This is very cool; good to see a dedicated page. I am very tidy on Naim stereo, but know next to nothing about AV set-ups. Last Christmas I got bored, pushed the speakers against the TV and dragged out a Nait 3. Along with a new Play Station, the holidays were transformed! Later on, after things returned to normal, I bought a 5-meter lead and with judicious use of a NAC102’s balance control, produced a good TV stereo sound.

We are now finishing a new house and better AV opportunities arise! So far, the stereo is in a nice dedicated space with speakers up to 7 metres away. The TV will now lie between the two L&R speakers – a metre either side. This will give us the best of both worlds – my interest is mainly music but I like the bigger sound for movies. So far, I have built two AV cables into the wiring – VHS/DVD to preamp.

My question is this: the VHS (I have yet to even buy a DVD!) sits under the TV, whereas the preamp is 6 metres away; cables from the AV kit to TV could be as short as 200mm; whereas the audio signal needs to get to the preamp and back to the speakers (13 metres). Maybe the electrons won’t notice, but I have no idea - is there any risk of a “phasing” delay between the video and audio signals?

Cheers.

Andrew Annakin
Wellington, New Zealand.

If I get you right, the video lead is longer than your audio lead and you fear that the extra 5m could cause a delay between audio and video, right? If so, I can calm you down. All my cables are multiple lengths and my source is directly next to the amp but 5m away from the TV and absolutly no delays. you could of course calculate the speed at which the signal travels through each cable and I think you would get a really really small delay
I have never heard such a delay. If at all, most delays are produced either inside the source or inside the AVR, but neither should occur in your system.

I think most delays and lip sync problems you read about these days are due to progressive scan and up scaling timings. The processing time needed to do these knocks the video slightly behind the audio. At the moment I use my Panasonic DVD/HDD recorder to process my SKY output from RGB SCART to Component Progressive scan. If I listen to sky from it's own audio output I get lip sync problems, however if I listen to the audio via the same DVD/HDD that is doing the RGB to Component Progressive conversion I do not see any sync issues. I think the DVD player must delay the audio automatically to compensate. As Alex says, I would not expect you to have any problems due to the cable lengths you mention.

Found some nice calculation:

Time a signal needs in your cable when 1m long (approx. if estimated that speed in cable is between 0,5 and 0,8 times speed of light):

t = 1m / 220.000.000 m/s = 1/220.000.000 s = 0,000000004,5 s = 4,5 ns

So, let's say your one speaker cable was 300m long and the other one is 1m long, then you would have 299m * 4,5ns= 1.346 ns or 1,3 µs. (BTW the requency would be 770kHz, which is irrelevant as far as sound is concerned but could become relevant for video signals).
As the signal in video cables travels approx with the same speed, and only the difference of the distances is relevant and not the absolute distance (meaning only 5m in your case), the audio signal would be about 2.25*10^-8 seconds slower, which is 22.5ns and hence absolutly irrelevant.

Totally unnecessary post if you want, but on the other hand shows how irrelevant such things can be when only the speed and timing is concerned, but how important it can get, when transmitting a video signal which (like XGa signal (1024 x 768 x 50Hz) has a frequency of 48Mhz and hence a period time of 42ns and on a 10m cable this means it has a running time of 45ns, which means as soon as reflections pop up within your cable, you can get severe problems.

So, don't worry, no problems to be expected.