When to use shorting plugs vs caps on unused I/O


Just wondering what is correct on BHK preamp/ amp/ Directstream Sr. Where are shorting plugs best used vs caps? Why?
Thx in advance


On the DS Sr: In general for safety you don’t use shorting plugs on outputs, this is true for the DS Sr. Use caps on the unused outputs if you want.

Shorting plugs are fine on the S/PDIF and AES inputs. If you have a USB cap that’s fine, I’d be wary of a USB shorting plug. The I2S HDMI connectors are electrically very similar to the HDMI spec so anything that works with general HDMI will work on the I2S inputs - in theory it could short the two sides of each differential pair together - there’s nothing to be gained by tying those four shorts to ground or power.


I also use shorting plugs only on my BHK unsued rca inputs. In my DS I use caps on my unsued rca outputs. As far as I know there are usb and hdmi caps available from Audioquest.


Thanks guys, was mainly referring to RCA/XLR vs digital. I guess the other question is whether shorting the unused inputs on the BHK preamp results in an audible difference- will report back.


Shouldn’t really matter so I’d be curious as to what you find.


After using shorting plugs on the unused BHK preamp inputs(RCA inputs 3-5) and caps over RCA inputs on inputs 1 and 2(I’m using XLR on 1 and 2) there is a definite lowering of the noise floor. Now I will try XLR covers on the unused inputs. I’m running some efficient speakers (93dB) and resting noise is easily discernible. Fun hobby chasing tiny gremlins back into shadow!


Shorting plugs installed in all the unused phono and XLR inputs and I’ve been using the BHK Pre this way for well over a year.
Like you said, lowered back ground noise and the system definitely sounds better this way, more engaging… The unused sockets seem susceptible to channelling RFI… I have done this for years on all my previous equipment, the results are repeatable… I inserted XLR plugs into the BHK inputs with the three connections joined together… Don’t short out an input if you are using the other on the same connection… Eg…If using an input XLR on say input 2 then don’t short the unused phono socket on input 2 and / or vice versa… But I only use one XLR input so all the other unused inputs are shorted… I am not really into the hifi daft stuff but this really does work !


I’ve got some RCA shorting plugs (removable pin to make them a cap as well) but wondering about unused XLR inputs. I’ve read only pins 2 and 3 need to be shorted?

I was thinking a simple 14awg wire to connect pins 2 and 3 would be quick and easy and free.


I actually joined all three together within the XLR. I never tried joining just the two. I just figured on closing off all inroads of noise. 14awg wire would be Ok; I can’t remember now what I used. I don’t think that’s important being such a small amount of wire used to join the connections together… It’s the shorting out that’s more important. Re: the RCA plugs, I just folded the ground connection onto the signal connection and soldered same.

I am not one for doing HiFi tricks: but I did notice an improvement by shorting out the inputs. Don’t short out the outputs !


I found no decrease in background noise by shorting the unused balanced inputs on BHK pre. Will try single-ended…


Well, I can only go with my own experience and what I gained from doing it. But, you know what it’s like with HiFi; I never noticed the night and day improvement that others hear by changing fuses or sitting equipment on springs, etc… If I remove them I want them back in so they work for me. This stuff is never a cut and dried fix for every system !


Absolutely, depends on the RF and EMI in the environment too. I only thought I’d try it as I’m running the quietest tubes I’ve ever heard and wondered if there was an easy reduction to be had. We’ll see with the RCA, bought a pack of 10 for less than my time to solder a bunch of old connectors (that I don’t keep anymore anyway).

I’ve also read that XLR doesn’t benefit much from shorting as much as single-ended as it is still able to reject the noise despite no connection (or think of it as a very short wire) by virtue of being balanced.


So true. I have PC stack in my listening room. The listening room is dedicated for the system with it’s own mains and breaker box, etc, etc. Mains filtration and purification, etc but when I disconnect the PC stack completely, which is on a separate mains supply to the HiFi, there is jump up in sound quality - which is very noticeable… I am in UK (Scotland the mains is 240 volts) so that will be a factor as well !


I’m afraid I hear zero difference in noise levels, using my most sensitive headphones, with the rca shorting plugs. I have to crank the preamp to about 3x normal levels to even hear much noise at all so I guess I’m lucky regarding the lack of intruding emi and rf via unused inputs.


If you don’t need them that’s great.

What I notice musically - the sound is cleaner, clearer with better definition - so definitely an upgrade to my system and my listening pleasure. Like I said, I didn’t hear big gains with springs and sand filled boxes under the equipment or the sonic value of super fuses, etc. But the shorting plugs are an improvement to my system. But, that said; there are so many variables in every aspect hence what works for one person won’t necessarily work for another. But it is a good thing you don’t need them.


For what it’s worth technically, on the BHK anyway, there’s no good reason to use the plugs and they should have zero affect. I never use them.


it’s a pity Paul.
Before I ever say, he should try.
I have a Mc C1100 preamp with a multitude of plugs.
I have them all close and the difference is very noticeable, a lot.
Try before you conclude


Agreed but the point I was trying to make, and I wasn’t making it well, is that it depends on the design. In the BHK it should not make a difference because it’s designed properly. In the Mc (I am guessing) they did something in their design that is helped by shorting the input. While that says to me a design flaw, it’s certainly great to have aftermarket tools that can fix that because I am sure otherwise it must be a very good preamp.


I use RCA shorting plugs on the empty outputs of my preamp (not a PS product), and they work fine for me. However, I wanted to point out that my RCA shorting plugs are AudioQuest brand. And if you go looking for them today, you’ll find that Audioquest no longer sells them. The reader can make assumptions about why that is.

For myself, I’m willing to wager that while on one hand, they rarely help, and even then, not much more than non-shorting caps. While on the other hand, users plugging them (incorrectly) into outputs has lead to a disaster or fifty. Limiting their RCA offerings to non-shorting caps was likely a self-protecting marketing decision, that generally leads to results that are about as good as the old shorting plugs.


I use BHK preamp, 300s & 250s and they DO make an improvement to my system - which is noticeable - or I wouldn’t use them . Improvements as stated. So are you saying I am wrong. ?