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Tone Capacitors - The Final Word

Discussion in 'Amp Tech Center' started by Doctor Detroit, May 7, 2016.

  1. Doctor Detroit

    Doctor Detroit TDPRI Member

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    I apologize for the length of this post, but certain things just have to be said to show the truth of the matter. I have not seen this in any writing aimed at guitar players and musicians of all types, so here goes...........

    The following facts prove that contrary to many rumors and postings by people who do not know their electronics, different types of capacitors cannot have any effect on tone circuits in guitars and amplifiers. The point is proven using standard electronics theory known to all experienced engineers and techs. It is based upon a simple consideration of the “series equivalent circuit” of a capacitor as shown below. For the benefit of those not familiar with this concept, it means just this: whenever a capacitor is placed in any kind of circuit, the actual circuit looks like this. In addition to the capacitor itself, which is what is actually desired, there also appear additional “components” called parasitic elements. Under some circumstances these unwanted additional elements could have a significant effect, including modifying tonal response functions. But why they don’t for our purposes is totally clear by considering real world capacitors of all types.

    upload_2016-5-7_2-1-56.png


    Here the basic facts about capacitors of ALL types that are used in musical electronics. First: the value of L is negligible at frequencies even remotely close to the audio range. It is typically in the range of a few micro or nanohenries – you do the math! So the inductance factor is non-existent (especially at audio frequencies), leaving only R and C to deal with.

    Since C is the primary concern in all cases, especially "tone control" circuits, the important question concerns how is R compared to C for a given component. The answer is slightly complicated because it is frequency dependent. The standard way of rating capacitors uses the "dissipation factor", which is kind of an expression of loss, or imperfection, of the cap. It is defined as the ratio of the value of R and Xc (capacitive reactance) and is usually rated in percentage. A cap with a DF of 1% at a given frequency will have an R equal to 1% of Xc. In order for DF to be of any concern in any tone-shaping circuits it must be at least 5-10 % or greater. Even 1% DF will be totally negligible. If you don’t believe this, just analyze any standard tone control using first a perfect cap (DF=0) and then increase the DF to 1% by adding some R – the difference will be insignificant.

    Now here is the bottom line: all capacitors manufactured and used in any type of standard electronic devices, musical or otherwise, and particularly those with values under 1 mfd., have a DF of less than .1%, and typically in the range of hundredths of 1%. One big reason for this is because in most electronics applications, caps with DF>.1% are generally considered junk by designers and would not even be saleable. The other reason is that the dielectric used in caps <1mfd is typically a low loss material (paper, mylar, mica, ceramic, etc.), which determines the DF.

    Conclusion: All capacitors used in audio equipment are essentially "pure" C. No R or L, just pure C. The circuit it appears in sees only the C value and doesn't care whether that C comes from a dielectric of mica, paper, ceramic, polyester, or Kryptonite. C is C – end of story. Hence, no possible effects on frequency response (tone) are possible. This implies that anything you have ever heard claiming that different types of capacitors have unique tonal characteristics, is pure fiction - and not even of the "scientific" type.

    BTW: All of the above is based upon the assumption that any capacitor under consideration is a good capacitor - it is not defective and conforms to the ratings of the mfr. Obvioiusly a defective cap can have huge effects, including complete disfunction or failure of the circuit!
     

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  2. ranjam

    ranjam Tele-Holic

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  3. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    Well, I'm glad we finally got that cleared up! Welcome aboard, Ranjam.
     
  4. John How

    John How Tele-Meister

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    I use only magic mushroom oil and zigzag rolling paper caps in my tone circuits. They gimme mojofunkin...
     
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  5. Jupiter

    Jupiter Telefied Silver Supporter

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    [​IMG]
     
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  6. Wally

    Wally Telefied Ad Free Member

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    Welcome, Doctor Detroit.
     
  7. cabra velha

    cabra velha Tele-Afflicted Ad Free Member

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    I'll add this to my citation manager app
     
  8. Middleman

    Middleman Friend of Leo's

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    Go get an electronics board, hook up 5 different types of caps of the same apparent value and route them to your guitar. Come back and report your findings.

