Mini DVI output to HDTV

I've hooked up my iMac to my TV (using an Apple mini DVI to VGA adapter and a 5 metre VGA extension cable) but I'm getting some 'ghosting'* that looks very similar to what you used to get if your TV reception wasn't perfect. Is there a kind and knowledgeable soul out there who might know why this is happening? I've read up a little on the problem and it seems it should only really occur with RF signals, although 'mismatched impedance along the communication channel' (whatever that means!) could also be the cause. Any and all advice would be much appreciated.

btw, the TV's a 1080p 40in Samsung, if that helps!

* by ghosting I mean the picture suffers from a very faint duplication of itself, laid over and slightly offset from the proper image.

Does your TV have DVI or HDMI inputs? You could try using the Apple Mini-DVI to DVI adapter, then a DVI cable to the TV or add a DVI->HDMI adapter on top of that and plug in HDMI to the TV. Not sure if this helps.

On a side note, I bought the DVI->S-Video adapter last night and got some terrible interference on my TV, so it went back right away. Looks like I'll be waiting until I can afford an Apple TV.

Balibari said:

'mismatched impedance along the communication channel' (whatever that means!) could also be the cause.

Click to expand...

Interesting, could be because of the length of the cable if that is true. Have you tried a shorter cable? (if you have one)

Thanks to you both for the advice.

I hadn't thought about trying a miniDVI to HDMI (don't know much about all this HD business yet!) but will do so now.

I did wonder about the 5m cable perhaps being the source of the problem and I'll pick up a shorter one to try too.

Thanks again.

It could be the quality of the extension cable as well as the length. I had a VGA cable that had ghosting, and only by purchasing a proper cable did it look fine. VGA cables should always be ridiculously thick.

Go for a DVI->HDMI cable.

That way the digital signals go all the way to your TV without being converted to VGA, and the Mac will probably detect what TV you have, and adjust the resolution automatically (mine did at least).

Mini DVI output to HDTV. Little help please?

I believe the ghosting may be caused by the analog VGA signal conversion to digital in the TV. VGA worked well enough in old TV's but stick to digital signals into your HDTV. We achieved wonderful results connecting a Mini-DVI to DVI adapter to our Mini then attaching a DVI to HDMI cable to the TV. (Both display ports on the Mini are video only) Our TV also has an "Audio In" connection for one of the HDMI connections on the back and this is the one we used to connect a separate audio cable to. The output is amazing at 1920 X 1200 (1080i). I think we spent less than $30 bucks for the adapter and DVI to HDMI cable. We already had several 1/8" mini to dual RCA audio cables laying around so we used one of those to hook up the audio. The Mini outputs digital audio out of the same port so we may switch to digital audio in the future but it's working so well right now we hate to "fix" it. By the way, our TV is a Toshiba 42" Cinema Series and the Mini is the latest model with the 9400M video card.