Two preamps connected to one amp?

Is there any harm and/or sound degradation in connecting two preamps to my McIntosh MC252 by utilizing the Balanced and RCA inputs? There is no Bal/Unbal switch on amp. Of course, only 1 preamp will be powered on at a time. My main preamp is the McIntosh C42, connected by balanced cables. I also have a tube preamp that I would like to use for a separate CD player. I would connect that to the amp using the RCA inputs.
Thanks for any info.