I understand balanced wiring is used to reduce noise and interference in longer run cables.
Correct
Balanced interfacing has better rejection of RFI (Radio Frequency Interference) which is detrimental to all audio signals and particularly damaging to the comparatively very small signal levels produced by microphones. Also because balanced systems, through their improved RFI rejection, allow much longer runs than unbalanced systems. They also do not require an ground in order to work (except for mics which require phantom power, where the third conductor (normally the screen/ground connection) is needed for the phantom power to work). An unbalanced connection uses a signal and a ground reference; removing either kills the audio. A balanced system is earth/ground free (aka "floating"). The screen is just that - a screen to protect the signal from RFI. It only needs to be connected at one end of the cable in order for it to work. The system will still pass audio perfectly without screen continuity through the cable as the signal is referenced independent of the ground. So, using balanced cabling with no ground continuity (i.e. screen broken at one end or the other) makes ground/earth loops much less likely. If they do unexpectedly happen when on location, with ordinary balanced cables you can always lift the ground at one end - something which isn't easily possible using unbalanced cables where losing the ground kills the link.
Why make unbalanced cable?
Principally because it's cheaper and easierto make than balanced cable. THe caveat to that is that good unbalanced cable is hard to make, and can be as expensive as a good balanced cable, though the reduced material content should make it slightly cheaper overall. There are more esoteric reasons for using unbalanced interfacing but the main reason that it's the chosen format for the bulk of domestic/budget, mass market audio is price rather than any suggestion that it sounds better.
Anything under than 25 ft, and you cannot tell the difference if it is balanced/unbalanced. Generally.
Generally maybe
The limitations are heavily dependent upon a combination of the qualities of the driver and receiver electronics, the screening properties of the cable and connectors and possibly most importantly the local conditions and RF environment in which they're used.
In an electrically benign environment with few, comparatively weak sources of RFI, unbalanced cabling is fine and may offer some quality advantages. In very electircally quiet environments it's not even necessary to use screened unbalanced cables. Some high end hi-fi cables are unbalanced and unscreened - just a pair of wires connecting the two poles of the chosen connectors.
Speaking personally, I wouldn't normally run more than about 10ft in unbalanced (though I run very little unbalanced audio at all (mostly home hi-fi) and none in my location rigs).
Why not make everything balanced wiring? is it price? instruments dont need balanced wiring? Do some things work better unbalanced?
Pretty much. Balanced cables, connectors, and electronics are all more expensive to make/impliment than unbalanced. In large quantity production, the difference between unbalanced and balanced connections makes an appreciable difference to manufacturing costs. There's also an element of necessity; equipment intended to work in the electrically quiet environments I mentioned earlier doesn't need balanced connections. Think of all the domestic AV and budget recording gear that's used in people's homes (generally pretty electrically quiet though it's getting worse as homes become more technologically busy) where the majority of connections frequently are short (<6ft, even <3ft) and they work fine. For this there's no need to use balanced connections and to do so would more or less double the manufacturing cost of the related parts of the system. In some high end hi-fi, unbalanced is deliberately chosen over balanced as the simpler electronics and simplified electrical characteristics of the cable are perceived as being an improvement over balanced circuits. (btw. I'm not arguing about the rights or wrongs of the two approaches - just pointing them out
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The choice between balanced or unbalanced interfacing is not related to impedance - that's not affected by balancing/not - rather, it's to do with improved noise rejection and to a lesser extent independence from grounding. Microphones normally use balanced connection because their output signals typically are very small indeed and they need as much protection as possible from outside interference. Line level signals relative to mic level signals are much larger (typically hundreds/thousands of times larger) and benefit relatively less from the improved interference rejection but they do sitll benefit, particularly over longer runs.
