Adding a tone control to a THAT corp compressor "One Knob Squeezer" design

[mordechai]

I am all into the crudely-drawn aesthetic.  It's what I call anti-structuralist deconstructionism.  Because nothing is more useful in every day living than mid 20th century French social theory.  :-)

Actually, it is both the treble cut and treble boost that I would like to retain in this circuit.  My goal is to have a device that works equally well on guitar and bass (I figure I'll put some of the caps on a switch to go between one or the other), so for some circumstances the boost would be more useful (I'm thinking for guitar) and in others, the cut would be better (I do like the sound of an Orange Squeezer on bass with a bit of a treble roll off). 

This is also why I wanted to explore the possibility of an adjustable threshold control, because I have found that this is a useful feature to fiddle with when using a compressor on either a bass or a guitar.  Not sure where it would go on THIS circuit, though, since the topography really is different than the original Squeezer.

As for the pot -- maybe customizing it with a parallel resistor across lugs 1 and 3 would do the trick.  So, taking a 25K pot, maybe, and bringing it down to a 12.5-ish K value...?

Of course, if the tone in the "neutral" position of a 10K is pleasing, then I guess I'd just go with that.

[mordechai]

Mark, is there any benefit to doing the tone shaping pre-compression as opposed to post-compression?  Why not have a version of this circuit on the output op-amp?

[Mark Hammer]

Doing it pre-compression alters what the rectifier is responding to.  The Marshall Edward the Compressor uses a sort of Big Muff tone control just ahead of the rectifier, such that the rectifier can be coaxed into responding more to the bass or more to the treble.  What I suggested here is not likely "strong" enough to do that, though I expect it is an empirical question.

If you can bring it with you when you visit, we can tinker.

[mordechai]

Unfortunately I won't have the parts to do that -- have to put in the order and then get the prototype version done up on vero.  But don't worry, I'll bring a nifty nascent project with me when I stop by that I think you'll find fun!

After doing more research, the 4316 version of the "One Knob Squeezer" circuit is probably a more feasible option for what I have in mind.  One of the engineers who developed it suggested putting the treble cut/boost circuit at the tail end of the circuit, on the output op-amp rather than before the compression circuit. 

But come to think of it -- it could be interesting to have tone shaping options both pre AND post compression.  At different settings one might be more useful than the other depending on the desired effect, especially because I plan on having a variable threshold function as well that I suspect will be pretty interactive with either option.

[mordechai]

So here, on this 4316-based circuit, I've adapted the tone shaping on the input that Mark suggested earlier in the thread for the 4320-based circuit. I tried to work with values that fit the circuit, similar to but not exactly like the 4320-based one...this is the section circled in purple, which would be "pre" compression tone shaping.  The section circled in red is where one of the designers of the circuit suggested a similar tone-shaping sub-circuit could be added...a "post" compression tone circuit:



 

Not sure whether this would be best served by something similar to the "pre" sub-circuit, or if a simpler arrangement (maybe a variant of Mark's SWTC) would be useful.  How would you all approach this?