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Wiring a balanced Mic as unbalanced


Neil Hampson

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OK, I should know this one, but as a lampie, you'll need to bear with me.

 

I have been asked to terminate some Beyer DT290 headsets for use with a TecPro system, now I know the Beyer is a balanced device, and that the canford is obviously unbalaced. my instinct is to join the shield to the cold leg of the mic and wire the hot as normal, or should I just ignore the shield and just wire across the hot and cold?

When searching I came across one site that advised to wire the shields to the shield pin and join the hot and cold together for the live.

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TECPRO CABLE REQUIREMENTS

Two factors affect the choice of cable for a particular system or installation. They are:

– Length of run – longer runs require larger cable

– Number of outstations on each cable run increasing the number of outstations

requires larger cable

In general, we recommend 0.5mm2 (20AWG) twin screened cable should be used

(Canford heavy duty cables FST-HD, HST-HD and HST-HD-R are suitable), as this

allows most flexibility of application. However, for short runs (up to approx 150 metres),

provided that no more than about 12 outstations are served, a smaller cable 0.22mm2

/0.25mm2 (24AWG) will usually be acceptable (Canford types FST, HST and HST-R are

suitable). For short cables of a few metres length serving only one station (eg. between

wall connector and beltpack), the core size is not critical.

Canford cable types HST-R and HST-HD-R have a polyurethane jacket, which has very

similar properties to rubber - ie. very abrasion resistant and resilient. FST-HD is a foil

screened cable specifically for installation purposes.

WIRING CONVENTIONS

System cable connectors: Headset connectors:

XLR 3 pin - Pin 1 Earth/screen

XLR 4 pin - Pin 1

Microphoneearth/screen

Pin 2 + 24v DC Pin 2 Microphone signal

Pin 3 Audio Pin 3 Earphones earth/screen

XLR 6 pin - Pin 1 Earth/screen Pin 4 Earphones signal

Pin 2 +24v DC XLR 5 pin - (BP116 and BP117 only)

Pin 3 Audio, circuit 1 Pin 1 Microphone earth/screen

Pin 4 Audio, circuit 2 Pin 2 Microphone signal

Pin 5 Audio, circuit 3 Pin 3 Earphones earth/screen

Pin 6 Audio, circuit 4 Pin 4 Left earphone signal

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When searching I came across one site that advised to wire the shields to the shield pin and join the hot and cold together for the live.
:pissedoff: B-) :blink:

 

I think I'd go for your option 1, though both should work.

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Option 1. Because if you join the hot and cold legs together you will cancel the signal out as cold is 180degrees out of phase with the hot. If I remember the Beyr Headsets have both balanced Mic and Stereo Headset(If there are two cups)

 

So

Pin 1 = Mic ground + Mic Cold

Pin 2 = Mic Hot

Pin 3 = Speaker Ground

Pin 4 = Speaker L + R

 

Hope this helps

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