RCA Shorting Plugs
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 |
Like many other threads on this forum that are essentially duplicative, I recently resurrected an older topic related to this subject. https://forum.audiogon.com/discussions/rca-caps Given the input (no pun intended) of Al and George (and others, thank you, btw) I will be giving this (shorting inputs) a try within a month or so. I’m hopeful to have the same or similar results to the OP, and agree that the noise floor is an important aspect to get under the best control possible (i.e. the lower the better). |
I have to warn you, what you are describing is as much about training your mind and brain as it is anything else. It is possible to seek this endlessly. I used to be a movie projectionist. I would see dirt and scratches on films to the point I was no longer able to enjoy a romantic comedy, while everyone around me did. Thank goodness for digital film! :) Don't trap yourself the same way. Having said this, part of this is, for me, not so much noise as room acoustics. Getting the room out of the way so my ears can listen through the system. The effect to my sense of well-being is much like going outdoors and staring at mountaintops over a lake. It is a sense of natural decompression like nothing else, but any aspect of your system can be pathologically pursued, so take a moment to put it in perspective. Best, E |
I recently made a bunch of shorting plugs for all of my unused inputs. A handful of RCA plugs, some 430 ohm resistors and a little bit of my time. I can't say that I notice any difference, but it was cheap and easy, so why not. Also, I just purchased a Manley Steelhead phono stage, and the factory recommends that all unused inputs should have them. Hmm, so why did they not supply them with the unit???? Anyway, that's what prompted me to make a bunch. Filled all the unused inputs on my ARC LS27 as well. It all still sounds as awful as it always has !! LOL (just kidding) Cheers |
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I used RCA caps previously. While they did make a difference, there was definitely a noticeable improvement going from caps to actual shorting plugs, like these: https://www.hificollective.co.uk/accessories/rca-shorting-plugs.html Adding a GutWire Ultimate Ground Cable to one of the RCAs took things even further, but that's another thread 😉 |
According to my calculations it’s unlikely that Cardas non shorting caps operate by preventing rf from entering the tiny diameter outlet/inlet. Maybe I’m not using the right dimension for the rf wave. I’m not claiming they don’t work, I believe they DO work. Ditto the unused wall outlets. Are they too small to worry about rf? RF wavelength at 800 Megahertz is about a foot. And at 10 GHz it’s more than an inch. |
There are at least two types of RCA shorting plugs I’ve seen. One appears to directly connect the positive and negative sides, these are all over eBay and can be had cheap. Just a metal stamping with a plastic overmolding. The other type has an actual resistor built into them and are more expensive. Whats’s the difference, and are they interchangeable? I just bought a bunch of the cheap eBay ones but am not sure they can be safely or effectively used after seeing the ones with the resistor. |
Jaybe, regarding the safety of using shorting plugs which do not have a resistor (on inputs only, of course), the only situation I can envision in which that might be a problem is the one about which I stated the following in the thread Gdhal linked to in his first post above: ... some power amplifiers which provide both XLR and RCA inputs, the intent being that only one of those inputs would be used. In some of those cases the signal pin of the RCA connector is wired directly to one of the two signal pins (usually pin 2) of the XLR connector. 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.Also, as I said in that thread: Consider the fact that the essentially zero ohm impedance presented to the input by a shorting plug is not greatly different than the very low output impedances (e.g., 10 ohms or perhaps even less in some cases) of some components that might be used to drive that input.Finally, if which type is used makes any difference at all I would expect the kind that provides a direct short, rather than a resistor, to be more effective. Everything else being equal, low impedance circuit points tend to be less susceptible to noise pickup than higher impedance points. Regards, -- Al |
@almarg In the related thread mentioned herein, I posted a question worthy (IMO) of your input (no pun intended) :) As that question has gone unanswered there, I thought I might pose the question here. Might or should there be a theoretical or practical difference when using shorting plugs on an input dependent on the class of amplifier? Reason I ask is that I’ve obtained and installed these: https://www.amazon.com/Viborg-Audio-Stopper-Plated-Protector/dp/B017DH76VS/ref=sr_1_1?ie=UTF8&qi.... While I cannot detect a difference in the way my MF M6si (class B or A/B) noise floor emanates the slightest "hiss" or "sizzle" (no music source but volume cranked past 12) with or without the shorting plugs, I can detect a difference when I put them on the LFE input (class D) of my Golden Ear Triton Reference speakers. Thanks, Al. EDIT: I'm aware of the difference in-so-far as the M6si I'm hearing the sound from the tweeter whereas in the T Refs the sound is from the woofer. So perhaps the shorting of inputs effects a particular frequency range more so than others? |
Might or should there be a theoretical or practical difference when using shorting plugs on an input of different amplifier classes?Hi Hal, I'm doubtful that any such generalizations could be made, as I would expect whatever benefit shorting plugs might provide (with or without resistors) to be highly dependent on the specific design of the component they are used on, as well as on the specific characteristics of noise that may be generated by other components in the system, and that may be present in the surrounding environment. Best regards, -- Al |
@almarg I appreciate the rather prompt response on your part. Very prompt for that matter as I added an edit to my previous post. Given what you have just stated, might or should there be difference based on frequency? In the case of the M6si I'm hearing the sound from the tweeter, whereas in the T Refs the sound is from the woofer. |
So perhaps the shorting of inputs effects a particular frequency range more so than others? ... In the case of the M6si I'm hearing the sound from the tweeter, whereas in the T Refs the sound is from the woofer.Hi Hal, My instinct would be to not extrapolate any general conclusions from your findings. Per my previous comment, pickup of hum or noise at various frequencies will depend on the specifics of the designs that are involved, and on the environment in which they are used, and will tend to have little if any predictability. Best regards, -- Al |
