Re: speaking of Super Distortion/Feedbackers

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11/17/1999 5:40 PM
Mark Hammer	Re: speaking of Super Distortion/Feedbackers Near as I can tell, that vibrato isn't intended, but simply reflects the difficulty of tracking the note fundamental and locking onto it.

 

11/17/1999 5:47 PM
GFR	I think the BOSS literature talks about the vibrato as an intentional feature.     Anyway, if it's PLL based you can try less filtering on the loop ater the phase comparation - it would make the tracking poorer and widen the vibrato... Probably changing a capacitor will do it.     I'm candidate for receiving a schematic if anyone can post it.

 

11/18/1999 10:57 AM

GFR

OK.     To increase the depth try increasing C36 and/or decreasing R62 or R60. The LFO is mixed to the "loop error" signal at pin 9 of the 4046 PLL. You need to increase the amount of LFO that gets mixed.     For a faster rate decrease C31 and C32 and/or decrease R42. That's what sets the LFO frequency.     For those without the schematic:     You have an input buffer that distributes the signal to 3 paths: a "fundamental detector", the "distortion" circuitry and to the JFET that does the bypass.     The fundamental detector is like what you find in an OC-2 octave down pedal. An active low pass filter followed by an "adaptive schimtt trigger" with rectifiers, comparators and a flip-flop - the net result is a square wave of the same frequency as the input. This goes to pin 14 of the PLL (signal in for the phase comparator). Pin 3 (the other phase comp input) comes from the VCO output (pin 4) frequency divided by 2 with a flip-flop. This way you have two outputs: at the same frequency of the note and an octave higher. The loop eror (phase comp output) from pin 13 is mixed to an LFO at pin 9 (VCO input). The two "feedbck tones" (following the note and octave higher) go to a simple anvelope generator like that used on the Blue Box, and after that there's the "overtone" knob that blends them. This goes to an active lowpass filter and then it goes to the distortion stage.     The distortion stage input receives a mix of the signal from the input buffer with the synth'ed "feedback" tones. Then there's an opamp stage and diodes to ground followed by a typical distortion passive tone control and theoutput buffer.     The DIY'er could do an "add-on" feedbacker for his favourite fuzz box with relative ease.     The most interesting part of the circuit IMO is the switching circuitry. I still haven't figured out all of it.

 

11/18/1999 12:59 PM

JR

Seeing as you seem to know the most about this pedal...   The guys over at tone frenzy are looking for anyone who could mod one of these in two ways   1. Better disortion   2. make it so the feedback tapers offinstead of ending abruptly. It is annoying that you cant get it to do this, not even by lowering your guitar volume or volume pedal. (obviosly because the pedal generates the note). I guess you could put the volume pedal after it, but it would be a nice feature built into the pedal.

 

11/18/1999 1:37 PM
GFR	The abrupt end is easy:     R89 C54 give the attack time   D14 R90 C54 give the release time - just increase R90 a lot.     You may need to add a resistor in series with D8.     Better distortion needs definition of what's "better".

 

11/18/1999 2:53 PM
Mark Hammer	The pedal uses a standard diode clipping pair. To change the distortion characteristics, you can futz around with the diode configuration (number, type, etc.), or take out some of the low-pass filtering here and there to get a more ragged tone.

 

11/17/1999 6:21 PM
Gus	Roger If possable can you send me a scan of the schematic I have been looking for one.

 

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