axe grinder

[Gus]

I looked at PAiA web page before this post to see if the Axe Grinder was still being sold.
I like how it does the mixing of the clean and distorted waveforms.
The schematics I find on the web seem to be missing an output coupling cap and a pull down resistor because the output look like it at about 4.5VDC.
I would change the switching to true bypass DPDT or 3PDT and an opamp change to more modern duals and remove the quad switch IC.

This looks like fun circuit to build and maybe adjust HP and LP frequencies


https://archive.org/details/JL11343

[PRR]

> an output coupling cap

John Simonton pinched pennies. "Most" inputs have blocking caps, so you may not need output caps. Now that caps are cheaper than potato chips, I agree you may as well do the right thing.

Same for your other classy changes: opamps and switches. Though more for simplicity than "clean sound".

[Mark Hammer]

Here you go.  The circuit cleaned up a bit, with added parts.  Younger viewers should remember that, when the circuit was first conceived, DPDT stompswitches were expensive and not as widely available.  And 3PDT switches were "available" but practically science fiction in the minds of pedal-makers, not to appear for well over another decade.  So, the CMOS switch inclusion was a sensible step.  And, although nobody really made use of it, much like the FET/flip-flop switching in the Boss and DOD pedals, it lent itself to remote switching very easily.

[duck_arse]

should there be a cap at M for the clean level pot?

[Mark Hammer]

I don't know if it would be required, but if it were my build, I'd move C11 from where it is to where the M indicator is.

[antonis]

That would result into DC roll-off less than unity on IC1D output, Mark..
(practically no big deal, but dunno..)

[Mark Hammer]

That would result into DC roll-off less than unity on IC1D output, Mark..
(practically no big deal, but dunno..)

Then simply add one there and leave C11 in place, to mimic what is in place, with C7 and C9.

[Gus]

Looking at the schematic Mark posted

The schematic looks like a good starting point for a bass distortion

For a bass distortion I would reduce C2s value. A first value to try would be .01uF or even lower in value so the lower frequencies don't get clipped as much.
I would also reduce R1 and R2 in value to pairs of 1meg to 2.2meg resistors
I would also use two dual opamps and use a FET input one at the input to the effect.
You could also adjust the low pass filter tone cap value.

More can be adjusted but the above would be a good place to start

[Mark Hammer]

All very good suggestions.  I would only add maybe a small value cap in parallel with R17 to keep any hiss manageable.  I don't expect the circuit itself to be particularly hissy, but it IS applying gain to the input signal, and even small amounts of hiss in the input signal can become objectionable if amplified.

There have been several clean/dirty blend pedals over the years.  The Voodoo Labs Sparkle Drive is probably the best known, but long before it, there was the Maestro FZ-1S fuzz, that included a dual-ganged pot for changing the blend of clean and fuzz.