Balanced and Unbalanced Interfacing

Robert Katz Leave a Comment

From: Allen Minor

I just purchased a Sony wireless microphone system. I have a Sony DCR-TRV900 digital video camcorder. The system includes a WRT-805A body pack transmitter with ECM-44BMP microphone, and a WRR-805A tuner/receiver. The tuner/receiver instruction manual states the output connector is 3.5mm dia., balanced. The camcorder used stereo minijacks connectors.

My question is this: “Can I simply plug this unit into my camcorder and begin shooting? or do I really need to get an XLR adapter such as Studio One. The salesperson said I only need to just plug it in; however, I am very wary of the receiver instructional manual which states “balanced.” I’m wondering if this might be an error in the manual as that is a pretty small output jack to be balanced.

Hi Allen. You are right to be wary about the output connector claiming to be balanced yet on a mini jack. Well, it is an inexpensive unit, cutting corners. In some ways you should be happy (I guess) you’re getting a balanced output, if you are really getting one.

Find a voltmeter. Even an inexpensive one. You can go to Radio Shack and get one for virtually nothing (under $10.00). Get a stereo mini-jack and plug it into the output of the unit. Measure between ground (the sleeve) and one of the inner connections. Note the voltage (AC) on an average passage. Play the same passage again, and measure the voltage between ground and the other inner connection. The voltage should be about the same, let’s say around or a little under a volt on forte passages. Then measure between the tip and the ring, the voltage should be around twice the previous. If not, then you do not have an (active) balanced line output. If you can’t measure any voltage there, or extremely low voltage (millivolts), then you probably have a balanced mike level output from the source, and an XLR adapter would be exactly what you
need, wired as follows.

If your Camcorder has a balanced line input on XLR, then you should make an adapter from the mini, tip to pin 2, ring top in 3, ground to pin 1. If your camcorder has an unbalanced line input on some other connector, then you should make an adapter from the mini, tip to hot (probably also tip, on a 1/4″ connector or RCA connector, I assume) and sleeve (ground) to cold (ground or sleeve on the camcorder). Ignore the ring of the mini in this case.

A qualified technician should understand what I’m writing and make the correct cable. If not, then don’t do the wrong thing. The result could be obvious distortion of your audio.

Hope this helps,

Bob

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