I'm set up principally for music but would like to play TV audio through Aux2 on my 122X.
A potted history of my set-up attempts...
In the beginning.
My TV is a Samsung UE46-6000 so has no RCA audio-out and the composites only play TV signal audio - so when you watch a DVD you get sound from the TV channel you were previously watching, not the DVD. So, I tried connecting audio-out from the DVD (RCA) direct to the 122X. This meant I can watch DVD films in glorious stereo. But, not TV. (to be frank, that would have been OK)
However, in a short while I get an intermittent buzz/hum from the speakers. It starts-off quiet and infrequent, increasing in volume until it is annoying and probably spaced 10-15 seconds apart. The buzz lasts for a couple of seconds. The audio has also lost lip-sync too, so time to turn off and have a re-think!
A revelation?
Er, no. I then tried a small DAC, connected via Toslink to the TV and with RCA outputs to the 122X. I can now hear what ever the TV is showing in glorious stereo and the audio quality is very good. BUT the buzz is back. Same thing again; about half way into a film you can faintly hear it on occasion - 15 minutes later it's 10-15 seconds apart and annoying as hell. No problem with lip-sync this time though.
In both cases when you stop playback, switch TV/DVD off and on and change input on the 122X to, say, CD and then try again, it seems to re-set. What ever was causing the problem has been 'purged' somehow.
The Hi-Fi is all plugged into a powerbar at one socket, the TV and DVD on another powerbar/socket. The DAC is USB powered and is plugged into one of the USB's on the TV. The RCA connection from DAC to 122X is a 10m ready-made and so the cable is nothing special; 'speaker cable' at your local highstreet TV/Audio shop. All the phasing is correct as far as I can see.
I'm at a bit of a loss. Is it mains hum? An earth-loop? RF interference to the interconnect? Or some other sort of feedback? The earthing on the 122X, powered by a flatcap, is via the usual route of powered Snaic.
I'd appreciate any thoughts on this as, whilst I'm not a die-hard home cinema buff, (otherwise I'd have a swish AV set-up by now!) It seems a shame I can't get it to function as a supplement to the weedy speakers you typically get on a 3cm thick TV... This may sound familiar to some of you who have connected several components, spread around a room, using varying cable types and multiple power points.
Sorry for 'war and peace' but it is a little frustrating.
Posted on: 21 April 2011 by 0x80
I recently got a Nait 5i connected to an external DAC with RCA. I experienced a loud hum as well, and discovered that its a grounding issue. The Nait doesn't connect the ground of the RCA connection like other amplifiers would, as far as I understand.
In order to get rid of the buzz I need to connect my DAC to earth. One way to do this is to connect a wire from the metal housing of your DAC, DVD whatever to the earth of your power supply.
I just joined this forum to see if I can solve this by hacking cable to connect to one of the DIN ground connections, since I prefer not to use an external wire connection to the housing. But that's for a different thread.
Search for "ground loop problems" on this forum and you'll find more info.
Posted on: 21 April 2011 by Conortsun
Thanks chaps. I thought it may be earthing - it seems to me (in simple terms) as if a small load is accumulating in the set-up somewhere and ultimately affecting something in the output stage of the preamp where it then gets amplified. I bet an electrical engineer would say that's poppy-cock! I'll have a try with the configurations, unplug the aerial etc. It may be cured through a little experimentation. I'll also look into the ground loop isolator too if all else fails.
On a separate but similar tack, I have earthing issues with my TT - that is another thread. If I can solve the TV earthing issue it may shed some light on the other.
My apartment's pretty old so it could be on the supply. Move house or grin and bear it may be the ultimate answer.
Thanks again. P
Posted on: 21 April 2011 by KRM
I have ground loop issues with home cinema amps plugged into the AV unity gain input on my NAC282. I solved them with a ground loop isolator. This worked very well, although I'm sure they're not ideal.
Another possibility is your cable. Many years ago I had problems with a sub which would occasionally hum. The hum would get progressively louder. It would stop if I switched off the sub and switched it back on. I eventually solved it permanently by getting a decent interconnect (Chord).
If your problem comes and goes perhaps it's not a ground loop? Ten metres is a bit long for an RCA interconnect.
Keith
Posted on: 28 April 2011 by Conortsun
Interesting. I have the DAC powered by the USB on the TV, a short Toslink and a long (10m) RCA...
Would it generally be better (and perhaps this may be the cure for the buzz/hum as KRM outlines) to have a 10m Toslink and short RCA's? I'll have to find a small 5v adapter to power the DAC. That shouldn't be a problem, or expensive.
Are there any (quantum) physics issues with a long optical link?
It seems reasonable to think a decent Toslink at 10m is less prone to interference being Digital/optical - and compared to 10m of high quality RCA audio it may be the more 'value enabled' option!?
