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Sub 37 unstable Feedback

Posted: Mon Jan 23, 2017 12:47 pm
by DStocker
Hello there,
Something on my Moog Sub 37 has grabbed my attention lately. When I go into the square and pulse wave range of any of the 2 oscillators and the feedback knob is turned completely up, the tone begins to change octaves randomly. My question is, if that is a normal behavior.

Thanks in advance.

Re: Sub 37 unstable Feedback

Posted: Mon Jan 23, 2017 10:37 pm
by bichuelo
I do think so. I don't have my unit at my side but hopefully I am able to do the same test tomorrow morning and confirm

Re: Sub 37 unstable Feedback

Posted: Tue Jan 24, 2017 11:05 am
by DStocker
Thank you!

Re: Sub 37 unstable Feedback

Posted: Tue Jan 24, 2017 11:24 am
by bichuelo
Indeed, when you get to the square and pulse the feedback goes nuts.

I couldn't tell if its the pitch that is jumping but the sound does go wild. The same behavior to a lesser extent is shown on the sawtooth and triangle. I found that if you turn the Sub 1 osc up it goes away, almost completely

Re: Sub 37 unstable Feedback

Posted: Wed Jan 25, 2017 9:54 am
by ObtuseMoose
Yeah, mine does it, too, and I LOVE it! I get some great effects by setting the feedback control just slightly before the wildness starts and then modulating the wave shape with an lfo, velocity, or pressure.

I definitely see it as a feature, not a defect.

--
Moose

Re: Sub 37 unstable Feedback

Posted: Thu Jan 26, 2017 12:06 pm
by DStocker
Ok, thank you all! This community is awesome!

Re: Sub 37 unstable Feedback

Posted: Thu Jan 26, 2017 4:04 pm
by _DemonDan_
Hi DStocker,

I think one way of looking at it is that the very point of feeding the output of a system back into itself is precisely to create these types of instability. And that the exact nature of these instabilities can vary per unit.

Why? Because the nature of system feedback strongly accentuates any aspects that have even the slightest amount of gain above unity. As the feedback amount increases, these qualities overpower other sonic aspects that have a gain that's less than unity.

So each unit, while being very similar to other units, may exhibit different feedback behaviors based on slight differences in their component values, as well as their trimpot settings.

Embrace the chaos!

Re: Sub 37 unstable Feedback

Posted: Fri Jan 27, 2017 4:26 pm
by Stevie Ray
Yes it is normal behaviour, and even desirable to some (including me).

Feedback by its very nature is inherently unstable and unpredictable and that's what makes it a fun and creative opportunity.

Check out Robert Fripp and Brian Eno's collaborations.

Re: Sub 37 unstable Feedback

Posted: Mon Sep 10, 2018 12:25 pm
by DStocker
Thanks again for your responses and explanations!