Low capacitance cables - Anyone have /ft ratings?

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by David Collins, Jan 7, 2011.

  1. David Collins

    David Collins Member

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    Tried searching the forum, but got tired of wading through arguments of what sounds best or whether it makes a difference. I was hoping someone may have some quantified measurements, or be able to refer me to a chart of the actual capacitance of some different cables. I'm basically looking for the lowest capacitance per foot, preferably available for a decent price.

    I vaguely recall seeing Elixer cables rated somewhere at around 10 ㎊/ft, which would be great, but can't find the reference. Anyone?
     
  2. David Collins

    David Collins Member

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  3. tdarian

    tdarian Gold Supporting Member

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    You might find the information here very helpful:
    http://www.lavacable.com/buying.html

    I would also caution about the lowest possible capacitance always being 'better", although I gravitate towards lowish capacitance cables myself. But as an example, I prefer the Sommer Grindycopbeast (27 pf/ft) to the Gotham Audio GAC-1 (22 pf/ft) with my gear and ears. The Gotham is subjectively "brighter" to me than the GCP, however I perceive Grindycopbeast to be clear enough given it's relatively low capacitance, with good "bite" but subjectively "fuller", assuming equal lengths.

    "Chervokas" has posted some great technical explanations for why we might perceive the sonics of cables the way we do in various threads here on TGP.

    Here is such a thread: http://www.thegearpage.net/board/showthread.php?t=828401 where capacitance is discussed as well as other design parameters. However, the Elixers could be great in your rig!
     
  4. Structo

    Structo Member

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    Yes you have to evaluate your guitar and amp setup before you choose a cable.
    If your amp and guitar lean towards being dark sounding then try a low pf cable.

    However if your rig already borders on ice pick city, then a cable higher in capacitance can help roll off the high end a bit.
    Something in the 35-40pf/ ft may help that.
     
  5. David Collins

    David Collins Member

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    Thanks tdarian and Structo - I'll look at those links a little more closely this afternoon.

    Just for the record, I don't plan on ever actually using these cables for playing. I'm not very picky with my personal setup, and am usually content with just about anything after a few tweaks on the controls. This is just for some controlled testing and comparisons under particular circumstances where I want to keep the capacitance of the cable as low as possible, and where what I feel sounds "better" is fairly inconsequential.
     
  6. wizard333

    wizard333 Member

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    Elixer is by far the lowest, at under 15pf per foot (11 or 13 as I recall). Other low caps like George L or Klotz LaGrange come in at 18-21pf/ft. It goes up dramatically from there.
     
  7. chervokas

    chervokas Member

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    Yeah, the capacitance of the Elixirs came up on a thread and I doubted the 10 pF/ft spec so I wrote to the company and they wrote back quoting 10 pF/ft for the cable and 15 pF for each of the plugs (they sell 'em terminated with molded ends). I'm not sure how they're achieving that number--I've never dissected, played with or even held one of them. But those are the specs.
     
  8. David Collins

    David Collins Member

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    Thanks much Chervoks - I'm sure I'll be picking up an Elixer cable or two. That does seem incredibly low, but I'll be sure to check when I pick one up. Next step will be look to see just how much capacitance other plugs may add, as I'll be dissecting the cable in to shorter sections.
     
  9. Shiny_Beast

    Shiny_Beast Member

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    Capacitence isn't rocket science, half the battle is probably just putting distance between the ground and the signal wire, I read somewhere it is thick cable. Sounds like they have another trick or two as well as they have applied for a patent.

    I don't know why some company doesn't market a nice thick ultrlow cap cable specifically to go from pedalboard to amp where it doesn't really matter how flexible it is.
     
  10. chervokas

    chervokas Member

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    Yeah, air is one of the best dielectrics there is (and it's about the cheapest dielectric material too!), so I suspect Elixir is using some kind of air gap. I assume it's coax so the sheild is carrying the ground connection.
     
  11. guitarjazz

    guitarjazz Member

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    A few weeks ago in Nashville the studio had some of these cables. I've always been skeptical about high-end cables but these sounded way better than what I was using. I like the 'Studio Pro' model the best..only $300!
    http://www.analysis-plus.com/
     
  12. GuitslingerTim

    GuitslingerTim Member

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    Belden makes studio cable in bulk with nothing but a foil shield around the conductor, which is probably the lowest capacitance cable made.
     
