[sdiy] frequency shifter

Gordonjcp gordonjcp at gjcp.net
Thu Mar 12 23:22:12 CET 2020

On Wed, Mar 11, 2020 at 10:05:45AM +0000, Tom Bugs wrote:
> My brain is not awake enough to closely follow Dave's description! But I
> remember there's a good basis in an old Electronotes - I didn't follow it
> exactly by any stretch but it really helped me design my own, the theory I
> took being:
> 1) make a quadrature sine/cosine VCO
> 2) audio input splits to two 6-stage all-pass filter
> 3) each filter-chain is followed by a RingMod/Multiplier with the modulating
> input coming one from sine / one from cosine
> 4) then you do sum & difference of the two ring mods to get up & down
> shifts.
> What I really enjoyed was adding feedback! In fact, redeveloping the ideas
> at the moment & adding in a bit of extra control + output mixing/panning.
> Really great audio processor, even at LFO rates where it becomes a wonderful
> phaser type machine.

If you want a digital implementation of it, look into Software-Defined Radio.

This might even still build:


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