MOD IDEA: would this make negative feedback of boss BF-2?

scoop · Post by **scoop** » 08 Jul 2018, 00:53

this is the full schematic

I figure this is the last opamp (buffer?) before the delay line goes to the resonance knob.

If I simply find a way to swap pins 2 and 3 of IC2 would that make the signal inverse?

Thanks for any advice!

phatt · Post by **phatt** » 08 Jul 2018, 02:04

Short answer,, NO.
longer answer; Quick fix mods without a deep understanding of how something works will just lead to tears.
Messing with pcbs is the fastest way to destroy a good working pedal.
If you want to fiddle with this circuit buy the parts and breadboard your dreams.

Phil.

scoop · Post by **scoop** » 08 Jul 2018, 13:51

well luckily there is a bit of room in the BF-2, I could possibly fit a daughter board in that inverts in the path of the resonance

marshmellow · Post by **marshmellow** » 17 Jul 2018, 19:58

In addition to what Phil said: you can't change the polarity of the signal at that point. It would upset the phase relation of the mixer in front of the BBD, as well as the mixer of clean signal and effect signal at the output.

Pdubs1120 · Post by **Pdubs1120** » 29 Aug 2024, 21:39

So it is possible to add negative feedback on a switch to a BF-2 but it would require a daughter board to be added that would definitely require the pedal to be rehoused into something with a bit more room. You can use a simple phase inverter stage like this one from parasit studios without the buffer and adding a decoupling capa or two. You would want to do it after R29. My suggestion would be to pull R29 off if the board and include in in your daughter board then use the pads of R29 and your send and return pads for the daughter board. I’ve done it on a rehoused and heavily modded BF-2 project of my own.

Pdubs1120 · Post by **Pdubs1120** » 29 Aug 2024, 21:42

Also, if one we’re so inclined, hypothetically you could use the buffered inverter I shared and make the BF-2 a stereo pedal with one side being the original flange signal and the other being the inverted flange signal similar to the Arion SFL-1 flanger.

mauman · Post by **mauman** » 30 Aug 2024, 02:48

You can also put the "out" and "inverted out" from the Parasit Studio inverter on lugs 1 and 3 of a SPST switch, make lug 2 the output, and you can switch between normal and inverted outputs. This circuit works from +9V to +30V or so, as long as the op amps and capacitors are rated above the supply voltage.

Pdubs1120 · Post by **Pdubs1120** » 30 Aug 2024, 03:45

mauman wrote: ↑30 Aug 2024, 02:48 You can also put the "out" and "inverted out" from the Parasit Studio inverter on lugs 1 and 3 of a SPST switch, make lug 2 the output, and you can switch between normal and inverted outputs. This circuit works from +9V to +30V or so, as long as the op amps and capacitors are rated above the supply voltage.

That’s essentially what I did with my mod only I left the buffer out so I could use the other side of the dual opamp for a clean boost and just put the phase inverter on a dpdt switch so one side of the switch bypassed the inverted and I’m side included the phase inverted for negative feedback.