  13. tdarian

    tdarian Gold Supporting Member

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    Truthfully, the Analysis Plus Pro Studio Oval cable sounds as good or better to me than anything I've ever tried with my guitars and amps.
    I tend to gravitate towards less bulky and more supple cables for day to day use, but would certainly use the A/P cables in a critical listening environment, like a studio for recording. However, I'm not so sure that these are (or are not) low capacitance cables....a magazine review review that was linked to the Analysis Plus site listed the Yellow Oval, which is close I believe in design to the Pro Studio Oval, as being fairly high in capacitance, at least compared to the Elixers and some others. And yet, I don't hear any high frequency rolloff as one might expect. Other cables, such as the 22 pf/ft Gotham Audio GAC-1, the 26/27 pf/ft Vandenhul and Sommer Grindycopbeast, and the Evidence Audio Forte (32pf/ft) have been uniformly and audibly more extended/brighter on the top end starting with the Gotham and less so moving up through the moderately higher capacitance Forte, consistent with alot of what I've read in these various cable threads.

    Regardless of what I'm hearing, I'm not sure if the Analysis plus is indeed lower capacitance or the lowest capacitance.
     
  14. David Collins

    David Collins Member

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    We can have debates over which cable is "best" over in the Gear forums. :p All I'm searching for here is lowest capacitance - quantifiable factor, indifferent to preferable tone.

    If it matters, here is current project I seek to use them for.

    [​IMG]

    This is a test box to demonstrate effects of changes in various factors. The idea is to be able to adjust settings to match just about any particular setting, then choose one or two factors to alter and be able to hear their effects in that application in real time.

    My thoughts here are that in general, the less treble is being lost through cable capacitance, the greater the odds of being able to hear the most subtle changes which may otherwise be obscured or outweighed by cable capacitance. I know it's not this simple, and shooting for one extreme end does not account for things such as resonant peak, etc, but you get the point.

    I'm not trying to make any rig sound better, just trying my best to arrange the system best as possible, so that if no discernible difference is heard with a particular change, one should not have to wonder whether it is simply being missed because high capacitance of the circuit is obscuring the results.

    The catch is that there is a lot of metal in this box -

    [​IMG]

    - and I've measured the box already to be around 230pf (depending on the humidity that day :eek:), even with all the caps disengaged. So since I'm already starting at a disadvantage here, all I'd like to do is minimize capacitance elsewhere. If I can use a 3' Elixer cable before and after the box, giving me in the ballpark of 120㎊ additional between cable and plugs, I could still end up with a sum of around 350㎊, or hopefully at least below 400㎊ between the cables and the box. This would still put me in the range of equivalent of a 10'-15' good quality cable, which at least still leans toward the low end capacitance of real world use.

    I know it's not perfect, in part at least because I'm throwing this capacitance around to different parts of the circuit, before, after, and within the controls. Still, the main goals of this box and the factors it is intended to compare are not really that sensitive to this particular factor. Nevertheless, I'd still prefer to minimize additional capacitance as much as practical.
     
  15. chervokas

    chervokas Member

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    David, that's a cool box and an interesting project. It is, however, as you state like starting with 15 feet of 26 pF/ft cable (or 10 feet of 35-40 pF/ft cable, which I would characterize as mid to high capacitance for guitar cable) so it's already going to have a profound impact on what you hear from a passive pickup guitar.

    Have you read this-- http://buildyourguitar.com/resources/lemme/ or this http://www.muzique.com/lab/pickups.htm? They give a pretty good description of what's going in terms of the resonanting circuit formed by the inductance of the pickups, resistance of the pots, and capacitance of the cable.

    It's not really a question of treble loss. Yes, the pot and the cable together will form a low pass filter that will roll frequencies at a predictable point (if you know the output impedance of the guitar and the capacitance of the cable you can calculate it mathematically. There's a good calculator here: http://www.sengpielaudio.com/calculator-cable.htm). But you'll have to load the circuit with a lot of capacitance and/or raise the output impedance (by increasing the pot resistance) to get that cut off point anywhere close to the highest frequencies an electric guitar produces (about 5khz, the highest fundamental on a 21-fret instrument is only 1.175khz, an electric guitar doesn't really produce any high treble, it's pretty much a midrange instrument).

    What's actually going on is the LCR circuit has a peak at a certain frequency, of a certain width and height (and a 12 db/octave roll off of frequencies above the peak). And when you change any parameter--inductance, resistance, capacitance-- you're going to change the nature of the peak, not only its frequency but also its height and Q--so the sonic results will be multi-faceted and affected by any change in any of the three elements.

    Furthermore, the resonant frequency is typically somewhere between 2khz and 5 khz, so it's above any fundamental the guitar is producing and it's audiblity will be dramatically affected by amplifier settings, speaker frequency response etc (many guitar speakers also have a similar frequency peak). It is a peak followed by a rolloff in the instrument's upper harmonics. I don't know what combination of inductance, resistance and capacitance would give you a peak that was well above 5khz and therefore completely not affecting the audible guitar signal. Ideally with a test like yours--in which you can only add capacitance above the box's baseline--you'd be starting with a peak that's above 5khz and therefore you'd truely have flat frequency response coming off the LCR circuit. I doubt you'll have that with 400 pF of capacitance inline to start with. Also, you'd need a speaker system that's dead flat from the guitar's lowest frequency (I think 82 hz in standard tuning) to it's highest harmonic (around 5khz) to be certain you're hearing everything that's going on--which is not what you're getting from a guitar amp.

