Headphones on a Yamaha A/V receiver with digital audio
Not sure if this is the best place to put this as my question spans a number of forums, but given that it's predominantly a receiver based question I thought I'd start here.
I have a Yamaha RX-V3900 receiver and some Sennheiser RS140 wireless headphones. I want to be able to connect my headphones to the receiver whilst not muting the speakers, so that for example if I want to go and do something in another room whilst someone else is watching a programme, I can still hear what's going on without it being really far too loud. I have been able to successfully do this for analogue sources by connecting to the MD/CD out RCA connections, which are intended for a recording deck. However, my receiver doesn't convert digital audio to analogue, so if I want to listen to a HDMI or optical source, I can't use the headphones without using the headphone jack at the front, which then mutes the speakers.
My solution to all this would be to buy a DAC that accepts optical input; I had this in mind: http://www.lindy.co.uk/spdif-digital-to-analogue-stereo-audio-converter/70408.html I plan to connect this to one of the optical out connections, then through a 2-into-1 jack to the headphones. The other half of the jack could be connected to the analogue connections as I currently have configured, and hey-presto whatever source I go for it should come through the headphones. I'm not looking for the last word in audio quality, just something that is reasonably clear with little extra interference and distortion. I am also assuming that as this connects to the headphone transmitter, and the headphones are powered by batteries, that I won't need a headphone amp for the source (it already works with the CD recording jacks anyway, which I presume are at line-level). Does this seem like a reasonable solution to the problem; should I be spending a lot more or less money on a DAC, what alternatives should I consider etc etc? Any advice is welcome!