1 pot, 2 switches or vice versa?

[Tunathedog]

Hi

I'm new to the forum, so hello everyone and nice to be here. I've built a few kit pedals successfully and a non-kit pedal with less success. I can work a soldering iron and read resistor codes, but I really don't understand how electric circuits work.

Here's my latest project: I'm trying to stick two simple stompbox kit effects into the cavity of an old Korean guitar that used to have a bunch of built-in effects that eventually stopped working. (One day I'll try and get them working again, but that's not going to be any time soon.)

Both kits have one pot and an on-off switch; that's it (one's a linear power booster from Jeds, the other's a distortion from Musikding).

After using most of the existing switches for coil-splitting and phase-shifting, I have room for either one pot, to be shared between the kits, and two switches to turn them each on or off in series; or two pots and one switch that will allow me to choose either, both or neither effect. 

Any tips on which would be better, and/or how to wire them? And what kind of switch would I need to give me those four options, if I go for two pots?

Thanks!

[antonis]

Hi and Welcome..

Could you plz tell us the way previous effects are (was) wired..??
(meaning, 1 on - 1 off, both on, both off, etc..??)

[Kevin Mitchell]

You can source a pot that has a switch that goes open when the knob is turned all the way down. The only downside is that they are only single pole - single throw AFAIK.

Do you plan on bypassing these effects at all? That will determine what kind of switching you need.

Also, share the webpages for the circuits you'd like to use so we know what we/you are dealing with.

-KM

[MikeA]

Two pots, one switch would be most versatile and least annoying.  You can set the pots and leave them at the proper levels, rather than adjusting one pot every time you switch FX.   The switch type and wiring scheme depends on your answers to the previous questions from antonis and Kevin.   

[idy]

What about push/pull pots that allows you to turn them on and adjust them?
Then three pots (distortion gets gain and level, booster gets level) two have switches in them.

[Tunathedog]

Thanks for all your replies. I'm only now getting a chance to reply.

Kevin:
Do I intend to bypass? Ideally, yes, though the LPB can just be turned down to zero. 

Which effects?
   This one is already in and working: https://www.jedspeds.co.uk/product-page/lpb
   Probably want to add this: https://www.jedspeds.co.uk/product-page/muff-fuzz

For info, the power input is wired to a switching pot (right name?) - i.e. the volume pot goes down to zero then clicks the power off.

The LPB is wired to a slider switch, which toggles between on and bypass.

If anyone's interested, the original effects were a bit of a mix: There was an "effects on/off" switch, which could bypass the whole effects circuit. The next switch turned "echo" on/off, another switch turned "whirilwind" (phaser, I think) on/off, and one between turned "echo" into "tremolo" or "whirlwind" into "wah". All of these were affected by a pot called "speed". Finally there was "fuzz", which was either on or off. Very handily, there was both an amp out and a headphone out, but the headphone out had already stopped working by the time I got the guitar. I've now used most of those switches for in/out of phase and coil splitting on the different pickups.

What I have to play with now is one slider switch and the two round holes for ("speed" and "headphone out"). I don't want to drill any more in case I decide to restore the old set-up at some point.

Here's a pic of this model of guitar: https://reverb.com/uk/item/557255-1960s-kay-effector-vintage-electric-guitar-built-in-effects-bigsby-univox-japan
The Bigsby's an addition, and the pickups were single coil, despite the humbucker covers. (I've swapped in humbuckers.)

IDY, that's an intriguing idea. I'll see if I could feasibly use the switch hole for a third pot.

[Axldeziak]

I've been trying to make sense of the Kay/Univox Effector circuit for some time. (I just keep coming back to it.) If possible could you fill in some blanks? Below is an years old diagram of the circuit.

What are the values of the pots? Are the diodes labeled in any way? Can you confirm the values of the opamp and transistors? On the diagram, below the MC1445P, there is a track that leads to nothing, (Beneath the 1M resistor, and to the right of the 47nf cap.) On yours is anything there?
Any info you could add would be helpful.

