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Coupling Cap quality in 500-C? Recommendations?

Discussion in 'Fisher' started by rufleruf, Nov 7, 2018.

  1. rufleruf

    rufleruf AK Subscriber Subscriber

    Messages:
    1,125
    I am working on my most recent 500-C and I got to thinking about coupling caps. I am pretty sure I am going to go the 220K resistor / .068uf capacitor combo route on this one. I usually use those yellow Illinois caps or Orange Drops for coupling, but got to thinking about fancy caps.

    I am curious to hear from those who have opted for fancy capacitors for coupling caps and the results they got. I am leaning towards using some Russian PIO caps off eBay, but am happy to hear other options. Please post links to places to buy them if mention a boutique cap. I found an older thread that was talking about Mundorf Supremes, but I couldn't find any for sale in the sizes referenced. I don't mind spending $20 per cap for the sake of trying this out.

    Also, if I go fancy for the output tube coupling caps, wouldn't I also want to use similar quality caps through the whole signal path?

    Finally, I have some super high end mil spec Micamold insulated PIO .1uf x 600V 1% caps that all test dead on .1uf. If I was to use these, what would be the ideal resistor value?
     

     

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  2. notdigital

    notdigital AK Subscriber Subscriber

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    2,246
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    The .068uf Russian PIO's are not only an economical substitute for the originals, they work wonderfully well in the Fisher circuit. I wouldn't spend $ beyond that. Since you already have Micamold PIO's on hand, I'd save a step and use them @ 200k.
     
    baconbadge likes this.
  3. 1rebmem

    1rebmem AK Subscriber Subscriber

    Messages:
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    Location:
    Wilmington, NC
    Matt,
    I ordered some Russian K40Y-9 PIO .068uF 400v cap's about a month ago and are due in within a couple of days.
    The size of them could be an issue as far as fitting them in place. They also have a metal case that I will put clear heat shrink on.
    When I get them I will post more info and maybe some pic's.
    Jef
     
  4. 1rebmem

    1rebmem AK Subscriber Subscriber

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    Location:
    Wilmington, NC
    Seems to me, yes. Only as good as the weakest link kinda thing.
     
  5. gadget73

    gadget73 junk junkie Subscriber

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    Location:
    Southern NJ
    I like basic film caps. They fit, and they work. The original ERO caps are not physically massive, so there likely isn't a ton of extra room to fit fancy caps in there. Most of the fancy ones are just huge for whatever reason.

    I'm also not a believer in capacitors having any real magic in the feedback loop, which is another reason I don't put fancy stuff in the power amp stage. Outside the feedback loop I've heard it, but never inside. The other night I installed the absolute cheapest film caps Mouser had in an amp, and it doesn't sound any different than when I had the big PIO caps that were about 10x the physical size in the circuit. The cheapos were Panasonic caps. I needed something of a given value and wasn't keen on spending a lot of money since they could be temporary.
     
  6. dsndblm

    dsndblm AK Subscriber Subscriber

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    Central Arizona
    Another vote here for the Russian K-40Y PIO caps. They fit inside the 500C without issue, sound really nice.
     

     

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  7. bhamham

    bhamham AK Subscriber Subscriber

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    Another vote for basic caps. I like to use the original ero-fol caps if they test good and have plenty of spare ones to replace the bad. I've tried the Soviet PIOs, orange drops and others but to my ears they sound the same.
     
    AlTinkster92 likes this.
  8. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Same here. If I have to replace, I'll use either C.D. DME Series Radials or Illinois Cap MKP axials. Sound difference is nil compared to the ERO-FOLS, and they are physically small. Larger caps also have a tendency to gather RF, so the smaller physically, the better.
     
  9. tcdriver

    tcdriver AK Subscriber Subscriber

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    Standard polyester caps in my Fisher 500-C. Matt, whatever you end up with I would like to know if you hear the difference and if so, what is the difference.

    FN-5B (800x366).jpg
     
  10. rufleruf

    rufleruf AK Subscriber Subscriber

    Messages:
    1,125
    I love it when I come back to a thread I started and it's full of good info!

    Sounds like a lot of votes for "don't bother" but no experience with Mundorf gold foil platinum supreme snake oil and parchment with a twist of lemon caps.

    I ordered some caps from Russia yesterday - the seller on eBay cut me a bulk deal, so I have a nice round 100 PIO caps coming: 20x .022/400 40x .047/250 20x .068/400 20x .068/600. I'll do a full signal path rebuild of one of the receivers on the pile and report back in 3 months.
     
  11. gadget73

    gadget73 junk junkie Subscriber

    Messages:
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    Test them for leakage first. I haven't had a bad one yet but those caps are old. I have run those caps in places, but I'm impatient and I can get stuff from Mouser in 3 days vs 3 weeks from Russia.
     

     

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  12. 1rebmem

    1rebmem AK Subscriber Subscriber

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    Location:
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    So on this coupling cap question, what do you guys think about the ceramic caps used in the phono section and other places?
    Some people would NEVER allow a ceramic in the signal path.
    I'd like to hear opinions/experiences.
    Thanks.
     
  13. Jon Kasper

    Jon Kasper New Member

    Messages:
    20
    My understanding is that K40Y work very well for output tube coupling caps. But overall, it’s advantageous to use a variety through the signal path, a mix of K40s and polypropylene, so as to avoid the sonic signature taking on too much of one variety and to add elements from one type of cap that the other may be lacking in. To create synergy.

    I’m working on recapping my 400 now and replacing the .09 cent Chinese caps the original restorer used , and am using:
    - mix of Vit Q and K40 in phono
    - K40Y for output tube caps
    - Auricaps for input coupling caps
    - remainder of coupling caps being a mix of 716p Orange drop film/foil w copper leads & K40s
     
    Last edited: Nov 10, 2018
  14. 1rebmem

    1rebmem AK Subscriber Subscriber

    Messages:
    48
    Location:
    Wilmington, NC
  15. 1rebmem

    1rebmem AK Subscriber Subscriber

    Messages:
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    Location:
    Wilmington, NC
    tcdriver......Nice looking work inside your 500C!
    Jef
     
    tcdriver likes this.

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