Hello again,
I now have two complete outdoor systems and it would be nice to have the same music in both the front and back of the house.
All my stuff is big (as most of you know) and not permanently installed. Just for party nights. So if purity of sound isn't the issue here...
How do I transfer 150 ft of low level signal from the master pre-amp to the slave pre-amp when my stuff uses only the RCA type phono jacks?
The reason I'm asking the question here in this forum is that I'm not familiar with the persons on the other forums, and this one has been good to me.
I love DIY loudspeakers, not wires!
Cheers,
Cal
I now have two complete outdoor systems and it would be nice to have the same music in both the front and back of the house.
All my stuff is big (as most of you know) and not permanently installed. Just for party nights. So if purity of sound isn't the issue here...
How do I transfer 150 ft of low level signal from the master pre-amp to the slave pre-amp when my stuff uses only the RCA type phono jacks?
The reason I'm asking the question here in this forum is that I'm not familiar with the persons on the other forums, and this one has been good to me.
I love DIY loudspeakers, not wires!
Cheers,
Cal
Depends.
Most decent cables have a capacitance of about 40 pF a foot. Assuming something worse at about 60pF per foot , gives you a total capacitance of 10KpF . With a load of 50K ohms or less and 150 feet of cable AND a source impedance of 100 ohms ( Output impedance of preamp ) you are ok at 20KHz . Down by much less than 0.2dB .
But with increasing output impedance ( Tube preamp ) you will start having HF loss. With a source impedance of 1K ohm you get about -4.0db loss at HF.
So if you have Z out of the preamp kept very low , you could still manage it. Keep the load impedance also less than 50K ohms. 10 to 22K would be good. 50 K will also work.
Cheers.
Ashok.
Most decent cables have a capacitance of about 40 pF a foot. Assuming something worse at about 60pF per foot , gives you a total capacitance of 10KpF . With a load of 50K ohms or less and 150 feet of cable AND a source impedance of 100 ohms ( Output impedance of preamp ) you are ok at 20KHz . Down by much less than 0.2dB .
But with increasing output impedance ( Tube preamp ) you will start having HF loss. With a source impedance of 1K ohm you get about -4.0db loss at HF.
So if you have Z out of the preamp kept very low , you could still manage it. Keep the load impedance also less than 50K ohms. 10 to 22K would be good. 50 K will also work.
Cheers.
Ashok.
Thanks for the responses,
So I am hoping if I read you two correctly I should be Ok if I run a good thick shielded cable with RCA jacks, and if I don't, then I get a line booster?
I hope I don't need that, but is there a certain wire I should consider using to make the cable? Is there any kind of issue with line loss? That's probably a dumb question but I'll leave it in anyways. I guess it's the capacitance I should worry about.
Oh, and I re-measured the situation and it's less than 100 feet.
Should I just make a cable and find out for myself?
Thanks again,
Cal
So I am hoping if I read you two correctly I should be Ok if I run a good thick shielded cable with RCA jacks, and if I don't, then I get a line booster?
I hope I don't need that, but is there a certain wire I should consider using to make the cable? Is there any kind of issue with line loss? That's probably a dumb question but I'll leave it in anyways. I guess it's the capacitance I should worry about.
Oh, and I re-measured the situation and it's less than 100 feet.
Should I just make a cable and find out for myself?
Thanks again,
Cal
The cable.
Hi Cal,
For audio you probably only need to buy well shielded cable with low capacitance. Belden and Canare make good cables. These are pro companies and do not make "hi-fi type" cables. By that I mean these are well engineered cables and fit any hi-fi application.
Canare http://www.canare.com/catalog.html
Cable type L-2T2S .
Belden www.belden.com
You can use mic /balanced audio cable which has two conductors inside. Connect one to the hot terminal on the RCA plug and the second wire can be connected to the shield and the ground on the RCA plug.
These have very low capacitance . The diameter of the cable is no real indication of the quality of the cable. Many 'hot' looking audio cables are quite fat. You will find that most of the 'fat' is only the flexible outer covering. You however pay a lot of money for that.
You can pick up Canare and Belden at any pro-audio shop or possibly even at Fry's . A good mic cable is what you should look for. You will end up with something reliable . If you pick 'audio ' stuff made in Taiwan or China , you will have to test them to determine their capacitance per foot. It should be less than 150pF per meter ( 50pF per foot).
Don't bother about line loss etc. Even dc resistance would not matter here. Wire diameter ............ if it is an unknown brand make sure the wire is thick enough to handle. Some Chinese cables have super thin copper conductors ... the place where they save on manufacturing costs. With pro-audio grade cables you don't even bother about this , they will be easy to handle.
Cheers.
Ashok.
Hi Cal,
For audio you probably only need to buy well shielded cable with low capacitance. Belden and Canare make good cables. These are pro companies and do not make "hi-fi type" cables. By that I mean these are well engineered cables and fit any hi-fi application.
Canare http://www.canare.com/catalog.html
Cable type L-2T2S .
Belden www.belden.com
You can use mic /balanced audio cable which has two conductors inside. Connect one to the hot terminal on the RCA plug and the second wire can be connected to the shield and the ground on the RCA plug.
These have very low capacitance . The diameter of the cable is no real indication of the quality of the cable. Many 'hot' looking audio cables are quite fat. You will find that most of the 'fat' is only the flexible outer covering. You however pay a lot of money for that.
You can pick up Canare and Belden at any pro-audio shop or possibly even at Fry's . A good mic cable is what you should look for. You will end up with something reliable . If you pick 'audio ' stuff made in Taiwan or China , you will have to test them to determine their capacitance per foot. It should be less than 150pF per meter ( 50pF per foot).
Don't bother about line loss etc. Even dc resistance would not matter here. Wire diameter ............ if it is an unknown brand make sure the wire is thick enough to handle. Some Chinese cables have super thin copper conductors ... the place where they save on manufacturing costs. With pro-audio grade cables you don't even bother about this , they will be easy to handle.
Cheers.
Ashok.
Anyone using long twisted pair intercon
You could try a cat 5 twisted pair unsheilded its cheap and both chanels could go up same cable as there are 4 pairs. Iam using a twisted pair x 2 for my cd to amp interconect but cant advise on 100 foot run but I'd give it a go. Any one using long runs of twisted pair for interconect
You could try a cat 5 twisted pair unsheilded its cheap and both chanels could go up same cable as there are 4 pairs. Iam using a twisted pair x 2 for my cd to amp interconect but cant advise on 100 foot run but I'd give it a go. Any one using long runs of twisted pair for interconect
Belden 8451 is a good cable. Capacitance is 34pf/ft.
When using this cable on an unbalanced system, connect the red conductor to the center pin of the RCA connectors. On one end of the cable, connect the black conductor and the shield to the ground of the RCA connector. On the other end of the cable, connect only the black conductor to the ground of the RCA connector. Leave the shield floating.
When using this cable on an unbalanced system, connect the red conductor to the center pin of the RCA connectors. On one end of the cable, connect the black conductor and the shield to the ground of the RCA connector. On the other end of the cable, connect only the black conductor to the ground of the RCA connector. Leave the shield floating.
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