Aux/monitor send to In ear monitoring system

Question

Hope someone can help, can't find exactly my situation.

I have a Mackie proFx16 v3 which has 3 × 6.3 mm (pre fader switchable) Aux sends. (Well 4, but one of them is dedicated to Fx.)

My band is currently using 2 × active floor monitors – i.e. 2 monitor mixes, one fed from Aux send 1 and 1 fed from Aux send 2. All works fine, but there's the usual issues of too much noise on stage and occasional feedback issues.

We want to move to in-ear monitoring but still with 2 “mixes”, one shared by myself and a singer and another shared by 2 guitarists/singers. I'm planning on achieving this by buying 2 x SHURE PSM 300 in-ear monitoring systems, each with 2 bodypack receivers. So one for 1 mix shared by myself and vocalist (AUX 1) and the other shared by the 2 guitarist/singers (AUX 2) - hence 2 body pack receivers with each transmitter, which is not a problem.

The problem I cannot find a definitive answer to is the best way to hook up each PSM 300 transmitter to the mixing desk from the relevant Aux output – i.e. what cable? Each Aux send on the desk is just one 6.3 mm output, but there are 2 (combo xlr/jack) inputs on the back of the Shure PSM 300 transmitter, Left & Right. It would seem to me that as there are 2 inputs it would be best to use them both, but...

Would it be best to get a TRS jack to 2 × 6.3 mm jacks cable, or simply a mono jack to jack cable feeding just one input on the back of the PSM 300? (There's a note in the PSM300 manual which says: Important: When connecting to only one transmitter input, use the LEFT/CH1 input. Set the transmitter to MONO to hear audio on both channels)

I'm not sure whether the Aux output of the Mackie mixer is Stereo, Mono or balanced mono, and frankly whether it makes a difference in the real world. I don't need to hear “stereo” in the ear monitors, but do need the sound to come through both earpieces, not just one.

I've tried researching online and ended up going off at tangents detailing TRRS (rather than TRS) cables etc. which is just confusing me.

Any comments/suggestions very welcome!

Answer 1

If you don't need stereo, connect one aux output to the left input and set the transmitter to mono. This is the most common configuration for a band sharing a limited number of monitor mixes.

Regarding TS (tip-sleeve) or TRS (tip-ring-sleeve) cables: in the live sound world, TRS cables with 1/4" connectors will usually carry a balanced mono signal or an unbalanced stereo signal (less common). A TS cable always carries an unbalanced signal.

The point of any balanced signal is RF (radio frequency) noise rejection. The importance of this noise rejection depends on the length of the cable, the amount of RF noise present, and the level of the signal. (Sound engineer joke: what do you call a long unbalanced cable? An antenna.)

If you have a long cable, lots of RF, or a weak signal (or any combination of these factors), you'll need a balanced run from output to input. For example: if you need to run a low-level (i.e. mic) signal 150 feet through a hostile RF environment, balanced connectors and cabling are a must. If you need to send a line-level (strong) signal a few feet, a balanced run is rarely necessary.

Your situation is the latter. Connect your aux output to the transmitter input with the shortest possible cable, and you should be fine with an unbalanced (TS) run.

Answer 2

Concerning the technical part of your question: having a look at the Mackie's product description, the Aux sends seem to be mono, but balanced (please verify). The PSM300's product description mentions "Connector Type: 6.35 mm (1/4") TRS".

So that's fine: you can connect one of the PSM300s with 2 TRS cables, and the other one with 1 TRS cable (use the left input, which is de facto standard for mono).

The inherent musical aspect of your question: from my experience both as a musician and a mixing engineer, it is always better or at least useful to have a stereo signal. But you can try and then decide who of your band's members is going to use mono and who is taking stereo.