On Wed, 28 Sep 2011, [email protected] wrote:
> I've run into similar issues with the M-Audio Delta cards - a need to > put isolation transformers in the audio lines to get a clean sound. A client of mine is using those cards in two studios. In the air studio, where he is only playing audio, they are fine, but when he installed the cards in his production room he had hum on his record inputs at -45 dB or so. When we looked at the cards closely, we found that the "balanced" inputs were single opamps with (if I remember right) 10K ohms in series with the inverting input and 10K ohms going to ground on the other side to create something that measures balanced but has no common-mode rejection at all. So, we added Western Electric 111C coils. What's amazing is that a piece of technology made by the phone company in the 1930's still sounds as good as anything that's ever been developed since. Rob _______________________________________________ Rivendell-dev mailing list [email protected] http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
