Sustain Problem Fuzz Pedal Design

[antonis]

Thanks so much for catching that error on the filter with R20 to ground after the tone stage. That makes sense that it should rather be connected to the virtual ground of 4.5V than genuine ground. I will make that change.

I'd make output amp stage a non-inverting one..
Both for in-out signal phase compliance and more easy gain calculation..

[duck_arse]

On that isolating cap suggestion, my thinking was that no DC current could flow because of the capacitors in the tonestack and the coupling capacitor after the tonestack, so I thought an isolating cap after U3 would have no effect. Am I missing something there?

hrrnngggg. not so. follow, from opamp out, R13> R16> R15> R14 and ground. it is generally considered to not be a problem, millions of big muffs can't be wrong, right? but well we do do it proper hereabouts.

[camzilla]

hrrnngggg. not so. follow, from opamp out, R13> R16> R15> R14 and ground. it is generally considered to not be a problem, millions of big muffs can't be wrong, right? but well we do do it proper hereabouts.

Ohhh, I see now. Thanks! It does seem to work fine but there's no reason not to shave off a few milliamps of dc power consumption.

I'd make output amp stage a non-inverting one..
Both for in-out signal phase compliance and more easy gain calculation..

That totally does make sense, but I think I'm gonna let laziness win this time since I've already started the pcb design LOL

[antonis]

there's no reason not to shave off a few milliamps of dc power consumption.

A few tens of microamps (μA), I'd say.. 

[Fancy Lime]

Power consumption isn't the issue but DC across pots *can* make some pots go all scratchy-scratchy when you turn them. No biggie for the tone pot because there is no massive gain after that point but as Duck said, we do do it proper hereabouts (which is my new favorite quote and will be posted on my office door first thing tomorrow morning). This sort of thing is much more relevant for gain pots, though.

Andy

[duck_arse]

posted on my office door first thing tomorrow morning.

Andy

done properly, we need a photo.

[pacealot]

For what it's worth, I added it to my sig line alongside idy's words of wisdom concerning bandwidth, if that helps!

(Narrator voice: "It did not, in fact, help...")