Cap from Collector to Emitter

[Blooze]

I was messing with a Electra Distortion circuit on the breadboard last night and found it was squealing when my guitar volume was all the way down and a little oscillation noise when the volume on the pedal was all the way up. I thought I'd throw a 100p cap from the base to the collector and see if that helped as it has before before I tried a little series resistance.  Installed the cap and the squealing went away at both ends and no change in sound of the circuit to my ears. I then noticed that I had put the cap from the collector to the emitter. So, being a new electronics learner, what exactly is going on here?  All I could find doing a google search was that a cap from the collector to the emitter was a positive feedback loop.

[antonis]

what exactly is going on here? 

Nothing special..
(just an "indirect" Miller effect..)

Simply consider Emitter at about 600mV lower following Base voltage..
(same as you'd throw 100pF cap lower leg on Base..)

a cap from the collector to the emitter was a positive feedback loop

By no means..

Positive feedback occurs when input & fedback signals are on phase..
(0^o or 360^o phase difference..)

[PRR]

Oh, it's positive feedback, but nearly-none due to the very low impedance at the emitter.

I bet a cap C to Gnd would do the same.

[Blooze]

Thanks folks.  Well, the misplacement took care of the problem and didn't seem to change the sound so........was just curious what was going on since I'd never read anything about doing it that way.

[antonis]

I bet a cap C to Gnd would do the same.

But it actually does it..
(via 47μF cap..)

[Rob Strand]

But it actually does it..
(via 47μF cap..)

Actually the OP's circuit has the emitter bypassed so that would make it look like a collector load as per PRR's post.

In general, probably not.      The cap loading on the collector is low-pass but the high-pass signal at the emitter adds back onto the collector signal.  It's one of those devil's in the details things.

IIRC, a few Philips consumer products had CE resistors.