I wanted a way to get Sky+HD Dolby Digital 5.1 to my second room over Cat5. My wife bought me these Cat5 a/v baluns for Christmas: £30 cat5 video and audio balun sender and receiver Audio Video Over Cat5 Extender Balun Kit Only £26.50 at TVCables My theory is to use the 75-ohm composite video "V" connectors on these unpowered baluns to pass the 75-ohm SPDIF coax signal over. I am planning to use them in addition to HDMI with remote control over Cat5 with something like this: £73 cat5 hdmi and IR return balun sender and receiver pair HDMI Over Ethernet with IR Extender Cat5e Cat6 Only £72.99 at TVCables I just tried this over a £5 20 metre cat5e cable. In short it works. I tested for about 30 minutes, admittedly without lengthy A/B comparisons. The surround processor is a Tag AV32R 192. I use Linn active bi-amped speakers and a kef 200c reference centre in an acoustically tuned room. I tested with three sources: 1. Sky+HD Amstrad box. From the orange coax spdif dolby digital output. Seemed to transfer the dolby digital audio fine. Material either showed as dolby digital 5.1 or dolby digital 2 with pro-logic2 engaged automatically, depending on the program material. It sounded fine, although I have never heard Sky box digital audio over a relatively high-end system before. It was certainly discrete 5.1 including the sub at times. 2. HTPC m-audio 2496 soundcard. Played Aladdin dolby digital 5.1 both directly in to the Tag and via coax cables, the balund and the cat5 cable. It sounded fine. The THX intro glass explosion and deep thump intro sounded as big as expected. Dialog remained clear and steering effects were working. It was definitely dolby 5.1 3. CD audio (not dolby digital) from my htpc via a Musical Fidelity V-Link SPDIF coax output. This is my best cd audio source and sounds great playing my ripped CD's in 44.1KHz/24-bit. Certainly better than and CD, DVD or blu-ray source I have owned. Over the 20m cable and baluns it sounded ok, perhaps somewhat thin compared to the V-Link directly. Probably irrelevant compared to a Sky box dolby digital output which is packet based and I think includes checksums for error correction) which I presume travels over a longer wire with less effects. I suspect this is also why many reviewers report lower and AV kit being ok for dvd/blu-ray but poor for CD audio. Two notes to add: 1. I have read that the HDMI output that I'm also planning to send over cat5 cable does not include dolby 5.1. Plus my tag surround processor does not take HDMI audio. 2. I think the older (Thomson) Sky HD boxes have optical SPDIF but not the orange coax digital audio out, so would also need a powered optical to coax converter to use this approach.