[sdiy] Dual Frequency Shifter update

[jhaible at debitel.net]

>  So, have you any samples we could listen to? I'd love to hear it.

May take some time before I hook it up for more audio recording.
(The whole thing is very unfinished - companders don't work well
on fast transients, for instance). You heard the upshift/downshift
demo?

>  It seems like the audio ranges from about 15kHz to 30kHz, so your fixed
>  filter need only work over a one octave range? 

No - when I have a smaller amout of shift, I'm mostly within the normal
audio range. So all in all, I need twice the audio range.
Anyway: this is no problem, circuit-wise. Main problem is to find a good
place where to put the extra board in the box without messing everything up.
I guess I must post a picture of the current state of the project, then
you knoww what I mean! ;->)

> How steep (or shallow)
>  a filter is it? A -12dB/octave filter 'shifted' up 15kHz would have a very
>  steep slope in this range. cool.

Yes, that's the result of shifting in lin scale and hearing in log scale.
First thing that came to my mind was change of Q - and you're right, it will
dramatically change filter slopes as well.

BTW, as two list members suggested, I tried upshift -> distortion ->
downshift. With very small amount of FS, the harmonics from the distortion
process are slightly chorused. (All harmonics that are created within
the FX chain beating with the originally present harmonics at the same
beat rate: the amount of the frequency shift.)

JH.

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