Just a few question...
I checked Hendrik's schematic and another couple of schemes that i found online.
Hendrik:
General Guitar Gadget
Looking to the "drive" section: on Dirk's schemes the resistor is only 3K3 instead of 33K of the other shematic, the cap is 0.22 VS 22uF,the feedback cap is 1nF VS 220pF and one goes to GND the other to Vbias.What's the correct one?
I tried to connect the 470ohm res both to GND and Vbias...I found the same distortion amount, quite the same tone, but the drive control was acting better when connected to Vbias.
Also the op out cap is different...
So which schematic shold be the correct one? (i know that on GGG schematic there are some mods in tone control and the second Op amp stage).
Then: i've built a sample SD9 with some very small mods...I removed the out buffer, and i connect the out jack directly to central volume pot lug.So i removed the 10K res, the 0.1uF cap and the 2M2 res (the one that goes from signal to ground).Could it be a problem? The effect seems to work proprebly, with a good tone etc etc...
Here there's also a small verolayout (verified, i built it) for the SD9.
The tone and the clipping stage are missing because i wired it externally to make some tests.I'm using a 1Meg Log pot for drive (but is not the best choice...i think the best way should be to use a 500K pot and to change R9 form 3K3 to 47K-100K).I also change C1 (from 47uF to 1uF) C3 (from 22uF to 0.22, as Hendrik schematics) and R6 from 510 to 570K.
Crim