RCA Shorting Plugs

@almarg 
Hi Al, appreciate your feedback. At one point you say

So if the XLR input is being used in those cases and a shorting plug is put on the RCA connector, the output circuit of the preamp or other component providing the balanced signal pair to the amp would have one of the two signals on its XLR **output** shorted to ground.

My AR pre does have both XLR and RCA inputs, I use the XLRs. So if the short to ground you mentioned happens, is that harmful to the unit or would it only result in the muting of the signal (or both?). Would I know right away from using the RCA shorting plug was having a bad effect, if any?

Thanks again.

Hi Jaybe,

It would be extremely rare for that issue to arise in the case of a preamp.

As I mentioned that issue would arise in cases such as power amps where the designer anticipated that only one of the two inputs (XLR or RCA) would be connected.  And of course nearly all preamps providing XLR and RCA inputs are designed to accept signals from different components that may be simultaneously connected to those inputs, and therefore the signals on those inputs would be kept separate internally.

I vaguely recall once reading a description of a preamp which might have been a very rare exception to that on some of its inputs, but it was not an ARC product.

And in any event such an occurrence would be immediately noticeable as a 6 db reduction in volume (since only one of the two signals in the balanced signal pair would be processed), and probably also as a degradation in sonics.  With damage (to the source component in that situation, not to the preamp) being very unlikely to occur unless the system is used in that condition over a long period of time.  Perhaps even months or never, depending on the particular design.

Best regards,
-- Al

May I get a consensus please on the merits or lack thereof of shorting a USB B input? Reason I ask is my amp has a USB(B)  DAC which I'm not using. If I switch to that input and raise volume to 12 or beyond there is, not surprisingly, some amount of noise at the speaker.

I've alread shorted my unused RCA unused inputs. I cannot seem to find (google search) USB B shorting plugs, and in fact certain articles appear to caution against shorting USB inputs.

Opinions and/or links to such a part appreciated.

Thanks.

Buy switching to an unused input your subjecting the input first active stage to an open circuit.
The simple fix is not to switch to it, if it’s not used.
By putting blanking/shorting plugs on the unused inputs doesn’t make the used inputs sound any better.

Cheers George