[sdiy] more pitch shifter thoughts

[Roy J. Tellason]

On Friday 07 January 2005 11:59 pm, PRCamann at aol.com wrote:
> In a message dated 1/3/2005 11:04:29 PM Eastern Standard Time,
>
> rtellason at blazenet.net writes:
> > I got to thinking about this subject some time back,  and came up with
> > some thoughts about things that may or may not work,  I never did get
> > around to playing with this idea.  Maybe you all could tell me why it
> > wouldn't work?  :-)
> >
> > Suppose you took a PLL circuit,  one input to the phase comparator would
> > be some filtered version of your input signal.  (The filtering would be
> > one of the tricky parts,  I guess.)  The PLL is also running a top-octave
> > chip, and maybe (maybe not?) some divider stages,  depending.  Things get
> > set up so that the lowest "note" available comes out at the same pitch as
> > the filtered version of the input signal...
> >
> > Then you've got the rest of the outputs,  the other "notes",  and maybe
> > octave-related versions of it,  all of which are going to be square waves
> > of course (unless you get one of those oddball top octave setups that
> > produces an assymetric output waveform for higher harmonic content),  
> > but in any case more filtering is going to be needed here...
> >
> > Take a selection of those outputs and you've got "chords".  Mix them,  do
> > whatever...
> >
> > Does this sound like it'd be possible to make it work at all?  If not, 
> > why not?

> It'll work.

Yours is the first response I've seen to that post...

> I built a few variations on this idea in the late '70's.  My favorite was a 
> unit I dubbed the "Uglifier" -- it had a distortion section consisting of a 
> Craig Anderton Ring Modulator (from the first edition of EPFM) and a Craig 
> Anderton Octave Doubling Fuzz with a pot mixing the two signals; a tracking 
> section consisting of a 4046 PLL with a 4024 7-stage divider in the feedback 
> loop, with the divide-by-32 output going back to the comparator input of the 
> PLL, and mixing pots giving combinations of 1 and 2 octaves up and 1 and 2 
> octaves down; and a second tracking section using a 4046 and a 50240 top 
> octave divider in the feedback loop, with a switch selecting the top or 
> bottom C as the comparator input (for an octave of notes below or above the 
> input tone, respectively) and two rotary switches selecting which two of the 
> twelve tones would join the mess at the output.  Played a trumpet through 
> this thing --- horribly lovely.   Still have it around someplace; have to 
> fire it up sometime.

Wow.  Sounds nifty.  Do you have a schematic for that thing someplace?

> Tried using an old PMOS organ chip in the feedback loop too.  Overheated
> quite a bit at the time but it worked.  If I ever dig out the chip I'll try
> again.

Don't those have oddball power supply requirements or something?  I've worked 
on some stuff that used them,  but never did too much with them in any DIY 
context.

> Had an idea a few years ago for a stompbox version of it similar to the
> Anderton Roctave Divider, but never got around to building it.

I have a copy of his book around here someplace,  not sure which edition it 
is,  but you're mentioning stuff I don't recall as being in there.  Is that 
stuff online someplace?

> But, yeah, it'll work.  The input conditioning is the hardest part....

That's what I was thinking,  too.