    These are conditions that never exist in the real world of guitars. In the real world you always have a resonant peak and roll off, it's always changing because you're switching between pickups or guitars, playing different frequencies (which effects the output impedance), rolling back the volume knob, playing through speakers with a peaks of their own, etc.....A lot of variables and a dynamic relationship between them in practice.

    Also, to wind up with any data that can be useful I think you'll have to a) measure the inductance of all the pickups (other than Bill Lawrence I don't know what other winder publishes inductance specs); and b) plot, I suppose w/ an oscilloscope, the resonance and the changes in the resonance as you change parameters.

    With this box you're already going to be starting from a baseline with is the equivalent of, like I said, 15 feet of fairly low capacitance cable. So you'll already have a characteristic resonant peak, presuming you're running your pickups straight into the box. At the very least you'll need to scope the shape of your baseline resonance.

    Too bad you're in Ann Arbor and I'm in metro NYC, I'd love to be around to hear and see some of the tests.
     
  16. David Collins

    David Collins Member

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    Thanks for the tips Cherkovas.

    Just to clarify a bit further though, I'm not planning to use this for any quantified laboratory testing, but rather as a demonstration box for teaching, both in the occasional class as well as demonstration for the occasional customer questions. So what I'm really after is a tool that can clearly demonstrate relative changes under a variety of conditions, as opposed to absolute.

    For example, demonstrating the difference between audio or linear taper pots for tone and volume, or how one may act differently in a master volume setting vs independent. Or it's handy for comparing different treble bleed circuits or tone cap values in real time, or how wiring a tone pot to the coil(s) rather than output tab of the volume pot can affect how the volume and tone respond.

    In most of these cases (being relative comparisons rather than absolute measurements) worrying this much about cable capacitance is somewhat like worrying about stray peanuts on the scale when weighing an elephant. Other comparisons however, such as changing a tone pot value from 250kΩ to 500kΩ, or switching volume from 1MegΩ to volume bypass can be far less dramatic. These effects can be much more minor, leaving me with concern that they may be made inaudible if the capacitance is too high, while having potential to affect a slightly more noticeable change with a low capacitance cable.

    So for the most part it's not too much of a concern for me, as most of the significant changes will remain readily audible and fairly unaffected, or at least still audible enough in comparisons to demonstrate what direction a change tends to shift a given tone. If I wanted to do more serious testing where I were recording and analyzing effects, I would be able to just wire things in to a standard circuit one factor at a time and get rid of all this complicated switching crap. This isn't really meant to serve as a serious test rig though, but more of a "Practical Electronics For Dummies" box.

    One of the things it's already proved quite useful for is demonstrating how heavily the effects of different arrangements can be dependent on the amp or impedance you are plugging in to. There are some A/B switching I've done which barely create any audible change at all through one amp, yet become ridiculously wide night and day through another. I know how things work on paper, and have worked with guitar electronics long enough to have a very good feel for how effects may influence tone, but being able to switch in real time I believe can give some invaluable insight, and help gain a more tacit understanding.

    I will admit that the factor of cable capacitance is not something I've spent a great deal of time on in the past. This kind of thing is really not the focus of my work. The majority of what I do involves more day to day repair work - fret work, neck resets, bridge reglues, setups, cracks and breaks of all sizes and shapes. I'm sure less than a third of my business involves electric guitars, and of those only a small fraction involve tweaking components related to this. Getting in to details so specific as this comes down to very, very small part of what I am usually concerned with. Still, regardless of how rarely a specific bit of knowledge may be relevant to my work, I find that a poor excuse not to try my best to understand it as well as I am capable. As time allows I will no doubt try to conduct similar comparisons with cables. I would like to at least earn enough tacit knowledge to reliably predict whether a change may likely be heard differently than in this test box, and which direction it may lean. I really feel like we're getting down to splitting hairs here under many circumstances, but not so far as to dismiss the effects as inconsequential.
     
    Last edited: Jan 8, 2011
  17. chervokas

    chervokas Member

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    Very cool. Actually one thing that might be interesting w/ respect to illustrating volume pot loading and cable capacitance is the impact on HF loss as you roll back the volume knob with different pot loads and cable loads. I suspect that that's where you'd hear the difference of the pot loading for a given cable capacitance and vice versa more than w/ the pot full on.
     
  18. Mike9

    Mike9 Supporting Member

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    eliot1025 Member

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