Roland SIP-301

[getdown]

I've been using a Roland SIP-301 bass preamp for many years, and still love it. Lately it seems to be producing more noise than is tolerable at the board. Maybe it's better electronics at the board end, or maybe the 301 is getting tired? Doesn't seem to have changed at the stage side, but the boys at the back are complaining.

I'm wondering if anyone has done any mods on the 301, ie chip changes for lower noise. It's full of discrete transistors (lots of C2240's) but also has several LF353N (JFET opamp) and NEC C4558C's.
Also, anyone have a circuit diagram for this unit?

Any ideas?

 

[bongomania]

In addition to upgrading the xtrs and JFETs, it's very common for older gear to need its caps replaced. That can be a source of noise in older preamps.