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Guitar cable capacitance -- how much is too much?

Discussion in 'Amp Tech Center' started by King Fan, Jul 25, 2020.

  1. edvard

    edvard Friend of Leo's

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    Measure the resistance of the cable.
    Take your cable resistance and cable capacitance and plug it in to the calculator here:
    http://www.learningaboutelectronics.com/Articles/Low-pass-filter-calculator.php

    There's your frequency cut-off (roughly; real-world electronics with all its gallimaufry rarely matches up with exact math)
    I have two 10' cables; they measure 40Ω/420pF and 20Ω/700pF. I calculate 9 and 11 MHz, respectively. Absolutely nothing to worry about at all.

    This doesn't take into account low-pass effects of amp/pedal impedance, but suffice to say as long as its 500kΩ and up, it will have a minimal effect.

    [EDIT] @TeleTucson, I just saw your post that was much more concise than mine. I was on Electronics 101 autopilot and probably posted frivolously. See below.
     
    Last edited: Jul 25, 2020
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  2. TeleTucson

    TeleTucson Tele-Afflicted

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    This is incorrect, cable resistance is irrelevant compared to the amp terminations and guitar pots. The cable does not form an RC low pass filter. The impedance offered by the guitar is a combination of inductance, capacitance, and resistance and needs to be modeled as a circuit. If you want to get even more rigorous, you can include the effects of eddy currents which provide damping as well.
     
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  3. alnico357

    alnico357 Tele-Afflicted

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    In 50-plus years I have owned one single cable that had an audible difference.
     
    Last edited: Jul 26, 2020
  4. Jon Snell

    Jon Snell Tele-Holic

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    It's all in the mind. Trust me, I still play bass ... sometimes when I have to!
     
  5. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Heh, yes, the gear search is all in the mind, and the tone target is all in the fingers...

    To be fair to Canare, if you *were* worried about capacitance, I'm reading the Mogami site about their 'high-capacitance' cables; they emphasize that for guitar cable with standard pickups, minimizing *microphonics* is a big deal; both Canare and Mogami appear to go all-out with conductive inner sheathing and other features that reduce cable noise -- but perhaps increase capacitance.

    I have learned to stop worrying and love the cable, if not the bomb. Thank you all!
     
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  6. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Thanks, sir. I missed this at first when I refreshed the page just now. That is exactly the kind of detail I set out to find. Very thoughtful and you made it *clear* -- which is a little detail I really appreciate.

    Thanks, Jason, all I could want to know -- and an entertaining and well-written article.

    Today I learned a bunch. A good day. Thanks again.
     
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  7. john_cribbin

    john_cribbin Tele-Afflicted

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    Before the internet, we just played guitar.

    Today, apparently I need one million dollars worth of scientific test gear before I even plug in.

    Nah, I buy a lead and plug in. Old school and proud.
     
  8. edvard

    edvard Friend of Leo's

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    But that IS what the cable makers are saying when they provide Capacitance per foot. And this whole discussion is moot if the cable does NOT act as an RC low pass filter. I am aware of the effects of impedance, volume/tone controls, laying the cable straight vs coiled up next to the amp, eddy currents, etc. but my point (that I apparently failed to make) is that unless you have ridiculously long cables and iffy impedance on your amp, the cable itself probably won't make a ton of difference. I don't even hear a difference with my really cheap Radio Shack 10' coily cable. Yes, ridiculously long cables will have an effect, but just like the tonewood debate, pickups and amp will probably have a greater effect on your sound.

    [EDIT] MAYBE I WAS A LEEEDLE MITE WRONG...

    Just for giggles, I whipped up a schematic and simulation in LTSpice, using somebody's measured specs of a '57 Strat bridge pickup with standard volume and tone dimed with a 1Meg load to simulate amplifier impedance (Yeah, yeah, I know, I know...) and based on values from my own cable that I measured with an imperfect DMM with Capacitance function.
    No cable, 5' cable, 10' cable, 20' cable, 50' cable, 100' cable.

    cables_sim_results.png

    I set the floor at -26.33, because that's -12dB from the inital -14.33dB, so you get a rough sense of the filter effect, even though it's not a true decibels-per-octave view. I think...

    And for transparency, here's the schematic I whipped up based on this:
    https://guitarnuts2.proboards.com/thread/7842/modeling-electric-guitar-ltspice

    cables_sim_schem.png

    Hmmm, so it appears that anything longer than 20'-25' will start getting noticeable, and at 100', it's completely obvious.

    And now we see one sound clip is worth a thousand calculations. Nice!

    Right with you John, right with you...
     
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  9. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Kudos to you for putting in the effort! Always nice to see when calculations back up theories and experience!
     
  10. jvin248

    jvin248 Doctor of Teleocity

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    .

    The fastest answer ... if you want the lowest capacitance cables, so you have more control to use your tone knob if you want to or not because a tone knob can't remove muddiness, is buy the cheapest cables you can find. If the ends break off then just buy and solder on quality replacement ends and you'll have the best cable you can get.

    The 'premium' cables want you to experience a 'warm' tone ... by clipping off the signal and making it muddier.

    .
     
  11. TeleTucson

    TeleTucson Tele-Afflicted

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    I'm happy that you made your own correction in red, and what followed, from your first paragraph that you started with ... :)

    In your description, it almost sounds like you've reversed your interpretation of the curves you created:
    The green one in your plot, showing the most dramatic change, is the "no cable" or buffer, while the one furthest left is the 100 ft. cable. So with peaks going from left to right in your plot, you are marching to higher frequency peaks from the gray curve for the 100ft cable.

