Friday, 19 March 2010

Patch Tips #5 LFO Freeze

Today's second patch tip - how to 'freeze' an LFO - comes courtesy of Dieter Doepfer.

This was something I hadn't thought of doing until I saw Chris Muir's Periodicity for the Buchla. I could see how one could achieve this if the LFO was digitally generated, but wondered if there was an analogue solution and asked Dieter after the workshop.

He explained that there was indeed a very simple, if imprecise, analogue circuit but, given a VCLFO like the A-147, it could also be patched by feeding a negative voltage to the LFO's CV input and forcing it to slow down to a crawl.

As you can hear, this works well for short durations, less so for longer ones:

In the patch, I sent the -ve signal to the A-147 via a VCA, which I opened with a manual gate from a Choices joystick. On release of the gate, the LFO races back up to its original speed and continues more or less where it left off.

Thanks for the tip Dieter!

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