RCA Y- cable or is an A/B switch required?

I would like to connect my CD player to two different preamplifiers (one stereo connection for my surround sound receiver and one stereo connection for my vintage McIntosh gear). In the old days, we simply used an RCA Y-cable for each channel, but I am curious if the sound quality or a possible line level instability might arise.  


A coaxial switch would be the best solution but if you make sure you turn off the amp you aren't using, it would probably be OK.

Just use the Y - connector for each channel on the CD player. No harm will come to it! 

What Jason said. A quality Y (like AQ or Morrow) MIGHT make a difference. 

He won't say that.

I recommend using the all-metal y-connectors. No short cable attached to it. Eliminates potential wire coloration!

@fuzztone : when I wanted to add some brand-new ICs I bought 5 pairs of the AQ Silver Extremes - a $400 IC! Got them for $90 each from HCM as close-outs from AQ. 

All AVRs have PCM compatible Toslink or SPDIF coaxial inputs. Why not use one of those for the AVR hookup?

I am about to experiment with y pieces to run parallel xlrs to then get back to one at amp


Forgetting optical for the moment, with a coax connection you usually have a low impedance output and a high impedance input to the next device in the chain.  If you put two inputs in parallel, there is a formula to determine what the resulting impedance (load) will be for the driving output.  Many of the folks on this forum are spec-happy and should have no problem doing the math. Now see if the resulting load impedance is within spec for the source device and how the output frequency and phase response will be affected.  You can probably easily see the difference on a scope just by running a tone or white/pink noise into the devices.  You will need to take three readings - with load A, with load B and with both in parallel. The loads will usually have a Z of under 100K while the scope will be a meg or so and will not affect this reading, although it might introduce a bit of noise depending on your bench environment.  This will tell you what is actually happening, but what Your and Your ears alone prefer is the deciding factor.  

I am about to experiment with y pieces to run parallel xlrs to then get back to one at amp

Careful! You don't want any common grounds if you are running balanced circuits..