Yet more thoughts on coupling caps

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Wakarusa, Jun 30, 2005.


  1. Wakarusa

    Wakarusa Member

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    Ran across this article. The subject is the impact on dielectric "soakage" in capacitors on hold-release circuits. Soakage is the tendency of the dielectric material to hold voltage.

    In a nutshell, the article suggests that (among others) polypropylene film caps have better performance for this metric. I'd suggest that this affect may be a good physical explanation behind some folks' preference for capacitors of one dielectric material over another in audio circuits.
     
  2. John Phillips

    John Phillips Member

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    Definitely. I strongly believe that there must always be a physics explanation for any of these small changes that people can hear. Even if it's bordering on so subtle that it can't be detected by measuring instruments, there must always be a plausible real cause.

    But I'd be very careful about concluding that 'better' components (from a pure electronics point of view) will sound better, especially in guitar amps. In fact, if I had to put money on it, I'd go for the opposite. Less-than-perfect components cause distortion in various ways, bad for hi-fi probably, but part of what makes an electric guitar amp sound good.

    IMO.
     
  3. TheAmpNerd

    TheAmpNerd Member

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    That is interesting, thanks Todd.

    John has a valid point.

    I like polystryene caps a lot. Also like selected
    use of Teflon too.

    Still to me, there is just something special
    about paper caps and some of the paper
    in oil type caps for coupling.

    I think Ken Fischer in one of his articles
    was describing his like of the 150 mallory's
    because they had a sound close to the
    paper caps.

    If you haven't populated your amp with
    Solen "Fast-Caps" I think you will find the
    high end on these very harsh and brittle
    sounding...even with age. I think the solens
    are a metalized polyproplene...is it because they
    are Fast?

    The strange thing about Teflons is they are
    so fricking efficient at passing the highs, you
    almost seem to lose the bass, so you need
    to compensate for that. RelCaps any one?

    Dr Z amps use the 150 Mallory in them.
    Clarke has his own brand from RelCaps.
    not sure what type they were, but the
    elongated body is a dead givaway
    that Bas made them at Rel for him.

    http://www.capacitors.com/

    What works for you?

    Why do you like them?
     
  4. Wakarusa

    Wakarusa Member

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    My intent here is certainly not to crack open the rotten egg of "which caps sound better". The answer there strikes me as obvious...

    it's the ones you like.

    Instead, as John alludes, I'm always looking for an explanation beyond snake oil (read: I like physics) to explain the differences that people might hear or claim to hear. The "soakage" phenomenon seems to add an interesting twist to that general discussion. Also in agreement (I believe) with John, I'm staying away from whether this characteristic makes a cap better or worse for audio amplifier use... just different.

    In another thread discussing the use of the word "fast" to describe caps I made (and still make) the claim that charge and discharge times are a fixed physical constant determined by the capacitance of the cap and the resistance/voltage it is discharging/charging through/from. The article certainly suggests another interpretation of "fast" with respect to capacitors, but now I fear that I've given the marketing fiends a new buzzword to explain what in the heck they mean by "fast" :(

    They'll of course tell us that this is what they were talking about all along ;)

    As far as paper and oil caps go, I avoid them. Moisture absorption in paper and a nasty mess when oil lets go (and carcinogenic PCBs if your oils are NOS) keep them out of my amps no matter how wonderful they might sound.
     
  5. TheAmpNerd

    TheAmpNerd Member

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    Better be carful of those old tube amps ya know,
    especially if they have electrolytics in them...
    PCBs and all that.

    Actually you problably are more exposed eating
    fish, or if you have older flourescents with ballasts
    in them from smaller signal or coupling caps.

    Most of the NOS stuff that I have are all mil grade
    and they are all glass sealed.

    The paper caps that I have made for me are also
    sealed.

    I haven't even tried the caps from Jupiter, the paper and
    beeswax guy, but they are supposed to sound good
    also.

    You really should try them, before you knock them.

    The important thing for me is TONE and Reliability.
    If it enhances someones creative expression,
    what lies in their soul better, then it goes
    in the amp.

    That my friend is hard to quantify.

    It is one of those things, you know it
    when you feel it, hear it, express it.

    As John say, yeah, you look for a way to
    try to explaing it to the logical self, to affix
    some sort of meaning to it, to quanitfy it
    with lab equipment....

    ....can you do that with music?

    That is the magic and the beauty of it,
    somethings things you try just happen
    to work out just right, you learn from
    these and take note of what you did
    and how.

    Just my .02.

    Run around in RelCaps site they were some other
    interesting information in there regarding
    cap selection too.
     
