I'm building a fuzz for a secret santa I do on another forumm..

[nightendday]

And it's for a good friend of mine that I bought my first mudhoney vinyl from. AWESOME dude.

What I want to do Is have a heavily modded Big muff, and a superfuzz in paralell. With a highpass/lowpass switch for each fuzz and a blend knob to blend the two.

I have the muff and superfuzz built and have the outputs wired as such for blending.

muff output - lug 1
superfuzz output - lug 3
pedal out -luge 2

How can I set up the switching for the filters and what would be the easiest way to build them?

[ashcat_lt]

The Big Muff has continuous fading between high pass and low pass on a pot.  Is there some reason you also need a switch?

[nightendday]

The Big Muff has continuous fading between high pass and low pass on a pot.  Is there some reason you also need a switch?

Well, since i want it on both... there's that.
BUT I'm looking for something more pronounced. like a 3 way toggle so that middle the circuit is left alone top bass is gone from pedal, bottom top end is gone from pedal. Almost like a biamping kind of setup.

[nightendday]

any ideas fellas?

[petey twofinger]

man that sounds cool !

[WaveshapeIllusions]

Easiest thing to switch around would be a state-variable filter. LP, BP, and HP outs. The dowside is that it takes 3 opamps, so I'd suggest using a quad chip. I don't know where you want to put it though. My suggestion, going off of your biamp comment, would be that a switch determines which side gets the LP and which gets the HP, with the filtering before the fuzz. Maybe use a rotary so one position bypasses the filter section.

Hope this helps.

[nightendday]

http://www.muzique.com/schem/filter.htm

I'm thinking about this setup?

6-6db/octave, and i can choose the frequency, and it's simple.

[WaveshapeIllusions]

Yeah, that would work well. Just make sure to drive the filter with low impedance so the cutoff frequency is accurate.

[nightendday]

Yeah, that would work well. Just make sure to drive the filter with low impedance so the cutoff frequency is accurate.

forgive my ignorance, but how could I ensure this?

[nightendday]

also, I'm in WAY over my head with this. 

But, I want to bypass both volumes and run a master volume. How in the hell do I do this. 

[WaveshapeIllusions]

Low impedance in this case just means to put a buffer before the filter. Are you putting the filter before or after the fuzz circuit? If it's after, you have nothing to worry about. If before, just use a jfet source follower to isolate the filter. Though it could interact with the pickups nicely... but the results are more consistent if you isolate it.

To run a master volume, just ignore the output volumes on their respective circuits. Use just one volume pot of the same value. Are you still planning on using the blend knob too? In my experience, the way you have it set up serves as a mixing resistor pretty good. You might want a small resistor on each fuzz output though, maybe just 100 ohms. You might want to add another gain stage after mixing depending on volume.

Also, I suggest making sure that the signals from each circuit add together in phase. Common emitter transistor circuits (basic gain stage) shift the phase 180°. Odd numbers will invert the phase, even will send the output in phase with the input. It's not normally a problem, unless you're mixing circuits. Then if they're out of phase things will cancel and sound weak.

The big muff has 4 gain stages, so it sends out the signal in phase with the input (assuming you didn't add or remove any). It looks like the superfuzz has 4 too, so it shouldn't be an issue. If things sound weak though, add another common emitter stage to one (unity gain is fine) and see if that helps.

Hope this helps.

[nightendday]

Low impedance in this case just means to put a buffer before the filter. Are you putting the filter before or after the fuzz circuit? If it's after, you have nothing to worry about. If before, just use a jfet source follower to isolate the filter. Though it could interact with the pickups nicely... but the results are more consistent if you isolate it.

To run a master volume, just ignore the output volumes on their respective circuits. Use just one volume pot of the same value. Are you still planning on using the blend knob too? In my experience, the way you have it set up serves as a mixing resistor pretty good. You might want a small resistor on each fuzz output though, maybe just 100 ohms. You might want to add another gain stage after mixing depending on volume.

Also, I suggest making sure that the signals from each circuit add together in phase. Common emitter transistor circuits (basic gain stage) shift the phase 180°. Odd numbers will invert the phase, even will send the output in phase with the input. It's not normally a problem, unless you're mixing circuits. Then if they're out of phase things will cancel and sound weak.

The big muff has 4 gain stages, so it sends out the signal in phase with the input (assuming you didn't add or remove any). It looks like the superfuzz has 4 too, so it shouldn't be an issue. If things sound weak though, add another common emitter stage to one (unity gain is fine) and see if that helps.

Hope this helps.

Some of that was over my head,  but yes, it did help alot. I was thinking of bypassing the volumes and and doing exactly what you just said. The blend knob is mostly there to blend how much of each fuzz you want. so that it can be run all muff or all superfuzz, if wanted, OR more or less of each. I thought putting the filters after would be best, looks like that worked out to my benifit. I'm assuming I would place the filters inbetween the boards and the master volume? How could I bypass the volumes on these two layouts?

I'm assuming that being that the muff is 100k and the superfuzz is 50k on the volume, I would use the 100k value.

[WaveshapeIllusions]

For the Big Muff, take the output from volume 3 into the filter section. For the Superfuzz, nix the balance pot and connect the wires that would have gone to pins 2 and 3. The filter sections would be before the blend pot. I'd suggest using a 50k or 25k for blending, one should give a good range. Lower values might increase the chance of bleed between sides when panned hard either way; higher values will have more volume drop in the center since half the pot's resistance is in line with each signal. I would suggest adding a gain stage prior to the master volume though, to make sure it blends evenly and to raise the signal after what the filters and blend cut out.

You could also use a dual-ganged blend pot, 50k/50k lin would work well. With those the resistive element is only on half the rotation, so at center there is no resistance in series with either signal. Panned either way, one pot starts shunting more to ground while the other leaves it at full level.

You'd probably want to have each fuzz on its own board, and then a small one for the filters and the output. I think 50k would suffice for the master.

[nightendday]

so really, I could just build the 4th stage of the muff again as my final buffer, and have the master volume after that? correct? You're a freakin saint. I love this board.

[nightendday]

So, lug 2 of the mix knob into the in on this, then the out to lug 1, lug 3 to the ground, and lug 2 is circuit output. Right?