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Omni i/o 2 channel preamp to pc a/d

No abuse apparently, owner plugged in a new microphone and blew one channel. Seems to have knocked out expensive instumention op-amp ( comparing the 2 ). I don't like the look of the electrolytic at the input, no input dropper resitor and a 48V phantom supply involved. Anyone any ideas ? don't fancy spending out on an expensive Burr Brown IC if it is only going to happen again. I've not often dealt with kit with phantom supplies - can any one direct to a resource of generic probs associated with 48V on signal inputs?

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N Cook
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channel.

2 ).

inputs?

There is 2 6.8K resistors from the 48V line to each of the balanced mike lines , so protecting the phantom supply. Each of these mike lines is connected via a 10uF/100V electrolytic directly to + and - inputs of the op-amp. So if a short to ground at the mike then the +48V side of the electrolytic goes to 0V and the other side must go to -48V or at least try to , op-amp supplies +-15V.

Modification of clamping diodes at the + and - opamp inputs?

Reply to
N Cook

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