Perverting a Boss DF-2

[Mark Hammer]

Just watched RJ Ronquillo's demo of the Beetronics Swarm pedal, which is clearly a 4046 PLL-based variable-interval fuzz.  I cay "clearly" because the intervals it is capable of producing are identifiably those derived by dividing down a higher pitch.

I got to thinking that, if the Swarm, EQD Data Corrupter, and Schuman PLL all use a 4046 to do the voodoo they do, and a Boss DF-2 also uses one to produce the synthetic feedback (as I assume its Behringer clone would, as well), maybe it's possible to tweak a DF-2 to produce other intervals besides unison and octave-up.

Note that the DF-2 is designed to emulate the onset of feedback, initiated by holding the treadle down.  The circuit has a built in envelope generator that provides a slow-ish swell to actuate the feedback-ish tone from the 4046.

I wish I could say HOW it would/could be done, but sadly I'm just the ideas guy and not the tech team.  Any insights into possibilities, folks?  My only possible insight would be that R89 (470k) produces the slow onset, so reducing it would produce a more instantaneous add-on tone.  I'll have to open up my own DF-2 and see if that holds true.

[amz-fx]

The signal you need is at F. Send it through a new CD4013 set up as a divider like 5b to get F/2, then that output signal through the second half of the 4013 to give F/4.

The F/2 and F/4 signals go through new transistors set up like Q11 and Q12 to sum at the C47/C40 junction. Forget adding an Overtone pot for the new signals unless you want to adjust the balance between them. One of both will always be on at any setting even if you use it.

So... one CD4013 chip, a couple of jellybean transistors and a few R and C will get it going.

In theory, anyway...    You could alternately sum F/2 and F/4 directly into Q2 to bypass the envelope effect, with a more square wave sound since it bypasses the LPF.

regards, Jack

[anotherjim]

You can get odd divisions with a 4017 instead of a 4013. It doesn't put out 50% square wave in that case, but the PLL loop detector doesn't care. For example, if the 4017 reset comes from its Q3 output, then its Q0, Q1 and Q2 will each pulse once every 3 input cycles. The output back to the PLL will be from Q0. From that, you can see that switching the chips reset to act from different Q outputs can give more odd or even divisions. It might result in an output of too highly pitched or thin in tone, in which case you may divide the harmonic output with a 4013 or 4 bit counter (which would restore 50% duty).