Octave Fuzz blend issues???

[11-90-an]

try inserting my ckt after C8 and C9... that *should* work...

What do you mean by ckt? The resistor blend configuration?

"ckt" is a shortcut for "circuit".
Yes, the resistor blend thingy.

[david1991ross]

I'll give it a shot and report back.

[antonis]

Still can't get your blending configuration..

You mix up octaved and clean signals and the sum (actually difference..) of them is again mixed with the same clean signal.. 

[david1991ross]

Still can't get your blending configuration..

You mix up octaved and clean signals and the sum (actually difference..) of them is again mixed with the same clean signal.. 

Do you have a suggestion to simplify while still using op amps?

[Ben N]

Your octave section is the same as Tim Escobedo's Octup Blender. Any reason why you didn't choose to also mix it the same way?

I've been modifying this schematic for awhile now and felt like I had success with not using the clean blend in the initial layout. I didn't want to have two pots and thought that I could just bypass the 500k pot in the schematic with a separate clean blend pot. Also I tried breadboarding it just now and got strange results. My LTSpice simulation confirmed my results.

If, as you say above, your goal is to be able to blend in varying amounts of octave-up with an always-on clean signal, then a pan pot is not the solution, because it simply varies the blend between the two sources. Instead, go back to the Escobedo, cut out the 500k pot (or turn it into a 470k-510k fixed resistor to ground) as you have done, and use just the 100k to blend in octave. No need for a pan pot, which doesn't do what you want anyway, no unnecessary mixing in of the clean signal at multiple points, as Antonis points out, just a fixed level clean with octave progressively mixed in or out via the diff-amp, and a nice, clean low-Z output without any more opamps or other tomfoolery.

If you are still getting octave bleed through even with the 100k at minimum, a suggestion: Flip the 100k pot around so that the octave signal goes to the wiper and the element connects to the coupling cap to the mixer; that way, when the pot is at min, the output of the octave is completely shunted to ground.

I suppose a buffer might help in keeping octave from bleeding back upstream, but that 10M feedback resistor ought to stop that from happening anyway, I would think.

[david1991ross]

Your octave section is the same as Tim Escobedo's Octup Blender. Any reason why you didn't choose to also mix it the same way?

I've been modifying this schematic for awhile now and felt like I had success with not using the clean blend in the initial layout. I didn't want to have two pots and thought that I could just bypass the 500k pot in the schematic with a separate clean blend pot. Also I tried breadboarding it just now and got strange results. My LTSpice simulation confirmed my results.

If, as you say above, your goal is to be able to blend in varying amounts of octave-up with an always-on clean signal, then a pan pot is not the solution, because it simply varies the blend between the two sources. Instead, go back to the Escobedo, cut out the 500k pot (or turn it into a 470k-510k fixed resistor to ground) as you have done, and use just the 100k to blend in octave. No need for a pan pot, which doesn't do what you want anyway, no unnecessary mixing in of the clean signal at multiple points, as Antonis points out, just a fixed level clean with octave progressively mixed in or out, and a nice, clean low-Z output without any more opamps or other tomfoolery.

If you are still getting octave bleed through even with the 100k at minimum, a suggestion: Flip the 100k pot around so that the octave signal goes to the wiper and the element connects to the coupling cap to the mixer; that way, when the pot is at min, the output of the octave is completely shunted to ground.

I suppose a buffer might help in keeping octave from bleeding back upstream, but that 10M feedback resistor ought to stop that from happening anyway, I would think.

This all makes sense, I'll breadboard it and see.