Need help identifying old interconnects

[Briank]

Thanks!. That's exactly why I prefer copper cable.

But WHY copper Gary!?

 

[Briank]

Well, crud, that blows my only reason for staying in this thread... I used to help review papers for the IEEE JSSC and was looking forward to something different.

lol sorry to disappoint. Ill try harder.

 

[Zapper]

Sorry if I'm repeating somebody as I haven't read past the 1st page.

This looks like RS-485 cable, maybe close to this. The impedance (conductor to conductor) is specified as 120 ohms. In the RS-485 application, it is driven with a differential signal. The line to line capacitance is 12pF/ft, and the line to line+shield is 22pF/foot. Other brands of RS-485 cable likely have similar properties. RS-485 cable is intended to drive data over long distances, so is designed for low dielectric and conduction losses.

If both conductors are wired in parallel and referenced to the shield, the impedance will drop and the capacitance will go up - I estimate 40pF/ft. The datasheet doesn't give a spec for that configuration. That wouldn't matter unless the cable were very long.

I'm in the "all decent interconnects have no sound" camp, so I can't speculate on the perceived qualities of this type of wire. The Belden RS-485 cables are very high quality cables intended for long life in harsh industrial settings, so they should serve well for a home audio application.

 

[Briank]

Sorry if I'm repeating somebody as I haven't read past the 1st page.

This looks like RS-485 cable, maybe close to this. The impedance (conductor to conductor) is specified as 120 ohms. In the RS-485 application, it is driven with a differential signal. The line to line capacitance is 12pF/ft, and the line to line+shield is 22pF/foot. Other brands of RS-485 cable likely have similar properties. RS-485 cable is intended to drive data over long distances, so is designed for low dielectric and conduction losses.

Those are very close but the original doesn't contain a drain wire. I think Blumlein nailed it with the Belden 89207 TwinAx. Good data tho, thank you.
If both conductors are wired in parallel and referenced to the shield, the impedance will drop and the capacitance will go up - I estimate 40pF/ft. The datasheet doesn't give a spec for that configuration. That wouldn't matter unless the cable were very long.

I'm in the "all decent interconnects have no sound" camp, so I can't speculate on the perceived qualities of this type of wire. The Belden RS-485 cables are very high quality cables intended for long life in harsh industrial settings, so they should serve well for a home audio application.

Im in the middle somewhere haha but perceptions need not apply, no worries. Question though, is there a typical impedance range diy-ers should stay in with building rca interconnects? I would have to think if a typical is around say 50-75, using one with 120 would surely have some consequence somewhere, no? Perhaps in only longer runs.

 

[Blumlein 88]

Those are very close but the original doesn't contain a drain wire. I think Blumlein nailed it with the Belden 89207 TwinAx. Good data tho, thank you.

Im in the middle somewhere haha but perceptions need not apply, no worries. Question though, is there a typical impedance range diy-ers should stay in with building rca interconnects? I would have to think if a typical is around say 50-75, using one with 120 would surely have some consequence somewhere, no? Perhaps in only longer runs.

Actually it was sam_adams who found the 89207 TwinAx, I just concurred.

The characteristic impedance of RCA interconnect makes no difference at any reasonable lengths at anything near audio frequencies. 20,000 hz has a wavelength near 50,000 feet in wire. So with the idea it couldn't matter at less than 1/10 wavelength you still aren't worried until about 1mile of wire.

 

[Briank]

Actually it was sam_adams who found the 89207 TwinAx, I just concurred.

My apologies sam. I must have mixed it up during the tornado. Thank you for reiterating, Blumlein.

The characteristic impedance of RCA interconnect makes no difference at any reasonable lengths at anything near audio frequencies. 20,000 hz has a wavelength near 50,000 feet in wire. So with the idea it couldn't matter at less than 1/10 wavelength you still aren't worried until about 1mile of wire.

Excellent, thank you.

 

[Zapper]

Question though, is there a typical impedance range diy-ers should stay in with building rca interconnects? I would have to think if a typical is around say 50-75, using one with 120 would surely have some consequence somewhere, no? Perhaps in only longer runs.

I concur with @Blumlein 88; the characteristic impedance makes negligible difference for most audio applications. (I say most, because there are probably some fringe cases, such as very long cables or high output impedances, where it will matter). The capacitance is more likely to have an effect for longer cables, where some amplifier outputs may degrade in quality when driving large capacitances.

As for 100 or 120 ohms, that's only when the two conductors are driven differentially, with opposite polarity on the two wires. In that case, no signal current is induced in the shield. The impedance will be lower when the signal is single ended and return current flows in the shield, likely in the 50 to 75 ohm range.

I also agree that your wire looks similar to 89207 TwinAx.

 

[sam_adams]

My apologies sam.

Heat of the moment . . .

Calculation of the characteristic impedance of an RCA connector can be done using this calculator. Sacrificing a connector by cutting it apart to get the necessary dimensions will show that the characteristic impedance is closer to 50Ω than 75Ω. That makes RG-58A/U a better impedance 'match' than any other cable. But, again, characteristic impedance really does not matter for our purposes.

The one really important spec for any shielded cable for audio use is the resistance of the shield conductor. We want it to be as low as is possible to minimize the voltage induced into the center conductor by the common-mode chassis currents flowing in the shield between any two devices. For unbalanced connections, a good coax cable with low shield resistance will be just as good as any shielded, twisted pair/star-quad cable from a noise perspective.

