FET Bass Preamp

[lion]

Thanks Bcarso!
I've now wired up a Baxendall tone circuit. To make up for the loss of gain through the tonestack I've added another JFET stage ahead of the CF stage - which brought up another problem. Even with the loss in the tonestack the signal seems to overdrive the new JFET. Tryed with different drain- and source resistors - but the only way I could get a clean swing was by inserting a dividing network 680/330k between the tonestack and the new gainstage. But it seems that this will also chance the function of the bass/treble action - maybe there's a better solution to the problem?
Rescale the components in the tonestack maybe - or inserting the pad ahead of the filtersection. Any advise will be appreciated.

Erik

 

[gtrmac]

I'm back with this project after installing a new power supply and the difference is surprising. I'm embarrassed to admit that I was using a crappy switching supply that I found lying around the shop and now I replaced it with a linear supply that I built using a PCB from Elliot Sound Products. The preamp sounds completely different. I assume that the old supply couldn't deliver enough current although I was reading +/-15V on the rails.

I still have the source bypass caps out in the two gain stages and I'm getting a nice clean signal almost to full gain. I'll try the caps back in later but I'm enjoying the way it sounds now. There is a little compression at the higher gain settings that sounds very nice.

I have a PCB layout done for my variation on New York Dave's Guitar Booster. I added a passive Baxandall type tone stack and another stage for recovery after the stack. I also have a SSM2142 balanced output stage in there.

 

[bcarso]

It's nice to avoid switchers unless you really need the efficiency. Their conducted and radiated noise gets into everything, sometimes being demodulated and hence producing audible noise. Their regulation is highly variable depending on the design, and at low load currents some of them go into a hiccup mode that is often at an audio frequency. Although many circuits have good rejection of power supply noise, simple discrete component ones often do not.