Replacing knob with switch?

[THRobinson]

Hey guys... I have a kit for a one-knob fuzz pedal, and wondered, can the pot be replaced with a 3-way switch? Basically OFF-50%-100%?

I have a Synsonics Terminator that I'm upgrading (ya I know... why? well... why not?) and it has a built in amp. Playing with the idea of adding the Fuzz to the amp and just a 3-way mini toggle because of space.

That something doable?

https://www.taydakits.com/instructions/one-knob-fuzz

[antonis]

https://www.taydaelectronics.com/electromechanical/switches-key-pad/toggle-switch/mini-toggle-switch-dpdt-on-on-on-mts2033.html

Read post #14 (Rob Strand) about wiring: https://www.diystompboxes.com/smfforum/index.php?topic=92705.0

edit: Do you wish to replace VOLUME pot..??
If so, you may do it with SPDT (ON-ON) switch with OFF setting for effect by-pass..

[RickL]

It's doable, but if all you're concerned about is space, why not just use a 9mm pot? They're no bigger than a dp3t switch, which is what you'll need if you're replacing a volume pot. And no more expensive.

[THRobinson]

@antonis kinda, I guess the volume adjusts the fuzz level? For this guitar I don't need a lot of adjustments... Figured a switch would work but, yeah those 9mm pots are quite little, though the top of the guitar would look odd with another knob added given how they're spaced.

[RickL]

Based on the link you provided, the pot controls volume. The amount of gain/fuzz/distortion is fixed. I think you're also going to want a bypass switch, unless you want the fuzz always on. If you just turn (or switch) the volume down to  zero you won't get sound out of it. If you only have one place to put a switch or pot, you could replace the pot with a 500k (or 470k) resistor (put it where lugs 1 and 3 of the pot would go) and take the output from the end of the resistor that connects to C4. That should be the end closest to R1 on the board. You might also get away with just taking the output directly from the same place without the resistor.

This will set the volume to 100%. Send the output to your bypass switch. You'll have to control the volume with the volume pot on the guitar, but watch out. When you activate the effect, it's likely to be way louder than it was when it was bypassed.

If you have room for the pot they supply and enough depth in your guitar you could replace the pot with a push-pull pot of the same value (500k log). Wire the switch on the pot as your bypass switch. You won't need an LED because the up/down position of the pot will indicate the switch's status.

[antonis]

@antonis kinda, I guess the volume adjusts the fuzz level?

No..
(RickL already answered..)



Fuzz "level" (actually, Gain) is set by R2/R3 NFB configuration..
For making it variable, you must make one of them variable, also..
The easiest (and more practical) way is to deal with R3 making it AC variable (for not altering bias) by replacing it with an equal value pot and connect C3 to its wiper, instead of its upper leg..)

[THRobinson]

Hmm... sounding more like a "don't bother, just make a pedal" situation.

[GibsonGM]

For understanding that, I will give you your 2nd "Like"    Worth thinking about, though.  One day it may turn into something cool that you will build.

[THRobinson]

Yeah, there are a few guitars from the 70/80s that had the built in effects, but also more real estate to work with. This is a 3/4 size guitar, thinner body, plus a 3" speaker in the way. Was an idea but... maybe another project.

[aron]

If you hand wire it, the circuit could be really small.

[THRobinson]

I wonder if the board itself can be distorted?

It's been years but I remember looking at the Smokey/Ruby amp (which I have the parts for but also never had the chance to make) and I remember looking at the notes that if you connected it one way to the main IC it was clear, and if you used a different pin it was distorted... I always planned to built it with a mini toggle switch to switch between the two.

Tried finding schematics for the guitar's amp board but never had much luck.

[nocentelli]

I wonder if the board itself can be distorted?

It's been years but I remember looking at the Smokey/Ruby amp

Why not open it up and take a few pictures of the board? There is a good chance the amp is just based on the same 386 chip as the ruby/smoky so connecting  pin 1+8 would give a large gain boost and substantial fuzz. If it's not 386-based, people might well be able to trace it from decent pictures and suggest how to mod it.