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audio outputs options

Hello! I'm planning to buy audio interface to connect my digital piano for computer recording. I'm newbie in computer recording, and my question is:

  • What is the best output (I mean, best quality) to use? 1/4 or XLR?
  • And also, how many cables to use: is one (either 1/4'' mono or XLR) enough? Or should I use both outputs to get better/stereo quality?

Thank you!

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    Keep it simple! Do what is the simplest for you... I noticed during past years but sometimes you have a nearly perfect setup in terms of sound quality, but it's so complicated to use (because you use XLR cables and your interface has only few XLR inputs) that it won't be better at the end...
    – Basj
    Oct 14, 2014 at 17:53

3 Answers 3

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XLR connectors should be your preferred route, as balanced cables have a much lower noise level by their design - they are constructed such that noise induced by electromagnetic interference cancels itself out, whereas signal doesn't.

If you want stereo, you need to use two cables. As you can see 1/4" has a Left and a Right, and XLR has a Left and a Right.

If you only use one, you will have mono.

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    Use L if you want mono, otherwise you'll probably get the R signal not changed for mono purposes. If you connect two cables - every digital piano I've tried will try to mimic a typical two mic setup, so L will have more bass and R more of the treble (some pianos switches these around, it's a matter of preference, as a player you'd like L to be the bassy side, but as an audience you expect R to be bassy because you look at the piano from the opposite side)
    – AlexanderBrevig
    Oct 14, 2014 at 7:58
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    Whether or not you have two mono audio tracks recorded, or one stereo track, will depend entirely on your recording setup. And as Alexander pointed out, by default these will be likely to emulate close mic positions.
    – Doktor Mayhem ♦
    Oct 14, 2014 at 8:02
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    This answer is misleading and IMHO wrong. The noise immunity of a balanced connection is not to do with the cable but with the input: a balanced input takes the difference between the 'hot' and 'cold' signals so that interference which is in phase in both leads is cancelled out. Unless the audio interface has a balanced input, you won't get any benefit from connecting to a balanced output; in fact if you use an inappropriately wired cable you may damage the output by shorting one of the signals to ground. Unless you find problems with interference then the 1/4in connection is fine here.
    – nekomatic
    Oct 14, 2014 at 13:11
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    nekomatic - if you read the question, you can see that he is wanting to buy an audio interface and is trying to decide whether to use balanced inputs. To make this work you need balanced outputs from the keyboard (which he has)
    – Doktor Mayhem ♦
    Oct 14, 2014 at 15:00
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    And nowadays, it is very common, even on cheap keyboards, to have balanced XLR outputs. One of my relatviely cheap guitars even has balanced XLR outputs!
    – Doktor Mayhem ♦
    Oct 14, 2014 at 15:00
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If you use a short length cable (for Home Studio use), it won't really change much.

Using balanced cables is good for long cables (10 meters long, on stage), but just for a 2-meters-cable connection : 

piano <--> audio interface

the difference will not be important.

I such situations, I go for 1/4 JACK because it's simpler for home studio use.

Note : I did a huge number of such tests when I started my studio years ago : even by listening carefully both signals (one recorded with XLR, the other with JACK) and analysing them in Sound Forge or any other tool like iZotope RX, I could not see a real difference (if 2 meters cable).

Of course if you plan to use long cables, that's a different story.

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    It also depend on the environment. A home studio /can/ get a lot of interference. The most important thing I've found with jacks is to never let them be parallel and close do AC. Always intersect as close to 90* as possible when crossing unbalanced signal with AC.
    – AlexanderBrevig
    Oct 14, 2014 at 8:59
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    What I've learnt from years of studio is that The best is the enemy of the good. / Less is more. For such simple things, using XLR everywhere is just a waste of time/money: the difference will often be unnoticeable. Better focus on more important things. Most audio interfaces I had (MOTU 828 MK2, etc.) had only few XLR inputs (2), but lots of line inputs (8)... If you want to use XLR everywhere, you're stuck. Just use the JACK inputs, and that's fine, 99% of the time, for short distance cable.
    – Basj
    Oct 14, 2014 at 9:28
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    I completely agree, but with jacks AC interference is a real issue - I just wanted to point it out.
    – AlexanderBrevig
    Oct 14, 2014 at 9:42
  • I use XLR pretty much everywhere - my home studio has more XLR inputs than 1/4". XLR is cheap (not as cheap as 1/4" but still very cheap). It means you have them when you need noise resistance. Why not just use XLR - they are fine 100% of the time! And the key here is - they do make a difference to your noise floor, even in an amateur environment, in fact possibly more important here as there are so many items that impact your noise floor!
    – Doktor Mayhem ♦
    Oct 14, 2014 at 14:57
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    I can confirm this answer: in a studio setup with a short route from keys to interface, there should never be interference problems even with unbalanced TRS connections. The end result will not sound provably different at all; the noise floor should in either case be dominated by thermal/DAC noise of the keyboards, which has nothing to do with the kind of connection used and, if the keyboard is half-decent, won't be audible in the recording unless you compress the track ridiculously. — That said, I agree that "XLR everywhere, why" is a good stance; live it's definitely superiour.
    – leftaroundabout
    Oct 14, 2014 at 17:07
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You haven't told us what model piano this is. The XLR outputs MAY be mic level, they could be line level. If you buy an affordable audio interface with XLR inputs they WILL be mic level. A line level signal will overload them. And input overload is a prime cause of bad piano recordings - it's a very dynamic sound and you need to set levels lower than you might suppose in order to avoid distortion.

So I suggest you play safe and use the 1/4" jacks. Doubtless the audio interface will be stereo, with two input sockets. So use two cables. Any "stereo" information will be retained - probably just some degree of "low notes to the left, high notes to the right" and some reverb trickery. One cable from the L/Mono jack will give you everything in mono down one cable. But note that if you plug this to one input of a two-channel audio interface, it will probably be recorded on just one channel. (Note also that there is no L/Mono option on the XLR outputs. You MUST use both.)

The balanced signal on XLR outputs is designed for long cable runs. It is more immune to noise than an unbalanced connection on TS jacks. But only worry about this if noise IS a problem. For short cable runs in a domestic setup, it probably won't be. (Not since we stopped using CRT monitors on our music computers!)

It may be that the 1/4" outputs offer a balanced signal on TRS jacks, and that your audio interface is similarly equipped. In which case you have another option. But let's not get complicated. Use a pair of ordinary jack cables into both jack inputs of the audio interface. Don't set the level too high, remember piano is a very "peaky" sound. If you get good results - fine. Any problems - come back and ask.

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