favorite squaring /low pass filter circuits?

[loss1234]

I have been reading over tons of old posts on octave pedals and guitar synths, plls,etc. I know for any of these there are two blocks I need to build (and could use in many circuits)

1. a good squaring (sine to square) block- i know there are tons of these out there, from comparator circuits to tim's simple square wave shaper.

but there are so many out there i cant seem to decide which is best suited for feeding an octave pedal and or PLL. anyone have any favorites or personally designed circuits that i should consider?

2. a low pass filter. i need a good, real simple low pass filter for cutting out the junk in the guitar signal. once again, i have searched through old posts but could use some recommendations.

i plan on building these out on perf-board as blocks that i can use to test other circuits so i need them to be pretty versatile.

i hope this makes sense.


thanks a lot

[slacker]

The Electrax guitar synth has a good fundamental extractor (lowpass filter) and squarer section, page 14 of the pdf.
I used bits of it to make an octave down pedal and it tracks really well http://www.diystompboxes.com/smfforum/index.php?topic=55644.0.

[loss1234]

so your slacktave front end might be a good starting point?

thanks

[slacker]

It worked well enough for what I wanted and it's simple, so I'd give it a try.
There's undoubtedly much better ones out there, Stephen Giles or Mark Hammer will most likely have some suggestions.