building a pitchshifter

[thomsondaman]

I am new to all this but am keen to learn. I am wanting to build my own pitchshifter, any advice on kits methods or general know how would be greatly appreciated. Cheers,

[thomsondaman]

Sorry although I would also like to a pitchshifter I was meaning something that can drop octaves or raise them. I have found kits that claim to raise but I unfortunately would take greater pleasure from lowering!

[samhay]

Are you OK with it being a bit fuzzy and not polyphonic?

[thomsondaman]

I'd prefer it to be polyphonic, if by that you mean clean but a bit of fuzz would be a nice add on.

[blackieNYC]

There are very dirty octave up and octave down pedals - the waveform is clipped,doubled,halved and definitely comes out fuzzy. They are, however, cool.
I was wondering just today - are there any all-in-one or sort of all-in-one cheater's chips that offer digital "clean" pitch control?  So many cheap commercial pedals out there. Guitar as well as voice pitch correction (129$ pedal with XLR). Is this the kind of thing that is likely to become an integrated circuit on its own? Kids' toys and what not? Like some loopers did.  Coolaudio or even AD?
On the other hand, I like pitch shifters. They used to make me sound unique. Now I want all pitch shifters but mine to go away.
".. because when everybody's Super, nobody will be." - bad guy in The Incredibles

[IEATNOISE]

Unfortunately your pretty much SOL if you want to BUILD a pitch shift that's NOT also a fuzz. Unless your handy with programming micro controllers. however, there are plenty of good, inexpensive, octave pedals out there that you could try modding. Arion made an octave pedal that usually goes for around $30. They use through hole components as well so..boom

[Elijah-Baley]

I'm planning to build an analog octave down, and if I can, I want to add the cleanest octave up. By the way, what is the cleanest octave up?

[ElectricDruid]

The only single chip solutions (currently) are the sort of voice-changer/pitch-shifter chips that appear in various kids toys. The audio quality of these is usually pretty dreadful and the data sheets can be sparse. Here's an example:

http://www.bucek.name/pdf/pt2361.pdf

I haven't looked this chip up on Princeton's site to see if they have anything more, or if it's in current production. There was another similar chip by Holtek, that Sparkfun used to supply:

https://www.sparkfun.com/products/retired/10574

The bit on this page about "The 8-bit A/D and D/A converters with a sampling rate of 8kHz ensures a high quality and high S/N ratio output voice." almost made me wet myself. Hohoho. Yeah, right. They should know better.

The other options are some more serious coding for either FV-1 or something more powerful (dsPIC/STM/etcetc). At that point a million possibilities exist.

HTH,
Tom

[robthequiet]

Presuming you have a guitar stompbox in mind...

I think it helps to understand what is going on in the box. Remembering that a guitar signal is essentially one analog signal coming down the wire, electrically speaking, making something that resembles a clean pitch shift, even octaves, does not have 6 individual signals to process, so as you process the entire waveform you don't get a discrete transformation of each string, but rather a complex signal that has been cut in half and had one half mixed in upside down to resemble a "doubling" of the waves, or leaving out one half to get the octave down. It's a very distortive process.

If you think of a tape device that can be sped up or slowed down, you can have a beautiful rendering of the wave going faster and slower, thus giving all of the components a proportional shift as you are keeping the waves intact, just playing them back without any slicing. This works because you have recorded material onto the tape already.

For clear results, you pretty much need a DSP solution, but that might be a path to pursue if you can write code.

So it's actually easier to execute an octave down with distortion because you can easily use a diode to chop the wave in real time and smooth it out with a tone circuit. One circuit type to do this would be a rectifier, if you'd like to look that up. I'm sure the senior cadre here will be able to recommend some projects to dive into.

[blackieNYC]

You had me at "kids toys".

"The bit on this page about "The 8-bit A/D and D/A converters with a sampling rate of 8kHz ensures a high quality and high S/N ratio output voice." almost made me wet myself. Hohoho. Yeah, right. They should know better."

Well, this is kind of interesting though.  I'm rarely looking for a 100% wet octave.  It will be blended.  Do you think this will track decently?  I could be wrong but it sounds like it might even be somewhat polyphonic? (the POG can handle a major triad pretty well).  If it is aliasing or something, it might still be a useful pitch shifter if it's not full-on fuzz or glitchy in its tracking.  What do you think?

[ElectricDruid]

You had me at "kids toys".

"The bit on this page about "The 8-bit A/D and D/A converters with a sampling rate of 8kHz ensures a high quality and high S/N ratio output voice." almost made me wet myself. Hohoho. Yeah, right. They should know better."

Well, this is kind of interesting though.  I'm rarely looking for a 100% wet octave.  It will be blended.  Do you think this will track decently?  I could be wrong but it sounds like it might even be somewhat polyphonic? (the POG can handle a major triad pretty well).  If it is aliasing or something, it might still be a useful pitch shifter if it's not full-on fuzz or glitchy in its tracking.  What do you think?

I agree, it is kind of interesting. I mean, it's not going to sound like much else in the pedal world, and that's a good thing. It might well be somewhat polyphonic. The 8KHz sample rate and 8-bit sampling is going to mean the sound has all sorts of digital artefacts all over it - imagine a 1980s home computer playing guitar, maybe?

If you can find one of the chips, I'd say go for it. I bet there are tons on eBay, and don't worry about fakes - this is not the sort of stuff that anyone would bother faking!

Tom

[slacker]

You could have a look at the EMM Harmony generator, this uses a PLL and a bunch of CMOS dividers to give a variety of pitch shifts and superimposes the original envelope on the output giving a relatively clean effect. I played about with it a few years ago and It's pretty good on single notes but a complete mess on chords.

http://hammer.ampage.org/files/EMMHarmoGen.PDF

[thomsondaman]

sorry I totally forgot about my post, its an octave up down I am definitely wanting that sounds clean. Seems by alot of the posts I'm hoping for the impossible but I spoke to a guy who advised the bit commander. Seems cool but I am afraid it might be too dirty sounding. Any input? Also I like the look of that harmony generator. Is it just the post or is that article older than time? The price being £15 and described as 'expensive' also leads me to believe this.

[smallbearelec]

Dean Hazelwanter designed one, but the page

http://www.generalguitargadgets.com/projects/20-modulationecho/124-dh-pitch-shifter

is gone from the GGG site. J D Sleep used to offer a board for it, so it may be out of production. You might e-mail and ask him. The Holtek chip that drives it:

http://smallbear-electronics.mybigcommerce.com/ic-ht8950/

is readily available and not expensive.

[thomsondaman]

cheers I will give him a shout.

[chuckd666]

Not sure if this was linked earlier - http://www.diystompboxes.com/smfforum/index.php?topic=88829.msg751138#msg751138

https://www.youtube.com/watch?v=CqJAjrYDC0s

Just realised the schematic isn't linked/available from that thread either.

[merlinb]

I am new to all this but am keen to learn. I am wanting to build my own pitchshifter

Your ambition exceeds your skill level. Pitch shift is one of the hardest things to do clean.
FYI smooth octave down:
http://valvewizard.co.uk/uboat.html