[bluesnoz]

Hi Ted, thanks for repairing the P4, I’ve just been testing it and it seems to work a lot better now thanks.

Cheers

[bluesnoz]

Hi Ted, thanks for the reply. I’ve just had a look at my stocks and I don’t have the right components. If you’re still willing I’d like to take you up on your offer and post the P4 to you for an inspection and service if possible. Perhaps you can email me.

Cheers

David

[bluesnoz]

Hi Ted, me again with a new problem on the same P4 preamp.

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 ?

Cheers

[bluesnoz]

Bingo !

Thanks Ted, problem solved.

Indeed when I looked inside the P4 there was no earth connection from the PCB to the gain pot on channel 1…. and no evidence there ever was one, I have the pictures to prove it 😯 Somehow this got missed in manufacture ??, my serial number is 112382 for your reference.

The difference after the fix is significant, no hum issues at all and just as clean as my Allen heath zed 10fx mixer. In fact P4 does sound slightly more open than the Zed, I’m very pleased.

Many thanks for your advice.

PS the powersupply is 12VAC so no problem there

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