Author Topic: Digital impedance?  (Read 631 times)

Offline Phase

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Digital impedance?
« on: February 26, 2017, 07:41:55 PM »
I'm running Mark's Xmos DXIO PRO3A USB/SPDIF converter, need to make a cable to run from the rca out into my Benchmark BNC (75ohm) in, what impedance cable must I run? 50/ 75/110 or what ohms?  There seems to be no clear answer here. Looked all over for specs no mention of the output impedance of the Xmos converter surely I must follow the Xmos impedance and not the dac?  Also can I use a normal rca plug? Apologies for all the questions.

Offline Rotten Johnny

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Re: Digital impedance?
« Reply #1 on: February 26, 2017, 07:51:16 PM »
use a 75Ω cable with the appropriate BNC.  AES3 is 110Ω.
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Offline Phase

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Re: Digital impedance?
« Reply #2 on: February 26, 2017, 08:07:10 PM »
use a 75Ω cable with the appropriate BNC.  AES3 is 110Ω.

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Offline Rodney_gold

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Re: Digital impedance?
« Reply #3 on: February 27, 2017, 03:14:14 PM »
Impedance is fubared if you have anything like a rca in the chain..
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Online chrisc

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Re: Digital impedance?
« Reply #4 on: February 27, 2017, 05:00:52 PM »
Over a short distance it makes no difference whatever.  Long runs or high power (read radio transmitters) then its important

Offline HGB2107

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Re: Digital impedance?
« Reply #5 on: February 27, 2017, 05:37:04 PM »
Use a good quality 75 ohms co-ax cable (like BELDEN) and use good quality plugs and you'll have no problems.

Offline pwatts

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Re: Digital impedance?
« Reply #6 on: February 28, 2017, 08:32:59 PM »
75ohms will get you the closest to the target but with rca it's a crapshoot. 75ohms cables tend to be a little more consistently shielded at least so it's still worth using over standard audio cables (even the expensive ones).

Offline Phase

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Re: Digital impedance?
« Reply #7 on: February 28, 2017, 08:59:52 PM »
75ohms will get you the closest to the target but with rca it's a crapshoot. 75ohms cables tend to be a little more consistently shielded at least so it's still worth using over standard audio cables (even the expensive ones).

Thank you kind Sir. I had a Van Den Hul - rca supposedly a 75ohm cable, suspected differently so bought a cheap multimeter(R200) It measured 30 ohms. Can't believe the difference, not sure if it's the new power supply or the cable but things are more crisp and clear sharper for a lack of a better word, noticed it immediately.

Offline pwatts

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Re: Digital impedance?
« Reply #8 on: February 28, 2017, 09:16:19 PM »
Thank you kind Sir. I had a Van Den Hul - rca supposedly a 75ohm cable, suspected differently so bought a cheap multimeter(R200) It measured 30 ohms. Can't believe the difference, not sure if it's the new power supply or the cable but things are more crisp and clear sharper for a lack of a better word, noticed it immediately.
Google 'characteristic impedance' and revisit this.

Offline handsome

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Re: Digital impedance?
« Reply #9 on: February 28, 2017, 09:19:56 PM »
multimeters measure resistance not impedance....

Offline Phase

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Re: Digital impedance?
« Reply #10 on: March 01, 2017, 05:54:53 AM »
Oops my bad! Saw 75ohms and assumed (yes I know). Been 25+years since operating one, I should put it back down.