What is the DH pitch shifter?

[mattpocket]

This guy in an experimental band wants a pitch shifter that when a knob is turned the pitch is raised or lowered...

Is this possible with the DH pitchshifter?

Any reccomendations or sound samples of the DH would be a beaut!

Thanks in advance guys! 

[Mark Hammer]

That circuit, clever as it is, is based on a now out-of-production chip from Holtek that did pitch-shifting in 7 specific intervals above and below input pitch.  It was also 8-bit A/D which is not exactly high-end audio, and requires significant lowpass filtering to sound decent.  A good idea, to be sure, and Dean always puts a lot of thought into things, but I suspect our standards are now much higher than what that chip could do.

EDIT: Out-of-production does mean it is unattainable or completely unaffordable.  The HT8950 can be gotten (http://www.smallbearelec.com/Detail.bok?no=258).  The real question is whether it is worth it in the long run.

[caress]

the holtek 8950 can be found for pretty cheap on ebay...i think i got 25 or 30 for around $40, i can't remember exactly.  sometimes they're on there, sometimes not...

[mattpocket]

Is it capable of going up or down in pitch as I turn the knob?

I'd probably get the part from smallbear...

Matt

[rocket]

try to find a datasheet of the chip, so you see better what it does.

is defintly LOFI. And the pitch is shifted only in fixed intervals : octave up an down fitht and a few more, but there are only 7 or intervals.

There exist 2 version with 16 and 18 pins the 18 pin version allows to select the interval with binary switches, the other only with up/down buttons

[Dan N]

http://moosapotamus.net/IDEAS/DHpitchshifter/DHpitchshifter.html

It's the chip from the old Voice Changer megaphones. Makes you sound liks a robot or alien.

[mattpocket]

Thanks!

[Dean Hazelwanter]

Everything the other folks said are true. It's definitely LoFi.

You can switch your pitch intervals, but it also has an 'oscillator' pot which varies the clock rate, which alters the pitch. While it isn't a DigiTech Whammy pedal that will make you instantly sound like Steve Vai, it might work well for this person in the experimental band.

[mattpocket]

Thanks for all the help guys!

CHOICES, CHOICES!

[sovtek50]

I've just finished one (made from a PCB from GGG). And it surely sounds otherworldly.. it's great! I didn't know what to expect, but it was worth it. But then gain, I love weird noises. The chip is actually very affordable. Robot switch isn't working yet, I'll have to check it. Haven't even installed the trem switch yet.
...sorry, gotta go back into space! 

[stm]

I checked that circuit some time ago and studied the HT8950 datasheet as well.  Being a lo-fi circuit (8-bit) I thought that proper filtering and a NE571 compander would help things out, however the largest inconvenient arises from the fixed shift intervals you can actually get.  IMHO they are not very useful for guitar, except for the 4ths and octave, but no 5ths or 3rds!

Going up you have: 4th, Augmented 5th (sort of), and octave.

Going down you have: 1 semitone less (sort of), Augmented 5th (one octave lower than above), 4th (an octave lower than above).

[oskar]

This chip is also obsolete but they sell it over here, 8-bit A/D      (so many IC's and so little time!)
There was a demoboard to go with it and perhaps it is still around.

http://www.elfa.se/pdf/73/736/07363237.pdf

[Pedal love]

Matt, I built one with Dean's schematic. I changed it by adding a homeade opamp splitter circuit at the end instead of the one in the schematic. I also added a potentiometer to the circuit somewhere. It did the pitch shift thing, against a straight signal up to about an octave with the changes. On its own it really didn't sound very good for that, the way I had it before.