Question about Pot values

[matmosphere]

Noob Question here. I'm building an Em-Drive. I've used my friends a bit and liked it but after the gain was up past noon I wasn't into how it worked with some of my other pedals. I tried to replace the gain pot with a 100k Alpha so I can tweak the sound just in that range, but I'm not getting anything when the circuit is turned on. Clean signal is working fine in bypass, but nothing at all when the pedal is on. Is there some reason this substitution isn't working, or do I just have some other issue? The circuit itself is insanely simple and I've double checked all my off board wiring. The only other thing I could think of is it could be an issue in the ground wiring. Both the board and Volume 1 are supposed to be grounded (which I haven't encountered before) I currently have them both connected at the dc input jack. Is grounding there causing the circuit to be incomplete? Is there some reason one or both would need to be connected at the guitar input jack? I have seen both ways on standard off board wiring diagrams and didn't know if there were instances were only one way would work. Wow, I think it took me longer to type all of this than it did for me to build the board.


http://tagboardeffects.blogspot.com/2013/01/emerson-custom-guitars-em-drive.html#comment-form

[Hemmel]

This might seem obvious, but just to make sure :
- Did you connect Volume 1 to the "sleeve" part of the input jack ? Volume 2 should go to output and volume 3 from one of the 100nF caps.

It's not unusual to see ground connections from the board to input/output jacks. As long as they're connected to the DC ground as well.

[matmosphere]

Thanks, I actually have volume 1 connected to the DC jack. Does it have to be connected to the sleeve of the input jack?

[Hemmel]

Thanks, I actually have volume 1 connected to the DC jack.

Make sure Volume 1 isn't on the 9V+ lug of your DC jack.

Does it have to be connected to the sleeve of the input jack?

Not if the DC ground jack is also connected to the sleeve of the input jack. DC jack ground creates reference point, that you can connect anywhere you want/need to. This can include the sleeve of input and output jacks, and most of the time, the first lug of a volume pot.

[slacker]

All the points that are ground need to be connected to each other, so in this case the sleeves of the input and output jacks, the negative of the the DC jack, the ground wire from the vero board and lug 1 of the volume pot. How you connect them together doesn't really matter for simple circuits like this, so long as they are all connected.

Using a 100k gain pot instead of 250k will work fine. The gain increases as the resistance of the gain pot decreases so using a 100k pot will just reduce the minimum gain.