Boss SD-1 Super OverDrive (Made In JAPAN) Guitar Pedal | The BYPASS BLEED ISSUE 🎛️ 🎸

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HIGH QUALITY AUDIO ALERT - LISTEN WITH HEADPHONES!

In the words of: Stinkfoot, from "The Gear Page" forum:

Over the years, much has been said/written about the SD-1 bypass bleed issue. At first, there was discussion if it was even a real problem - not everybody could even hear it (I didn't, at first). This was probably because the fizz was being covered up by other things (amps set slightly dirty, for instance) or simply wasn't there because the user wasn't running the pedal at high enough gain settings. And that is still true today, of course - not everybody hears it, or sets the pedal up so it can manifest itself. So if you have an SD-1 and don't know what all the fuzz is about, don't worry :cool:

Anyway, at first glance it looked like a simple case of the JFET that mutes the output from the distortion circuit not being able to close fully. The weird thing was that it didn't seem to matter how the volume pot was set (which it should, if the mute JFET was the problem). This theory was finally debunked when someone physically removed that transistor, and found that the bleed was still there. And not only that - it was present even at the input buffer stage, pointing towards a fundamental problem with the circuit itself or the physical layout of the circuit board.

Over time, a couple of solutions were devised, both involving adding transistors to open or close paths, and using the pedal's switching system to control them. The first was the mod linked to earlier in the thread, which basically manipulates op-amp's gain setting when the pedal is bypassed (so there isn't enough gain to create a fizz in the first place). A later mod borrowed from the DS-1, and simply muted the input to the op-amp in bypass mode (so the drive section isn't handling any signal at all). Both mods works fine, even though they're only addressing the symptoms, rather than the root cause of the problem.

The mod suggested by @Silvio55 above seems to involve physically moving R1 (the main input resistor) to the input jack - basically from one end to the other of the input wire. Electrically speaking, that shouldn't change anything. But when looking at the board itself, I can see that R1 is located right next to D4 (one of the clipping diodes), and physically moving R1 would of course move the input signal farther from that clipping diode. Going by the description above, I'd try removing R1 and moving the brown wire from connection point 3 to where R1 was (use the hole closest to C1 - farthest away from the top end where all the wires are). Then desolder the brown wire at the input jack, solder R1 (or a fresh 10K resistor) to the end of the wire and solder the resistor to the input jack lug where the brown wire used to be. Now, I haven't tried this myself yet, so I can't say if it does the trick or not. But at least that's how I interpret what's being proposed.

Interesting bits and go-to sections…
- Intro Duesenberg Starplayer Tv Mike Campbell/Deluxe Reverb: 00:00
- Starplayer - SD1 Bypass - Deluxe: 00:21
- SD1 On: 00:29
- Bypass/There is the Problem: 00:46

The Gear:
- Duesenberg Starplayer TV Mike Campbell Signature
- Fender Deluxe Reverb Amp
- Boss SD1 Super Overdrive (Made in Japan)
- Beyerdynamic M88 TG
- Shure SM7B

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