Oscillating "Rosieray" and "Chaos" by Mark Hammer-what did I do wrong?

[earthtonesaudio]

I just breadboarded a couple of Mark Hammer's distortions, the "Rosieray" and the "Chaos."  They both oscillate a lot when I turn up the gain, and I was wondering where that could be coming from.  I'm assuming that the circuits work fine for other people (though I wondered about the Rosieray which appears to have positive feedback to the second opamp, unless there's some phase shift I can't figure out).

Some important info:  This is my "prototyping/worst possible scenario" breadboard, and so the in/out leads, and leads from the pots are unshielded wire.  Also, for each build I'm using a TL074 quad opamp, with the other two opamps not connected to anything.  I know the unshielded leads could be a problem, but I wasn't sure about the opamp.

Can someone point me in the right direction? 

If Mark Hammer reads this, what's up with the feedback through the tone control from the second opamp back into the non-inverting input?  Does the tone control shift the phase 180 degrees?


Thanks!

[Mark Hammer]

That WAS a problem with the Roseyray, though it is not something I ever experienced (or had reported back to me) with the Chaos.

One of the omissions from the original schematic of the Roseyray was a DC-blocking cap that would prevent DC from the output of the 2nd stage from being fed back to the its input.  I "borrowed" the bias voltage from stage 1 and re-used it in stage 2.  Not a bad practice in itself, but with the inintended feedback path it produced unintended results.  Stick a 1uf-3.3uf polarized cap just before the 6k8 resistor and at the output of the 2nd stage, and you should be okay. 

As for what is plaguing the Chaos, I have no idea.