RCA Caps

Excellent response as always Almarg, I was going to mention the same thing. I also, have not experienced a difference when using the RCA caps. I need to mention that I have never had a problem with EMI/RFI either and therefore YMMV.

I am gonna buy some clear plastic jobbys, anyone that does vintage knows that the jacks are closer together and with the plastic jobbys I can cut the edge off to fit. I just wanna keep the dust ( dead skin ) off.

I have tried RCA plugs off and on over the years, but I could never hear a difference.

A well-designed selector switch of a preamp will short all inputs except the one selected. With the old style rotary selector switch this requires an additional "deck". No doubt this deck has been eliminated to reduce cost.

IMO, for unused rca INPUT jacks shorting plugs are preferable to caps, although of course in many cases I would not expect either one to make any difference.

@almarg 

Is it even remotely possible that shorting plugs could cause some kind of "damage" (loosely and widely defined) to whatever audio equipment one would happen to install them on?