Protocol on mixing -10db and +4db line levels

I'm putting together a bi-amped system and I'm planning on powering all four channels from a Carver AV-64 amp from the day. The Carver has a built-in 75hz crossover which I plan to try, but it may not be the ideal roll-off point for my speakers so I want to keep my options open. I happen to have an ART cx310 active crossover network that seems like it would do the job well, but given that it only has XLR and 1/4" I/O (definitely pro gear) and the Carver only has RCA (definitely home gear), I worry that sending what is probably a +4db signal into jacks expecting a -10db level might cause problems. But I'm not really sure how line voltages work and I would love some clarification. My whole system is going to be something like:

Computer -> USB DAC -> RCA cables -> Passive Attenuator -> 1/4" cables -> Crossover (either ART CX310 or built-in on Carver) -> Carver AV-64 -> Maggie MMGs and 2 Passive subs

Thoughts? Somebody want to explain why there are two different line level standards and why it matters?

I wouldn't worry about the difference in line-level standards. "+4 db" undoubtedly refers to +4 dbu, which is a line-level standard for professional equipment, and which corresponds to about 1.23 volts. A consumer-oriented cd player or other digital source, probably including your USB DAC, will commonly output a full scale (maximum) value of 2 volts or so, which is considerably more than +4 dbu!

"-10 db" undoubtedly refers to -10 dbV, or 10 db below 1 volt, which in turn is approximately 0.32 volts. 1.23/0.32 corresponds to a difference of a little under 12 db, which simply means that you will have to reduce your level controls to settings that are 12 db lower than you would have to if the you were putting a full scale voltage of -10 dbV into the Carver.

But keep in mind also that you will not necessarily be putting a +4 dbu signal into the Carver. The full scale (maximum) signal that you would put into the Carver will correspond to the full scale output of the DAC reduced by the attenuation provided by the passive attenuator, and further reduced by the attenuation corresponding to the level control settings on the CX310, the adjustment of which will in turn take into account the desired volume, the sensitivity of the speakers, and the gain and sensitivity of the Carver.

In general a more significant consideration would be how to interconnect the balanced and unbalanced interfaces. This paper may be of interest. Fortunately, however, I note that in the case of your CX310, according to the manual, all you have to do is to utilize unbalanced cables terminated with 1/4" TS (tip-shield) phone plugs, and you're all set!

-- Al
Very informative response Al, thanks a lot

What Al said.....

Something like these would work if you already have RCA cables

Most pro gear these days will work either way, and like your crossover if you plug in a single ended 1/4 inch plug it will automatically configure itself for SE operation.