Reply To: Group Outputs / Mix Outputs Signal Strength

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DoctorG
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At the risk of insulting someone’s intelligence, let me explain how a balanced signal connection (XLR) works.

An XLR connection uses two signals that are out of phase with each other. The positive-going signal is on pin 2, the negative-going signal is on pin 3, and pin 1 is ground. When connected to either a proper transformer-coupled or differential amplifier circuit, the negative-going signal is inverted and added to the positive-going signal, giving a signal twice as large as the positive-going original. Any externally-generated noise signals induced into the signal wires will be in-phase in both wires, and the inversion process effectively subtracts one noise signal from the other. This further enhances the signal/noise ratio in a balanced circuit.

To use an XLR cable with an unbalanced circuit, the proper way is to use pin 2 as the signal and pin 1 as ground, leaving pin 3 un-terminated. You don’t get the 2X signal boost, or the induced-noise reduction, but this avoids the problem of grounding out the negative-going signal on pin 3. In most cases, this grounding should not cause problems, but it could. At any rate, grounding it does not help in any way.

With regard to the original issue – low signal levels at the Mix outs, I can’t help but think that the Mixes have not been set up properly. The inputs must be assigned properly to each mix and the levels of each signal into the mix must be set as desired. The Mix Masters then control the overall mix output level.