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Square waveTremolo pedals?

5/27/1999 11:54 PM
Square waveTremolo pedals?
Hey. i've got a BOSS trem and while it does the job, I''m interested in finding out what other trems might be out there that actually hit that square wave tone. like an old VOX not a fender. I bought a Diaz tremodillo and it's nice but that fender-y sine wave just isn't for me. I need a deep, square. Any help? True bypass preferable.
5/28/1999 7:25 AM

The EH Pulsar tremolo does this. Not true bypass, though in the original pedals.
5/28/1999 9:02 AM
Michael Burgundy

...but easily installed, as in all EH pedals, right?
5/28/1999 10:59 AM

Not so easy in this case. The output level is not quite the same as the input level, a just-noticeable drop. The Pulsar and clones used a "cancel" that just set the gain to "always max". My Proton shows how to wire true bypass but I've have feedback that some people preferred the "cancel".  
By the way, I'm just in the prototype stages of a stereo Proton, with either square wave or triangle modulation and either follow or alternate on the stereo outs. I changed out the two-transistor astable for a 555 and CMOS flipflop that preserves true 50% duty cycle from top to bottom of the speed range, which the original Pulsar does not do. I'll let you know how it works.
5/30/1999 4:46 AM
Paul Perry

Perhaps a CMOS version of the 555 would be easier to keep switching spikes out of the system, I remember it was a real bitch with a tremolo I built once. And, I never got a variable gain cell better than the portable radio one used in the Dunlop.
5/30/1999 3:36 PM

"Perhaps a CMOS version of the 555 "
Yep, that's what I was using. Actually, I don't think even the bipolar one would be a problem. There is almost no load on it, and both the power and ground are separated to the analog and digital sections so that I can be sure that no switch transient current flows through the analog side traces, which is where most of the switch noise comes from.  
Is Dunlop using the LM1035 or the TDA1526(?? I think) tone/volume/balance chip? I looked at those. They look good, but suck a lot of current.
5/28/1999 9:15 AM
Mark Hammer

PAiA still sells the tremolo project from the Craig Anderton book, and that one does square or triangle wave tremolo. Given the flexibility of the circuit and the extra unused inverter sections, you can make a ping-pong tremolo very easily (out 1 off while out 2 on). The kit don't come with bypass switches, but they are cheap enough that adding on your own still keeps the price low enough.  
Strikes me that just about every two op-amp LFO circuit I've ever seen has both a square and a triangle output (and inverter-based circuit, as in the Anderton pedal). Most sweep LFO's for phasers, chorus pedals, and flangers work like that too. There may be a few issues about signal amplitude, but you could probably tap the square wave output of the LFO on just about any pedal that uses one of these textbook circuits.

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