Experimenting with RM clones

[yeeshkul]

I made RM clone for my friend. I lined up my own beloved piece with the new one to compare the sounds and found that the new unit plays audibly better - the sound is crispier with more harmonics, simply brilliant. That is the mystery because all the pieces are the same, even the tranny is the same and hfe of this piece and the old one differ just slightly - 78/74.

Well i found out that i was adjusting R3(the emitter resistor) instead of R2(leaving R2 on 68k) by mistake. Can this be the cause? If yes then i can only recommend it

[hubble]

which RM pedal?

[mac]

When I read about biasing, many pages say that the (470k, 68k) pair set the reference base voltage and has little effect on the sound. I doubt it. A (100k, 15k) pair set the base voltage at the same level, but the 15k is shunting the signal to gnd more than 4X.
Maybe using a 56k or 82k instead of the 68k may have no audible effect, or even using a 4.7k or 3.3k instead of the 3.9k. I still do not know for sure what is the effect of the voltage drop between C and E, Vce.

If you are using an electro cap (I hate them), try replacing it with another electro or tantalum. If you can measure the ESR and real capacity, better. Or simply add a 1uf greencap in parallel, they are more efficient to deal with high freqs.
I do not think that an electro cap is a good choice for a treble booster. Many users won't agree, but I think that the worst poly or ceramic is better than the best electro.

mac