Cleanest square wave tracker?

[egasimus]

Working on my guitar synth... I have made some progress with the waveshaper, but I still need a good square wave tracker. So I'm looking for info on the different approaches to this. There's the MXR Blue Box, the Shocktave, the Slacktave, the Synthbox, the EHX Microsynth, and there's probably more, I'm sure of it. I heard a demo off YouTube which made me think the Blue Box tracks very nicely, but I'm open to suggestions. Gotta breadboard them all, but meanwhile - what have you tried?

[anchovie]

The Slacktave one is great. Hearing a Blue Box track nicely is a novelty!

[Mark Hammer]

Make sure that the amplitude of the wave you're trying to track is fairly consistent, and that you have primarily fundamental, with little harmonic content to distract the tracking circuitry.

As for the Blue Box "tracking very nicely", that strikes me as testament to how little one ought to depend on Youtube videos as a source of truth!!  It is a particularly jumpy pedal, unless you tweak it just right, have all the component tolerances in your favour, and feed it the right signal.  I'm trying to debug one these days that likely has differential response to the envelope voltage by the two transistors on each side of the Blend pot.

Last but not least, such tracking circuits prefer stiff strings.  If they ruled the world, all players would use medium-heavy gauge flatwounds, with a flatwound G.  That's one of the reasons why they all tend to underperform below the 7th fret: the string has too much "wiggle" to it, the closer it gets to open.

The PAiA Rocktave provides an excellent illustration of such tracking.  It uses a compander chip to force the input to be more consistent, and to cut the expansion out when the string starts to enter that point in its decay cycle where it gets unreliable as a pitch source.

[Processaurus]

Take a look at the fundamental extractor from the Boss OC-2, in japan they came up with one of the more successful analog solutions.



Their fundamental extractor is the section in the bottom area, which starts with your guitar signal at R8 and ends with a square wave at the fundamental frequency at pin 13 of IC7 (the last section of IC7 divides the fundamental square wave by two, to make an octave down).

Music From Outer Space adopted the same circuit section for their DIY Sub Commander guitar synthesizer.

Note, this circuit is one of the better ones at tracking guitar, but listening to the square wave at pin 13, it doesn't end notes gracefully, it kind of sputters and chokes a little.  It is meant to drive something that has a volume envelope that decays before it gets to the bitter end of the note.

[joelindsey]

would Time Escobedo's "Simple Square Wave Shaper Made Simpler" work for you? I was playing around with it on the breadboard a few minutes ago and it makes a decent square wave. Or are square wave trackers something entirely different?

http://folkurban.com/Site/SimpleSquareWaveShaperMadeSimpler-712.html

[egasimus]

^ well, the tracker is the part up to U1, and the shaper is the part from U1 onwards 

So I know that compression helps, so I was thinking of something along the lines of a 3080 compressor in front of the OC-2 tracker, and the tracker is made of 741s to make use of their low bandwidth

[Mark Hammer]

Since the outcome you wish to produce is only "derived" from the input, and not necessarily a "copy" of it,  the compression one uses can simply consist of a hard-clipped filtered version of the input.  The clipping will secure you a fixed amplitude range/value but it will generate a lot of harmonic content you don't want for tracking purposes.  That's where the filtering comes in.  For that matter, a little bit of filtering before the clipping (to generate less harmonic content), and some filtering after clipping (to remove what has been added) may do the trick nicely.

or, you could use some form of dynamic compression.  Your choice.