Carbon film vs. metal film? Discuss...

Discussion in 'Shock Brother's DIY Amps' started by King Fan, Dec 3, 2019.

  1. gusfinley

    gusfinley Tele-Holic

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    I'm currently putting together a Vox "AC15" (top boost and normal channel) using JMI-style construction ( repro chassis, tag boards, repro cabinet, etc.) I elected to use carbon composition because if it works and sounds good, why not make it look the part as well? I'll be using modern best-practices such as star-grounding and sheilded wire to keep noise down and as long as they don't cause a problem I'll leave the CC resistors in.

    If I'm not building something vintage spec, I use carbon film for asthectic and possibly sonic reasons. I've built some nice and quiet amps with them, I'm not sure that going to metal film or wirewound resistors just due to number on the spec sheet translates to any actual improvement in audio performance.
     
  2. mabinogeon

    mabinogeon TDPRI Member Silver Supporter

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    You'll have to start another thread on polyester vs. polypropylene caps.

    I have all kinds of opinions on that, as well :lol:
     
  3. King Fan

    King Fan Friend of Leo's

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    Yeah, a lot of boutique shops and high-end builders here go the all-CC route. "Looks" vintage is a bit ironic in an amp we may only look inside once a year, but you know how it looks in there every time you play it.

    A great 'cheat' to quiet the 'all-CC' amp is to use MF on the input wiring. Noise from these few resistors gets amplified far more than any others in the circuit.

    Hey wait, you guys, now you got *me* discussing CC resistors. OK, NO CC *and* NO CAPS. (Good luck, yer honor.) :)
     
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  4. David Barnett

    David Barnett Doctor of Teleocity

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    I don't find double-blind, or really any form of A-B or A-B-X testing in audio to be useful for anything except gross differences in frequency response. The problem is that "what is heard cannot be unheard". Let's say you're listening to a test track to compare audio amplifiers. You listen to amplifier A, then switch to amplifier B and hear some small detail in the track that you never heard before. You switch back to amplifier A and there it is. The more you switch back and forth between the two, the more they will sound the same as the brain learns to compensate.
     
  5. D'tar

    D'tar Friend of Leo's

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    Choices!!! Too many dam choices I say! I like the grungybrown ones with the colorful stripes and the sleak orangy brown pinkish ones without stripes and blue is one of my favorite colors but then the stripes kinda ruin it for me. Whats a guy to do!
     
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  6. mabinogeon

    mabinogeon TDPRI Member Silver Supporter

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    And then try to hear a difference at band volume in a noisy bar...
     
  7. King Fan

    King Fan Friend of Leo's

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    That's interesting. What *do* you find useful, then? I'm a hobbyist photographer, and I can switch back and forth between two shots or two edits all day long and still see them as different. Not blinded, much less double blinded, but you get the point.

    Speaking of double-blinded reminds me of my favorite study, titled "A double-blind study of early hearing in puppies".... Dang, good thing the researchers couldn't inadvertently clue in the puppies about what they were hearing.
     
    Last edited: Dec 4, 2019
  8. King Fan

    King Fan Friend of Leo's

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    Ah, we were just talking about blind testing, but for you, sir, perhaps something slightly different. We imagine you like to listen to music while building amps?

    blindfold.png
     
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  9. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    precisely.
     
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  10. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    If the differences are so subtle that you "hear" something, and your brain compensates for it so you hear it in the next sample, and so forth, then there IS no difference. That's the bottom line.

    Were there differences in the audio world that were not subtle but, in fact real and identifiable? Sure, like when I heard the difference between a Technics CD player and an Arcam CD player. Jaw-dropping. Of course, that was mostly due to a single unit in the build--the D/A converter.

    Double blind doesn't "fail" when used. But when you are trying to discern between very minute sonic qualities, the double blind test will say, essentially, these two are the same.
     
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  11. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    By the way, @King Fan , this has been a fun discussion!
     
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  12. aging_rocker

    aging_rocker Tele-Meister

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    Quote of the day award for you, sir :)

    I agree with this 100% (+/- 5% tolerance) - the 'drift' is cumulative, and so you get great or not great sounds from 'identically' specced kit. This is why it's very difficult to replicate the sound of a truly great amp, but it doesn't stop anyone trying, thankfully :)

    True. Out there in the real world, the vast majority of components are completely untouched by human hand. Until the tinkering begins, of course...
     
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  13. King Fan

    King Fan Friend of Leo's

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    Heh. I'm gonna borrow that so I can be more agreeable in the future. :)
     
  14. D'tar

    D'tar Friend of Leo's

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    LOL

    I agree with you...... /

    I agree with you also..... /
     
    Last edited: Dec 4, 2019
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  15. jtcnj

    jtcnj Tele-Holic

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    I dig these in the weeds discussions, but mostly as a spectator.
    My level of understanding is not very deep.

    I dont buy into absolutes where subjectivity is in play, because by definition it is somewhat subjective.

    Generally I go with what experienced builders recommend. I use the Aiken on Resistors article as my guideline.
    I dont think I could hear much difference.

    I have ordered iron from Hawk USA twice and the shipping wasnt horrible, Tube Depot gets most of my small parts orders and shipping is reasonable from Tenn. to NJ.
     
  16. David Barnett

    David Barnett Doctor of Teleocity

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    But with a visual comparison you can look at both at the same time.
     
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  17. gusfinley

    gusfinley Tele-Holic

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    I used to frequent the Plexi Palace / Vintage Amps forum and there was a fellow there that had the magic recipe for Vox AC style amplifiers.

    He seemed to know which "drifted" values sounded good and which ones sounded bad. He would have customers send him new amps to "vintigify" for them - that is remove the fresh new "in-spec" resistors and replace them with fresh new resistors with drifted values.

    Sometimes drift is a good thing!
     
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  18. dan40

    dan40 Tele-Afflicted

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    For anyone looking for different options in new carbon comp resistors, Justradios up in Canada sells several different brands. Prices are very fair but they do have a $20 minimum order which may be restrictive to someone only looking for a few. They have a good selection of other resistor types and just about any value capacitor that one might need for a tube circuit.
     
  19. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    I also like Aiken's comments. Seems to be well grounded to me.
     
  20. King Fan

    King Fan Friend of Leo's

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    Yes, but in fact alternating the images at full-screen (say in Lightroom) is actually more revealing. If you're A-B'ing two sources and you can't unhear a detail you heard before, then you're listening for detail, not tone. Tone is like color balance or saturation in a photo -- alternating comparison clarifies rather than obscures the difference.

    Now before i go nuts defending A:B tests of resistor type, I have yet to see someone build two identical amps with different resistor types. Our friend @BobSmith did something close, though. I've tried all-MF vs. CC in selected spots and listened before and after soldering, but of course that wasn't blinded, and the time interval there can mess with your auditory memory.

    Oh, yeah, also... what *do* you like better than A:B testing? :)
     
    Last edited: Dec 4, 2019
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