Another Sansamp GT-2 oscillating like crazy

[therecordingart]

I've built four of these now and two oscillate like mad on high gain settings. The differences between them is the quiet ones don't have bypass switches. I'm guessing those extra runs of wire are doing it?

Any ideas on killing oscillation? There aren't any ground loops because my non-isolated DC jacks turn my enclosure into my ground plane for my non-insulated input/output jacks. When I start poking around I can kill the oscillation by touching the tip connection of the input jack, but it's difficult to play guitar doing that. When pushing wires around I can hear some variations in the oscillation, but with 40 wires coming from that board it's difficult to narrow down where to move them.

[PRR]

> oscillate like mad on high gain settings. .... bypass switches.

Do NOT bring the output and input of a HIGH-gain amp "near" each other. It will oscillate.

Obviously bringing Out and In to the same half-inch switch is a "bad idea".

Play with the Out and In wires. Run them away from the switch in opposite directions. Change the IN wire to shielded, shield to PCB Ground near In point. Add 470pFd to ground on the Input jack. Swear, cuss, and rip-out the bypass, use two relays one at each side of the box.

[therecordingart]

> oscillate like mad on high gain settings. .... bypass switches.

Do NOT bring the output and input of a HIGH-gain amp "near" each other. It will oscillate.

Obviously bringing Out and In to the same half-inch switch is a "bad idea".

Play with the Out and In wires. Run them away from the switch in opposite directions. Change the IN wire to shielded, shield to PCB Ground near In point. Add 470pFd to ground on the Input jack. Swear, cuss, and rip-out the bypass, use two relays one at each side of the box.

Awesome! Thank you very much! I got the swearing part down to a science. I'm dreading the day that my 17 month old daughter stomps through the house mumbling swear words to herself like daddy does when he is building stuff. 

[therecordingart]

> oscillate like mad on high gain settings. .... bypass switches.

Do NOT bring the output and input of a HIGH-gain amp "near" each other. It will oscillate.

Obviously bringing Out and In to the same half-inch switch is a "bad idea".

Play with the Out and In wires. Run them away from the switch in opposite directions. Change the IN wire to shielded, shield to PCB Ground near In point. Add 470pFd to ground on the Input jack. Swear, cuss, and rip-out the bypass, use two relays one at each side of the box.

Bypass switch was the culprit. I ended up ripping it out for the time being because right now I have a crazy toddler that wants to play anytime I sit down with a soldering iron. Thank you for the help. Another lesson learned.