The signal you see displayed as first LED illuminating on CH1,3 & 4 suggests ground bus modulation, but this shouldn't reflect a problem in any practical use of the mixer.
- the symptom is a result of the fact that input gain levels on unused channels are all set to maximum and signal input to CH2 is clipping the channel bus;
You can notice that only the first LED on CH1,3,4 meters illuminates - and only when CH2 signal level displays peak levels(i.e. as the RED LED lights up).
The result is that - because signal level input to CH2 exceeds the limits of the bus as the signal peaks - the excess current dumps to ground (this is normal), but it seems the amount of current dumped in this case is sufficient to momentarily increase the noise floor above normal levels, this change is picked up as low level signal input on the other channels because the channel pre-amps are unloaded and/or gain is adjusted to max
Simplest way to resolve this issue is re-set the gain structure correctly:
- Attenuate CH levels (so CH2 signal input doesn't clip hard) and turn down the gain on used channels (if the channels are unused, the gain shouldn't be up, and in any event setting input gain to is less than ideal!).
If the input connections for CH1, 3 & 4 are also unterminated - the effect would be more pronounced.
- please refer to p13 of your XONE:92 User Guide for more detailed information on configuring gain and operating levels: http://www.allen-heath.com/media/1623.pdf
In either case, you shouldn't be able to hear audible signal from the mixer's outputs and re-adjusting input gain resolves the issue.
Test by routing CH2 to X side of the cross-fader and other channels to Y; then set the x-fader position all the way to Y and monitor the output;
- If you hear a pulse at the outputs, corresponding with the the 1st LED lighting up, or if the symptom persists after input gain is adjusted correctly for normal levels and genuine practical use, something else is affecting the symptom
In these cases, the cause will be repairable and you should contact your retail supplier, or the official A&H distributor in your country for further assistance with service arrangements.
Details and links to our global distributors are available via the following link: http://www.allen-heath.com/where-to-buy/