XLR to RCA interconnect. Does mixed connectors provide less noise compared RCA to RCA?

I was going to suggest the Jensen Transformers, but Auxinput beat me to it. Though I would disagree that they are 'a lot of money'. For $300 bucks, they cost less than many RCA cables, and XLR should provide you more audible improvement for the money.

One reason to go TO an XLR at the amp is when the XLR inputs have greater impedance than the RCA equivalents, often XLR inputs are double.

Usually, although not always, the reason for the doubled impedance on XLR interfaces (inputs or outputs) compared to RCA interfaces is simply that the XLR spec reflects the sum of the impedances of the two signal legs. And the impedances of the two legs are generally made equal, to optimize noise rejection. So driving a single-ended signal into one leg of a balanced input, with the other leg of the input grounded, will in most cases not improve impedance compatibility compared to an RCA-to-RCA connection of the same equipment. And for the same reason an XLR-to-XLR connection will often result in an impedance ratio between two components that is no different than an RCA-to-RCA connection between the same components.

Although in some designs, in which the XLR and RCA interfaces are handled by circuit stages that are separate and independent, the balanced and unbalanced impedances may differ by either more than or less than the factor of two that is commonly seen.

Using an XLR output to RCA may help isolate from ground loops as the RCA pin and shield will be actively driven, with very high impedance to ground and the shield only connected on one end.

Assuming a direct XLR to RCA connection is made (i.e., a transformer such as one of the Jensen models is not being used), obviously a return conductor must be provided between the two components, whether it be a shield or, alternatively, a conductor within a shield that is connected at just one end. Assuming the RCA input is unbalanced (a balanced RCA input would be very unusual), if that return conductor is actively driven the actively driven signal will usually end up being connected to the destination component’s circuit ground, which in turn will usually be connected to that component’s AC safety ground through some low impedance or in some cases even directly. Not good news either way, with hum or conceivably even damage very possibly resulting.

As suggested by some of the others a Jensen transformer (or at a considerably higher price point something like an SMc Audio Flex-Connect, which is also transformer based) is the ideal way of interconnecting XLR and RCA interfaces.

Best regards,
-- Al

The only real benefit that you might get is if you run a true XLR cable and then use a Jenson Transformer XLR-to-RCA converter

The Jensen Iso-Max is a good device. As auxinput stated, you can
use a fully balanced XLR cable from the CDP and convert the signal to RCA . The question is whether or not this will result in superior sonics compared to a good RCA interconnect.

The Jensen unit does require a low to medium impedance cable be used. I found the Jensen to be very transparent sonically, so the sonic signature of the interconnects being used remain true.
http://www.jensen-transformers.com/product/pc-2xr/

Question for Almarg - Al,  would the impedance of the XLR be different to the RCA - if so could that have an impact on sound qualjty?

Any thoughts as to which one should have the greater impedance

Thanks