How would you add a blend knob control to a Fuzz Face?

[bushidov]

Hi All,

So I made a Germanium NPN based Fuzz Face that I am very happy with. But I'd also like to make one for my Bass. Like a lot of "bass" effects, I'd like to add a clean blend mix pot into the circuit, but this is where I know things get messy.

I know that when you put a buffer behind a fuzz face, it messes with the sound a lot, but at the same time, most "bass" effects that use a blend knob typically use op-amp buffers to spit off the sounds, creating a dry and wet signal. But I can't use an op-amp buffer because of the "messes with Fuzz Face circuits" issue.

So, how could one make a clean mix to a Fuzz Face circuit, but retain the fuzz face sound/tone/etc? I've seen some posts here on DIYStompboxes, but it usually leads to dead links and images, so no real good examples that I could find easily.

Any suggestions?

[Quackzed]

i'd think input- big cap- blend pot- output (after vol pot) at high fuzz volume settings itll squeel as your taking the fuzz output and feeding it back to the input but it might be fine at normal volume setting. if not try a 10n to ground between the big cap and blend pot. might behave...

[bushidov]

So, I tried it with and without the 10nF cap to ground. Neither made much difference.
Here is my schematic (although I didn't use 2N5088's, but rather Germanium NPN Transistors with relatively similar hfes:


So when I did this, there was a lot of squeel/shrill that didn't disappear until I had it fully over to the clean/dry channel on the blend pot. In the middle (50/50), I got some fuzz and maybe some clean, but the volume dropped a ton. When fully maxed to fuzz, my once full and beefy fuzz was thin, shrill, and lost a lot of bottom end and mids.

I've tried something like this before and found this doesn't work. But I don't think I tried the 10nF trick, so I thought for a moment that might have been the magic bullet I missed last time, but alas, no that doesn't work either.

So, how do we make a blend pot actually work on a fuzz face style circuit?

[soggybag]

I think you need to buffer the signal from the input to the blend knob. Imagine an LPB-1 in between.

Without it there is a path for the output back into the input through the blend pot. It's going through the resistor but its a feedback path.

[Psychophonic]

I recently bought 3 Arbiter germanium FF clones from a guy. They have 3 knobs, which struck me as odd. The one pedal I've tried so far sounds great. I'm thinking the third knob is a blend. I can take a gut shot if it helps at all.

[bushidov]

Hi, I think I got a solution to the problem.

I think you need to buffer the signal from the input to the blend knob. Imagine an LPB-1 in between.

I found a schematic for moosapotamus's 360 Fuzz, which is I guess a take on the Acoustic 360 Bass Fuzz?


Anyways, in lieu of what soggybag quoted, this schematic idea seems to apply. Putting an LPB-1 type circuit in parallel with the Fuzz Face and then using two 10K resistors to tie them back together does make the "volume knob" of the LPB-1 into what could be called a "blend" knob. It's not blending the clean and wet signals, so much as it is injecting clean signals into the wet signal. I do get a volume drop because of the 10K resistors, but the tonal qualities do appear to remain, so I think this is a winner.