[sdiy] frequency shifter

Eric Brombaugh ebrombaugh at gmail.com
Sat Mar 14 18:09:32 CET 2020

On 3/14/20 5:26 AM, ColinMuirDorward wrote:

> Has anyone seen this implemented in a digital FX unit?
> Here <https://www.fullbucket.de/music/freqshifter.html>is a vst I'm 
> looking forward to trying out.

There are lots of digital implementations of frequency shifters out 
there - the quadrature oscillator / multiplier is a fundamental 
operation of most digital radios and the dome filter (aka Hilbert 
Transform, aka analytic signal converter) is straightforward to 
construct with allpass networks.

There are a few sites out there that discuss this. I think the oldest 
one I know of is from C Sound:


Olli Niemitallo gave a good backgrounder on construction of a Hilbert 
Transform filter:


I've implemented the Hilbert approach in several synth modules:



The algorithm is simple enough to run in a low-end ARM processor.


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