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DF-2 switching conundrum: the flip-flop flaps

7/11/2000 3:36 PM
Mark Hammer
DF-2 switching conundrum: the flip-flop flaps
Terry Moxness from Calgary asked me about a switching problem he is having with his Boss DF-2 Feedbacker/Distortion. I have one of these too, and have looked at the schematic, but it goes outside the perimeter of my expertise, so I am foisting it on the more diligent of you, as an intellectual exercise.  
To summarize:  
The DF-2 is a very standard 2-diode fuzz whose design is essentially a BMP with one transistor gain stage and one op-amp gain stage, and clipping diodes only in the 2nd stage, and a BMP-style tone control. It also includes a parallel path with a 4046 PLL chip that produces a steady tone whose frequency is synced to the fundamental of what you are playing (*See below for some curious design tidbits if you like octavers).  
Stepping on the footpedal turns it on and off, as per usual on BOSS pedals. If you step and HOLD, however, the indicator LED flickers, and the "feedback" signal is brought in. This is true at any point. So you can go from OFF to FEEDBACKER, from OFF to DIST, or from DIST to FEEDBACKER.  
The schematic shows a 4001 and a few transistors used as an exotic flip-flop to engage the relevant FET's usually employed by BOSS for signal switching.  
What Terry got in his box was this: You could go from DIST to FEEDBACKER and back again, but it wouldn't go to OFF/BYPASS. Clearly the switch itself works, but one of the 3 possible states remains unrecognized.  
What gives?  
(*Much to my surprise, the DF-2 is actually an octave *divider*. "What!?" you say. How could it be an octave divider if it produces overtones? Curious thing, that. The VCO syncs to the fundamental being fed in, but it outputs a much higher tone. That tone, in turn, goes through a 4013 flip-flop and gets divided in 2 then in 4, JUST LIKE a Bluebox or any other run of the mill octave down effect. These "octave and two below" tones are then mixed in your desired proportion, and blended in with the regular fuzz when you hold down the pedal. If one could figure out a way to output a lower frequency from the on-board VCO, then your DF-2 "feedback" tones could actually be a surly growl that fades in when you hold down the pedal. Neat!!)

Mark Hammer Download schematic -- 7/11/2000 4:20 PM
CJ Landry Re: DF-2 switching conundrum: the flip-flop flaps -- 7/11/2000 6:15 PM
Gus The first thing that stands out is ... -- 7/11/2000 9:17 PM
John Greene q{(*Much to my surprise, the DF-2 i... -- 7/11/2000 9:20 PM
Tonda Help with DF-2! -- 7/29/2000 3:21 PM
Tonda Re: DF-2 switching conundrum: the flip-flop flaps -- 7/31/2000 11:23 AM