RCA Shorting Plugs


I am coming to the conclusion that success in home audio reproduction is largely about lowering the noise floor. There are so many different types of “noise”, from so many different sources, that we only really “hear” by their absence.

I have had caps on the unused RCA inputs of my ASL passive autoformer preamp, ever since a friend suggested them way back. I recently got some actual shorting plugs (with resistors), from Hifi Collective in the UK, to replace them. I was surprised by how much difference they made. Transparency, resolution and musical flow all increased, along with the “realness” of instruments and voices. There is also more sense of the space around them.

I know some preamps short the unselected inputs, but, if yours doesn't, these shorting plugs are inexpensive, and definitely worth trying.
tommylion
If the selector switch is not switched to the input/s that you have the shorting plugs on, it is an open circuit, and a shorting plug should have no effect on an open circuit as it is not connected to in your case the Autoformer, and in an active preamps case, to the input stage transistors.

Cheers George   
I think its effectiveness could also depend on the design of the selector switch. Most high(er) end preamps have relay actuated selector switches which should completely isolate the unused inputs from the one in play.