Covers on unused RCA inputs?


Years ago, I vaguely remember being advised to put little plastic covers on the unused RCA inputs on the back on my preamp. These plastic plugs had a piece of metal that connected the two poles of the RCA input. The theory was, by bridging the two sides of the RCA input, ambient RFI and static electricity were blocked from entering the preamp, resulting in a lower noise floor.

Of course, these plugs could only be used on RCA inputs, not outputs, as this would short circuit and possibly damage the preamp.

Has anyone heard of these gadgets? Does anyone use them currently? Thank you.
javachip
You're probably thinking of shorting plugs; I use them on the unused phono inputs on my Lamm phono stage and Jadis preamp (the rest of the inputs are currently used). Cardas also makes metal caps to put over the unused inputs. I can't say how much of a difference the shorting plugs make in my system, as I haven't really noticed much of a difference, but they don't hurt.
It's not clear to me how a plastic cover would block those pesky little RFI who are sneaking around all the time looking for a way to get into our preamps!

A well-designed preamp input selector will short out all inputs other than the one selected. This is to prevent "bleed-through" of signal from sources that are not selected but may still be turned on. For example, a FM tuner while you are listening to a record. (Don't ask me why one would do that).
The original reason for shorting plugs wasn't RFI but because many early preamps would make a popping sound as you rotated the selector swith past unused inputs. I haven't had (heard) that problem for a long time, but I use shorting Camacs in my Levinson 26s pre anyway, because it reduces my OCD ;--)
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Covering the unused inputs does help, at least in my rig. I opted to put poster putty on the unused inputs being it was what I had. Nice and cheap.

Next time I may put a small piece of aluminum foil over the input and then the putty