    Sometimes you have to get out of the library.
     
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  9. ranjam

    ranjam Tele-Holic

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    It seems we go through phases, and it all comes from a lack of basic electronics education. Let me go way off topic for a moment. I forget the jazz drummer who said it, but he opined that the lack of good drummers these days who can 'swing' comes from poor teachers. Original rock 'n' roll drummers were just jazz drummers who could swing. Every 4/4 song from people like Little Richard had a lovely lilt to it, with a hint of a shuffle or swing from drummers like Earl Palmer. Move forward, we get lousy rock drummers with no jazz background teaching the newest kids to be lousy rock drummers who can't swing. They can only do a meat-and-potatoes 4/4 beat.
    When I was in high school way back when, one of the text books was an RCA Receiving Tube manual. No ****. You had to learn magnetism, we made our own transformer on a big-ass stove bolt (it worked!), and we actually made our own capacitors. Not very large values, but we did it. We did experiments, and we learned to 'swing', if that makes any sense. I took that over to college, and worked on black and white tube televisions. When we did color television, we were never told certain capacitors would give us reds that were just a little 'better', or blues that were more blue. Doing RF circuits, were were only taught that paper capacitors had too much inductance at RF frequencies, so ceramic discs were the way to go.
    These days, my son in high school can't read handwriting, but he can text like a mofo. The electronics classes he takes don't teaches him how to 'swing', since those topics get swept under the rug so he can learn transistors and ICs.
    We went through phases of these 'gurus' who were admittedly self taught. Any interview I read with names like Gerald Weber admits he taught himself electronics from reading books at the college library. He has no background in TV servicing, radio repair, nothing. Even Leo was a radio man from back in his day. He learned how to 'swing'. But now we get ****ty rock drummers teaching only basic 4/4 beats. We went through a phase of cloth wire having the 'tone'. You could buy repro cloth wire, as if that would make your amp builds sound better. We went through a phase of 'point-to-point' wiring (even though a tag board is not point-to-point), and kits to put in your Bassman reissue, as if that alone would make it sound like a real tweed Bassman. I always waited for a point-to-point board kit for my Boogie, or my Bogner, or my Soldano; they never happened. I just have to live with the crappy tone 'as-is'. We went through 'matched output coupling capacitors', carbon composition resistors, and now directional cables. Oh, gerald Weber started the 'paper bobbin' OPT myth. So many myths, all coming from lousy rock drummers. We can buy repro 'bumble bee' capacitors, even though anyone with TV experience will have changed a million of them. They were lousy paper capacitors that always leaked. In your Les Paul it doesn't matter, so we can buy a $30 repro of a lousy cap, because lousy rock drummers believe they have a tone. If more of us had a background in 'jazz' (if that makes sense), less of this 'rock' would exist. There would be less posts here about the 'best' capacitor to put in a 5F6A clone. ;)
     
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  10. Doctorx33

    Doctorx33 Tele-Afflicted

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    Great post, I understand all of it except for the part after "I apologize..."
     
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  11. JD0x0

    JD0x0 Poster Extraordinaire

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  12. Plan9

    Plan9 Tele-Meister

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    I'm not a believer in any sort of magic tone mojo. Pretty much I want a capacitor to have capacitance in the labeled amount and nothing else. Which is why I tend to stick with widely available, cheap, reliable film caps. But I think your model over-simplifies things. E.g., ceramic caps tend to be microphonic and non-linear, so I think it's a mistake to use them in audio:
    http://electronics.stackexchange.co...itor-which-one-is-preferred-in-audio-circuits
     
  13. srinivassa

    srinivassa Tele-Meister

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    You just admitted that caps have inherent resistance and inductance. Don't you think different caps from different processes would have different resistance and inductance properties? Wouldn't that make them sound different? Especially in old process caps where the deviation from 'perfect' might be a lot more.

    I mostly use metal film caps too, as I am just not that picky apart from the actual value of the cap.
     
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  14. R.S.Fraser Sr.

    R.S.Fraser Sr. Tele-Meister

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    Apparently, OP's treatise was not the final word on Tone Caps,
    since there have been a dozen posts in this thread already.

