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System Cable Capacitance Question from a New Audiophile

Hey all, first discussion started here. I want to start off by saying that I have learned so much from reading these forums and that I appreciate the awesome collective knowledge that this community is comprised of.

I am a young audiophile transforming my system from an integrated peachtree nova 150 to separates. A little background, my speakers are kef LS50s, powered by a red dragon audio s500 power amp. I just removed my peachtree from the chain and inserted a humble schiit sys to use as a volume control directly into my s500 and the sound opened up significantly. I will upgrade the preamp eventually but am focusing elsewhere at this point.

I am not worried about the cable between the s500 and the sys, but the cables between the sys and my DAC/phono pre. My primary concern is choosing a cable that won't eliminate any of the high frequency audio information through the passive. Lets brake up the two sides of the system.

Digital: My DAC is a metrum amethyst which I was assured by metrum would output more than the specified voltage into my power amp so I am not worried there. However what are some general guidelines for the capacitance of a single ended cable? The run will be 1m.

Analogue: I have a rega planar 2 with a nagaoka mp200 cartridge running through a project tube box s. Any guidelines for the cable running from the phono pre to my sys?

Any help would be greatly appreciated. I have tried kimber PBJ cables and some morrow audio cables, so looking to keep the interconnect price under 300 each if I can. I would like to upgrade the rca connectors as I have found really great sonic improvement with doing that.

Thanks! 
ajnackman
chayro
2,984 posts
 
I honestly think you are over-analyzing the situation. Most modern cables are made with low resistance and capacitance, so just pick up a modestly-priced cable from Signal Cable, Morrow or Clear Day and forget about it for now. By far, one of the most common complaints by audiophiles is harshness, so I think you’ll have nothing to worry about in the reproduction of high frequencies. Just get your system up and running and later on you can focus on some new cables to fine tune your system if necessary.
ajnackman OP
60 posts
 
I understand what you're saying. My system is currently working, I think my hesitation is from reading that cable capacitance can affect the sound of a system, especially when using a passive preamplifer. At the moment I am really happy with how the system sounds, just curious if there are any rule of thumb's with the passive. Thanks for the comment!
tgrisham
1,291 posts
 
Capacitance is relevant to length. For one meter it won’t matter. It only matters for single ended for long runs. I am a fan of the cables mentioned but for the money I recommend Blue Jeans cable LC-1. Good luck. 
ajnackman OP
60 posts
 
Are there any recommendations for silver coated copper cable for phono/vs digital signals or RCA connectors pure copper vs silver? 
almarg's avatar
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almarg
9,670 posts
 
I would make several points regarding the original question:


1) Cable capacitance is directly proportional to length, as Tgrisham indicated. For a line-level interconnection it would be very rare for the capacitance of any decent 1 meter cable to be audibly significant. (That is not necessarily true, btw, for a cable connecting a turntable to a phono stage or preamp).


2) The concern that cable capacitance may present in conjunction with a passive preamp mainly involves the connection from the output of the preamp, not the connection to the input. That is because the output impedance of a resistor-based passive preamp such as the Sys and many others (as opposed to transformer-based passive preamps) is typically very high, and driving a high capacitance cable from a high output impedance can result in roll off and/or undesirable phase shifts in the upper treble region. The output impedance of most source components is usually much lower than the output impedance of a resistor-based passive preamp, which usually eliminates that concern unless the cable is particularly long.


3) The output impedance and the output voltage of your DAC make it a good candidate for use with a passive preamp. However, although I was unable to find specs or measurements for the output impedance of your phono stage or the input impedance of your amp, I suspect that using a passive preamp between those two components, including the Sys you are presently using, is and would be less than optimal at best. I would expect that the output impedance of your tube-based phono stage probably rises to relatively high values at deep bass frequencies, due to the use of a coupling capacitor at its output (the impedance of a capacitor rises as frequency decreases), and I would think it more likely than not that the input impedance of your particular amp is relatively low.


Therefore it may not be possible to choose a resistor-based passive preamp having resistor values that are high enough to not load the phono stage excessively, while also being low enough to drive the amp with good results. And in fact I wouldn’t be surprised if the 10K specified input impedance of the Sys (and it will actually present a lower impedance than that to the phono stage, by an amount that depends on its setting and on the input impedance of the amp) is resulting in audibly significant rolloff in the bottom octave or two when you are listening to records. The degree to which that may matter, though, will depend on the deep bass extension your speakers can provide.


4) All of the foregoing applies to resistor-based passive preamps, such as the Sys and many others. Transformer-based passive preamps are different animals altogether, and involve different considerations.


Best of luck as you proceed. Regards,

-- Al


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