Boss - SD-2 Dual OverDrive  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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ieatyouforbreakfast
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Post by ieatyouforbreakfast »

What exactly are the differences between the SD2 and SD1? I can't seem to find any schematics..

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kusi
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Post by kusi »

schematic attached
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Boss_SD2_schematic.JPG

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Greg
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Post by Greg »

Hmmm - more than a little different to an SD-1.
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gturo
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Post by gturo »

I owned this pedal in the past. Despite the fact the lead channel is very high gain (I hate high gain overdrive and distortion boxes, I'm in love with the use of more overdrives in series), this pedal is very usable.

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Post by Bernardduur »

I love it on bass!

Though I modded it
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D-Day
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Post by D-Day »

Is there any reason for gutshots of this? I see the schematic up there so no need for a trace. But I have one of these on loan if anybody feels a need.

gravityman
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Post by gravityman »

Hey guys, I need a little help. I have one of those clickless true bypass relay modules. In normal pedals, you'd remove the wires going to the anode and cathode of the indicator LED and wire it to the + and - terminals on the board the the module, but in the case of the SD-2 im not entirely sure. Based on the schematic above, it seems that there are transistors (?) on the anode side of the bi color LED. Basically, I'm not sure where to wire the (+) side of the bicolor LED because If I do so, it could skip the part of the circuit that switches between Lead and Crunch. The wiring on the anode side of the bi color LEDs seem to pass through a network of other sub circuits, but I'm sure somehwere along the line they unify to tell whether the FX circuit is switched on. Im wondering where that point is exactly because I think thats where I can tap the (+) LED of the relay model.

Please advise!

Thanks!

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Gila_Crisis
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Post by Gila_Crisis »

I got an old SD2 lately, what a very cool pedal it is! Btw after playing it stock for a while I performed few small mods (a good starting point was the Wampler book):

Crunch Channel:
C36 Jumper
C47 remove
D4 2x 1N4001 in series (D6 and D7 are left stock)
C24 47n
C12 470n

Lead Channel (this is more or less the Wampler "better low gain" mod with few tweaks from my side, btw don't worry, the maximum gain available is still very high!)
R28 1k
C10 330n
R29 270k
D14 2x 1N4148 in series
D15 1N4001
C31 100n
C38 33n (or swamp C38 with C24, this way both channels have a better tonal balance/voicings, before crunch was way to bright and lead to dark)
C43 470n
R90 jumper
Zwischen Ordnung und Chaos fangt die Musik an

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