Starquad cables, sometimes referred to as "double balanced", go further in using a twisted pair of conductors on each signal connection. This gives an improved RFI performance, but only from sources which are not in direct contact/very close proximity to the cable, at the expense of a typically higher capacitance resulting in more HF losses. They're only really beneficial in environments with high electrical/RF noise, e.g. lighting switch/dimmer rooms, theatre lighting bars, areas near large RFI sources like radio transmitters electric motors, badly supressed fridges, etc.. Over shorter lengths (<20metres) the effects of capacitive losses aren't too bad (though they are frequently audible when A/B'ed against non starquad cables) and if you're at all concerned that you might pick up electrical noises the slight HF losses are a worthwhile tradeoff for a clean recording. On very long runs, a good quality double screened twisted pair cable usually gives almost as much RFI rejection with better sound from reduced capacitive losses.
Mackie mixers have a balanced/unbalanced 1/4 inch main out plug, why use unbalanced? I'm assuming the mixer can tell if the wire is balanced or unbalanced.
The mixers are simpy designed to allow people running balanced or unbalanced audio systems to incorporate the mixer with the minimum of fuss over line levels, connectors, and wiring. The mixer can't "tell" as such but the ouput driver circuitry works in such a way as to drive each connection appropriately. Obviously, an unbalanced output can never be truly balanced without some additional components; whereas a balanced output, if it is appropriately designed, can drive an unbalanced load, albeit usually with some implications for the level performance of the circuit. (There are some balanced circuits which won't work properly/at all into unbalanced loads.)
I understand you cannot tell if it is balanced/unbalanced just by the connector (XLR, 1/4 inch).
Correct
Any three pole connector (XLR, TRS, etc.) may be wired as balanced or unbalanced - or sometimes as a conversion between the two. However, if it's a two pole connector like an RCA or TS jack, then it's a fair bet that you're looking at unbalanced.
What about RCA plugs. Are these always unbalanced?
Yes. In theory a two pole connector may be used to transmit true balanced floating, unscreened, audio but in practice this is so rare in modern recording use as an interface between pieces of equipment as to be discounted. If you see an RCA or TS jack, it's safe to assume a mono, unbalanced signal. Two wire balanced connections are sometimes used inside equipment but not normally outside as the usual balanced audio interfaces incorporate a signal screen requiring a third conductor (at least at one end).
1/4 inch mono (I think it is TS?) and 1/4 inch stereo (TRS?) can be either balanced or unbalanced?
No. 1/4" two pole (TS) jacks are
very unlikely ever to be balanced (see comment above).
1/4" three pole (TRS) jacks could be either mono balanced (+,-,Screen), mono unbalanced (signal, ground (usually screen)) but this could be wired in different ways onto the three poles and it's always wise to check an unfamiliar cable just in case it uses a wiring convention you're not set up for. A TRS jack could also be a stereo unbalanced (left+, right+, common ground (left-,right-)) connection (e.g. headphones). (As an aside, some audio equipment uses XLRs for headphones. I have some UK built broadcast gear which uses XLRs on some of it's headphone outputs.)
what about TA3 and TA5? I guess the same?
Pretty much the same. normal audio wiring for a TA3 is as for a three pin XLR but I guess there's no reason it couldn't be used as a stereo/mono unbalanced connection. Some portable mixers/stereo recorders use TA3s as unbalanced stereo connections for buss linking when joining things to get more channels.
TA5 and 5 pin XLR are an accepted standard for transmission of balanced stereo using a common ground/screen. Typically this is wired:
Pin 1 Common Ground/Screen
Pin 2 Channel 1 (L or M) +
Pin 3 Channel 1 (L or M) -
Pin 4 Channel 2 (R or S) +
Pin 5 Channel 2 (R or S) -
Another possible use is as a 4 channel common ground/screen unbalanced connection, e.g.
Pin 1 Common Ground/Screen
Pin 2 Channel 1 signal
Pin 3 Channel 2 signal
Pin 4 Channel 3 signal
Pin 5 Channel 4 signal
Sorry, got a bit carried away there
I hope at least some of it is helpful and makes sense.
Topic: Newbie questions regarding balanced vs. unbalanced cable (Read 5249 times)