giuliomoro was that actually needed ? The audio inputs on the CTAG are AC-coupled. What issues were you encountering?
It might be due to the (possibly wrong) way i hooked up the preamp, but it sounded and looked like the signal had a significant DC offset that made the positive part of the waveform clip. The signal coming out of the preamp was centered around 4.5 volts (i think), since I used the negative pole of the battery as ground.
giuliomoro Can you show a bit more details of your circuit, like a high level block diagram of what is powered by what and how the different parts are connected together? Where is the noise coming from? How are you powering the pickups?
Here is a rough sketch of the setup:
The mic and preamp are powered by the same 9v battery. The BB/Ctag and the amp by the same power supply, with a step down regulator for the BB. When I power the BB from my computer, all is well, but when trying to use the regulator to power the BB, I get this high frequency jittery noise when the BB is booting up. So my question is basically how create some kind of bypass filter to be able to power both the speaker amp and the BB from the same power supply without that interference. A workaround for now would be to use a powerbank or separate supply for the BB, but since it's all going to be mounted on the bass, I'd like to keep it as simple as possible.