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Old 10th April 2009, 10:21 PM   #1
G is offline G  United States
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Default Using coax for signal wiring?

Hi all. I'm in the process of buying parts for two separate components and I'm trying to decide what kind of wire to use for signal wiring. I am thinking of using this for that purpose:

http://www.canare.com/index.cfm?obje...2B810B1D1F094B

All of the inputs would be shielded. It seems to have a pretty low capacitance rating. Thoughts?
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Old 10th April 2009, 10:32 PM   #2
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The capacitance is high: 21pF/foot. So not a good choice if the driving source impedance is very high, or for a long cable run, as you'd get HF rolloff.

That's true of most RF coax cables.

If you want shielded cable like coax, you can look for high-Z unbalanced microphone or musical instrument cables, they have lower capacitance.

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Old 10th April 2009, 10:40 PM   #3
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Quote:
Originally posted by pmillett
The capacitance is high: 21pF/foot. So not a good choice if the driving source impedance is very high, or for a long cable run, as you'd get HF rolloff.

That's true of most RF coax cables.

If you want shielded cable like coax, you can look for high-Z unbalanced microphone or musical instrument cables, they have lower capacitance.

Pete
The source impedance is surely low. This pre will be getting it's signal from a Aragon A2D2 Dac. I can't imagine the source impedance being more than 600 ohms or so and I'm guessing it's probably lower. Let's say however that I want to be able to use this pre with a source that has a much higher output impedance, what wire would you recommend Pete? BTW, thank you for your reply.
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Old 10th April 2009, 11:20 PM   #4
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RG-59 coax cable is pretty much the standard line level cable in audio, isn't it?
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Old 11th April 2009, 02:17 AM   #5
nhuwar is offline nhuwar  United States
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Quote:
Originally posted by Evenharmonics
RG-59 coax cable is pretty much the standard line level cable in audio, isn't it?

I don't think so. As far as I know it mostly shielded twisted pair with a drain line on the shield too.



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Old 11th April 2009, 03:39 AM   #6
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Default Signal cable

Greetings, for all of my audio DIY projects I use RG-174 coax made by CAROL. Got it at Digikey, 35 bucks for 100 ft. on a roll. Its rated at better than 90% shielding which is what you want.

I don't know what that other person considers high capacitance but 21 Pf. per foot is nothing. The 174 is 31 Pf. per foot and there is NO loss at audio frequencies. At 100 khz. 100 feet of 174 has a loss of .4 db, see specs.

The best microphone cable I saw from BELDEN has at best 33 pf per foot but is a quarter of an inch in diameter, HUGE!!

And the best part of using 174 is it is only about .125 of an inch in diameter. Very small and easy to work with, very forgiving of bends.

You are using it for input and output signals from a preamp so you should have no problem with the 174. The input/output coax cables that Marantz used for their stuff during the 70's I measured at a whopping 230 Pf per foot. Now THATS what I would consider high capacitance. But it made no difference to the audio, my 2270's all sounded great. I have 4 of them now.
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Old 11th April 2009, 04:29 AM   #7
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I once built a preamp with a different Coax on each of five inputs that ran from the back panel to the selector switch in front. The length was about eleven inches. I remember that of the ones I tried, Canare was easily the worst. What surprised me was that the best (or the one I liked the best anyway) was a mic. cable from Gotham with a spec'd capacitance that IIRC wasn't that much lower, but was very clean sounding. Specified for microphone use, I think the type number was GAC-2.
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Old 11th April 2009, 04:46 AM   #8
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I appreciate all of the replies but I have to say this. If you are looking for a difinitive answer to a question.........................don't ask here.
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Old 11th April 2009, 04:50 AM   #9
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I'm kinda partial to RG-316.

the mil rated stuff is nice.. silver plated braid and conductor, ptfe insulation. costs a fortune new, though.
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Old 11th April 2009, 03:19 PM   #10
nhuwar is offline nhuwar  United States
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LOL I agree G. If you want opinions ask here, but sometimes thats just as good.


Colt45

You still have a capacitance issue with it and since it's of small diameter you capacitance is higher 31pF per foot.


Nick
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