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"Low Capacitance" Cables?

MattHooper

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Hey folks,

I have to do a bit of re-cabling in my system so I want to ensure I end up with the appropriate cables. (I've always used a mish-mash of stuff, old interconnects like the Kimber PBJs I bought decades ago, cast offs from other audiophiles etc).

I have the basic understanding (I think) that there is often a sort of trade-off between lower capacitance in a cable and noise rejection. So a lower capacitance can be a good thing insofar as high frequency roll off (over length) will be less of an issue, but it can come with some vulnerability to electrical noise/interference. Whereas designs like star quad tend to be better at rejecting noise, though typically have higher capacitance and at given lengths high frequency roll off can be an issue. Is that generally correct?

I'm looking at some XLR cables (between my Benchmark DAC and my Phono stage in to my Benchmark LA4 preamp), between 1 and 3 feet.

I also need some RCA unbalanced interconnects from the DAC and Phono stage to my Conrad Johnson preamp. And also from the LA4 and CJ preamp to my CJ tube amplifiers. A couple 3 footers and a couple 4 footers.

Apparently the Conrad Johnson entire Premier series of composite-triode preamps is very sensitive to interconnect capacitance, and low capacitance cables are advised

My question is: What spec makes for "low capacitance?"

I see capacitance listed as #/pF/Ft

Is there some #/pF/Ft below which we'd consider an interconnect "low capacitance" vs "high capacitance?"

For instance I was looking at the Audioblast cables on amazon or some of the cables offered at Benchmark.

For 4 foot RCA interconnects, Audioblast claims low capacitance at 38.2 pF/Ft
Whereas Benchmark uses Belden 1694A, which is listed at a lower 16.2 pF/Ft


Both are advertised as "low capacitance" and can I presume there would likely be no real world difference in performance - even in regard to my CJ preamp - if we are talking 3 - 4 feet unbalanced interconnects?

Similar questions about the XLRs: The Audioblast XLRs are Star Quad designs, but still claim "low capacitance" (conductor to shield) at
34.15 pF/Ft

The Benchmark XLRs are also Star Quad (Canare) and have almost identical capacitance specs (which they claim to be low capacitance).

So I figure I should be good to go with those?

Thanks.
 

Blumlein 88

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At those distances I'd say any of those cables are fine. Only some unusually high capacitance would matter. And even then likely only for the C-J. What is the output impedance of your C-J?

The output impedance of the L4 is only 60 ohms. You could do the calcs, but at your distance just not an issue.
 
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MattHooper

MattHooper

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At those distances I'd say any of those cables are fine. Only some unusually high capacitance would matter. And even then likely only for the C-J. What is the output impedance of your C-J?

The output impedance of the L4 is only 60 ohms. You could do the calcs, but at your distance just not an issue.

Thanks!

The CJ manual says: "output impedance less than 700 ohms"

JA measured it here:


BTW, is there an answer as to what numbers constitute "low capacitance" at least with regard to interconnects?
(I wouldn't even know what "unusually high capacitance" numbers would be if I saw them).
 

Blumlein 88

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For 60 ohms with 6 feet of cable at 40 picofarads per foot your signal is only down .08 db at 100,000 hz.

Same cable with the C-J assuming 700 ohms is .9 db down at 100,000 hz.

Now with RCA cables the RCA jacks may add 100 to 200 picofarads extra. So roughly maybe the droop of .9 db happens at 50,000 hz for the C-J. I don't happen to know the capacitance added by XLRs.

I seem to recall some strange cables being 100 picofarads per foot. What really is meant with most cables is you wouldn't want to use the C-J with a 100 ft cable. With a 100 ft 40 picofarad per foot cable the CJ would be down to -8.9 db around 100,000 khz just from cable. The L4 would only be down -1.2 db under the same conditions.
 
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Holmz

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Low capacitance cables = high inductance cables. Make the distance between wires high and you have it. Not a good idea, however.

There is also going to lower dielectric constant, which is linear in the equation of capacitance.



I'm looking at some XLR cables (between my Benchmark DAC and my Phono stage in to my Benchmark LA4 preamp), between 1 and 3 feet.

I also need some RCA unbalanced interconnects from the DAC and Phono stage to my Conrad Johnson preamp. And also from the LA4 and CJ preamp to my CJ tube amplifiers. A couple 3 footers and a couple 4 footers.
...

Being lazy I just use Mogami starquad for both RCA and XLR.
But then again, a lot of my cables are XLR on one end and RCA on the other, so going StarQuad I can always covert them to XLR—>XLR later if need be.

For my cart—>phono I got a few feet of silver wire with cotton insulation…
I need to build that into a cable in a couple of weeks.

Then I can try Phono—>Pre as XLR—>XLR or RCA—>RCA, but likely the later as I only have 1 XLR input and the DAC is XLR output.

