hiss problem with racked pre/eq modules

[Giganova]

Hey guys ---

I've recently racked up two ADM 2783 Mic Pre & ADM 1540 modules, which are powered by a bi-polar 24V power supply. When I use my LDC mic (a Gefell M930 with a ROLLS phantom power supply), there's an audible hiss. The louder the signal is, the louder the hiss gets (especially at the attack). Apart from that, the sound is phantastic.

Do you have any ideas what could case the hiss? Is it overloading? Or a problem with a balanced -> unbalanced signal flow? I could provide circuit and wiring diagrams if that'll help attacking the problem.

Thanks for yoru input & help!

 

[Henri Devill]

That preamp doesn't suppy phantom?Do you have this prob with other mics dynamic ect.?

 

[Giganova]

That preamp doesn't suppy phantom?

well, it could, but I haven't wired up the phantom power supply of the pre coz it was a bit too complicated for my electronics skillzzz.

I haven't fully tested it with a dynamic mic yet, primarily coz a dynamic mic won't give me the signal that I could hear the hiss (its not very loud, but clearly audible with SDCs and LDCs). Also, I don't use dynamic mics.