Boss OD-1....meh

[Mark Hammer]

Had a troublesome circuit built into a 1590B with two control-knob holes drilled in it, so I sifted through quickie two-knob circuits for something to throw together after dinner.  Settled on the earlier OD-1, using a 3403 quad op-amp instead of the bipolar transistor buffers.  Omitted the switching FETs and just connected the volume pot wiper to the .01uf cap feeding the output buffer.

In many respects, it is really a tone-control-less SD-1.  Works fine, and is quiet, but nothing to Skype about (I'll assume no one "writes home" anymore).  In general, needs to have its entire passband shifted down a bit (i.e., more bass, less treble).I'd mod it, but I really don't expect any sort of transformation that would make me think "Wow!", so it will stay as is.

This circuit should probably not command prices on e-bay that are any higher than what Musician's Friend currently sells a DS-1 for.

[Mark Hammer]

Okay, so I thought I'd give it one more shot.

I installed an on-off-on toggle to either have it stock, add some more capacitance in parallel with the .047uf cap to yield a little more oomph (rolloff lowered to 400hz from 720hz), or add a 68pf cap in the clipping stage in addition to the low-end rolloff shift for a little more roundness when the gain is cranked.

Still not the stuff of dreams, but more in the direction of usable.

[DavenPaget]

Now i get it , someone needs to know 'them 

[newfish]

Okay, so I thought I'd give it one more shot.

I installed an on-off-on toggle to either have it stock, add some more capacitance in parallel with the .047uf cap to yield a little more oomph (rolloff lowered to 400hz from 720hz), or add a 68pf cap in the clipping stage in addition to the low-end rolloff shift for a little more roundness when the gain is cranked.

Still not the stuff of dreams, but more in the direction of usable.

Very much agree.

The whole 'Op-Amp overdrive' fraternity seems to suffer from a serious lack of bottom-end.
The minute you add your 'stock' O/D box into the signal path, you lose all that lovely 'boom' that made you buy your amp in the first place.
The SD-1, Tubescreamer, OS-2 all sound a bit thin for me - and I'm not a thrasher by any stretch of the imagination.

I favour a 1K5 / .47uF in my SD1 - which to my maths starts to drive at roughly 225Hz. 

We like 'em chunky...   

[Mark Hammer]

Although keep in mind that the entire ethos underlying the TS topography is that the naturally occurring differences in amplitude between lower and higher notes result in disproportionate clipping across the fretboard, so some pre-clip tonal shaping can even up the clipping.  If one adds too much bottom, you lose the purpose of the circuit (although it can still be a desirable sound).  I elected to keep the added bottom in mine modest so that one could add a bit more girth with SC or other thinner-sounding pickups (or coil-cancelled HBs), or revert back to normal starved-bottom when using HB pickups.  The idea is to have comparable smoothness for any type of pickup, without sacrificing too much.