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I understand that TS cables are mono and TRS cables are capable of delivering a stereo signal. However, if a jack supports TRS, could I still run a TS cable to it (and if so, what happens), and if a jack supports TS and I run a TRS cable to it, what happens?

Edit: here's my context: I have a mixing board (a yamaha mg124cx) with separate L and R channel outputs that I need to run to my audio interface (a Focusrite Scarlett 2i2), which has two TRS inputs. Should I be running TS cables from the mixer's L and R to the two different audio interface inputs, or should I merge the output of my mixing board to be run on a TRS cable?

  • 2
    It is important to know the specific use of the cable and the way a TRS cable reacts to a mono output will vary depending on what it is input to as well as the parameters of the specific equipment on each end. There are situations where you can use a TRS cable or a TS cable and either will work the same. Do you have a specific application in mind? The answer to your general question can only be "it depends ..."! – Rockin Cowboy Mar 2 '15 at 17:23
  • Tarun, thanks for the details; as you noted, specific music hardware is on-topic. I've cleaned up the comments a bit (please take further scope discussion to Meta). – Matthew Read Mar 2 '15 at 22:06
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Now you've asked a specific question, you can have a specific answer!

Your yamaha mg124cx has its stereo main outputs arranged as a pair of balanced TRS 1/4" jacks. (The outputs are duplicated on a pair of balanced XLR sockets, which carry an identical electrical signal. But we don't need to worry about that for now.)

Your Focusrite Scarlett 2i2 has combo jacks, accepting a microphone signal on an XLR plug or a Line input on a TRS jack. You will use the jack inputs.

If you use a pair of 3-conductor cables, with TRS jack plugs, you will get a balanced connection. If you use a 2-conductor cable with TS jack plugs you will get an unbalanced one. The balanced option has theoretical advantages. In practice, I can confidently state there will be no discernable difference.

There is no way of using a single "stereo" cable.

(As well as the connection to the Focusrite Scarlett 2i2, you will have to decide where to attach your monitor speakers. It may well be that you decide to use the Main Out for them, feed the audio interface from the Group sends.)

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TRS (Tip-Ring-Sleeve) is the name often given to the connector, rather than the cable as such, though of course they would usually be used with a 3-conductor cable. This could be used for stereo purposes, but it could also be used for other things : e.g. as a mono send/mono return for an insert effect (like a compressor on one channel of a mixer), or as a balanced signal carrier.

If you had a stereo output socket (TRS) and plugged in a mono plug with only the tip and the sleeve, you'd be grounding one of the channels (probably the right, which is usually wired to the ring) which is not a great thing to do (https://sound.stackexchange.com/questions/25577/stereo-and-mono-cables-and-jacks-what-happens-when-you-cross-them), and you'd only get the left channel coming over the cable. If you were to plug a stereo (TRS) plug into a mono (TS or TR) socket, you'd get your mono signal coming down either the left or the right channel (probably the left, as this is usually the tip), but you'd leave your right input channel 'floating', which is not ideal.

When it comes to balanced or unbalanced audio, many sockets are designed so that plugging in a TS jack gives you an unbalanced connection, while a TRS allows a balanced connection to whatever's at the other end of the cable.

In summary, you're unlikely to do any harm mixing up stereo and mono cables, but it's a good idea to know the contact arrangement in the equipment you're plugging into so you can use it as designed.

EDIT re. your equipment
Yamaha mg124cx : http://www.yamahacommercialaudiosystems.com/downloads/manuals/mixers/mg/mg124cx_manual.pdf Focusrite Scarlett 2i2 : http://d3se566zfvnmhf.cloudfront.net/sites/default/files/focusrite/downloads/7317/scarlett-2i2-user-guide-v2.pdf

The Yamaha manual says it has "TRS phone-jack type balanced outputs"; the Focusrite manual says "Set the LINE/INST switch next to the socket...to LINE if you are connecting a line level source such as the balanced output of a stage piano via a 3-pole (TRS) jack." (but for 'stage piano' there, we can read 'mixer')

So my guess is you want to get 2 TRS cables, one for left and one for right, and with a bit of luck that should give you balanced, stereo connection.

  • In audio interfaces, sleeve is usually grounded, so connecting ring to sleeve will ground the ring, not bridge the channels. – Bradd Szonye Mar 3 '15 at 3:47
  • @BraddSzonye thanks for the heads up. Any better now? There's a similar question at sound.stackexchange.com/questions/25577/…, but I'm not sure if that's quite spot on! – topo morto Mar 3 '15 at 7:54
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As I am sure you are aware - the TRS connector tip is capable of transmitting a stereo signal (separate left and right signal) from a stereo output jack to a stereo input. The output jack must be wired as a TRS output in order to route the separate stereo channels into the appropriate wires inside the cable. You will find this scenario on stereo headphones.

In many cases a TRS connector is used on a two core balanced cable to deliver a balanced signal which will reduce electrical interference and hum instead of an unbalanced signal form a single core cable and TS connector. In mixer and interface applications, this is more commonly true than using the TRS tipped cable to transmit a stereo signal.

For the application you described, it sounds as if you wish to send the two individual outputs from the two channels on your mixer as a stereo (left and right) signal into your audio interface. I am sure you want the stereo signal to be routed into your interface so that it can then be routed into your computer and maintain the stereo separation selected on your mixer.

To do this properly, you will need to understand how your particular interface works and then use the appropriate cable to connect it. An audio interface will output into your computer where your DAW software can render two channels in stereo. To input in stereo you would send each stereo channel (left and right) into a separate input on the interface.

If your interface has a mono/stereo selector switch, then you can use one channel as the left input and the other as the right by selecting stereo mode.

Merging the left and right output from your mixer into a single plug in your interface is not likely to accomplish what you want. If your mixer has balanced TRS output jacks (like a separate balanced out for each side of a stereo output) and your interface will accept a balanced input through a TRS plug, your best bet is to use a two core balanced cable with a TRS plug on each end.

Good luck.

EDIT: The answers that were edited or added after you provided specifics on your equipment are on point and provide good information specific to your equipment. However I am leaving my answer as a general answer for future visitors who may have different equipment.

  • "Many audio interface devices have two channels but each channel is a capable of processing a stereo signal if the signal is delivered through a TRS connector plug." I think you'll need to give some examples of that! – Laurence Payne Mar 2 '15 at 23:57
  • You may be right (as you so often are). Some interfaces will have a stereo line in jack to accept input from an mp3 player on a TRS plug, but can't find example of a dual purpose smart plug as envisioned. Edited answer to remove erroneous assumption. Thanks again. – Rockin Cowboy Mar 3 '15 at 3:25
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If it's a headphone cable, or a mini-jack cable connecting domestic equipment to a computer, a TRS connection may be stereo. In a home recording setup a 1/4" TRS plug will much more likely be carrying a balanced mono signal. In the pro world, you're probably see XLR connectors, one for mono, two for stereo.

Point being, TRS is TRS. It isn't "stereo".

  • Very true - TRS does not mean stereo. Good point. But it is capable of delivering a stereo signal to an output designed to receive or transmit a stereo signal. Some devices will react to the TRS in a way that assumes stereo. But not all. You are correct as well about XLR connectors. – Rockin Cowboy Mar 2 '15 at 21:16
  • I edit the question based on your brilliant observation about the mis stated assumption in the question. Good one. – Rockin Cowboy Mar 2 '15 at 21:30

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