    And the beat goes on
     
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  15. LutherBurger

    LutherBurger Poster Extraordinaire

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  16. Wally

    Wally Telefied Ad Free Member

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    chuckling, I am. RS, this is exactly why I simply welcomed Doctor Detroit. I knew that the subject could not possibly be closed. This debate will never be finalized.
     
  17. JD0x0

    JD0x0 Poster Extraordinaire

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    I'll just offer some first hand experience, too. I swapped from polyester film, to polypropylene film coupling caps in an amp and noticed a slight change in tone, that wouldn't be attributed to a slight variance in capacitance, due to tolerance. I saw some scope pics on Amp garage(which I'm having trouble digging up), and the Polyester showed slightly different distortion characteristics compared to PP of the same value. There's definitely a reason that certain (boutique) amp builders use a mix of compositions, rather than just using PP, which is the most stable.

    Outer foil orientation of film caps also makes a small difference. There's not some 'Holy Grail' and more expensive doesn't necessarily = better, but there's definitely a significant enough difference for me to stock multiple compositions, for fine tuning my personal amps. I dont buy into mojo, and I dont think vintage or NOS is necessarily better, either. In fact, the amp I did the swapping on, was a vintage amp, with the highly regarded Yellow Mallory type Polyester caps. The amp now has a mix of Polyester and Polypropylene caps in the signal path.

    Ceramic vs Silver Mica, is also a pretty noticeable difference, in certain applications, at least that's what I've noticed when swapping composition. Again, tone wise, neither is necessarily better or worse. Ceramic caps kind of suck, but they're cheap. Still, you see them used in $50,000 dumbles for the tonestack and snubbing caps, in pF values, when silver mica could just as easily be bought and would have better stability and longevity, typically. The ceramics, due to their relatively poor audio performance(see post #11), offer a different sound, and it seems a lot of players preferred the ceramic in those applications. Try it yourself. I wouldn't spend hours doing component swaps, if I thought it was placebo, I'd just use the most stable components, but they dont always sound the best in every application.
    If you do a google on this you'll also find a general consensus of amps builders that find SM generally has a more 'HiFi' 'brighter' or 'sterile' description, while ceramics are often described as 'grainy.' I have a feeling that graininess is partly due to the added odd order harmonics that the ceramics can generate. Polystyrenes are often described as 'smooth'

    Ill let people try for themselves and draw their own conclusions. Again, like most of these things, it isn't something that's going to jump out at you, most of the time. You're not going to make a trash amp suddenly sound amazing just by putting a different type of cap in, but if you're into fine tuning the last 5% of an amp's tone, cap composition, IMO, can definitely make a significant difference.
    I think there's many differences people overlook. ESR, transient response/time constant (PP is faster than PE, for example) etc.
     
    Last edited: May 7, 2016
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  18. cousinpaul

    cousinpaul Friend of Leo's

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    Even so, I bet there's few here who'd even consider replacing the ceramics with film in a vintage Fender amp for an "upgrade". Same with a vintage guitar's original tone cap. Repairs are a different matter but a lot of ceramic equipped gear is still going strong after 50+ years of service.

    By the same token, I don't think I'm going to be scouring the internet for vintage caps to replace the Mallory 150's in my tweed clone or the greeny's in my partscaster. I'm more concerned with my playing than stuff like that.
     
  19. richa

    richa Tele-Afflicted Ad Free Member

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    Yup. The unsuitability of ceramics (at least certain types) in a hifi audio path has been asserted by people much smarter than me. Hifi being the operative word.

    I admire your valient and noble aspirations doctor detroit. But even if there were not a but, it would scarcely matter, as others have alluded to. Many of the opinions about this are not falsifiable so a proof that rests on falsifiability (even if it took absolutely all variables into account) is not going to carry much water. :)
     
  20. maxvintage

    maxvintage Friend of Leo's

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    Let's not forget the leaky pipe analogy

    Think as the circuit as a water pipe. The tone cap is a valve that bleeds off some of the water. You never taste the water that bleeds off.

    I mean to people understand what shunted to ground means in this context?
     
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