I have read some posts on this topic (or some of the other topics on the subject on this forum) where people have responded to this. Any extra length of cable, sockets, switches has the potential to degrade the sound quality, even if only in a minor way. First, a disclaimer - I don't have a box, and it's been years since I've used a double-y connector (and enjoyed the benefits them). I'm in the process of reconfiguring my system and will incorporate some mono capability for vinyl. The box appears to use reasonable quality sockets, and I assume that the wire is of reasonable quality, the length of wire used is very short. So I would expect the impact to be minimal, which has been reported by some who have bought it. However, it does require another set of interconnects, which is introducing extra length into the system, so it would be wise to ensure that both sets of interconnects used with the box are of at least reasonable quality and have an overall minimal usable lenght (as always, higher quality cables assist with good sound). A double-y eliminates the requirement for another set of interconnects keeping the signal path shorter. They do introduce another connection into the system. People have reported that using cheap+nasty double-y's have substantially improved the quality of listing to mono vinyl compared to listening in stereo. One person reported changing the cheap+nasty double-y's for a set of Monster y-cables, and found they provided higher quality sound compared to the cheap+nasty's. It was acknowledged that while Monster products can be a step up from cheap+nasty, that they are not regarded as high-end audiophile products. We can conclude that using double-y's made from audiophile-quality cable and connectors would provide higher sound quality, however, these don't appear to be commonly made by high-end cable manufacturers. If I were to make one, I would have a box with one set of input sockets and a switch to accept the phono cable. Rather than having another pair of rca sockets, I would have a short length of audiophile-grade phono cable with quality rca plugs to go into the amp. Of course, it all depends on the quality of your system. I doubt that much difference would be perceived on a consumer-level stereo, whereas differences would be easier to notice on a very high-end system.