Boss OD-1: output volume... low?

[Plexi]

Hi forum!
Spent my saturday afternoon between mate and this great great OD.
Nice and creamy mids out there, anyone around here tryied this one?
http://www.hobby-hour.com/electronics/s/schematics/od1-overdrive-schematic.gif

But! (as always, there's a "but"); is that normal the mid to low output here?
I know they're different kind of animals: but I was expecting more volume output, like the Boss BD2.

[aion]

Try lowering the value of R10 to maybe 1k... from the looks of things, the circuit actually has about 50% more volume available, but the volume control has a fixed range of essentially "0 to 7", with 8+ being taken up by that 4k7 resistor.

I had someone try this out when building my Corona (OD-1 PCB) and they said it worked splendidly and put the volume right up to where they wanted it.

[Mark Hammer]

I made myself one of these a few years back, and quite like it, too.  I worked from the first-issue schematic, which used an RC3403 quad op-amp instead of a dual and transistors for the input/output buffers.  Haven't been able to compare the two issues against each other to determine if that chip injects anything unique.

I modded mine (refer to schem below) with a 3-way DPDT toggle that sets it to stock, more bass (cap in parallel with C5) or more bass and further treble cut (parallel C5 value plus feedback cap between pins 6 and 7).

Need more output?  Bump up the gain of the stage after the clipping (pins 1,2, 3 in your drawing).  Stock, it is set to unity gain and a treble rolloff starting around 884hz.  Make R8 (in your drawing) 22k and drop the cap value from .018uf down to .0082uf, and you'll have the same rolloff but with a gain of 2.2x instead of 1x.

Because this comes after the clipping stage it will only change the output level and not the tone.

[Plexi]

Try lowering the value of R10 to maybe 1k... from the looks of things, the circuit actually has about 50% more volume available, but the volume control has a fixed range of essentially "0 to 7", with 8+ being taken up by that 4k7 resistor.

I had someone try this out when building my Corona (OD-1 PCB) and they said it worked splendidly and put the volume right up to where they wanted it.

Thanks!
That's closer what I tried: I jumped that 4k7 resistor.
The amount of output volume increase a bit.
I will try 1k resistor: I know it could be lower than a jumper...but, maybe stop forward voltage? (sorry my ignorance)

I made myself one of these a few years back, and quite like it, too.  I worked from the first-issue schematic, which used an RC3403 quad op-amp instead of a dual and transistors for the input/output buffers.  Haven't been able to compare the two issues against each other to determine if that chip injects anything unique.

I modded mine (refer to schem below) with a 3-way DPDT toggle that sets it to stock, more bass (cap in parallel with C5) or more bass and further treble cut (parallel C5 value plus feedback cap between pins 6 and 7).

Need more output?  Bump up the gain of the stage after the clipping (pins 1,2, 3 in your drawing).  Stock, it is set to unity gain and a treble rolloff starting around 884hz.  Make R8 (in your drawing) 22k and drop the cap value from .018uf down to .0082uf, and you'll have the same rolloff but with a gain of 2.2x instead of 1x.

Because this comes after the clipping stage it will only change the output level and not the tone.

Mark!
As always, helping   

Trying to get 'inspired' on the Voodoo Lab OD and the huge amount of output that it have, I increased R10/R8 in my drawing ("feedback loop"?), as you suggest, but to 56k and 100k (instead 150k on VL OD). The amount of volume increase a LOT...but with it, bass...and kill the mid-highs.
But you're rigt: that values will 'balance' the response y guess.
I'll try the mods you suggest there!


I was thinking in replace the pots for Log ones... would be a better sweep?

[Mark Hammer]

The rolloff of that second op-amp stage - which serves as a fixed treble-cut stage - depends on both the feedback resistance and cap value.  I recommended 22k, so that the 22k/.0082uf combination would result in more gain but with the same rolloff.  Cranking up the feedback resistor to 56k or 100k, using the same cap value, will necessarily move the treble-cut rolloff much lower.  56k and .018uf gives a treble rolloff starting at 157hz, 88hz if using 100k.  Dropping the cap value to .0082, with those two different feedback resistance values yields treble rolloffs starting at 346 and 194hz, respectively.  Better, but not rock and roll.

I still recommend using the 22k/.0082uf combination.  If you use it in tandem with 2k2 for R10 (in your drawing), you boost the output in that second stage, and get to keep more of it at the Level pot.  If you're desperate for even more output, use 39k and 4700pf.

[Plexi]

The rolloff of that second op-amp stage - which serves as a fixed treble-cut stage - depends on both the feedback resistance and cap value.  I recommended 22k, so that the 22k/.0082uf combination would result in more gain but with the same rolloff.  Cranking up the feedback resistor to 56k or 100k, using the same cap value, will necessarily move the treble-cut rolloff much lower.  56k and .018uf gives a treble rolloff starting at 157hz, 88hz if using 100k.  Dropping the cap value to .0082, with those two different feedback resistance values yields treble rolloffs starting at 346 and 194hz, respectively.  Better, but not rock and roll.

I still recommend using the 22k/.0082uf combination.  If you use it in tandem with 2k2 for R10 (in your drawing), you boost the output in that second stage, and get to keep more of it at the Level pot.  If you're desperate for even more output, use 39k and 4700pf.

Great!
I'll try to change that values... thanks again!

So.. Log pots will improve the sweep?
(I would test, but I have to purchase them, and wait a week).