the "skunk" project v2 schematic

[Steben]

Cheers,
I'm hoping in constructing a device like this in the near future:



Diode 1 is germanium. The pair of diodes schottky. The bullet holes stand for a socket, to experiment mwith other combinations.
With "voice" towards bass and right tweaked trimmer at the diode, I'm hoping to emulate a Fuzz Face. If you toggle the voice you can sweep from treble boosted overdrive back to wooly fuzz.

[Mark Hammer]

Interesting that you have a tone control before the clipping section.  There was an earlier pedal by Maxon that used essentially the identical circuit to a TS09 except that the tone control section preceded the clipping section instead of coming after it.  Your idea is somewhat similar except that you have a tone control after as well.

One very critical aspect to pay attention to is that the BMP-style tone control that you use suffers substantial signal amplitude loss as you sweep towards the treble side.  That will have big implications for how much gain you'll need in the clipping section to actually produce clipping from those diodes.  Of course, I'm saying this without any notion whatsoever of the component values chosen.  It may well be that your component values in the pre-clip tone stage just move a notch around a little rather than producing wooly-through-to-nasal like a BMP control.

In general, though, nice idea.  Kind of like that Akai unit with the 7-band pre-clip graphic EQ and and the 7-band post-clip EQ, except with a much lower parts count and fewer knobs to get lost in.

[Steben]

Thanks for the reply. It makes you wonder why there are no values chosen yet, right? 

The pair of biasing resistors in front of the opamp would be rather high (1M), so that makes the loss less harsh.
I think you suggest between the lines to chose an EQ response without a mid notch, which would be the case. I guess an as-simple-as-possible-device has no need for a pre-gain notch.

[Mark Hammer]

Yeah, I guess my insinuation is that the low end rolloff of the highpass section be noticeably lower than normal so that you don't suffer too much amplitude loss as you turn the "voice" control treble-wise.  That just requires a slightly large cap value on the treble side to correct things. 

As many folks have learned from their various fuzz builds, it doesn't take a huge amount of bass rolloff change at the input to alter the character of a distortion.  What that also suggests is that perhaps you may want to augment the "voice" pot with fixed resistors at one or both ends so as to productively constrain the amount of shift in input spectral content.  E.g., if the plan was to use a 100k pot, then use a 50k with a 22k or 27k on each end, or maybe even a 50k with a 33k on one side and an 18k on the other.

Finally, Jack O's articles on the BMP control is well worth reading for ideas about how to use it to introduce mid peaks as well as notches and rolloffs.

[Steben]

Finally, Jack O's articles on the BMP control is well worth reading for ideas about how to use it to introduce mid peaks as well as notches and rolloffs.

indeed. the article that started it all actually...

Another thing maybe: could it be the feedback diode can be omitted to implement Joe's soft compression opamp? or both? Iguess the compression opamp features a more transistorlike responsecurve?