Preamps, balanced and unbalanced lines out...

Can you connect both the balanced and unbalanced lines out of a preamp simultaneously?

Say perhaps balanced to the amp and unbalanced to a powered sub? Or perhaps balanced to one amp and unbalanced to a different amp?

If I want to do this, what capabilities must I look for in a preamp?

Most preamps will output simultaneously to both balanced and unbalanced outputs. Usually you don't have to do anything to make this happen.

I know there are a few that can switched through the menu system to output to either or all.

I have done this many, many times.
As Mofi indicated, usually both outputs will be active simultaneously, or they can be made so via menus.

However, in a lot of designs the balanced and unbalanced outputs are driven by the same output stage, and in a lot of those cases the RCA output is internally connected directly to the non-inverted signal pin on the XLR connector. In those cases using the RCA and XLR outputs simultaneously may result in at least a slight degree of compromise sonically, depending on impedances, cable lengths, and a number of other variables.

Ideally you would want the design to provide separate and independent output stages for the RCA and XLR outputs. The manual might indicate whether or not that is provided, or else an email to the manufacturer would hopefully provide an answer.

-- Al
The fairly new Classe CP800 is designed to output specifically to a split system like what you have. I use mine to run my Snell Type A reference system. It's the best I've heard yet. Joe
Thanks Mofi and Al for your replies. I had considered contacting the manufacturer; now I know what question(s) to ask. Thanks again,