  6. jetlag

    jetlag Member

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    Regarding the Jupiter beeswax caps. I looked into them since I've always liked the tone of the old paper caps and the yellow astrons - just don't like their terrible reliability. I emailed the gentleman that makes them asking for the temp specs on them. While I don't remember the value, it was very low. Thus these caps are not suitable for most guitar amp applications. They are meant to be used in certain stages of audio amps like hi fi where temperature design is used to keep temperatures below a certain threshold. He also stated that you won't get much of a sonic benefit using them unless you are running them near their design levels. He suggested the use of Mil foil 'n oils for my applications, which is what I did. I bought lots of foil 'n oils off ebay in many "normal" values and really like them. So far they are all 100% spot on for capacity and have zero leakage. Very high quality parts with good tone.
     
  7. TheAmpNerd

    TheAmpNerd Member

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    JetLag,

    FWIW, I've seen a few MI amps with the Jupiter caps in them. I haven't played through them nor heard them.
    Beeswax being hydrophillic (likes to obsorb moisture)
    didn't seem like a good mix with Carbon Comp resistors
    in the vintage stuff. One of these days I'll get around
    to trying some, just so I can have a listen.

    I can just see it now, you are at a gig in the middle
    of summer, and your vintage vox/marshall/fender
    bites the dust. Good think you carry a back up!

    You open the amp the next day only to find a puddle
    of melted beeswax....only a paper wrapper and two
    lead where a cap used to be.

    Moving along, so how do those oil caps sound to you?
     
  8. TheAmpNerd

    TheAmpNerd Member

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  9. TheAmpNerd

    TheAmpNerd Member

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    I stand modified on some of my stetements;
    foolish me..forgeting that amp builders in general
    are not static.

    So what we used in x amp...we don't use
    any more, switched to y cap in the newer model
    of x amp and featured in z amp.

    Now is it because of a price change or sonic charactoristics
    we are open to, because we have matured?

    OR

    Is it because as we pass through our 40s and on, men's
    high frequency hearing goes to ****...therefore we compensate?



    However, I think the data shows something
    different. Please anyone correct me if I'm wrong.
    The data show that:
    1. Teflon is the best in this metric
    2. Polypropylene (B) 2nd
    3. NPO Ceramic (A)next
    4. polystyrene (A) 4th.

    Followed by
    5. Polypropylene (A)
    6. NPO Ceramic (B)

    It would be nice to know what the A & B types
    are. Anyone care to send the Author an email and
    ask him. I'm sure he'd be thrilled to discuss his
    research.

    Sorry for rambling here, just thought I'd put that out
    there.



    I do have a question though, what is the difference in
    the make up of an NPO ceramic cap and a standard ceramic cap?
     
  10. jetlag

    jetlag Member

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    AmpNerd, (that doesn't seem kind to say)

    Regarding the NOS foil 'n oils ............. I like their sound. I won't use a bunch of descriptive terms and such because coupling caps can be subtle in their differences in sound in guitar amps. Plus it's all so subjective. But everytime I've had to replace yellow astrons in tweeds (or replace orange drops that were replacements for astrons in old tweeds), I'm happy. They just seem neutral and sound "right." Not too fast, not too slow, not too bright, not too dark or muffled. Maybe not as cool as healthy old astrons - they seem to have a lot of zip or something. I can't say that all the time about orange drops or plastic caps. Even NOS ones (that test good). Haven't put foil 'n oils in BF amps yet - those blue film caps don't seem to go bad (thank god).
     
  11. TheAmpNerd

    TheAmpNerd Member

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    I know, but it is just a fact. Hearing goes whether
    we like it or not. Especially being exposed to the
    DBs of music instrument amps and playing live
    music is even worse.
    Generally yes, I agree. I guess when you go from something that doesn't work so well to something
    that does work well, it sounds good.

    Some caps though I just don't like, they may be zippy
    but sound bad. Others are muffled, perhaps it is high
    end roll off.

    Then there are some that are just magical. Over a
    range of amps, in different circuits they just sound
    right, feel right, and the guys who play through
    the amp when you are finished, love it.

    You just know it when you hear it. One guy here described it on a Two Rock thread as "swirl"
    It will swirl in my head too. The other thing
    I get when I play a chord, is I'll get goose
    bumps down my back when it is that beautiful
    sounding.

    It is also what John and Todd are illuding to in this
    discussion. Trying to quantify it, so you can try and
    figure out what works and why and what doesn't.

    I submit the following, sometimes you can't quantify
    it, it just works. Or, it is what it is. There is an art to
    it. A feeling to it. You know when you get there.
    Other musicians know it too. It is getting that tone
    in your head, out into the world.

    Like art, the collective works by the masters were not
    ALL great, but those that are really stand out.
     

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