Carbon film vs. metal film? Discuss...

Discussion in 'Shock Brother's DIY Amps' started by King Fan, Dec 3, 2019 at 10:46 AM.

  1. King Fan

    King Fan Friend of Leo's

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    OK so it's easy to read about the known vices (noise, drift) and possible virtues (second-harmonic resistor distortion) of *carbon composition* caps, but are there differences between CF and MF? Many nice builds and smart builders seem to use CF. Is this in preference to MF, and if so, why? I've drawn a blank in my research on this.
     
  2. RottenTheCat

    RottenTheCat Tele-Holic

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    From Google
    Metal film produces less thermal noise than carbon. Metal film resistors also typically have a much lower inductance/capacitance than carbon so they(metal film) work better at higher frequencies. Carbon has no real advantage except that they are cheaper.Jul 29, 2012
     
  3. King Fan

    King Fan Friend of Leo's

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    Google, eh? May need to check that out. :)

    That corresponds to my sense of things, and I guess price matters if you're buying a lot of 'em and building big circuits. The only other factor I could guess at is that people like the pretty tan color of typical CF over the cold blue of typical MF.

    To tell the truth, I sometimes get the vibe that people are hoping to capture the magic of 'carbon' or avoid the cold of 'metal' -- but from the little I know I kinda concluded the mojo in CC, if any, is to be found in the second 'C.'
     
  4. schmee

    schmee Poster Extraordinaire

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    Metal oxide for me. Very heat resistant and always dead on value. Although, other than value accuracy I don't think resistors make much difference.
     
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  5. D'tar

    D'tar Friend of Leo's

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    We are stardust
    Billion year old carbon
    We are golden
    Caught in the devil's bargain
    And we've got to get ourselves
    Back to the garden

    Joni Mitchell

    Carbon film lets us use modern components and still feel like maintaining sort of vintage mojo!

    Metal film let us be super accurate and reliably quiet for those who dare not succumb to pier pressure.

    The price is negligible for a hobby builder unless EVERY penny counts.

    How do they sound? I won't go there.
     
  6. Whatizitman

    Whatizitman Friend of Leo's

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    Which are cheaper? Who has free shipping?

    That pretty much drives my decisions on resistors and caps. :D
     
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  7. King Fan

    King Fan Friend of Leo's

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    Excellent. I know MO are heat resistant -- I've used 'em for B+ dropping and cathode bias, and over tube sockets. (I also now use ceramic composition or reduced-mass wirewound resistors around power tube sockets.) But do MOs have pros or cons higher up the signal chain?

    Beautiful, D'tar. Stardust, Joni Mitchell, Hoagy Carmichael, ancient supernovas... mojo, magic, music... all good.

    As for your 'feeling' of vintage mojo -- I'm sure that's a big part of it.

    And for sure we are *not* going to discuss whether CC or any other mojo makes any difference we can actually hear. :D
     
  8. Middleman

    Middleman Friend of Leo's

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    I went through all this years ago and here is what my experiments and consolidated findings were.

    EQ and preamp section please, no metal. Just not harmonically pleasing to the ear.

    I did some experiments with this in my vintage vibrolux when it was time to recap a few years ago. I replaced all the caps with orange drops components. The results was it absolutely sounded clearer, more powerful but tonally lifeless. It was just loud and hard sounding. After a couple of months, I replaced everything with as original as I could locate them, capacitors. The result was a more rounded, pleasing tone with richer harmonics and yes, slight distortion characteristics.

    One man's experience. If you want a more edgy clean and pushed sound, go metal. Maybe in a loud surf type band. If you are looking for more resonance and rounded traditional rock guitar tone, try to find something like the originals. There are lots of vintage type caps out there today.

    One man's experience.
     
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  9. jsnwhite619

    jsnwhite619 Friend of Leo's

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    I've read where people have said they used all metal film and the amp turned out too bright, or sterile, etc. - warmer sounds from carbon comp & carbon film. If the above is accurate about metal film working better at higher frequencies, I could see the argument being made where MF "working better" at high freq. allows more highs to accurately pass through, thereby CC or CF NOT working as well at those frequencies may filter them out/loose them along the way, and end up with a "warmer" tone. No experience in comparing the two, just taking a guess.

    Sent from my moto g(6) using Tapatalk
     
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  10. King Fan

    King Fan Friend of Leo's

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    Dude, I love and respect everything you say. You're a builder after my own heart.

    But I beg you, as a friend and gentleman, pleeasssse let's not introduce the subject of *caps*. Those wars have been fought, and will continue to be fought, far beyond the bounds of logic and proportion.

    Like someone who types entirely in lower case, this thread is now "NO CAPS." :)

    EDIT: Ack, sorry, I see I had stuck 'caps' and 'capacitors' in the tags here. Stupid tags!! Stupider KF!!!
     
