Ernie Ball VP Jr. Mod insight?

[Tuxedo3]

Hey guys, I'm working on a mod for the EB VP Jr. that gets rid of tone loss, similar to T1M and JHS (mine is way less refined than theirs). Anyways, the idea is simple, the board is basically 2 buffers for 1 input, one of the outputs is always on (tuner) and the other is controlled by a pot. When the pot is all the way one (heel up position) it sounds exactly how it should. But as the heel begins to go down there is a tad bit of hum/white noise that comes through the channel. When the heel is all the way down the only noise from the channel is white noise. I have pin 1 going to ground, pin 2 is the input to the buffer, and 3 is the output. Am I doing something incorrectly? I can provide even more detail if you'd like.

[m-Kresol]

did you check your output without the pot, ie. did you check your layout/pcb is working as it should other than that?

[Tuxedo3]

The output seems to be working well without the pot, it's a little noisy still. I'm not sure how to minimize that. For some reason it's much noisier when the pot is in an in between position.

[HamSandwich]

Care to draw a schematic?

[Tuxedo3]

Care to draw a schematic?

This is it, I used the Fuzzdog Spluffer as a template for a JFET buffer (since I use opamp in mine) and changed the in/out of buffer 1 to accommodate the pot. So the pads at the tops are labeled 1-3 on the pot.

[m-Kresol]

did you try to audioprobe the circuit to find where the noise is introduced?

one follow up question: in the heel up position when you got no noise... is this with or without playing? is the noise there when you have no input?

[madbean]

You don't need R1, R2 or R5 in this design and you may even be introducing noise through R2. Make R3 1M to 4M7 and it will work fine. Try breaboarding this schematic with the same value pot in your volume pedal and see if you get any noise. It'll only take a couple of minutes.

[madbean]

You can also try the volume pot at the input of the (my drawn) circuit. In that case you would use a 10k resistor in the R5 position (your schematic).