Asymmetric clipping turning into Symmetric for bigger signals

[Vivek]

Steben's circuit is the starting point of a diode function generator.




60mv input signal in Red
600mV input signal in Teal

[Steben]

Could a non master volume push-pull amp actually work another way round?

Like when you start pushing it the power amp saturates, but because its nature it can only do it symmetrically. If you push it more the preamp starts to clip too and that can get asymmetrical. (And if the duty cycle goes off enough the power amp cannot make it symmetrical any more.)

Thats how modern amps work definitely, yet with the option of only using preamp distortion.
Vintage amp simply have little preamp gain to fully use the duty cycle shift UNLESS..... as I said one boosts the input with fe rangemaster stuff

[iainpunk]

AFAIK modern amps generally don't allow the poweramp to saturate, but a separate limiter/saturator (clipping section) just in front of the poweramp, since most poweramp IC's really clip in a nasty, inharmonic way. with a bunch of odd spikes, oscillations and other artefacts that are independent of input frequency.
the generation solid state amps before the current modern amps did clip in that way, like the older SUNN and Peavey solid state amps, which still have transistors or mosfets in the output stage, instead of an IC.

but to be perfectly honest, i like class D modulator clipping the best, perfect sharp knees and no weird stuff going on!!!

cheers, Iain

[Steben]

AFAIK modern amps generally don't allow the poweramp to saturate, but a separate limiter/saturator (clipping section) just in front of the poweramp, since most poweramp IC's really clip in a nasty, inharmonic way. with a bunch of odd spikes, oscillations and other artefacts that are independent of input frequency.
the generation solid state amps before the current modern amps did clip in that way, like the older SUNN and Peavey solid state amps, which still have transistors or mosfets in the output stage, instead of an IC.

but to be perfectly honest, i like class D modulator clipping the best, perfect sharp knees and no weird stuff going on!!!

cheers, Iain

I referred to modern tube amps

[iainpunk]

ow oops, sorry, i don't consider tube amps to be modern... since the last notable innovation was over 15 years ago and they haven't changed much since the mid 90's... except that class D tube amp a classmate made for his dad. (well, class A/D, and its for hifi)

cheers, Iain

[FiveseveN]

the last notable innovation was over 15 years ago

If you don't mind, which one was that? I'd say after Simul-Class the different flavors of power scaling became the popular thing. But I don't really follow the tube scene so now I'm curious about what I might have missed.

[iainpunk]

the last notable innovation was over 15 years ago

If you don't mind, which one was that? I'd say after Simul-Class the different flavors of power scaling became the popular thing. But I don't really follow the tube scene so now I'm curious about what I might have missed.

its what orange calls the headroom/bedroom switch, its basically power scaling to make the output power way lower without loosing the same sound, quite a genius ad underrated idea!!!

cheers, Iain

[pruttelherrie]

the last notable innovation was over 15 years ago

If you don't mind, which one was that? I'd say after Simul-Class the different flavors of power scaling became the popular thing. But I don't really follow the tube scene so now I'm curious about what I might have missed.

its what orange calls the headroom/bedroom switch, its basically power scaling to make the output power way lower without loosing the same sound, quite a genius ad underrated idea!!!

cheers, Iain

I don't get it.

From https://orangeamps.com/articles/headroom-bedroom/

First it states: "power amp overdrive (the holy grail of guitar tone)"
And later: "The Bedroom mode drops the output (...) by manipulating the signal headroom in the phase inverter part of the circuit."

That doesn't make sense?
Also, it sounds like a PPIMV (which is useful on for example a 2203/2204 Marshall since the PI is compressing before the powertubes, but might not be on other amps, OTOH it might be useful on these Orange amps?).

[iainpunk]

what i have been told, the power tubes in these orange amps are not overdriving, because the voltage gain is less than 1 due to the low impedance on the plate, the current gain is really high however. the power tubes are more powerful than the phase inverter allows to go through, preventing the power tubes from clipping by phase inverter clipping earlier than the power tubes. this is ''the orange sound'' as i have been told. i am paraphrasing tho, its hard to find the schematics from amps with the head/bed switch.

its basically a PPIMV but done with clipping instead of reduction

cheers, Iain

[teemuk]

...And by doing so it loses most of the dynamics associated with power amp clipping. 

[iainpunk]

...And by doing so it loses most of the dynamics associated with power amp clipping. 

orange amps never poweramp clip anyways, so no difference there