Build suggestions for a "pitch shift" type effect

[tommycataus]

Hey guys, I'm hoping you can help. I have a Vox VT40+ amp with modelling capabilities and digital effects built in. It's pretty nifty and has some nice stuff going on:

https://www.youtube.com/watch?v=DQmOcB7wz9k

I really like this "Pitch Shift" effect and would like to build a similar stand alone effect, that has two knobs - one to blend the wet/dry, and the other to alter the pitch. It sounds synthetic with single note runs but is really nice on chords. Would really appreciate any ideas on the following:

- Is this possible to do without any digital programming, just with standard through-hole parts?

- Does anyone know of any sort of effect that does this sold commercially?

- Is there a schematic out there?

I'd imagine a Digitech Whammy could handle this but I've not got around to buying one yet... Assistance is greatly appreciated!

[tommycataus]

Or, even just a method of adding another frequency, not necessarily variable. Like a clean octaver, but with 5th or 7th harmonic?

[induction]

Clean octave is generally a DSP thing. I've heard rumors of analog clean octave up, but I've never seen direct evidence

Polyphonic octave is purely a DSP thing. The Whammy V5 has a polyphonic mode, but none of the previous versions do. EHX makes some very nice pitch shift effects (POG, HOG, etc.), all DSP of course.

[tommycataus]

Having built a few octave pedals I know that most are not clean. I read somewhere that analogue pitch shift or harmonizing is possible in theory, but doesn't track so well. I'd just be interested to know what it actually sounds like and if there are any schematics out there, but yeah it's a plan of mine to buy a Digitech Whammy eventually (from memory I think it's V5 that runs off a 9v supply too). I'll keep looking, thanks for the input

[GibsonGM]

It's a good study, something worth looking into, Tommy, because it's educational.   I've played around a little with the idea, but couldn't take it to the "next level", when DSP is cheap and so readily available!  Maybe you will (?) 

Best I've ever achieved with clean octave is a very 'hearable' octave up, but it sounds so artificial as to be done by a robot...like an old Casio keyboard, ha ha.  Then, you have the fundamental that you have to try to suppress, which doesn't seem easy to do with a low parts count.

Just could never get anything 'believable', so I dropped it...the dirty octaves add more harmonics, and maybe that's why they've stayed that way - they're not so sterile...

[Digital Larry]

Having built a few octave pedals I know that most are not clean. I read somewhere that analogue pitch shift or harmonizing is possible in theory, but doesn't track so well.

Just a guess, but this could well be based on the FV-1 DSP as it has that "warbly" sound which is inevitable from the way the pitch shifting is done on that chip.  The rate of the warbliness depends on the interval and how long the pitch shift buffer is.  An analog "octave" pedal is often called an "octave fuzz" because it creates the effect by full wave rectifying your signal.  This creates a lot of second harmonic (the octave) but the sharp points at the fold-over (zero crossings of the original signal) create a lot of higher order hash as well.

I know this isn't the DSP section, but in the event you are interested in seeing and hearing some of the things that the FV-1 can do, including (finally) the pitch shifting, you can get the SpinCAD Designer program over at my forum (you'll have to register in order to download it).  This is a Java program so it runs on Windows, Mac, or Linux, and it will let you build up and simulate a wide variety of FV-1 sounds right on your computer without any investment other than time.

http://www.holycityaudio.com/forum

Also, if you don't like the idea of soldering small chips you can buy the SKRM modules from Experimental Noize.  Yes, getting all set up to program these is not super straightforward, so I won't belabor the point.  Results are proportional to your ambition and perseverance.   But at the very least the SpinCAD program eliminates the need to learn DSP programming.

[lars-musik]

I don't know if you've already seen this, but the project file is in my "to-do" folder since quite some time. The pedal features one and two octaves down and one up. One of the great Gaussmarkov projects.

Pearl OC-07
http://gaussmarkov.net/wordpress/circuits/octaver-clone/

Here's a demo of the original: