This one has me stumped. Any electronics wizards out there?
Here's the scenario:
I've got several different 3 band on-board preamps (Aguilar OBP-3, Bart NTMB and Nordy 3 band) mounted in pedal style boxes with bypass footswitches so I can do direct comparisons and also use them with passive basses that I don't want to modify. I've been running them each on their own 9v battery and everything works fine. I recently put them all on a makeshift pedalboard and wired them to a common 9v supply, so that I can leave them all wired up without running the batteries down.
Here's the problem:
They all work fine in that configuration, but for some reason the Nordy preamp has a lot of hiss and noise on the output, even with the preamp gain trimmer and the EQ pots on minimum, but only when it's running on a 9v supply. It's well below the bass signal level, but very noticeable when I'm not playing. It's nice and quiet on a battery. I've tried two different supplies, various value filter caps on the 9v line to the preamp board, checked my wiring several times and called Nordstrand. The guy I talked to had no idea what would be causing it because they've always run them on batteries. They're very busy getting ready for NAMM, so Carey wasn't available and I didn't want to be a pest over relatively minor problem that's probably being caused by me using it in a configuration for which it wasn't designed. Like I said, it's a minor problem, but it's bugging me that I can't correct it.
Anyone have any ideas on what could be causing it and what could be done to correct it?
If it weren't for my wife, there'd be no adult supervision at my house...
Last edited by ric426 : 01-16-2014 at 05:40 PM.