@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. |
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Buy switching to an unused input your subjecting the input first active stage to an open circuit. Hi George. To clarify, I'm not wanting or expecting the unused input to sound better. What I am expecting, however, is that by shorting an unused input, its potentially negative effect that it has (if not shorted) on a *used* input is minimized. |
If it’s not used why switch to it?? And negative affect to what?? I believe it has already been clearly established as FACT [on the basis of this and other related (shorting inputs) threads here on Audiogon], that shorting unused inputs **can only be advantageous, even if only theoretical** (electrical theory). In other words, there can be no disadvantage in shorting an unused input from an electrical perspective. So, in consideration of the aforementioned.... I would switch to an unused and un-shorted input to glean whatever noise I can, in order to subsequently switch to the same input *when shorted*, in an attempt to then determine if the noise - from that input -has been reduced. So, in consideration of the aforementioned.... The negative effect *can* be "input cross-talk" that the amplifier is unable to filter. Meaning, while the amplifier is amplifying the signal it is receiving from its currently in-use input, it is also amplifying the un-wanted noise resulting from the unused input(s). So, in consideration of the aforementioned.... The benefit is that while listening to the in-use input, the overall systems noise floor has been lowered. In this context, "lowered" means "reduced by any decibel level greater than zero". So, in consideration of the aforementioned.... Is there a shorting plug for USB B input? |
Elizabeth, I’ve never understood why some people put resistors in shorting plugs for analog inputs. As I mentioned earlier in the thread, from the perspective of the input circuit a plug providing a direct short would be little different than if the input were connected to a powered up component having very low output impedance, that is not providing a signal. Hal, I’m not particularly familiar with the design of integrated circuit chips which provide USB interfaces, but I suspect that what you read to the effect that USB inputs should not be shorted is correct. First, USB interfaces are bidirectional, with communications occurring in both directions on the same differential pair of signal lines when something is connected that can be communicated with. So a USB "input" is also an output. Second, I believe such chips are designed to pull those lines to certain voltages when nothing is connected to them, via internal resistors, and shorting them may affect those voltage states in adverse and/or unpredictable ways. So I would recommend against doing that. Best regards, -- Al |
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Non shorting plugs prevent rf from getting inside the component. Dust actually won’t go into unused outlets/inlets unless there’s a good crosswind. 😀 Yeah, I know what yer thinking: The holes are too small for rf to get into them. Just like rf gets into unused wall outlets, including non audio outlets. Same idea. RF is like Chickenman. He’s everywhere, he’s everywhere!! 🐥 |
This is pure BS, because if they’re not used they are not connected to any active amplification circuitry!!True that an unused input is not connected to active amplification circuitry. However, it is somewhat irrelevant within the context and spirit of this thread, and as a reply to my statement that you were quoting: "shorting unused inputs **can only be advantageous, even if only theoretical** (electrical theory)." The unused inputs could be close enough to active amplification circuitry, causing the unused input to contribute to the overall "noise floor" of the system. Granted, in a perfect world the amplifiers active input would be adequately shielded to prevent what I’ve described, but as you know, we certainly are not living in a perfect world. This is why I indicated "shorting unused inputs CAN only be advantageous, even if only theoretical". I did NOT indicate it *necessarily is or always would be* advantageous. Non shorting plugs prevent rf from getting inside the component.I think what you mean to indicate here is that non shorting plugs *could* mitigate the effect of rf from getting inside the component; not prevent it. RF has a habit permeating audio related gear regardless of whatever is done to prevent it. |
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I tried the shorting plugs as well and they were brilliant, certainly could hear a difference between shorted and non-shorted.The problem it is difficult to get the truth out. When someone like tommylion tries something out and it works, we get people who have never tried this mod before, start putting forward their biased and one-sided point of view.Just because they have some qualification in electronics they feel if something does not fit their textbook opinions then it must be wrong.What lab tests and results of artifically controlled experiments give, and what happens in the real world, can be two very much different things.The shorting plugs reduce the noise floor and allow more detail to come through. Exactly what tommylion described i found the same thing after much listening, and my wife agreed.If you do not have a noise problem you will probably hear little improvement.If you want to learn more try this, then report back:1. Solder a 100 ohm resistor across a working input, not an unused input.2. Listen.3. Post your findings here. |
If you want to learn more try this, then report back:1. Solder a 100 ohm resistor across a working input, not an unused input.2. Listen.3. Post your findings here.Keep in mind that most source components and most preamps and line stages cannot drive 100 ohms with good or even half-way decent results. And as you may be aware the manufacturers of many tube-based source components and preamps recommend **minimum** load impedances in the area of 20,000 to 50,000 ohms. There are some source components and preamps which can do that, and of course 100 ohms would be a reasonable load for many low output moving coil phono cartridges. But the great majority of components providing line-level outputs can't come close to driving an impedance which is that low, while providing reasonable results. Regards, -- Al |
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While I suppose there may be some poor designs that could be damaged working into a 100 ohm load, eventually if not sooner, in general I would expect the combination of the 100 ohm load and the output impedance of the component itself to limit the resulting current to values that would not cause damage. Some components providing line-level analog outputs can even withstand a direct short, i.e. zero ohms. Regards, -- Al |
