Wang

Jerry Wang — Wed, 29 May 2013 17:53:19 +0000

I assume that you are talking about guitar amplifier and it makes sense. The saturation distortion from the output transformer saturation dominates and has become an inherent part of the sound quality of a guitar and guitar amplifier. This type of distortion is odd order in nature and makes the odd order distortion from class AB bias insignificant. Further improvement from class A bias simply misses the points.

However this does not apply to the HiFi amplifier between your music source and speakers.

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