Recently when disconnecting an RCA cable from a computer I was surprised to receive a shock from the male connector at the end of the cable. The other end of the cable was plugged into a stereo, which was off at the time.

I found that if I deliberately touched the connector, it would deliver a continuous series of shocks.

I'd characterize the shocks as "mild"; they're definitely unpleasant and would likely make a person drop the cable (which I did) if it catches them unaware, but if you know they're coming the sensation isn't intolerable. It's below the intensity that you might get from, say, a desktop-sized Van de Graaff generator, but the individual shocks occur at a more rapid rate (like perhaps 1-2 per second).

Is this normal behavior for an RCA cable that's connected to a powered-off appliance? If not, what might be causing it and how might it be fixed? Is this evidence of a significant defect and/or safety hazard that effectively should relegate the stereo to the junk heap?

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    \$\begingroup\$ I would say not normal, but explainable with more descript/ on all AC or grounded devices at each end. It doesn't seem like normal AC line filter leakage but insulation partial discharge acting like a partial discharge relaxation oscillator. Not sure where the high voltage is coming from. But it's not normal. Is PC grounded safely? or floating? Stereo's are ungrounded with transformer isolation. Is line neutral reversed? \$\endgroup\$ Commented Apr 16, 2017 at 8:46
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    \$\begingroup\$ It sounds like your stereo isn't grounded properly. Some improperly grounded equipment can build up a static charge in its ground circuit that can give you a rather unpleasant (or, in rare cases deadly...depending on the equipment) shock if you end up "becoming the path to ground. Usually the current is low & it's "fixed" whenever another, properly grounded device is attached to the same ground (current flows to ground through other device. Unfortunately, this isn't an altogether rare occurrence in audio equipment (from my personal experience). \$\endgroup\$ Commented Apr 16, 2017 at 8:47
  • \$\begingroup\$ define all models connected, even if off , some cheap stereos don't have a hard OFF switch (rather secondary solid state switch hence leaky line filter) and are never grounded, but can be to make safer. \$\endgroup\$ Commented Apr 16, 2017 at 8:58
  • \$\begingroup\$ The PC is grounded. The stereo sits on top of a large subwoofer, with a few inches of foam padding between the "feet" of the stereo and the subwoofer cabinet (to dampen the vibration from the subwoofer). So perhaps part of the issue is that the stereo is basically 'floating'? Stereo model is a Yamaha RX-596. \$\endgroup\$
    – aroth
    Commented Apr 16, 2017 at 8:59
  • \$\begingroup\$ Subwoofer model? could be AC powered directly and has poor leakage to line with DC build up and relaxation charge /discharge arc rate of 1-2 per second from some fault \$\endgroup\$ Commented Apr 16, 2017 at 9:01

1 Answer 1


It is not normal, but is expected. I do not think there's something being failed, damaged or defective.

These two devices are having different grounding designs.

You PC, most probably, is having 3-wire plug, and its chassis is being connected to PE.

The Yamaha receiver you use, with its service manual available here, does not have PE grounding, instead it is having C157 and R184 in its "sub power supply" (page 29) which seems to be operational even when main switch is turned off.

The only safe way to interconnect such devices (PC with PE and receiver with no PE) is to unplug Yamaha receiver and all other devices it is connected to from the power receptacle, connect RCA cable, and then plug receiver back into the power.


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