Question: vol pot value adjusting for a handbuilt pedal with too much output.

handsomerik

I've built a boiling point clone using the jmk pcb. It has too much volume available. Unity vol is at less than 9 o clock. Because there's so much vol on tap it makes tiny adjustments not easy and if you catch the knob even slightly with your foot you get a huge volume boost. 

Is there a way to tame this to lower the total output of the volume knob and bring unity to nearer 12 o clock. 

The value of the pot is 100KB. I have already tried switching it our for a 50KB and was surprised that it made very little difference.

randomhandclaps

Yes. An inline resistor prior to tab 3 of the pot or after tab two, prior the the footswitch. If you can fit one in a variable resistor with obviously allow you to tune it to perfection. 

With a standard in, out, ground board volume setup the size of the pot makes no difference to the volume range, it would usually just effect treble roll-off through the range.

handsomerik

Thanks a lot @randomhandclaps. I'm still a little unsure though. Do you mean to put a resistor inline in the wire that runs from the pcb to lug 3 of the vol pot?

Or do you mean to put the resistor between lugs 2 and 3 on the volume pot?

Or something else?!

What value resistor would you try with this circuit?

Here's the build doc if it helps:
http://jmkpcbs.com/wp-content/uploads/2014/03/Steaming-Kettle.pdf

Thank you for your advice

randomhandclaps

Yeah, you got it with the first one. It can be either a resistor inline from the board output wire to tab 3 (leaving tab 2 untouched) or as presumably you've already solder the pot and board up I would be more inclined cut to the the wire going from tab 2 to your footswitch halfway along and insert the resistor there with the aid of a bit of heatshrink to shield it. That way there will never be any strain on the resistor wires (which tend to give put with to much movement) and you don't have to desolder and resolder stuff you have already done. The other bonus is that once you have the wires stripped you can experiment with winding in different values until you're happy and then solder it in. Guessing the right value is tricky at a distance but I would start with 10k and see where that gets you.

handsomerik

@randomhandclaps
But the wire to the switch doesn't go from volume lug 2 like it would on a vero build. There is a wire that goes from the output on the pcb to the switch. Would that be the effectively the same thing and could I put the resistor into that wire?

Thanks

randomhandclaps

Yeah mate. Just do it exactly the same but to that wire.

handsomerik

@randomhandclaps Ok. Looking at the schematic on the build doc the middle lug of the output wire doesn't go directly to the output tab. There seems to be some circuit in between. Is this ok?

randomhandclaps

I've just had a chance to look at the schematic. Yes just ignore where the volume is and put the resistor inline with the wire going from the board to the 'effect out of the foot switch. Alternative you could increase the value of R15 as it's performing the same fiction albeit just prior to the boards output filter. To avoid damaging (especially whilst experimenting with values) the board though I'd go with inline on the wire.

ICBM

You need the resistor *before* the volume control not afterwards (ie between the circuit and the volume pot, not between the pot and the switch), or it will make almost no difference. Try 220K or 470K first.

handsomerik

@ICBM you mean on the wire that runs between the pcb and lug 3 of the vol pot?

ICBM

handsomerik said:

@ICBM you mean on the wire that runs between the pcb and lug 3 of the vol pot?

Yes.

ecc83

Personally I would just make up a 2 resistor attenuator AFTER the pot, values in keeping with the pot value.

Introducing a simple series resistance will cause HF loss if any decent length of cable is used.

Then again! I could be looking at the wrong schematic! OP, care to post the one you are using?

Dave.

juansolo

If you're just wanting to change the taper of the pot and move where unity is, and make the lower setting require more movement, stick a A100K in. If I've got that the wrong way around and everything now comes on instantly, it wanted to be a reverse log pit C100K

This of course won't change the ultimate output of the effect, but it should make the vol pot behave better. Just don't dime it.

simonbeckwith

@handsomerik On the back of this, is it possible to reduce the amount of gain available from a dirt pedal. I like the overall tone available from the Carl Martin plexi tone single channel but it has way too much gain. I run it barely at 9oclock if that helps?

handsomerik

I wouldn't know how to do this sorry. Maybe start another thread and see if someone wiser pipes up!