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Audio Wiring Question.

Mornin' All,

On Saturday night I set up a mobile  disco for a party. The set up included a double deck record player with mixer, separate amplifiers and speakers. The system is stereo. I made a mistake in the wiring and one channel was not working. I later discoverrd that I had inserted a mono 1/4 jack inch plug into a stereo 1/4 inch socket on the breakout box from the disco console before the amplifiers. This created a short circuit for one channel at the line level stage.

So, why did this not damage the output stage of the mixer due to the short circuit|? Are they inherently protected and failure safe?

Z.

Parents
  • Probably because the mixer only produces a low level signal output, which is protected against short circuit by a resistance in series with the output. For example, 1 volt output, in series with say 100 ohms, short circuit current only about 10ma.

    Inserting the wrong type of jack plug  is an entirely foreseeable mistake and the equipment should be designed to survive this.

Reply
  • Probably because the mixer only produces a low level signal output, which is protected against short circuit by a resistance in series with the output. For example, 1 volt output, in series with say 100 ohms, short circuit current only about 10ma.

    Inserting the wrong type of jack plug  is an entirely foreseeable mistake and the equipment should be designed to survive this.

Children
  • Good answer.

    However I have noted manufactures of equipment saving lots of money for large production runs by omitting a simple diode (cost to humble me of 7 pence each if bought individually) as reverse voltage protection. Not sensible I think