Hi,

First, I'm sorry about my poor english but I hope You will understand my problem (and hopefully I will get some help..).

I have Focusrite ISA-428 and MH-442 AD expansion card. I was just recording acoustic bass and I noticed a strange noise. I used Sennheiser 441 mic. I tried all the channels of 428 (1-4), same noise every time. When connected to Sytek MPX-4A (via AD, ch. 5-8 ) I didn't notice any noise. Then I tried my other mics: With all my dynamic mics (421,441,57,M201), there was that same noise when I used 428s channels 1-4, and no noise when I recorded through Sytek. And there's no noise when I use my condenser mics, no matter what channel I use.

Digi 002R, 428, Sytek, monitors, DAW, everything is connected to the same AC circuit. Then I tried the following: In my control room ONLY 428 connected to the AC, mic into ch. 1 (then 2,3,4), I listened using the insert send of the 428… same noise.

This thing is driving me crazy! Can You tell me what is my problem and what should I do to get rid of this noise?

Thank You !
-Jomppa-