I am pretty sure it doesn’t matter, and if it does it will matter most on the Cart—>Phono as that is low voltage/current and the most sensitive to capacitance.
 

KSTR

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I'm looking at some XLR cables (between my Benchmark DAC and my Phono stage in to my Benchmark LA4 preamp), between 1 and 3 feet.

I also need some RCA unbalanced interconnects from the DAC and Phono stage to my Conrad Johnson preamp. And also from the LA4 and CJ preamp to my CJ tube amplifiers. A couple 3 footers and a couple 4 footers.
I would kindly suggest you overthink your component placements.
For the unbalanced connection, focus on them first and make them as short as any possible and use cable with very (!!) low shield resistance, like double braid shield coaxial cables. Use RCA plugs that can be tightened, and clean contacts first. Power these devices all from the same outlet. It might even be possible to connect all the chassis with extra "bonding" connections.
This assures the highest possible signal integrity for those unbalanced connections, and for very short lengths any cable capacitance is effectively irrelevant.

For the XLR's cables, length is not as relevant and the sources you have to drive them even for longer distances are perfectly fine. However, to follow the "short cable rule" always is a good thing.
 

tuga

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Hey folks,

I have to do a bit of re-cabling in my system so I want to ensure I end up with the appropriate cables. (I've always used a mish-mash of stuff, old interconnects like the Kimber PBJs I bought decades ago, cast offs from other audiophiles etc).

I have the basic understanding (I think) that there is often a sort of trade-off between lower capacitance in a cable and noise rejection. So a lower capacitance can be a good thing insofar as high frequency roll off (over length) will be less of an issue, but it can come with some vulnerability to electrical noise/interference. Whereas designs like star quad tend to be better at rejecting noise, though typically have higher capacitance and at given lengths high frequency roll off can be an issue. Is that generally correct?

I'm looking at some XLR cables (between my Benchmark DAC and my Phono stage in to my Benchmark LA4 preamp), between 1 and 3 feet.

I also need some RCA unbalanced interconnects from the DAC and Phono stage to my Conrad Johnson preamp. And also from the LA4 and CJ preamp to my CJ tube amplifiers. A couple 3 footers and a couple 4 footers.

Apparently the Conrad Johnson entire Premier series of composite-triode preamps is very sensitive to interconnect capacitance, and low capacitance cables are advised

My question is: What spec makes for "low capacitance?"

I see capacitance listed as #/pF/Ft

Is there some #/pF/Ft below which we'd consider an interconnect "low capacitance" vs "high capacitance?"

For instance I was looking at the Audioblast cables on amazon or some of the cables offered at Benchmark.

For 4 foot RCA interconnects, Audioblast claims low capacitance at 38.2 pF/Ft
Whereas Benchmark uses Belden 1694A, which is listed at a lower 16.2 pF/Ft


Both are advertised as "low capacitance" and can I presume there would likely be no real world difference in performance - even in regard to my CJ preamp - if we are talking 3 - 4 feet unbalanced interconnects?

Similar questions about the XLRs: The Audioblast XLRs are Star Quad designs, but still claim "low capacitance" (conductor to shield) at
34.15 pF/Ft

The Benchmark XLRs are also Star Quad (Canare) and have almost identical capacitance specs (which they claim to be low capacitance).

So I figure I should be good to go with those?

Thanks.

Low capacitance would be below 20pF/m or ~6pF/ft if my early morning math is correct.
That I know of only a couple of unshielded cables (DNM and discontinued Cyrus) fit the description.

For low-level phono signals you will might need shielding.
 

tuga

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BTW, is there an answer as to what numbers constitute "low capacitance" at least with regard to interconnects?
(I wouldn't even know what "unusually high capacitance" numbers would be if I saw them).

Braided cables have high capacitance, spaced conductors = low capacitance:

Kimber Hero braided single-ended – 73pF/m (6x)
Blue Jeans LC-1 coaxial single-ended – 40pF/m (3x)
DNM spaced-shotgun single-ended – 17pF/m (1.5x)
Cyrus spaced-shotgun single-ended – 12pF/m (baseline)
 

dlaloum

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Data cables are inherently low capacitance - things like CAT6/Cat7 are readily available...
 

thewas

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Low capacitance is important for the cables from the turntable to the phono stage (even more if it cannot be corrected to the desired value at the phono preamp), for all other cables its value plays practically no audible role for non pathological lengths or constructions. This means it is good to place the phono stage close to the turntable and use short cables there, also for external noise induction.
 

RayDunzl

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I'm looking at some XLR cables (between my Benchmark DAC and my Phono stage in to my Benchmark LA4 preamp), between 1 and 3 feet.

Without actually answering your question, here's a quote from the DAC2 HGC manual, pertaining to HF rolloff:

1667650707494.png
 
OP
MattHooper

MattHooper

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I know I asked for it, but my total inability to fully grasp the technical aspects of electricity have me going cross-eyed from many of the answers.

