Mattangles Posted August 2, 2011 Share Posted August 2, 2011 Hi Guys, I am having a few issues with a infrared hearing system and wondered if anyone could help. The set up is as follows: Dynamic mic runs through a tielne and then gets split 2 ways via a standard XLR y split lead. Each of the XLRs then feed into one side each of a berhinger 2 channel tube preamp. One side is used for the infra red and the other is used for the show relay. I have taken an XLR straight out of the preamp and up into the sennheiser SI1015 modulator. The issue I am having is that I am getting a massive hum through the system, even when I take the input out of the preamp. Id put this down to a fault on the preamp, however the other side of the preamp that feeds the show relay is clean. This stays apparent even when I swap them round so they are on opposite channels. I have also tried lifting the ground, changing the cables etc. No success though. However I did run a feed direct from the LS9 desk into the modulator and I recieved a clean signal. Could there be some sort of impedance problem leading to the modulator? Any suggestions would be appreciated. Im probably being really stupid but ive tried everything I can think of. Cheers all. Link to comment Share on other sites More sharing options...
dbuckley Posted August 3, 2011 Share Posted August 3, 2011 The problem lies between the preamp aznd the modulator; unplugging this cable should make the audio go silent. Ground loop. Transformer isolation will be the most sure-fire way to fix it. Link to comment Share on other sites More sharing options...
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