Connect mixer to fm xmtr, noise-free, xlr to unbalanced? Can I run the length first balanced, then adapt? (Church)

Question

I'm trying to wire up a CZH 12V CZE-7C FM TRANSMITTER at church with stereo, its just pushing mono right now. I have to make a purchase to get the correct cabling.

The xmtr is installed in the foyer, near a foyer amp, where the feed is split to the xmtr, which is just connected mono currently.

I at first, wanted to just replace the whole cable run straight from the mixer, as xlr, then at the last second adapt, but then i wasn't sure if this xmtr is balanced, or unbalanced inputs. I'm thinking its consumer(1/7wt) hence unbalanced, but if i can get a confirmation, i would be grateful.

So i was going to go xlr to balanced 3.5mm trs at first https://www.amazon.com/gp/product/B07VRWK7DH/ref=ox_sc_act_title_1?smid=A3SP9D0HBLLG4I&psc=1, then i realized this may be a mistake. I don't want to fry anything either. Would that have fried something?

I an use some advice on the correct cabling:

Starting at the back of Mackie24x4 mixer, can i use the aux sends 5/6 with a ts mono/ts mono y splitter adapter cable to patch straight into the stage loom here? (xlr or trs, which is better here?)

I also have available tape outs which for some reason i cant get to work on my recorder, so not sure i want to play with them. I also have headphone2 out, but thats tied to master headphone vol, so that wont work. I want to setup the cleanest stereo run as possible.

Here's some of the equipment i was looking to buy, the dirt cheapest xlr patch cable, 50', to go from sanctuary stage box(half as close as mixer) to the back of the foyer amp/fm xmtr stack 1- http://amazon.com/Moukey-50ft-Microphone-Female-Cables/dp/B07FY4RLKK

(Dirt cheapest based on the premise that xlr shouldn't need to be shielded and oxyfree should it? i mean balanced, is balanced, and phase corrected already, so shield not apply, I'm thinking....)

From there i'm thinking i'll need one of the following

• normal unbalanced trs stereo adapter like this https://www.amazon.com/CableCreation-Stereo-Compatible-iPhone-more-Black/dp/B077VMZ52B/ref=sr_1_13?dchild=1&keywords=xlr+to+trs+3.5mm+male+adapter&qid=1601147468&s=musical-instruments&sr=1-13
• or a xlr to 3.5mm stereo unbalanced hard adapter https://www.amazon.com/dp/B07VB39G1H as opposed to the 3.5mm "balanced" adapter cable linked above.

Will that work?

Is it worth it to do the run via xlr on this type of application, to keep the noise down on a mixer output like this, instead of just using trs line all the way? I figured since the xmtr may be consumer-end, and the run will end up at least about '100', but about 150', since our stage box has a huge coil of extra. So will there be some reducible noise here if i run xlr, or will that not apply here? e.g.

• does the phase cancellation still work all the way to the foyer, assuming i keep it xlr all the way to the foyer for the length?
• or does somehow adapting it from xlr to unbalanced line turn change the circuitry back at the mixer to change the way the xlr now gets its feed to unbalanced non cancelling somehow?

Now, how can i adapt this new feed in the foyer correctly to this little CZH 12V CZE-7C 3.5mm trs? (unbalanced, or balanced?)

NOte, this has both mic and audio input. whats the difference? is one maybe balanced and one unbalanced, or is one maybe different resistance to accomodate a mic, or are they the same and just labeled bad?

Also, how would "you" run it, if different, to ensure the signal is totally noise free, 150'from mixer, through the stage box (xlr, or line?), to foyer split, then adapt to this xmtr???

Answer 1

Well, the critical question is about the inputs on that... thing, the FM transmitter. They're obviously not conforming to any professional audio standards. I would guess the audio and mic inputs correspond basically to the line in and mic in on a PC sound card. In which case the biggest difference is the gain, and possibly also the impedance. You almost certainly want to use the audio input.

And that can, if the device is stereo as advertised, only be an unbalanced stereo TRS. (Balanced with XLR or TRS is always mono, unless you have two separate cables.) –Which immediately implies that using XLR to TRS adaptors doesn't really make any sense, because those are for balanced connections. You're right that it would make sense to use balanced instead for a long connection; OTOH it's dubious whether any noise introduced by a long unbalanced connection will be significant at all compared to the noise from the radio connection which, with this device, I suspect will be quite horrible regardless.

So, the most sensible option is probably to just combine the stereo channels to TRS unbalanced stereo right after the mixer. That requires a 2×¼"TS ⟼ 1×¼"TRS stereo-merge cable. Then extend the connection with headphone extension cables (¼"TRS jack ⟼ ¼"TRS plug), and at the end scale down to ⅛" with a reverse headphone adaptor.

       ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
       ┃                               ┃
       ┃            Console            ┃
       ┃ Aux5 Aux6    MainOutL MainOutR┃
       ┗━━━┯━━━┯━━━━━━━━━━━━━┯━━━┯━━━━━┛
       ¼"TS│   │¼"TS      XLR│   │XLR
           │   │             │   │          ┏━━━━━━━┓
           │   │             └──────────────┨ Power ┃
           └─┬─┘                 └──────────┨  amp  ┃
             │                              ┗━━━━━━━┛
             │
             │⅛"TRS
        ┏━━━━┷━━━━┓
        ┃ AudioIn ┃
        ┃   FM    ┃
        ┃ Transmit┃
        ┃         ┃
        ┗━━━━━━━━━┛

A technically better option is to use balanced connection for the long way, and only de-symmetrize right before the transmitter. That requires a passive DI-box used in reverse direction. A good affordable stereo model is the ART DTI.

In particular, it would certainly make sense to use the existing (hopefully balanced) connection to the foyer power amp and only split there. That would require this wiring:

       ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
       ┃                               ┃
       ┃            Console            ┃
       ┃              MainOutL MainOutR┃
       ┗━━━┯━━━┯━━━━━━━━━━━━━┯━━━┯━━━━━┛
                          XLR│   │XLR
                             │   │
                             │   │
                             │   │
                             │   │
                             │   │
          ¼"TS┏━━━━━━━━┓¼"TRS│   │
      ┌───────┨In1 Out1┠─────┘   │
      │ ┌─────┨In2 Out2┠─────────┘
      │ │ ¼"TS┃        ┃¼"TRS
      │ │     ┃   DI   ┃
      │ │     ┃        ┃XLR          ┏━━━━━━━┓
      │ │     ┨    Out1┠─────────────┨ Power ┃
      └┬┘     ┨    Out2┠─────────────┨  amp  ┃
       │      ┗━━━━━━━━┛XLR          ┗━━━━━━━┛
       │
       │⅛"TRS
  ┏━━━━┷━━━━┓
  ┃ AudioIn ┃
  ┃   FM    ┃
  ┃ Transmit┃
  ┃         ┃
  ┗━━━━━━━━━┛

Note how the console output is connected to the DI output, the transmitter input to the input. That's not a mistake: in a passive DI, there's really no distinction between outputs and inputs; the crucial thing is that the “inputs” are unbalanced and the outputs balanced.

Also note that having most of the connection balanced is not a guarantee to be hum-free. You may need to experiment with grounding as well – it's hard to predict what will be best, but I'd suspect in this situation you should actually connect the transmitter's ground to the console's.