Effects oscillation while unplugged

[step]

Hi guys, I've built a few veros and in some of them (OCD, Timmy, etc.) I have the same problem again and again. Effects work OK as expected but when I unplugg an input cable, there is a high pitched oscillation generated by the circuit. It happened first on my OCD so I did the same circuit for the second time and it behaved the same. It's not adaptor problem - is the same with 9V battery. I thing is some kind of systematic fault. Any idea?

The only component I use in other type than the most of you are the nano values caps (foil). I can't get exactly the type most of you use, so I use WIMA type - boxed foils (http://www.wima.com/en_index.php).

Can the cap type be the problem? Or some kind of bad wiring? Grounding? IC's oscillations?

Thank you a lot for the job you do here!

[boratto]

I´ve got this same problem with the rat 2 circuit.

[induction]

Oscillation can sometimes be caused by capacitance in the wiring. Does it go away with a cable plugged into the input? Open up the pedal and move the wires around while it's oscillating. Any change?

[step]

If the cable is plugged into the input, there is no problem, no oscillations - strange.

I'll try if change of wires position cause difference. Thanks...

[step]

If I move wires, the tone generated by the circuit fluctuates a little (its frequency). So are wires too long? Or bad type? I use stranded wires.

[induction]

Your input wires are picking up signal from your output wires, like the parallel plates of a capacitor. When you plug in a cable, the intrinsic capacitance in the cable is coupled to ground, so the cable bleeds these stray signals to ground,  and you get no oscillation. When you move the wires around, their capacitance changes, and the pitch of oscillation adjusts itself.

The best solution is to keep your wires as short as possible,  and avoid parallel wires. Try to have your wires cross at right angles (the arrangement of wiring to minimize crosstalk is known as 'lead dress'). Using shielded cable on input wires can help as well, but is often unnecessary if the layout and lead dress is ok.

In a pinch you can put a resistor or cap from the circuit input to ground to stop the oscillation,  but this can have an effect on the sound of the circuit. If you can solve the problem with proper lead dress, you'll probably be better off.

[step]

Thanks mate, It sounds like real cause of the problem. I'll try rearangement of wires! Thank you a lot!