    Last edited: Dec 3, 2019 at 11:49 AM
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  11. schmee

    schmee Poster Extraordinaire

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    I don't really, know but I started using them years ago, mostly because the CC I tried buying were dog doo now days. Some new 100k ones were like 140k etc. Way off. But have used oxide in my BF Fenders pretty extensively now for years and I dont hear a detriment.
     
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  12. King Fan

    King Fan Friend of Leo's

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    (EDITED due to severe coffee deficiency. Sorry.) For sure, Jason, I've read threads like that too. I hadn't ever heard about 'working better at higher frequencies', which could be a factor. You're absolutely right -- I have have heard cold, sterile, etc. I always kinda figured they were talking about MF's known lack of the (supposed) sweetening effect Mr. Keen discusses regarding CCs.

    But that's my question. Does anyone suggest (factually or logically) that CF somehow shares the electronic features that (may) make a difference in CC? If so, I haven't seen it.
     
    Last edited: Dec 3, 2019 at 11:54 AM
  13. David Barnett

    David Barnett Doctor of Teleocity

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    The "...works better at higher frequencies..." description is in reference to stuff way outside the range of human perception. Like RF.
     
  14. King Fan

    King Fan Friend of Leo's

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    Heh, tried that Google thing. Cool. That thread was the first hit. Hmmm, it's StackExchange, so maybe mixed opinions and facts? OK, one guy's take, but sounds well-informed. But wait, he seems to lump all 'carbon' together? Or at the end, maybe he's just talking carbon comp? Unclear. Quoting:

    "If you are going to be doing a lot of analog electronics, you should buy metal film. Metal film produces less thermal noise than carbon. Metal film resistors also typically have a much lower inductance/capacitance than carbon so they(metal film) work better at higher frequencies. Carbon has no real advantage except that they are cheaper. If I was only going to work on digital stuff, I would buy the carbon comp."

    The court will re-open the case...
     
  15. King Fan

    King Fan Friend of Leo's

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    Excellent, and in fact I now see the original question on StackExchange was, "Most of my projects will involve microcontrollers, such as the Arduino and other...."
     
  16. Peegoo

    Peegoo Tele-Meister

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    Some experts claim carbon film produces less shot noise than metal film, but there are others that claim the opposite.

    I've tried both types and while you can see it on a scope, it's all a wash once the sound is out of the speaker and mixing with the bass and drums and vocal caterwauling. To me, it's like changing from Phillips to slotted screws to hold the pickguard on your Tele.

    It's not going to matter when you're playing. That's just me. The fact that there's no true consensus after many years is quite telling.

    Professional driver on a closed course. Your mileage may vary.
     
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  17. mabinogeon

    mabinogeon TDPRI Member Ad Free Member

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    Metal film for me. Specifically, Dale RN65D resistors. Super low noise, 1% tolerance. In the power supply I use Dale CPF3 resistors. I am colorblind and appreciate that they both have the values printed on them, rather than having to decode the stripes.

    They both also have non-ferrous endcaps (which some say sound better than resistors with magnetic endcaps*), if you're into that sort of thing.

    *Morgan Jones, Valve Amplifiers, pg. 125
     
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  18. King Fan

    King Fan Friend of Leo's

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    Yes and yes. I appreciate the virtues of MF over CC. And I use the mil-spec Dales, with 1% tolerance and printed values, in my own builds.

    But the case on the docket today is "MF vs. CF." We only invited Mr. CC here to note that *his* pros and cons are well-known. The court appreciates his cooperation and long service, but we also know his calendar is overflowing with concert dates and appearances at boutique amp shops. He is free to go. :)
     
  19. theprofessor

    theprofessor Friend of Leo's

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    I love this thread. I think everyone who has pitched in so far has more real-world experience in all this than I do, but hey, it's the Internet, so I can still have an opinion, right?

    I have used metal film between the inputs and V1 of the amps I've built, and that's it. The rest has been carbon composition or metal oxide in the power-dropping section or as grid stoppers or whatever. I don't mind the extra carbon comp hiss, and to my mind, a quiet amp is largely about the grounding scheme and the solidity of the solder joints, anyway. But again, I don't care that much. 60-cycle hum doesn't bother me; P-90's don't bother me. It's all a part of the harmonics.

    But this bit from Ken Fischer did make me shy of using more metal film than I have:

    And there are a lot of things I've found that I just don't think work for anything. Like metal-film resistors -- I've never heard an amp with metal-film resistors that didn't sound harsh. A lot of guys will say, "But they make the lowest noise." Oh, absolutely, they're far lower-noise. Carbon film is lower-noise than carbon comp, but metal film is way lower noise than either one of those two. Yeah, you can get less noise, but you won't get as good a guitar tone. (from Dave Hunter, The Guitar Amp Handbook, p. 236).

    So, of course, that solves nothing. But it is one guy's opinion.

    And since I have no personal experience with carbon film, I'll just eat my popcorn and watch the thread.
     
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  20. mabinogeon

    mabinogeon TDPRI Member Ad Free Member

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