Physics explains why rock musicians prefer valve amps | Hacker News Reader

Physics explains why rock musicians prefer valve amps

phys.org

13 pointsdnetesn11 comments

Modeling analog amplifiers to produce good sounding guitar distortion is well understood in the music DSP plugin industry. There are several products for doing this (search for tube amp VST plugins). It isn't a new concept.

Modelling has come a long way in the past decade, probably to the 'close enough' level for just about anybody. Still doesn't quite have the sound or feel of the real thing though.

So this opens up better solid state and digital modeling of tube amps? I sort of figured DSPs were already doing a lot of this with amp and mic profile models.

I don't think there's anything new in this article. They're actually talking about the difference between Class A and Class AB amplifiers, most old valve amps being of Class A design and the trend with solid state amps being towards Class AB. Depressing that this made phys.org.

Very few classic tube guitar amplifiers were Class A, the vast majority being AB. Really the only ones that were class A are single tube amplifiers like the Fender Champ. The Vox AC/30 that everyone thinks is class A is just cathode-biased class AB. The Marshalls that Hendrix played through, the Fenders that Steve Ray Vaughn used, and the Boogies that Santana is known for, all class AB.

Sure, class A does tend to have more even-order harmonics, compared to AB, but even class AB tube amplifiers have more than any solid state one.

So... did these tube AB designs have particularly asymmetrical lobes to their gain curves? Otherwise I don't see where these even order harmonics are getting introduced.

Yes a bit due to asymmetry in the phase inverter circuit driving TD push-pull, but mostly because the odd harmonics are naturally cancelled out in the output transformer.

This article would be greatly improved if they connected actual double-blind sound evaluations with the physics. Who cares what the physics show if it's not connected directly to what people hear.

I hardly think hearing impaired musicians are any sort of gold standard for how audio sounds.

The article would be greatly improved with some images of the sine waves and the varying levels of harmonics.

It would be interesting to see how well (quantitatively) modelling amplifiers emulate this.

I think a Bugera may have been a mistake.

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