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Filter Cap Question??

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Lonely Raven, Jan 11, 2005.

  1. Lonely Raven

    Lonely Raven Member

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    Jun 29, 2004
    Location:
    Bolingbrook, IL
    I'm thinking about building a 5E3 from scratch, and I had a
    thought from something I saw in another forum.

    If I remember correctly, low ESR filter caps help give the amp
    more snap.

    Are PolyProp caps low ESR? And if I wanted snap from the
    amp, would useing big Solen PolyProp caps as filter caps
    help any? They are only a few $$ more then Electrolytics, and
    I think I'd only have to deal with their size as an issue.

    Edumakate me some on if this would work and have the results
    I'm thinking they would, please!
     
  2. TheAmpNerd

    TheAmpNerd Member

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    Tejas
    Try a Relcap PPMFX (if I recall) in a 20uf, 600V.

    It should fit and work fine.


     
  3. Lonely Raven

    Lonely Raven Member

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    Cool, that *is* another option!

    But am I thinking about this incorrectly? Am I throwing money
    away? While experimenting is fun, I really can't afford too much
    of it!

    Thanks!
     
  4. wrecked

    wrecked Member

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    Sep 22, 2004
    Location:
    Canada
    Hi Lonely Raven!

    If you're working from a somewhat limited parts budget, I'd emphatically suggest that instead of buying expensive, "designer" components, you look at getting different parts values for experimenting instead. If you've already got a wide selection of the different values of resistors, caps, pots, etc., by all means test out the fancy stuff, but I think there's a lot more potential for change in the values of what you put in (and also relatedly, the layout, since to change it you'll need more parts). The price of a component has absolutely no correlation to whether or not it will improve your amp, so start with the cheap stuff and work your way up, as money and motivation allows!

    I should have prefaced this by saying that I don't really consider the large value/voltage metallized polyprops to be a "designer" part, as compared to generic electrolytics they have drastically different electrical characteristics. I wouldn't be surprised that people can reliably detect a sonic change, but the question remains if the difference would even be in the subjectively "right" direction. Not to infer any other type of comparison, but on paper solid state devices can look a heck of a lot better that tubes ;)! Although polypropylene caps might have very low ESR, which is typically a plus from an engineering perspective, there's no indication which of the two part types will sound better to you, so why not get the cheap parts first and experiment with the costly stuff when you have the funds? I'd bet every time that the better amp will come from a workshop that's fully stocked with generic parts than from one with only a BOM's worth of expensive components. There's arguably just as much difference between a ceramic disk and a 715p Orange Drop as there is between that OD and a fancy teflon-and-depleted-uranium-foil number anyway.

    If you like the sound of polypropylenes as filter caps, then by all means it's probably worth the few extra dollars, especially as they don't dry out with age like electrolytics and won't need to be changed to the same degree. They're often rated for higher working voltages than electrolytics and will handle high heat much better too. Some manufacturer's life-time ratings are pretty dismal for general 'lytics, and although the measurement is usually done at increased temperature (which drastically shortens life) and the pass/fail test is more rigid than just filtering in a a tube amp, some caps are specified to last only 1000 hours. How long do power tubes typically last, again?:eek: My sermon on expensive parts aside, should you like the electrolytic's tone better due to the increased ESR, ESL or DA, it shouldn't be impossible to duplicate those effects with the benefits of the Solens by adding external components like some series resistance or inductance and/or by parallel resistance or RC networks! That might be quite the interesting area for an experiment!

    In summary, what I'm suggesting is that you might hear the difference, you might not, you might like the difference, or you might not, and finally if you don't like the difference, you might be able to make the Solens sound like the "worse" electrolytics. How's that for conflicting advice! :)

    Good luck!
    Matt
     
  5. TheAmpNerd

    TheAmpNerd Member

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    Does that rAwk or what? Buy new stuff, use for 6 mos,
    then you get that great vintage tone for the next 35 years: )

    It don't get much better than that.
     

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