Sunday, 18 April 2010

Patch Tips #8 - More Feedback

Getting the Plan B M12 SVVF to self-oscillate and 'sine-shaping' à la Bubblesound µLFO. An update to this post and part of my ongoing drive to sell the Doepfer A-133 VC Polarizer.

If you've read that post, you'll know how I go about this so, without further ado, here's the Plan B M15 sine being fed back to varying positive and negative degrees:

And here it is being used as a modulator:

I don't have a µLFO and don't know the Bubblesound circuit, but this certainly seems to yield similar results:

I'd be interested to hear from any µLFO users whether the sine-shaping also causes a change in frequency as per my examples.

Feedback with the Model 12 yields some very interesting results! Depending on the amount of feedback, internal resonance setting and input gain, I got some wonderfully wild sounds. This is the bandpass output being fed-back negatively:

Part of the sound is down to clipping on the input circuit as you can see from these 'scope shots:

Surprisingly, I found that it is possible to FM the M12 at audio rates, although of course not with the precision or clarity you'd get with a non-vactrol-based filter:

The sine output of the M15 was used to FM the M12. The output of the filter was also sent to the sync input of the VCO, resulting is some pleasing, if groggy, harmonic stepping.


dalas v. said...

I haven't noticed any effect on frequency with uLFO sine shaping. It just affects the timbre.

Navs said...

Thanks for the confirmation, Dalas. I was confused by a recent video posted at Muff's forum where it looked like the frequency was being affected, but now I know!