Amp Sound Module v1.0; solid state amp attempt

[Steben]

Here you have it, my first compiled circuit of an "amp sound module".
It basically aims at master volume amp architecture:
- you have some preamp tube hint kicking in at high gain after the power amp already started distorting with slight bias shift by splitting clipping diode sections in clamper and feedback loop.
- Tone controls are found after master volume.
- The ratio of gain levels of preamp vs power amp need some experimenting and this imposes constraints on the preamp circuit before this, which means a input stage is to be designed.
Supply has to be at least symmetric +9V to -9V or the headroom will be too low.
This circuit needs a following linear power amp of choice.

Biggest problem is time and means to start building this.

[Steben]

Hi guys!
Any ideas / experience in making the tone stack and second stage combination more workable?
I could make the stage high impedance (but this brings in noise?) or make the tonestack low impedance. Yet I cant seem to find ideal values with the same frequency response, especially the bass control is quickly too subtle.

[PRR]

Both stages are wired as inverters.

Why??

The low input impedance loads-down the guitar or loads-down the tonestack.

Compare the ~~2k into stage 2 to the 100k-1Meg of the tonestack and it is clear why "the bass control is quickly too subtle."

The working impedance is *already* determined by your choice of guitar and tone-stack values. Loading-down with low impedances won't really reduce hiss (you'll have to turn-up more to get good signal).

Get it "working good", knobs do something you like, before thinking about hiss.

[Steben]

Both stages are wired as inverters.

Why??

The low input impedance loads-down the guitar or loads-down the tonestack.

Compare the ~~2k into stage 2 to the 100k-1Meg of the tonestack and it is clear why "the bass control is quickly too subtle."

The working impedance is *already* determined by your choice of guitar and tone-stack values. Loading-down with low impedances won't really reduce hiss (you'll have to turn-up more to get good signal).

Get it "working good", knobs do something you like, before thinking about hiss.

The input is supposed to be the lower impedance output of an input stage. This can be a jFET stage, buffer, elaborate preamp, ....
The first stage is inverting because of the character of the clipping circuit.
The tonestack is indeed too high in impedance. The solution can be a high input impedance stage and yes this can be a non inverting one.
But, in tube amps, impedance and noise is relative since the amplitudes are much higher than in solid state amps. A given noise with tens to hundreds volts of signal is low compared to the same noise with ten volts max.
In other words: i'm thinking of a tonestack that lets the stages have a lower inpedance. Experimenting with Duncans TSC gave me comparable results yet they show a lower bass response.



The difference with tenfold smaller impedances compared to a standard tonestack is almost none. With a factor of hundred you get small range and lower bass.
This leads me to accept a compromise and choose tenfold smaller.