While I agree that turning down the amp levels is likely a good solution it does assume that the rest of the
system gain structure is correct. One thing that could be related to that, or that may be another option, is that the Nexia SP allows you to set the analog output
level associated with a 0dBFS digital signal independently for each output with options of 0dBFS equating to 0, +6, +12, +18 or +24dBu at the analog output. I don't know your amp's sensitivity or maximum input
level but if the output of the Nexia SP is set for 0dBFS being +24dBu then that is likely much greater
level than the amp's sensitivity so the
level controls on the amp may need to be turned down.
Added: I realized that what I postedis probably just a bunch of numbers to some, so maybe it would help to explain it a
bit more.
For a digital signal the levels are defined in dBFS (Full Scale) where 0dBFS is the highest
level that can be represented. When converting from analog to digital (A/D) or digital to analog (D/A) one of the steps in that conversion is defining the relationship between the analog levels and the corresponding digital levels. A common way of doing this is to equate the maximum peak digital signal
level (0dBFS) to a maximum peak analog signal
level. In many devices this conversion is fixed and you have no choice, but because devices like DSPs are often inserted between other devices that may have varying maximum analog input and output levels, some
DSP devices let you adjust the relationship in order to better match their input and output levels to the connected devices.
As an example, if you are sending a
mixer output to a
DSP and the
mixer has a maximum analog output
level of +24dBu, then you would ideally want the
DSP input A/D to be set such that +24dBu equals 0dBFS. But if the maximum output of the
mixer is +18dBu then that would essentially be wasting 6dB of
headroom and S/N, which could be aided by setting the A/D conversion at the
DSP input such that +18dBu equals 0dBFS.
This can become quite relevant to
amplifier inputs as while amplifiers typically accept input levels of +20dBu or more, they often have a sensitivity, which is the input signal
level that provides full output, that is much lower with a sensitivity of +3dBu to +7dBu (1.1V to 1.7V) being pretty common. The options for input signal levels that are greater than the
amplifier's sensitivity are to
attenuate the signal at the
amplifier input, which is what the amp's
level controls effectively do, or to
attenuate the analog signal right before the
amplifier, perhaps at the output of the device before the
amplifier.
In this case, if the
DSP is set for a maximum output
level of +24dBu, that is set such that a 0dBFS digital signal equals +24dBu at the analog output, then you could easily require significant attenuation at the
amplifier. But if the
DSP outputs were set so that 0dBFS equalled +6dBu or +12dBu at the analog output then you still can get full
amplifier output but without needing as much attenuation at the
amplifier.
One negative to this approach is that any
clipping is much more likely to happen in the signal chain before the
amplifier and some people prefer to have the amplifiers clip first. Just another example of there being different approaches with pros and cons for different situations.
