Hello Martin -
Thank you so much for your answer!
Can I follow up with two more questions in the newbie way please?
Martin wrote: "... Two are associated with the preamps, to help you set a suitable position for each of the rotary gain controls."
So, Martin - if the red light goes off here, that means it's purely an analogue problem? ... relating only to exceeding the voltage capacity of the preamp?
Yes - they are measuring the analogue levels at some stage of the preamp.
If so ... what is the best way to figure out what position to put the trim knob at? The Omni i/O has other inputs besides through the preamps (the aux ins, FX returns, e.g.), I guess all these sum to the final signal that is monitored by the output signal clip LEDs?
If you're talking about the preamp clip indicators then you should simply lower the gain controls slightly whenever you see them lit, as this shows you are perilously close to clipping.
Martin wrote: "... The other two monitor the output level of the Omni mixer, with 'clip' indicating a level of 2dB below clipping. As you say, these clip LEDs are prior to the send/return sockets, so I suspect it will monitor the level going to your compressor input."
Martin, by any chance could this be backwards? Looking at the flow diagram on page 16, I think the output level LEDs of the Omni Mixer are well downstream of the insert point to the compressor? ... and it's the preamp LEDs that are upstream of the compressor input point?
Just had another look at the Omni manual, and page 17 shows the two final output level LEDs are immediately prior to the Record/Monitor/Headphone outputs, and therefore after the insert return, while the preamp LED are just before the Insert send, so you hsould be able to use the first two as send level indicators and the final two as return level indicators.
Last question for clarification please, Martin: When you say it "indicates a level 2 dB below clipping" - does that mean 2dB below Full Scale?
Hmmm... It's not immediately clear whether any of the four 'clip' indicators are in the analogue or digital signal path (i.e. before or after the converters).
2dB below analogue clipping is not wise, and is likely to sound harsh, so I'm hoping it's 2dB below digital clipping and that the analogue path still has some headroom at this point, in which case you're right that it would be -2dBFS.