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Q. Is it safe to leave a dummy jack plugged into my headphone socket?

If your keyboard has speakers you wish to disable while monitoring to the line outputs, then putting an unconnected jack plug in the headphone socket is a harmless means of muting them.If your keyboard has speakers you wish to disable while monitoring to the line outputs, then putting an unconnected jack plug in the headphone socket is a harmless means of muting them.

I have a Casio PX310 digital piano. When jacks are inserted into the (quarter-inch) line out sockets, the onboard speakers are not muted. They are muted when headphones (or a jack) are inserted into either of two 1/8-inch headphone sockets. The line out volume is also controlled by the onboard speaker/headphone volume control, so it’s not an option to just turn it down. So, to mute the onboard speakers, is it safe to just insert an open-circuit stereo jack into the headphone socket, or would it be better (for the onboard amps) to present it with a dummy load? Elsewhere I read that a 100Ω resistor from tip to sleeve and ring to sleeve would do it, but I don’t believe anything unless I hear it from the SOS experts!

SOS Forum post

SOS Technical Editor Hugh Robjohns replies: Yes, a dummy jack plug or adapter will do just fine — and it won’t cause any problems! 

Published December 2015