How can I take sounds from PC through Phantom XLR connector

[PaulL]

Hi All,

New to this, and hope that somebody can give me some direction.  

Local school has a 12 track mixing desk (at the rear of the room) that has Phantom power connected to an XLR multi-input box on stage (box has 12 inputs).  A number of these XLR connectors are used with suspended ceiling microphones and wired handheld microphones on stage.  The other mixing desk inputs are used with wireless microphones and Sennheiser EW112P G4 with clip on mikes.

I need to somehow come up with a way of taking a sound output from a PC (3.5mm output) that is on stage and feeding this to the mixing desk.  Can I convert the 3.5 audio so I can plug into the XLR phantom interface?

I do have some Sennheiser wireless units (Similar to EW112P G4) - could I take the sound output from PC straight into this unit and wirelessly transmit to the receiver at the rear of the room and interface to the mixing desk? 

Apologies in advance if my terminology is poor. 

Many thanks for any advice.............

Best regards - Paul

  

[Stuart91]

Something like this should do the trick. 

If the desk has "global phantom" (i.e. every XLR has phantom, rather than a switch per input) you need to be careful that nobody plugs in a minijack to XLR adaptor cable - it will take something out. 

[PaulL]

Hi Stuart91,

Thanks for the link - yes I think that would do the trick.

agree - its global, and I have been careful with that........ 

Appreciate your help - great to be able to ask questions by people in the know.

Many thanks - Paul 

[paulears]

'Take something out'? How? If mixers use global phantom power, the voltage is applied to each XLR input individually, through the usual two resistors across pins 2 and 3 of each input channel. If you did short it out by using a cable that has the pin one of each XLR connected to pin 2 (or 3) then the other channels will be fine. The downside is about half the 48V goes to the computer - but death is not assured, only possible. The safest option is to use a DI box as the transformer breaks the path for the voltage, and helps with the impedance mismatch. You could buy two really cheap ones instead of a stereo one -- for less than ten quid each. AND they'll be useful for other things too!

[J Pearce]

48V into a headphone output is pretty reliable at killing the output.

I’ve seen multiple devices of various backgrounds lose audio output this way.

[Keith_]

Yes, but I am wondering how those Senn receivers are protected from the 48V if it appears on every channel. I agree a transformer is ideal to block DC, but I have used a pair of 64V electrolytics in the path as recommended on  https://www.soundservices.co.uk/circuits-wiring-connecting-terminology-repairs/  (phantom power and radio mic receivers). Perhaps Paul would like to point you to a suitable mono transformer box.

[sandall]

2 hours ago, paulears said:

The downside is about half the 48V goes to the computer.

Sounds like a risk of "taking something out" to me.

[sandall]

2 hours ago, Keith_ said:

Yes, but I am wondering how those Senn receivers are protected from the 48V if it appears on every channel.

Don't know what Sennheiser do (IIRC my old Trantec kits had transformers on their outputs), but being plugged into 48v phantom is an occupational hazard for ANY mic with an XLR connector, so they will be designed be phantom-resistant.

[timsabre]

Most "electronically balanced" audio devices like radio mic receivers drive their outputs through bipolar electrolytic capacitors to decouple phantom power.

[Stuart91]

As Jon says, my concern was with the 48v taking out a headphone output if connected directly - the DI box will provide the isolation that the OP needs and also produces a balanced signal which is better suited to the longer run to FOH. 

 

My experience with Sennheiser Evolution receivers is that G2 and later seem to cope fine with phantom applied. If G1 receivers were connected to phantom (typically with jack to XLR adaptors in order to run up a multicore) they wouldn't behave nicely, but wouldn't break. Lifting pin one on the XLRs gets around the problem (as long as it's a balanced TRS jack into the receiver). 

Far neater to use XLR to jack adaptors at the desk end too, and bring them in a line input. 

[J Pearce]

4 hours ago, Stuart91 said:

bring them in a line input. 

That's a dying idea. A lot of desks now have just XLRs that get padded down for line input.

 

Back on topic for the OP - buy a DI box. Stereo or 2 mono - 2 mono might add flexibility as Paul suggests. Bluetooth DI boxes are also a thing that can be handy for avoiding the "I haven't got an adapter for USB-C" and "my adapter's stopped working" and "I can't use the adapter AND charge my device" discussions.

[Stuart91]

52 minutes ago, J Pearce said:

5 hours ago, Stuart91 said:

bring them in a line input. 

That's a dying idea. A lot of desks now have just XLRs that get padded down for line input.

Agreed - although most desks that have only global phantom will have separate jack sockets. 

Jon, how have you got on with Bluetooth DIs? I've been wary of relying on Bluetooth in anything approaching a production environment, but it might be an easy solution to dance teachers etc. turning up. (I'm fed up with my Lightning adaptors all going walkies...)

[J Pearce]

I wouldn't use a bluetooth DI for a proper show, but for rehearsal rooms, "warmup inputs", use in the bar etc. they are bloody great. Much less hassle for us, no need for muting for connect/disconnect, less wear and tear on cabling etc.

We have some of the Denon DN-200BR units, which work brilliantly (aside from the naming issue discussed in a different thread).

[sunray]

2 hours ago, J Pearce said:

I wouldn't use a bluetooth DI for a proper show, but for rehearsal rooms, "warmup inputs", use in the bar etc. they are bloody great. Much less hassle for us, no need for muting for connect/disconnect, less wear and tear on cabling etc.

We have some of the Denon DN-200BR units, which work brilliantly (aside from the naming issue discussed in a different thread).

The crazy thing... I've used these with the matching transmitter for music links a number of times and it had never occurred to me they are bluetooth.

[sleah]

24 minutes ago, sunray said:

The crazy thing... I've used these with the matching transmitter for music links a number of times and it had never occurred to me they are bluetooth.

Denon do an almost identical rx/tx set that use 2.4Ghz, which is probably what you've used. Don't think they are bluetooth though - just 2.4Ghz digital, bit like Line6. The unit above is a kind of add on to the range that does bluetooth.

I could be wrong... 🤔