 

[Sir Sanders Zingmore]

In a recent discussion with a dear audiophile friend of mine, and audiophile of 40 years who is mentoring me in my journey, when discussing interconnects he mentioned the best sounding interconnects he's ever heard, Discovery cables,

I bet he only told you half the story

 

[Briank]

I concur with @Blumlein 88; the characteristic impedance makes negligible difference for most audio applications. (I say most, because there are probably some fringe cases, such as very long cables or high output impedances, where it will matter). The capacitance is more likely to have an effect for longer cables, where some amplifier outputs may degrade in quality when driving large capacitances.

As for 100 or 120 ohms, that's only when the two conductors are driven differentially, with opposite polarity on the two wires. In that case, no signal current is induced in the shield. The impedance will be lower when the signal is single ended and return current flows in the shield, likely in the 50 to 75 ohm range.

Ok so basically a non issue considering both center conductors are used for signal and the shield for ground.

I also agree that your wire looks similar to 89207 TwinAx.

It is very close although the 89207 inner jacket looks like an fep “tube” vs extruded on the cable in question, probably doesn’t matter. Stated diameter is 6.5 vs the subject at 8.25, although that could just be a matter of conductor gauge sizing.

 

[Audiofire]

This is not the exact cable in question since they are not currently in my possession but it is an exact representation;

Image snatched from this link that also says "military M17 specifications ... widely used in local area network, data center, and high-performance computing connectivity":

Twinaxial Cable

TWINAXIAL CABLE For data transmission and information systems applications Thank you for contacting Nemal Electronics! We'll be in touch soon. Name This field is required Email This field is required Phone This field is required Company Name This field is required Message This field is required...

nemal.com

He has been using a pair of Audioquest and Tara labs interconnects that are somewhat close but has always wanted the Discovery cables in his system.

Alas ...

Don't take advice; A wise man doesn't need it and a fool won't heed it.

 

[Briank]

Image snatched from this link that also says "military M17 specifications ... widely used in local area network, data center, and high-performance computing connectivity":

Twinaxial Cable

TWINAXIAL CABLE For data transmission and information systems applications Thank you for contacting Nemal Electronics! We'll be in touch soon. Name This field is required Email This field is required Phone This field is required Company Name This field is required Message This field is required...

nemal.com

Alas ...

Such a fine line between advice and information isn’t it? Thank you for searching, I didn’t know if there were any differences in the mil spec data type cables or say a microphone cable specifically used for audio.

 

[sam_adams]

It is very close although the 89207 inner jacket looks like an fep “tube” vs extruded on the cable in question.

Belden changed the construction of their 89207 TwinAx sometime between 2022 and 2024 from the extruded solid to the extruded tube:

2022 spec:

2024 spec:

The Vampire cable was probably a work-alike version.

 

[Audiofire]

Such a fine line between advice and information isn’t it?

Fine line between information and misinformation, especially for your friend

 

[Briank]

Fine line between information and misinformation, especially for your friend

What are you referencing?

 

[Briank]

Belden changed the construction of their 89207 TwinAx sometime between 2022 and 2024 from the extruded solid to the extruded tube:

2022 spec:
View attachment 353660

2024 spec:
View attachment 353661

The Vampire cable was probably a work-alike version.

Sweet, you rock man! Much appreciated!

 

[Audiofire]

What are you referencing?

Glad you asked, because there is a great hint here in the test frequencies used (way beyond audio cable specifications):

https://www.amphenol.co.jp/military/catalog/MIL-C-17CoaxialCableSpecifications.pdf

The point of this thread remains whether we are trying to deal with audio or radio (no matter whether you deny)

 

[Briank]

I have some homework for ya, Audiofire. Find another rca interconnect on the internet for sale that’s made right now with a twin axial cable, one cable per channel, and a copper based Tiffany style, single termination connector just like I pictured that solders both conductors in the center pin and folds the braided shield back over the jacket with a shield for ground that’s only held in place with spring tension.

 

[Audiofire]

I have some homework for ya, Audiofire. Find another rca interconnect on the internet for sale that’s made right now with a twin axial cable, one cable per channel, and a copper based Tiffany style, single termination connector just like I pictured that solders both conductors in the center pin and folds the braided shield back over the jacket with a shield for ground that’s only held in place with spring tension.

I don't care about that nonsense, since the standard connectors are BNC like this link:

BNC Series Connectors

BNC SERIES (50ohm) CONNECTORS Small-size coaxial connectors, conforming to IEC60169-8 standards. Thank you for contacting Nemal Electronics! We'll be in touch soon. Name This field is required Email This field is required Phone This field is required Company Name This field is required Message...

nemal.com

Technically, connectors are not even necessary for audio cables, but you don't seem to care about research

By the way, I don't recall that you mentioned anywhere what is broken in the cable. Determine continuity of conductors as pointed out on the very first page. But I have really lost patience with this thread.

 

[Briank]

I don't care about that nonsense, since the standard connectors are BNC like this link:

BNC Series Connectors

BNC SERIES (50ohm) CONNECTORS Small-size coaxial connectors, conforming to IEC60169-8 standards. Thank you for contacting Nemal Electronics! We'll be in touch soon. Name This field is required Email This field is required Phone This field is required Company Name This field is required Message...

nemal.com

Technically, connectors are not even necessary for audio cables, but you don't seem to care

ok I’m sorry, let’s talk about what YOU want to talk about haha. So you’re more into radio than audio and the cabling in question is used more frequently in that industry, same with bnc connectors. Whether or not you care about rca interconnects doesn’t mean I don’t have a right to be inquisitive about a cable construction I’ve never seen before…..whiiiich was the point of the thread. I searched for DAYS before I posted here. But maybe my wording wasn’t just right for googles algorithms.

As to the topic at hand, of course I don’t care, and I’m aware they don’t. Ever make a speaker with paper plate? I didn’t ask about the cable so I could remake the cable with no connectors and tell my friend I’m just gonna duct tape the coax to his amp.