External display help - maximum length of run...

nabisco

macrumors newbie
Original poster
Sep 12, 2008
25
0
ok,

I just got a new 13" MBP to replace my 2006 Core Duo Macbook. Any help you may be able to offer would be greatly appreciated. Here's the problem:

I used to connect my macbook to my projector (Panasonic AX-200) using an :apple: mini-dvi to DVI adapter, a DVI to HDMI adaptor, then a 10m HDMI cable to my projector. This worked flawlessly, both for mirroring and extended display.

When I got the new machine this week, I bought a cheap mini displayport to HDMI adapter off ebay to go with it. Using the same 10m cable, this would show the extended desktop for about a second then go blank, then repeat this cycle indefinitely. I then tried using a shorter HDMI cable to check the adapter and mini displayport. This worked perfectly.

However that was with a 2m cable, I need a 10m run for the cable. So, I bought an :apple: mini displayport to DVI adapter today, hoping that the cheap ebay adapter was the source of interference or impedance. However, using the same setup as my macbook, albeit with the new :apple: adapter, it doesn't display an image at all. Again, using the 2m cable works perfectly.

The video settings are 720p as they should be, and I've still got the macbook and checked that it still works, so my question is for signalling geeks I suppose. Is there a power issue here? Is the mini displayport just outputting less juice than the mini dvi? Do HDMI cable impedances vary significantly?
 

Hellhammer

Moderator emeritus
Dec 10, 2008
22,164
581
Finland
Maybe the DisplayPort signal has to be converted more which will cause weaker signal thus lower range. Have you tried another 10m HDMI cable? Is 10m really needed or would 8m be sufficient?
 

nabisco

macrumors newbie
Original poster
Sep 12, 2008
25
0
Thanks for your fast response.


That is a possible issue, but as far as I'm aware, there is no signal conversion, the adapters are just to relocate the pins. I think mini displayport is multi-signal compatible, or am I mistaken?

The 10m cable is plumbed in to a large extent so I'd prefer to avoid having to replace it. It was my understanding that HDMI cables could run for quite large distances (15m+). It still doesn't explain why the Macbook seems to perform better than the new Macbook Pro
 

Hellhammer

Moderator emeritus
Dec 10, 2008
22,164
581
Finland
Thanks for your fast response.


That is a possible issue, but as far as I'm aware, there is no signal conversion, the adapters are just to relocate the pins. I think mini displayport is multi-signal compatible, or am I mistaken?

The 10m cable is plumbed in to a large extent so I'd prefer to avoid having to replace it. It was my understanding that HDMI cables could run for quite large distances (15m+). It still doesn't explain why the Macbook seems to perform better than the new Macbook Pro
At least when it's done vice versa (HDMI to DP), it's more complicated and a total conversion is needed. I don't know is that the case. AFAIK, +10m cables need some kind of active extensors so the signal stays stable
 
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