Ok, for the XLR cables between my Benchmark DAC and LA4 preamp, and between my Phono stage and the LA4...at 3ft lengths, 34.15 pF/Ft should be fine, right?
(I haven't really found any XLR cables that aren't in the star quad design, so that seems about as low capacitance as I'll find).

For the RCAs, as mentioned I'd go up to 4 feet long. I want low capacitance for the signal, BUT they will also be hanging at the back of my rack dodging various power cables and power bars. I just don't know how concerned I need to be about this, or how far away to keep the RCA cables from power bars, power cables etc.

The Audioblast cables claim to be well shielded but higher in capacitance: 38.2 pF/Ft. But should that be low enough for the preamp? As far as I can tell trying to put all the answers here together, it should be fine(?) Otherwise I can just get the lower capacitance RCA cables from Benchmark, using the Belden cable at 16.2 pF/Ft capacitance. But is it well shielded enough to put aside worried about noise interference?

Here's the description:

 

Doodski

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hanging at the back of my rack dodging various power cables and power bars. I just don't know how concerned I need to be about this, or how far away to keep the RCA cables from power bars, power cables etc.
I've experienced failure of the video circuitry due to coiled wires at the rear of a AV system with a 12 foot actuated satellite dish outside. The audio was not affected when compact disc was a source but the dish had no sound & no video. Those where some fairly large tight coils of wire that the customer wound into his perfect circle. For the average audio gearhead just keep the wires loose and random. No coils, no tight wrapping and no zip tying tightly etc.
 

rwortman

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Here is is a calculator for RC low pass filters. Plug in your output impedance as R and total cable capacitance as C and it will show you the frequency where it begins to roll off. You will find that you have no worries. http://sim.okawa-denshi.jp/en/CRtool.php
 

dlaloum

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I know I asked for it, but my total inability to fully grasp the technical aspects of electricity have me going cross-eyed from many of the answers.

Ok, for the XLR cables between my Benchmark DAC and LA4 preamp, and between my Phono stage and the LA4...at 3ft lengths, 34.15 pF/Ft should be fine, right?
(I haven't really found any XLR cables that aren't in the star quad design, so that seems about as low capacitance as I'll find).

For the RCAs, as mentioned I'd go up to 4 feet long. I want low capacitance for the signal, BUT they will also be hanging at the back of my rack dodging various power cables and power bars. I just don't know how concerned I need to be about this, or how far away to keep the RCA cables from power bars, power cables etc.

The Audioblast cables claim to be well shielded but higher in capacitance: 38.2 pF/Ft. But should that be low enough for the preamp? As far as I can tell trying to put all the answers here together, it should be fine(?) Otherwise I can just get the lower capacitance RCA cables from Benchmark, using the Belden cable at 16.2 pF/Ft capacitance. But is it well shielded enough to put aside worried about noise interference?

Here's the description:

Cat7 data cables are low impedance and shielded.... from memory 14pf/ft but you would need to terminate them yourself (obviously) - the plugs will cost you 10x what the cable does.
 

DonH56

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Holmz

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For the RCAs, as mentioned I'd go up to 4 feet long. I want low capacitance for the signal, BUT they will also be hanging at the back of my rack dodging various power cables and power bars. I just don't know how concerned I need to be about this, or how far away to keep the RCA cables from power bars, power cables etc.

The Audioblast cables claim to be well shielded but higher in capacitance: 38.2 pF/Ft. But should that be low enough for the preamp? As far as I can tell trying to put all the answers here together, it should be fine(?) Otherwise I can just get the lower capacitance RCA cables from Benchmark, using the Belden cable at 16.2 pF/Ft capacitance. But is it well shielded enough to put aside worried about noise interference?

What do you think that the shield does?
And what is it shielding from (E-field, magnetic, RF)?

I would not worry a whole lot about the capacitance as the driving source usually has a low impedance and the preamp or amps usually have a high input impedance.

That is not at all true for the cart to phono stage though… and most carts say use 100-200 pF, so it is not a crime to have a bit of capacitance, and the connectors might add some as well.

Oddly I made some short 1M XLR to RCAs (StarQuad Mogami), and one of the speakers pick up the radio station now when the volume is railed…
I’ll need to put RCA plug with resistors on the unused input and see if that mitigates it.
I have no idea where and how it is sneaking in.


I know I asked for it, but my total inability to fully grasp the technical aspects of electricity have me going cross-eyed from many of the answers.

Ok, for the XLR cables between my Benchmark DAC and LA4 preamp, and between my Phono stage and the LA4...at 3ft lengths, 34.15 pF/Ft should be fine, right?
(I haven't really found any XLR cables that aren't in the star quad design, so that seems about as low capacitance as I'll find).

And the balanced gear says do not worry about the cable, so I can see your chin scratching…
 
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