    Because you seem like an EE type, if you want to really get into a model like this, then you can eliminate the "voltage source" in the circuit (because in reality there is not one) ... and instead put in a magnetic flux generator which is what the string really does to the coil. The benefit of this is that it automatically gives you the simple way to realistically capture eddy current effects because the flux generation by the string drives voltage in the coil but also also voltage and currents in nearby conductors.

    I first developed and posted this approach right here on TDPRI a few years ago, and now if you google, "guitar pickup equivalent circuit" you'll see that it is pretty widely noted, or especially if you google "guitar pickup equivalent circuit eddy".

    The TDPRI post is below, and of particular note are post #50, after it was done in a rigorous way, and post #77, where an analytical version is provided with the math.

    https://www.tdpri.com/threads/physically-based-eddy-current-equivalent-circuit.846745/page-3
     
    Last edited: Jul 26, 2020
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  12. gkterry

    gkterry Tele-Afflicted Silver Supporter

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    It's all bunch of hogwash. Go buy a long coily cable and play your guitar.
    Forget all that psycho tone hunter junk.
    We would all be better guitar players if we spent the time used on this nonsense practicing our craft instead.
     
  13. TeleTucson

    TeleTucson Tele-Afflicted

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    Can't disagree with this part of your quote. :)

    In fact, I guess it would be silly to even have more than one guitar if we can practice on the one we have. :eek:
     
    Last edited: Jul 26, 2020
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  14. deytookerjaabs

    deytookerjaabs Friend of Leo's

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    Personally, I do this thing now where I pack an extra few cables.


    IMO, they make a big difference. Some rooms are bright, sometimes you're stuck right against your amp, some rooms are dead, some are dark/lively. Since I don't use many pedals or anything I find the difference in the cables gives a more definitive feel than playing with knobs as knobs have this thing where the amp can still feel sterile yet ya go from biting to mud.


    So, I have a long "retro coil" that really has an obvious EQ tone shift/muffle in a good way thing, a normal coil cable that just sounds neutral and one of those "pro" audio cables that's noticeably brighter than the other two. Mostly I end up with the neutral or retro cable.

    Before this I'd always had an extra couple cables anyways for backup, it's nice to tinker before your set/rehearsal.
     
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  15. Fretting out

    Fretting out Poster Extraordinaire

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    I didn’t read the whole thread but recently I was looking up Albert Collins and apparently he used an ungodly long cable

    150! FOOT!

    29C34B1E-4856-4525-B5F8-23C1051D90CE.jpeg
     
  16. moosie

    moosie Doctor of Teleocity Silver Supporter

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    Can't answer @King Fan's question, but I use a buffer as close to the guitar as is reasonable (10 ft). If I want treble cut, I'll do it myself. Another way to say how much is too much: I can hear the difference between a 3 ft cable, 10 ft cable, and an 18 footer. No, not in a band situation. :lol:

    I'm saying why not just shoot for as high of quality a signal is you can reasonably get (and you get to decide what's reasonable), and then monkey with it downstream as you wish.
     
  17. edvard

    edvard Friend of Leo's

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    I'm a humble man, I will readily admit to when I make mistakes, else I never learn anything. I can't stand being proud of being wrong.

    HA! Barely if at all. I can make some squiggly lines while I'm tinkering with fuzz pedals and pre-amps, but that's as far as it goes. Thank God for tools like LTSpice, oscilloscopes, and breadboards; I hate math...

    Verrrry interesting, and thank you for the link. I used a voltage source because it's easy and "good enough" for most purposes, and everybody else does it, so... :oops:
    Seriously, I kinda knew intuitively that a pickup wasn't a 'mere' voltage source, but I don't have the training or smarts to figure it out on my own. Your post is very enlightening and helpful to clarify my suspicions. Maybe you should hook up with Antigua over at the GuitarNuts2 forums, he's done many posts about things of that nature, and is where I plagiarized my pickup model from.

    I still don't notice a difference in sound from my cheap coily cable...
     
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  18. gimmeatele

    gimmeatele Tele-Afflicted

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    Will anyone even notice? If they are drinking and dancing they probably wont be worried. :)
     
  19. johnDH

    johnDH Tele-Meister

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    Well there's no doubt that cable capacitance has a huge effect on your guitar tone. Once you realise it, then it is a personal choice about what you prefer and whether you want to amend anything in your set-up as a consequence. But the tonal difference between say a 10' and a similar 20' is at least as significant as say between a couple of different pickup choices.

    I like good quality cables for all sorts of reasons, but I dont find a need for very low capacitance.

    For me, I like the sound of an average capacitance 10' cable but I find a 20' one to be more mellow than I prefer, but others may have different views. So since I go guitar to pedals to amp with total 20', I make sure I have a buffered pedal in the chain. This lowers your signal impedance after the buffer, so the second cable is not affecting the tone.

    Am I wrong to care? nope, but nor does what I prefer have anything to do with anyone else.

    Also, I genuinely get as much interest and enjoyment out of working with the technical side of guitar gear as I do from playing. Even in 2020, there are heaps of new ideas to work with.
     
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  20. jrblue

    jrblue Friend of Leo's

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    Other than at the extremes, I have not found cable capacitance to be of any real concern. Given the tendency of modern effects, amps, and pickups to deliver, and often exaggerate, harmonic detail, notably highs, the degree of filtering produced by a decent cable is a non-issue for me. In actual practice, the "worst" (to me) cable I have used has been a very expensive, ultra-low capacitance, super-boutique cord that performed as advertised -- unfortunately, as it sounded sharp, harsh, and unpleasant (though you could adjust most of that out). Obviously, super-high capacitance cables can just strip too much harmonic content and are lousy. I use various Lava and Divine Noise cables and love the performance and excellent materials/build quality. I make these choices based on use and sound in my rig, with my guitars, not by doing math (other than to read specs and know what to avoid).
     
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