Just got myself a pair of pencil condensers for recording guitar and tried them out with the P4. Unfortunately on applying phantom on the P4 with both mics plugged in there is a very loud low frequency hum…. This goes away when the phantom power is switched off. There is also very little hum with only one mic plugged in and phantom on….until the volume on the single mic is increased, then the hum returns temporarily.
I’m guessing that perhaps a capacitor on the phantom power regulation has dried out and can no longer deliver clean power over a few mA ? The mics (Thomann SC140’s) themselves are fine and have been used on a couple of other preamps with no problem.
Any advice appreciated ?