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I have a mac mini with 3.5mm audio out which I want to connect to an amplifier which is in another room, 20 metres away - the speakers are cabled back into the classroom. As well as a typical 3.5mm jack, it is also optical out which supports a "toslink mini-plug adapter", whatever that is. Given the distance, would I be better looking for a optical cable, an rca cable splitter from the classroom, 3.5mm cable which uses a splitter at the amplifier or something else? I am playing video, so audio latency is also an issue.

Amplifier connections

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Deleted my answer as it isn't relevant at 20 meters instead of feet and would potentially have latency issues. I also updated the question to include the fact it needs to be a low latency solution. –  AJ Henderson Jun 4 '13 at 12:48

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Your consumer grade optical link (the mentioned TosLink is Toshiba's name for a consumer standard) has a technical limit of 10 meters. It has been reported as being useable at up to 30 meters, but quality may suffer.

For best quality, what you probably want to do is go to a balanced format for the run. I don't know what you have available at the amplifier, but if it has the ability to take XLR (a circle with 3 holes in it) inputs, you could use a device called a direct box to switch the unbalanced output of the computer in to a balanced XLR cable which could safely make the 20 meter run.

If not, you might be able to make the run using a shielded 1/4 inch or even 1/8 inch cable since it is a somewhat powered signal, but it's going to depend a lot on the level of shielding and the amount of electrical interference in the area.

It might also be possible to use a direct box on one end and then use a balanced to unbalanced adapter on the other end, but I'm not sure what the performance implications of this would be as I've never personally tried it. I'm not even sure it would work correctly without a powered device on one end.

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Thanks for the very informative answer. The amp does have xlr so this looks like your solution might work great. Would this be what I am looking for? amazon.co.uk/Behringer-DI20-Ultra-DI-Channel-Splitter/dp/… –  mark Jun 4 '13 at 13:26
    
@Mark - you could use something like that, though the active design means you need to either be able to supply phantom power from the amplifier rack or will need batteries. Phantom power is sometimes marked as a "+48v" button. If it doesn't have phantom power, you can use a passive DI like this. Keep in mind that XLR cables are also mono, so if you want to preserve stereo, you need to split the audio and go through two channels. –  AJ Henderson Jun 4 '13 at 13:32
    
Passive sounds great as the amp doesn't seem to have phantom power. I've added an image of the amplifier, more info is found here: dasaudio.com/wp-content/uploads/documentos/documentos_d/… –  mark Jun 4 '13 at 13:40
    
@mark - is there any other signal processing in the rack? It's possible they are going directly in to the amplifier, but it is typical to have some signal processing prior to the amplifier in many setups. If you are able to take a picture of the entire rack it might help more unless the amp is the only thing there. –  AJ Henderson Jun 4 '13 at 13:46
    
I only have the amplifier. Is that a bad thing? –  mark Jun 4 '13 at 13:53

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