Tell me all about the Boss ODB-3 with Monte Allums tri-gain mod

[Jean-Luc Pickguard]

I've just bought a modded ODB-3, but it came without any documentation. I have found some settings I like by trial & error, and as I also have an unmodded ODB-3 which I bought just before I saw the modded one, I can compare the two and appreciate that the mod does represent an improvement.

 

Does anyone have any documentation about what the three position mini toggle switch is specifically switching between? Is selecting different clipping diodes? If so which ones are in which position?

[paul_5]

The Monte Allum does a few things - boosts low/mid frequencies, takes some of the 'fizziness' out of the stock pedal, and (i think) the switch just selects different pairs of clipping diodes, and in one position asymmetrical clippers (two diodes going one way, a single one the other way). 

 

They also 'upgrade' the opamps to a pair of more modern opamps so that the signal to noise ratio is improved.

 

This diagram is from Brian Wampler's excellent publication on pedal modifications, and details if not the exact Monte Allum mods, then something very close to it.

Edited May 22, 2023 by paul_5

[NoirBass]

I’ve just finished doing this mod and can tell you the three positions are:

 

1/ LED clipping - this is the stock clipping in the ODB-3. (Two red LED’s)

 

2/ middle position - lifts the LED and the standard diode. Leaving the single red LED doing the job of clipping.

 

3/ standard diode - less volume but richer sound.(red LED plus diode)

 

Hope that helps

Edited May 22, 2023 by NoirBass