Single ended vs xlr balanced
Can a well designed rca cable compensate for ground loop?It **might** make a difference in some cases, due to differences in the resistance of the shield or other return conductor, and depending on whether the shield **is** the return conductor, or if the shield is connected only at one end and a separate return conductor is provided within it. But in general I would expect susceptibility to ground loop issues to be more dependent on the internal grounding configurations of the components that are being connected. And in many cases also on how AC power is distributed to the components (e.g., from a single outlet vs. multiple dedicated lines, etc.), and through what kind of house wiring it is distributed (e.g., within metal conduit, or with Romex, etc.; see this paper). ... if balanced is the favoured "vehicle" for long runs ..... why are probably 98% of all xlr cable adverts for sale a seemingly average of 1 metre long? I wanted 8-10 metres but are they ubiquitous?Interconnect lengths of 1 meter or thereabouts are of course more often needed in home audio applications than long lengths such as 8 to 10 meters. And since most cable parameters and most cable effects are proportional to length, using a greater length than necessary will generally worsen whatever sonic effects the cable may introduce, as well as increasing the cost of the cable. I would say that the short answer to most of your questions is simply "it depends." And unfortunately many of the dependencies don’t have much if any predictability. BTW, you may find this paper to be of interest, although it deals mainly with pro audio applications. I’ll quote two sentences from it: So why doesn’t everyone do it [the right] way? Because life is messy, some things are hard to change, and there will always be equipment in use that was made before proper grounding practices were in effect.Regards, -- Al |
I, like many, use both Balanced and Single ended cables. (not in the same time). I’m sure we all have spools of cable lying around. I switch them in and out every now and again for a change of pace. My Levinson amplifier requires I use a "U" shaped shorting straps when in Single Ended mode. However, Single Ended input signals are converted to Balanced signals immediately upon being received at the amplifier, and are handled as Balanced signals thereafter. I can detect the difference in the cable manufacturer and a slight change in db. However I cannot assume to claim which type is superior. Mostly I just listen to the music. N |
Pro grear uses a ground lift switch, which completely disconnects the ground, leaving only the (+) and (-) signals connected. Usually a totally benign or definite improvement. There’s no way to do this with an RCA cable, except to use the safety ground as your reference point, kind of a scary thing from a noise and quality perspective. You can do some cute things like using a balanced cable (shield plus 2 conductors) and connect the shield only at the preamp, while the GND conductor gets connected at both ends. This may minimize EMI / RFI noise pick-up, but the ground loop problem remains the same. Another "tricky" thing to do is in a stereo pair only use 1 conductor in total for the ground. For instance, Left has the signal plus ground but right only has the ground. These are just tricky tweaky things that I don't expect would do much good. One other design trick is to treat the receiving end of an RCA connector as if it were balanced. That is, instead of connecting the shield at the amp end, you insulate it, and either use a transformer or instrumentation buffer. It's also nice in that some transformers sound really great. :) JR does this to warm up some of his amps. Best, Erik |
One more point about using long interconnect cables, such as the 8 to 10 meter length you referred to: If the output impedance of the component driving the cable is on the high side at mid and high frequencies, say something like 500 ohms or more, you would want to make a point of using cables having low capacitance per unit length (say around 60 pf/meter or less). Otherwise the interaction of the output impedance of the component with the capacitance of the total length of the cable may result in a perceivable rolloff of the upper treble, undesirable phase shifts of high frequencies, and the perception of sluggish transients and compromised dynamics, to at least a slight degree if not more. Component output impedances are usually specifed at a mid frequency such as 1 kHz, but in most cases will not be greatly different than that value at high frequencies. All of this applies regardless of whether the cables are balanced or unbalanced. Unfortunately, though, there are many manufacturers who don’t specify the capacitance of their cables. If (as appears to be the case) a component in your system drives an analog line-level signal into a particularly long interconnect cable, such as 8 to 10 meters, and if the component has a highish output impedance as I described above, I would contact the manufacturer if necessary to determine the cable’s capacitance per unit length. If that information cannot be determined from either the manufacturer’s website or by contacting the manufacturer directly, I would look elsewhere in selecting the cable. Regards, -- Al |
