QSC ISIS 215SB User Manual page 15

CONNECTIONS- XLR Connection Recommendations and Pinouts
XLR Connections
The XLR inputs are electronically balanced. To maintain the benefits of balanced, pro-audio connections,
make all connections to the 215PCM using balanced, high-quality cable and connectors. If balanced inputs
are not available, use a unbalanced-to-balanced converter, such as a "DI" box or proper audio transformer.
Unbalanced connections are prone to noise and interference pickup as well as ground-loop induced hum. If
your system has signs of noise or hum, disconnect all inputs to verify the source of the noise. If the noise
disappears, the noise source is not the 215PCM, but the input device and interconnecting cables.
If the input cables are short and the venue location free of most electrical noise, unbalanced input
connections might be acceptable. It is not the preferred method, but it is sometimes necessary. No damage
will be done using unbalanced connections, just a reduction in audio quality and performance.
All store bought balanced professional audio XLR cables are properly wired for use with the 215PCM. In
cases where you may need to make or repair your own cable, the pinout (or connection locations) for
balanced and unbalanced XLR's is provided, below.
Balanced XLR connections.
Unbalanced XLR connections.
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