Need to clean up ground

[Keppy]

I'm designing a ring modulator. After trying many different ways to null the carrier signal in the output, I disconnected the oscillator from the multiplier and...nothing changed. I still heard the bleed.

Turns out the carrier is nulling perfectly well (in a way) on the intended signal path. I'm dealing with bleed/ground pollution. Poking wires and such doesn't seem to really affect it, so I'm focused on cleaning up my ground. Any tips? What's good practice here?
Do I even need to worry about it, since it's ALMOST tolerable now, and when it moves from breadboard to pcb/enclosure it's liable to clean up some?

FWIW, I'm using a sine wave VCO courtesy a pair of LM13600s on a bipolar power supply of +/-9v. I can get it all the way down to <1 Hz, and there's no audible ticking in the LFO range. Dang audio frequencies...

Oh, I almost forgot. I was using 220uF filtering from the rails to ground. Anything from 100uF to 470uF (the largest I have) sounds about the same. Lower than that increases bleed. Adding a smaller cap in parallel with the large ones ALSO increases it. Didn't see that one coming.

[liquids]

Sounds like an interesting circuit.

Breadboarding can be worst case scenerio for bleedthrough and noise, but in that case, it's a good testing ground for the same reason.

Check out the synth forums...electro-music and what not.  Synth DIY stuff usually uses high voltages, large swing audio/lfos etc, so keeping stuff clean in that realm of stuff is part of their design process.

What comes to mind, if I'm not mistaken, is frequent use of filter caps as close to the power pins of each chip as is possible and at each chip.  Also, do use ceramic caps in parallel with your large electrolytic caps for filtering, sometimes progressive values...but don't take my word for it, that is just a faint and partial recollection of general tips, and may be incorrect at that.    

[Keppy]

Thanks! The weird thing is, when I added a ceramic to the main power filtering, it got substantially worse. 

I've done a few things that've helped, though, and I'll add some spots for extra filter caps when I lay out the circuit.

As far as it being an interesting circuit, I think it is. It's probably a little less interesting than I think though, based on the fact that every cool idea I have for it turns out to have been done already.