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-   -   Cable Distortion Measurements: Part Deux (http://www.diyaudio.com/forums/everything-else/24582-cable-distortion-measurements-part-deux.html)

Steve Eddy 21st December 2003 02:02 AM

Cable Distortion Measurements: Part Deux
 
The original thread having been closed (see http://www.diyaudio.com/forums/showt...threadid=23440 ), I'm starting this thread for the discussion of the followup measurements intended to address the concern that John and Bruno hadn't measured the same cables.

To that end, I made up two sets of identical cables. Each set included an old Radio Shack Gold interconnect that I had laying around here which was well used but hadn't been used for at least a couple years. A brand new, unused Radio Shack Gold interconnect. A bog standard giveaway cable which were included with my DishNetwork boxes. And finally, just to add some interest, a cable made up using Manhattan/CDT M4214 which is an RG 174/U type.

The reason I threw this last cable into the mix is because its center conductor (7/34 stranded) is made of copper clad steel.

I figured that if the distortion John is measuring is indeed being produced by the conductors themselves, then using a ferromagnetic conductor such as steel should result in distortion significantly greater than even the most bog standard copper or silver conductors.

Interestingly, of the four cables I sent John, the cable with which he measured the LEAST distortion, was the copper clad steel core RG 174/U.

Here's John's response from the other forum:

Been there, got the cables, measured them.
RS cables are slightly the worst, but not too bad, el cheapo cable came in slightly better, custom 174 came out best. No cable was quite as good as the reference, but not bad.
Signifcantly worse were some cables here already.


The old Radio Shack Gold and the giveaway cable are on their way to Bruno (they were sent the same day that I sent John's cables). The new Radio Shack Gold and the RG 174/U are ready to send to Bruno on Monday.

se

SY 21st December 2003 02:32 AM

I'll be interested in seeing the measurement details, especially repeatability and replicability. Do you know what the "reference" was?

Steve Eddy 21st December 2003 02:35 AM

Quote:

Originally posted by SY
Do you know what the "reference" was?
I think John's still using some model of van den Hul as his reference cable.

se

john curl 21st December 2003 05:27 AM

My test frequency is 5KHz and my level is 70mV with a 600ohm source and 2Kparalleled with 50K load.
Let's see first if Bruno can find ANY distortion at all.
Sy, I don't need to be second guessed by Steve Eddy. If you have a question, please ask me.
I have found an expensive VDH video cable terminated with VDH connectors works very well. I have also found that a JPS cable works at least as well, but it is less flexible, so it is more difficult to use on a regular basis. Both cables are shielded 75 ohm types, and both have a distortion residual at about -120dB or better.
Steves cables measure worse than this, by 5 to 10dB typically.

Steve Eddy 21st December 2003 05:39 AM

Quote:

Originally posted by john curl
My test frequency is 5KHz and my level is 70mV with a 600ohm source and 2Kparalleled with 50K load.
Thanks. I'll pass that on to Bruno.

Is 600 ohms the lowest you can go with regard to your source impedance? It would be interesting to measure the RG 174/U cable with as much current as you can manage and at a much lower frequency which would maximize the nonlinearities due to the steel core. What's the maximum level of your 1700B's oscillator?

Quote:

Let's see first if Bruno can find ANY distortion at all.
If the cables I sent are in fact producing distortion at -115 to -120 dB relative to the fundamental as you say, then they should stick out like a sore thumb seeing as the System Two Cascade's generator's thrid harmonic residual is at -130 dB and clearly visible on the previous measurements that Bruno made.

se

fdegrove 21st December 2003 05:49 AM

Hi,

Anyone care to measure my silver darlings or silver + gold ?

Cheers,;)

Steve Eddy 21st December 2003 06:04 AM

Quote:

Originally posted by fdegrove
Anyone care to measure my silver darlings or silver + gold ?
Well, unless you expect them to have sufficient distortion that it'll show up on the System Two Cascade, I don't see much point.

So far none of the cables Bruno has measured on the System Two Cascade have shown any signs of distortion. That's why I decided to send the steel cored RG 174/U cable in hopes that SOMETHING might be sufficiently nonlinear that it'd be within the System Two Cascade's reach. Can't think of anything worse than copper clad steel that would stand much chance of being used at all for audio cables.

If the RG 174/U doesn't do it, I'll go over to Mills and get some nichrome wire and try that.

se

fdegrove 21st December 2003 06:24 AM

Hi,

Quote:

Well, unless you expect them to have sufficient distortion that it'll show up on the System Two Cascade, I don't see much point.
I don't, and I KNOW they don't ....

Quote:

Can't think of anything worse than copper clad steel that would stand much chance of being used at all for audio cables.
Yes....Good to see you "think" although I'm not sure anything useful will show up.

Cheers,;)

johnferrier 21st December 2003 06:26 AM

Quote:

Originally posted by Steve Eddy
...get some nichrome wire and try that.
So, it's nickel that is "bad"? Just wondering because the Vishay bulk metal foil resistors are nichrome. Steve when I wrote about these before, you mentioned "ruthenium oxide", not having the details that these particular resistors are constructed with nichrome. They are "non-inductive" but I guess they could be magnetic.


JF

Steve Eddy 21st December 2003 06:28 AM

Quote:

Originally posted by fdegrove
I don't, and I KNOW they don't ....
If you KNOW they don't, then perhaps you could send a set to John. If his measurement of them turns up distortion then we would KNOW that the distortion he's been measuring is in fact being produced by his 1700B.

se


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