high gain = big problem

[Dimitree]

Hi guys
I've a strange problem on 2 pedals I built. Both have a lot of gain: one is a FA1 clone, so a lot of clean boost, and the other is a pedal that I've designed, nothing special, even here there is lot of gain (but different design than the FA1), something like +30 voltage gain, and I'm using a LT1054 that gives me +16V and -14V, while in the FA1 I'm using standard 9V.
both pedals works well, but, when in bypass (true bypass with DPDT), there is a high pitch noise, really audible over the bypass signal.
In the FA1, this happens (in bypass) when I set the volume pot over 12h. then the noise comes in, and if I move the treble pot, I can change the pitch of the noise.
In the other pedal, more gain I set, more noise I have. If I set to lower gain, the noise is less audible and then disappear.
If I unplug the power, the noise disappear, and the bypass is now clean.

why this could happen? I don't know what to check. I've tried both with my power supply and a fresh 9V battery, same results.  

[trendyironicname]

I'll look over the schematic when I get home and if no one else beats me to it, try and walk through it.  Step back through everything you've got hooked up to "ground."  If you have the bypass wired right, that's the only point of injection for you.  the fa1 was the belt booster thing, right?

[Processaurus]

If the inputs to your high gain effects are left floating, in a true bypass switching arrangement, they will often oscillate, and be picked up by the bypassed signal, just by being in the same box. 

The solution is to ground the input in bypass, either with the footswitch, or in a solid state way with a FET, transistor, or analog switch (if a pack is already being used), if it isn't possible with your mechanical bypass switch.

[Dimitree]

ok so the problem could be this one?
I should try to ground the effect when bypass. The only problem is that I have pcb mounted switches, so I need to find a way.
btw if this is the solution, it is a good new! I thought it was something else
thanks