Normal behavior for a high impedance input with 20 meters of unterminated cable connected to it.Hi there, hoping someone with better skills can help me please.
I have a long 25 meter RCA (budget one, no shielding) running to the SAT input on my old Pioneer AX10Ai AV Receiver.
It works but is noisy when unconnected at the far end.
The line is to allow a small mixer and guitar to be used outside.
Strangely when the mixer and reverb unit is connected to the RCA wall plate, and tested with a microphone, the noise goes! And the input to Pioneer and output to garden Evid speakers is perfect .... no noise, no hum, no loss. Good but odd.
The RCA is housed in a waterproof wall enclosure. It feeds into metal trunking in which there is data, power and indeed irrigation pipes and then back to the house. The cable itself is an Amazon cheapo.
Wandering if it's earthing? And if it is, is there anything I can do about it?
As I say when connected it works very nicely, but when unconnected at the far end it's hums away quite badly.
Would very much appreciate any help you might have. Many thanks in advance
Hey Vern, many thanks for taking the time to help with that.Normal behavior for a high impedance input with 20 meters of unterminated cable connected to it.
You could make a shorting plug or a plug with a 100 ohm (or less) resistor from the pin to the shell that you plug in to the end of the cable when the mixer is not plugged in. That will solve the issue.
The simple way: Assuming the end of the cable in the waterproof box has a male RCA connector on it,Hey Vern, many thanks for taking the time to help with that.
I'm trying visualise precisely what you mean and how I might execute that. I can use a soldering iron after a fashion but not quite knowing operationally where to start with that. Do you have any pictures and a slightly more drilled down explanation please? Apologies, it's an area I'm less familiar with with but can do most things with a bit of explanation and hand holding. Many thanks in advance
Top man Vern, that's my mission today to do exactly as you mention and put that to the test.The simple way: Assuming the end of the cable in the waterproof box has a male RCA connector on it,
1: buy a short cable with a female RCA connector
2: cut the cable about 3" or 4" from the female connector end
3: strip the outer insulation an inch back, unravel the shield wire
4: strip the inner conductor half an inch back or so
5: twist the two together and tape with electrical tape
6: plug the RCA connector in the waterproof box into the shorting cable you just made
7: close the box.
When you want to use the input, unplug the shorting cable and connect the device you are going to use. Save the shorting cable for use when you unplug the device.
BTW, it's a good idea to do both steps with the receiver powered off or at least with the volume turned down to avoid possible speaker damage.
