Audio Transmission about 1000 meter - Page 1
Forum section: electronics / projects

author: skcode1
author_rank: Newbie
timestamp: March 01, 2012, 10:34:26 pm
content: I need to feed same audio signal to 10 power audio amplifiers each spacing at 120 meters.how can we use a twisted pair cable to connect all these amplifiers serially (like RS485 for example)any ideas or circuits please.

author: amspire
author_rank: Super Contributor
timestamp: March 01, 2012, 11:58:49 pm
content: You can get audio baluns for Cat5 cable that can go up to about 700 meters, but that does not offer taps for the intermediate amplifiers. In your situation, you will probably need a chain of baluns each doing 120 meters, and you will probably need a preamp at the end of each balun to restore the audio level and drive impedance for the next balun stage. You could use these baluns to drive a different twisted pair cable, as long as the transmission line impedance of the twisted pair is about 100 ohms.An example of a stereo balun that will do 120 meters is ebay item 350497983541.If you only need mono, and the signal feed can be in the middle of the chain, it would be possible to carry audio for 4 amplifiers on a single Cat5 cable using baluns, and so with two cables going in the two directions you could feed up to 8 amplifiers. you would need baluns like the Nile C5-A2 to get the distance. Each amplifier would have its own pair of wires on the CAT5 cable.Richard.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 02, 2012, 12:10:25 am
content: If the Amps all have high impedance inputs,you could probably do it in a very similar manner to RS485,with a termination at the far end.You would need to be able to adjust the Amp gains separately,as the last in line will have more line loss.The above is frowned on in Broadcasting,& the way it would normally be done would to be to use Splitter Amplifiers to provide ten 600 Ohm (or 40 Ohm),standard level outputs,which you could run to the 10 Power Amplifiers separately.The Public Adress people would do it differently again,using one large Power Amplifier,which is designed to drive a so-called"100-volt line",which then has suitable impedance loudspeaker units attached at the correct intervals.Whatever you do,use proper audio cable,& "XLR" connectors--they are designed for this kind of service,domestic audio stuff is not,nor are computer cables & connectors.

author: amspire
author_rank: Super Contributor
timestamp: March 02, 2012, 12:46:13 am
content: A better solution to my CAT5 baluns may be to get a high quality 600 ohm transformer, such as Mouser part number 673-T6003NL and phone wire.Normally telecom-type 600 ohms transformers are designed for 200Hz to 4KHz frequency responses, but this transformer is very good from 200Hz to over 20KHz.You may be able to get away with intermediate transformers without any 600 ohm termination, and have the last transformer with a 600 load on the secondary. The transformers give you a 1500V AC isolation between the amplifiers which is good.

author: skcode1
author_rank: Newbie
timestamp: March 02, 2012, 05:41:11 pm
content: Any one have a circuit for twisted pair Tx and Rx cause i need about 10 of them.

author: skcode1
author_rank: Newbie
timestamp: March 02, 2012, 07:45:56 pm
content: I need circuit for Differential op amps circuit to get my audio signal thru CAT5 cable

author: vk6zgo
author_rank: Super Contributor
timestamp: March 05, 2012, 08:14:09 am
content: Quote from: skcode1 on March 02, 2012, 05:41:11 pmYou've moved the goalposts!This is not at all like your original request.

author: Unknown
author_rank: Unknown
timestamp: March 05, 2012, 03:19:21 pm
content: Quote from: vk6zgo on March 05, 2012, 08:14:09 amAudio Transmission about 1000 meter! Easy

author: T4P
author_rank: Super Contributor
timestamp: March 05, 2012, 04:46:22 pm
content: Audio Transmission about 1000 meter ... Too easy , it might be slightly overkill depending on your application andpositioningbut it all matters , 1000 meter if you crank it up enough , probably ?No really ...

author: dcel
author_rank: Regular Contributor
timestamp: March 07, 2012, 05:17:08 am
content: Laughing so hard about fell out of the chair!Uncle Vernon had me going with the megaphone, then I scroll to Dave S' post, wow. Funny stuff!@OP Don't forget the delays, 10 amps and speakers spread out 1000m is a lot of air to cover. Time offset correction will be necessary.Chris