[sdiy] frequency shifter

ColinMuirDorward colindorward at gmail.com
Wed Mar 11 03:51:12 CET 2020

Thanks, Matthias.
Looks like the PAL filter used the 3320 to do an APF (and switchable to
LPF). Well, that's exactly what I did. It sounds lovely as a phaser, just
like what you'd expect. It's so easy to build and so much better than all
my digital phasers. Not sure why, but I really find the digitals fail in
this department.
I haven't found a lot of implementations of this APF topology in pitch
shifting applications.
This UAD article opens a new can of worms by introducing the APF type used
in reverbs, which I think is different from the analog/filtering type of
APF, in that it adds a delay component. Anyone, please correct me if I'm
wrong. This is actually another thread topic I've been wanting to start for
ages.*Phaser type APF vs reverb type APF.*
Also, can you explain like I'm stupid the difference between pitch and
frequency shifting? It sounds like a linear vs exponential thing, but must
be more to it than that...

On Wed, Mar 11, 2020 at 1:36 AM Matthias Herrmann <
Matthias.Herrmann at jeppesen.com> wrote:

> Thomas Henry did this with his 1982 “PAL Filter”. And by mixing the
> original signal into the filtered signal you can mimik both pitch-shift and
> frequency shift effect. I am currently building his filter and wil soon be
> able to check this with my own ears.
> The effect is shortly discussed here:
> https://www.uaudio.de/blog/allpass-filters/
> Cheers,
> Matthias
> *From:* Synth-diy [mailto:synth-diy-bounces at synth-diy.org] *On Behalf Of *
> ColinMuirDorward
> *Sent:* Wednesday, March 11, 2020 3:01 AM
> *To:* *SYNTH DIY <Synth-diy at synth-diy.org>
> *Subject:* [sdiy] frequency shifter
> Hi, I got a little lost trying to understand what a frequency shifter is.
> I mean the pre-digital method used by Moog (I think?).
> I recently built a 4pole APF, and was really impressed with some of the
> pitching effects I could achieve with it. I'm guessing this is an entirely
> different method than the frequency shifters like Moog and JH have done.
> Is the APF method used by anyone? What are its limitations, and what is it
> even doing?
> Well, I guess I'm just looking for some conversation on the topic of
> analog frequency/pitch shifting methods. If anyone has any
> thoughts/experience they'd like to share.
> Cheers,
> Colin
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