Sound Projects R203 (Lectrolab)

[Wittgenstein]

Thanks Phillip & alexage for the factory schematic. I just so happened to pick up a R203 that I saw on Ebay for about $100 that was in great shape, including the original speaker. It was converted to a 3 prong cord and someone had changed a few of the caps (saving me time). I was playing my recently built 6G15 reverb unit through my 5F1 champ and this R203 the other night (switching back and forth), and I think it almost sounds better with the Sound Projects... lol. The previous owner had also disabled two of the inputs leaving only the third working. I assume this was to reduce hum, but I plan on hooking them back up with different values. Instead of R1, R2, & R3 all being 22K, I'm thinking of trying 10K for R1, and 47K for R2.

I checked my speakers serial number against my friends amp (sleepthieves) and they were only off by 13 numbers. His is made from compressed cardboard, where mine is thin wood which is much more rigid.

[nashvillebill]

Change just R3 to 47K.

If you look at the original schematic, J1 is a shorting jack, If you plug in just J2, J1 is shorted to ground so the input impedance is now (R1+R2)/2 or 11K. If you plug into J1, the impedance is just R1 or 22K. So you already have the 11K or 22K choice.

Now on my R200B, the jacks were not in the order shown, so you may want to confirm which jack is the shorting jack.