[Tunathedog]

Hi Axideziak

Pots seem to be (through the old solder and rust) Speed: 100k, vol.: "A500k" (with switch), tone: "D500k"
The mystery track does indeed go to nothing. There's an empty hole in the PCB above it.
The transistors are as on the diagram (K49 says "K49 H283D").
Opamp: mine says "MC1458C / I / L8048"
The diodes are unmarked as far as I can see. I'm attaching a photo.


Hope that helps!

[Axldeziak]

Thank you for the info! I really appreciate you taking the time to look and take that close up pic of the diodes. Now I know at least two types of diodes were used, green striped, as well as red striped. (Most of the pics I've been going over for almost a year now look like they were filmed in Glaucoma-Vision so it's hard to see the details.)

If you don't mind, one more question. On the diagram, the Trem/Echo switch shows a loose blue wire. In the pics I have found it appears that it goes to one of the pickups. The other wire of the pickup seems to connect directly across from it at the contact where the orange O wire is shown. Can you confirm this? (In the pics I have the wire colors have blue/green reversed with green being connected where blue is shown in the diagram, as well as orange being white. I've also found red/white being used on the pickups.)

Thanks again!

[Tunathedog]

You're welcome!

Can't help you with that last question, though. I long ago disconnected the wires from the pick-ups and the solder on the board is so brittle that most of the wires  have fallen off (indeed two more did while I was looking at it this morning). I've got the board itself intact, but none of the wiring that connects it to the rest of the guitar. Happy to take more pics of that, though, if it helps.

[idy]

Note that the old LPB 1 was not wired to a toggle for bypass like a modern stomp, but the toggle also turned the power off and on, which would pop like a@#$% if retained.

The LPB-2 was in a stomp box and had both the toggle and the footswitch.

[Axldeziak]

I've got the board itself intact, but none of the wiring that connects it to the rest of the guitar. Happy to take more pics of that, though, if it helps.

If your willing to take pics I don't think anyone would be adverse to seeing them. Especially since your board appears to be different from any others posted. (It's the first I've ever seen to have red diodes and caps.) I know they used a crayola box of random wiring colors, seemingly whatever they had in stock at the time. But it makes me wonder if perhaps yours is an early, or late edition. Something outside the general production run.

[Tunathedog]

Here you go!

[Axldeziak]

Thanks again for posting pics! It's very much appreciated.
Hopefully now I can complete my layout for all this!

[Mark Hammer]

Seeing what your inserted circuits consist of, I will suggest the following:

• a volume pot for the booster
• a push-pull volume pot for the Muff
• a 3-way toggle for treble cut on the Muff

You can set the booster for something closer to unity gain, OR use it to push the fuzz harder, circumventing the need for a gain control on the fuzz.  The harder you push the fuzz, the more you will need something to mellow the tone of it, at least a little.  The fuzz is unlikely to ever be clean, however, requiring some sort of bypass should you actually want a clean tone, whether of itself, or simply to push some other effect.  So the fuzz volume control should have some accompanying switch that will allow it to be bypassed.  Doesn't HAVE to be true bypass, although I imagine that would be "cleaner".  If you can find a 100k volume pot with a SPDT switch on the back, that lets you tap the output either off the booster volume pot (which remains hard-wired to the input of the fuzz) OR off the fuzz volume pot.

The tone-toggle should strap in a feedback cap in parallel with the 470k feedback resistor in op-amp 1.  Adding in 68pf, gets you a rolloff just under 5khz, while strapping in 150pf gets you a rolloff just under 2.3khz.  The 3-position on-off-on toggle would get you stock (no treble cut) or either of the two other rolloffs.  If you find the stock sound too fizzy - especially when you push it - consider putting 47pf in parallel with the 470k feedback resistor, and using the toggle to add onto that.

[Tunathedog]

Thanks, Mark! Should keep me busy. Hope you're enjoying the holidays.

[Mark Hammer]

I'm retired. EVERY day is a holiday.   But thanks.  Enjoy yours.