[PD] frequency-shifter
Frank Barknecht
fbar at footils.org
Fri Dec 20 15:36:01 CET 2002
Hi Orm,
Orm Finnendahl schrieb:
> did anybody implement a frequency shifter using single-sideband
> modulation with Hilbert-Transform in pd?
>
> If so, I'd be very much interested in it.
If I remember correctly, you're on Linux, right? Then maybe this LADSPA
plugin (use with plugin~) by Steve Harris might do what you want, and it
shouldn't be too hard to port to PD native:
[Quoting http://plugin.org.uk]
Bode frequency shifter (bodeShifter, 1431)
A Bode/Moog Frequency Shifter is a popular analogue synth module, it
works by shifting all the frequencies of an input signal up or down by a
specified frequency. This version shifts in both directions at the same
time as its almost no extra work and its often useful to have both
directions.It doesn't actually work in the same way as an analogue
Bode/Moog, which use Dome filters as the core, it uses a Hilbert
Transformer, which is much simpler to implemtent in digital systems. The
output is very similar though, and people are familiar with the name
Bode.The theory of operation is pretty simple, and uses some clever maths
to cancel out the upper or lower sidebands of a ringmodulator applied to
the input signal. Read the source if you want more information. The
Hilbert Transformet coefficents came from mkfilter, the excellent filter
calculator, available at
http://www-users.cs.york.ac.uk/~fisher/mkfilter/.
ciao
--
Frank Barknecht <barknecht at dradio-online.de>
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