Adding SWTC

[rocket88]

so i'm working on a circuit design that to some extent is a modified fuzzface, and one of the things i want to do is add a SWTC right after the fuzz circuit, so the output cap goes right into the SWTC. my question is that according to AMZ the SWTC uses a 100k pot for both the tone and volume, but the normal fuzzface has a 500k pot for the volume. should i use a 500k or 100k pot for the output? the other thing is, according to jack there is such little volume loss that i wouldn't need to add a gain recovery stage before the output, should i just plan on adding one like the LBP anyway?

[Frank_NH]

I added the SWTC2 (the version which is both a treble cut and boost depending on the tone pot position) to a Crunch Box and it worked really well.  I used Jack Orman's stated values for the resistor, pot and cap values, but you can experiment.

One thing I have always wondered about with Volume pots is how a specific pot value (e.g. 100K) is arrived at for a given circuit.  I found some useful information here:

Beginners' Guide to Potentiometers

Specifically, it states:

"The source impedance should normally be no greater than 1/10th (0.1) of the pot's stated resistance. Further, the load resistance or impedance should be 10 times the pot's resistance to prevent the taper from being adversely affected. You may (of course) be deliberately loading the pot as described below, but the following stage must still present a high impedance unless its impedance has been included in your calculations."

Pot values like 100K apparently satisfy this requirement for many effects circuits.

[rocket88]

thanks frank. i'm planning on using the SWTC2 as well, in fact i'm using the same treble cut/treble boost, but in the application you used it in the output pot was already 100k, while the fuzzface its 500k. i'm not sure what a difference it will make changing the pot value will make. the goal is that i want just to add a tone control without changing anything else about the circuit.

[Frank_NH]

I would go ahead and try the 500K pot in the SWTC2, leaving all else the same.  I don't think the tone circuit will greatly affect the volume.  Let us know how it turns out!

[rocket88]

i'll give it a shot. just to make sure what i've done makes sense. here's a schematic of a fuzzface with the SWTC2



and resulting layout



they look like they match to me. but can i run the jumper between tone 3 and volume 3 ? i figured it would be easier to do that then have them actually connected. also, since tone 1 and fuzz 2 are on ground can i just have a jumper like i put in?

[Frank_NH]

I believe your design will work fine.  The 500 K pot is in parallel with the 100 K tone pot, so you may want to try a linear pot versus audio, but a lot of these things are a matter of preference so use what you like.

Also, let us know how this sounds.  I haven't built a fuzz in a while and this looks like a nice circuit (I stopped making fuzzes after building a Univox Super Fuzz clone )...

[rocket88]

i hear ya frank, right now i'm just buttoning up a modified small clone, i just have to run out and get 2 resistors i'm missing, so cross your fingers it fires right up. that layout is crazy, i'm praying its good.

the layout i posted is just a normal fuzzface with an added SWTC2, but not what i'm working on. what i've got should be a little more nasty and heavy, i'm just waiting for some new transistors to come in, since the ones i have on the effect without the SWTC2 are rare and stupid expensive for mean because i can only find them overseas in spain, so shipping makes $3 transistors like $8-10 .