A bought a couple of Crown pro power amplifiers with only XLS inputs several years ago and have had problems with hum, so they have been taken out-of-service.

Recently, I purchased a 7.1-channel pro Denon pre-amplifier with ONLY XLS outputs. On the back of the pre-amp, near the XLS outputs, is a switch for balanced or unbalanced output. The switch applies to all 8 XLS output jacks (7 main channels and 1 sub-woofer). In addition to the 8 XLS output jacks there is an additional RCA jack for an unbalanced sub-woofer pre-amp output.

Currently, I have 7 of the main non-sub-woofer channels running from unbalanced RCA jacks into Denon non-professional power amplifiers. To do this, I'm using XLS-TO-RCA conversion jacks.

Is it possible to power sub-woofers in this system using the pro Crown power amplifier with only XLS input jacks? When I switch the Denon pre-amplifier output from balanced to balanced output, the 7 main channels are not receiving sufficient output to the unbalanced power amplifiers.

It seems like the Denon pre-amp is designed to run all balanced or all unbalanced output sources.