Boss SD-1 mods for less bass

[Silvio55]

Hi! After some troubles I got my SD-1 true bypass clone working fine.
The idea is using it for solo boost only, so less bass would make the mids and higher mids more apparent, sort of like a treble booster.
Many people seems to mod it for more bass, and the starting point for mods seems to change C3, I would decrease instead of increasing its value.

Are there other points in the circuit I should check before? What's your advice on it?
Thanks!

[ElectricDruid]

The stock 4K7/47n gives a roll-off at 720Hz, the classic tubescreamer value. You could halve the cap value to 22n and go up an octave and see how it sounds.

R7/C4 are providing some lowpass to smooth the distortion after the clipping amp. That's set at only 880Hz, so if you want a brighter tone, you could reduce that cap a bit too.

R9/C6 are higher up (nearly an octave) but also smoothing the sound out a bit, so again, that's one to look at.

I suspect that you'd get more mileage out of tweaking C4 and C6 to increase the high mids, rather than tweaking C3 to remove more bass. But that's only a guess. If you make C3 too small, you're just cutting all the fundamental out of your notes.

It's a very mids-focussed design, I'd say. The clipping amp rolls off the bass and mainly clips midrange and upwards. Then the subsequent stages roll off plenty of treble to smooth things out and stop it getting harsh. What's left is mids, pretty much.

HTH

[Silvio55]

The stock 4K7/47n gives a roll-off at 720Hz, the classic tubescreamer value. You could halve the cap value to 22n and go up an octave and see how it sounds.

R7/C4 are providing some lowpass to smooth the distortion after the clipping amp. That's set at only 880Hz, so if you want a brighter tone, you could reduce that cap a bit too.

R9/C6 are higher up (nearly an octave) but also smoothing the sound out a bit, so again, that's one to look at.

I suspect that you'd get more mileage out of tweaking C4 and C6 to increase the high mids, rather than tweaking C3 to remove more bass. But that's only a guess. If you make C3 too small, you're just cutting all the fundamental out of your notes.

It's a very mids-focussed design, I'd say. The clipping amp rolls off the bass and mainly clips midrange and upwards. Then the subsequent stages roll off plenty of treble to smooth things out and stop it getting harsh. What's left is mids, pretty much.

HTH

Thanks! I will try changing C4 and C6 then. I wanted it to sound more like a Rangemaster (not exactly but closer) so I thought that cutting more bass before clipping would work.

[Mark Hammer]

There is a difference between modifying how much bass hits the clipping circuitry, and how much bass is coming out of the pedal after clipping has occurred.

Which my first instinct was also to shoot for C3, on reflection I thought it might be better to do the bass reduction further along instead.  The rolloffs around the clipping stage are intended, as in a Tube Screamer, to provide for roughly equivalent clipping across the entire fingerboard, rather than more intense clipping for the low notes and less for the higher ones.  So I recommend leaving the frequency profile around the clipping stage as if.

Instead, consider reducing the value of C7 to maybe 100nf, which will reduce the bass leaving the pedal after all the other stuff has been done to the signal.

[Silvio55]

Thanks!! I have zero experience in overdrive circuits other than just build clones.

[antonis]

Thanks!! I have zero experience in overdrive circuits other than just build clones.

Just locate all High Pass filters, calculate their respective corner frequency and make R/C mods to make them higher, according to your taste..
(it's just as simple as is said..)

[Mark Hammer]

Thanks!! I have zero experience in overdrive circuits other than just build clones.

You won't be able to say that much longer! 

[Silvio55]

Thanks!! I have zero experience in overdrive circuits other than just build clones.

You won't be able to say that much longer! 

Yeah, I hope so!! Thanks to all of you! I will be experimenting with this circuit and see what comes out!