Asymmetrical waveforms !

[Nick]

But (if they do, maybe this is a question for a audiologist) that's something that's happening to you, not the sound of the trumpet.

[JamesD]

I need to think on what you said and the possible rabbit holes but I agree that we fundamentally agree but express it differently. Thats part of what I enjoy in these discussions as it good to get that different perspective...

Running out of energy so I need to stop for a while...sorry

James

[JamesD]

Oh quick observation on the trumpet... The distortion level orcrather distortiion profile various with how strongly it is blown assuming the 'tonguing' doesn't chsnge...so power through the instrument rather than percieved volume. ..

[Nick]

I've measured PP amps reducing the even harmonics of a mudic signal by comparing FFTs of a single note produced by an oboe... I tried six different amps and the 5 PP amps all reduced the second and fourth harmonic whilst the se amp increased them

Thinking more on this, it will also depend on the relative phase of the hamonics. Back to Nelson here I guess. If the transfer function is such that the gain is reduced as the signal goes away from 0v then the result will be different than if it was increased. With push pull it will either be increased (or more likely) decreased. But never be increased when one and decreased when the other. With single ended it will always be decreased when +ve and increased when -ve (or vice versa).

[Nick]

Oh quick observation on the trumpet... The distortion level orcrather distortiion profile various with how strongly it is blown assuming the 'tonguing' doesn't chsnge...so power through the instrument rather than percieved volume. ..

Yes, that why I constructed the situation of the player in a field where the volume was only altered by the distance from the player. I would have preferred the player to be hanging from a crane, but thought that was a bit much.

I agree, loads of things will alter the distortion profile, and they may also alter the volume at the same time, but that doesn't mean that the volume is itself altering the distortion profile correlation and causality and all that. If you misread that as causality it will make you start to justify that an amplifier distorting more as it gets louder is in some sense correct (that's the sort of rabbit hole I was talking about).

But your points about power as opposed to voltage was not ignored earlier.

[steve s]

But you could also read into that if the trumpet was blowed harder, that's very similar outcome to turning the amplifier volume up... not that it matters that much

[Nick]

But you could also read into that if the trumpet was blowed harder, that's very similar outcome to turning the amplifier volume up... not that it matters that much

I disagree a lot, if you can't tell the difference between a trumpet being blown harder and the amp being turned up then the system is broken. That's entirely the opposite from what I know you want from a HiFi.

But that's a great example of the rabbit holes

[steve s]

The one watt amp I brought to owston sounds worse than broken if I turn that up too much...

[IslandPink]

That's entirely the opposite from what I know you want from a HiFi.

The Vox Olympian being the best example of how to do things correctly ?

[Nick]

The speaker part at least certainly seemed good yes.

[steve s]

There are sections in this regarding the effects of asymmetric drive and feedback, seems like they would only have an effect in poorly designed amps
I've read the whole article a few times, and found it competently written and easy to understand
And it's not all about a 6v6 amp

http://www.amplitudemodulation.com.au/vtamp.html#topcc

[Nick]

Yep, but that's talking about the effect of overdrive generating asymmetric effects in the amp (or at least I think it is), which is connected to the rectifying effects that I think James touched on. Its in effect talking about a amp in a fault condition, we would normally not want a amp to be anywhere close to that condition.

I don't find it entirely clear what its saying, but that's probably my fault trying to work out exactly how the circuits fit together.

[steve s]

There are snippets in other sections too, but he explains them to me quite logically although I've read most of it 3 times

How logical his logic is, is another matter !

[JamesD]

Nick said

Yes, I would expect that. You are taking a signal that is mostly a sine wave with some harmonics, passing that through an amplifier that generates a set of distortion harmonics from that signal where the odd ones will dominate. You then add those new harmonics to the original signal and the result will means that the even harmonics will remain as before or cancel which even harmonics can do when added and the odd ones will sum and increase, so you would expect a larger level of odd harmonics in the result. I know it is a process of multiplication instead of addition, but the bulk of the generated harmonics will be from the fundamental so will align with the original signal harmonics.

Ok I understand this to mean that the relative balance of even to odd harmonics is changed by the amplifier in favour of increased level of odd harmonics relative to the even harmonics... and the argument makes sense but so does my assertion, at least to my mind, so more testing required with a, say, 400Hz and 800Hz test waveform from a very clean signal generator into some PP amps and an SE amp or two... Oh well I won't be doing that anytime soon...

[Nick]

Yep, I am aware that I am quibbling about a point that starts to look more like a non point after a bit. If it walks like a duck and quacks and all that. I stick with my solution though and that is an amplifier that does as little damage as possible, that way no harmonic was harmed in the making of the film.

It is a lot less fun to argue about though...