Silver Jubilee capacitors

Discussion in 'The Workbench' started by Joe L, May 31, 2014.

  1. Joe L

    Joe L Member

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    Does anyone have a source or information on the axial ceramic capacitors in the Jub? They look like resistors but are definitely capacitors. I'm pretty sure they are rated at 100v from research I did a long time ago and the circuit design confirms this by only using them where the rating won't be a problem.

    I've built a version with normal film caps and it does sound great but there is a certain high midrange distortion that I don't hear with mine.

    Any info would be greatly appreciated!

    ..Joe L
     
  2. RickyLee

    RickyLee Well-Known Member VIP Member

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    Interesting. I have never seen ceramic caps with axial leads.

    Or are you talking about those lime green resistor looking caps? I do not remember seeing anything like that in my '89 Jubilee 2550.
     
  3. Joe L

    Joe L Member

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    If you had a Jub Ricky, you had the axial ceramics in it. They looked like 1/4 watt resistors with color bands for indicating value. The axial mustard colored caps are easy to find and are just multilayer ceramics.

    The 900 Dual Reverbs have a ton of them.

    Here is a link to a bunch of pictures of the Jubilee.

    ..Joe L
     
  4. RickyLee

    RickyLee Well-Known Member VIP Member

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    Good to know.

    I had some lime green resistor looking caps in my SL-X. I yanked them things outta there. I had read that replacing those made the amp sound better. Maybe these ones I am talking about are different than the ones you are referring to?
     
  5. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    I have never looked into them and have never had to replace one. If they are good enough for the Jubilee then they are good enough for me. :D
     
  6. Joe L

    Joe L Member

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    Likely they were the same construction. The 900 Dual Reverb uses a shite load of them. And you would think that with how many Marshall amps use them, someone would have an idea of who makes them.

    ..Joe L
     
  7. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    They are axial tubular ceramic capacitors. I have no idea who the manufacturer may be.
     
  8. RickyLee

    RickyLee Well-Known Member VIP Member

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    Possibly out of production?
     
  9. Joe L

    Joe L Member

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    I got some ceramic disc caps in today of the appropriate voltages and changed out the film caps to match the original. I've only played it for about a half hour but it seems to be very close to what I remember of my friends amp. It now has that midrange aggressiveness that it was lacking with the film caps but still sounds ok clean. Of course, it will take more than a half hour to really wring it out and make a final judgement, but it's moving in the right direction.

    Caps changed per the 2550 schematic dated 15/5/87:

    C2
    C5
    C6
    C7
    C8
    C9
    C10
    C19
    C20
    C25
    C26

    ..Joe L
     
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  10. RickyLee

    RickyLee Well-Known Member VIP Member

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    Cool.

    I am now wondering if I should try the same thing with my 2555 Clone.

    Where did you purchase the caps at?
     
  11. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    The various types of capacitors will make a difference in final sound.
    A few of the guys use to talk about that once in a while like the clown man, Joey.
     
  12. wakjob

    wakjob Well-Known Member

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    I usually pull all those pink and green axial ceramics out of 900DR's, 3203/4203, and series 1 Valvestate amps. Only because I'm suspect of their temp. co.

    Depending where they are in the circuit, I replace them with c0g/np0 axial ceramics from Kemet, AVX, or Murata. Sometimes, again depending on where they are, I'll use a poly cap. Polystyrene can work sometimes for pF ranges.

    There's less high end 'hash' and a cleaner sound in the distorted signal from the non-linear properties of lesser ceramic caps. Likened to replacing a ceramic cap with a silver mica in a all tube circuit.

    But, it's those gritty/nasty bits in the harmonics that is sometimes needed from those cheap disks, as I've found out a couple of times. Sometimes the best parts don't always make the best tone. You can take it too far and end up with an amp that doesn't have the core sound you started with, or lacking those magic subtleties around the edges.
     
  13. wakjob

    wakjob Well-Known Member

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    Joe, did you replace ALL these caps with ceramic disks?

    *edit* nevermind, I think I understand how you worded it.
     
    Last edited: Jun 12, 2014
  14. Joe L

    Joe L Member

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    I've played it some more since changing the caps and switched out the crappy set of tubes I use to test with to my favorite Jan Philips long plate 12AX7s and an old pair of Siemens EL34s from the 80s. The Siemens still match to withing a few tens of milliamps even though they are about half way thru their useable life. For now I am happy with the sound of the amp and it really cops the grind of Joe Bonnamassa's live sound from the "A New Day Yesterday" dvd. I do have a bit more gain on tap due to paralleling the first stage with both sections of a 12AX7.

    On the caps - you read a lot of conflicting info on the effects of caps on the sound of both hifi and guitar amps. All the research I have done indicates that if a cap has a very low reactance at the frequency it is passing, it won't matter a bit what type you use. But since we use caps for tone shaping in guitar amps, and quite often they are passing signals with some intentional effect on limiting the bandwidth of the amp, it is quite possible to hear differences between capacitor types.

    So on the 2550 - I didn't want to use Class 1 caps because they can be quite linear. But I didn't want to use something that was going to drastically drift with temperature either. So I settled on the Y5P and X7R series which have pretty good tolerances and reasonable temperature specs. Also, low voltage caps change value with voltage much more than film caps I wanted to stay with 50-100v parts where possible. And where the original used multilayer caps, I wanted to duplicate that.

    Now that you know my reasoning - these are the Mouser part numbers I used.

    C2 - 594-K473K20X7RH5TH5 - Leaded 0.047uF 100volts 10% X7R
    C5 - 140-50P2-102K-RC - Ceramic Disc Capacitor 50V 1000pF Y5P 10% Tol
    C6 - 140-50P5-222K-RC - Ceramic Disc Capacitors 50V 2200pF Y5P 10% Tol
    C7 - 140-50P2-221K-RC - Ceramic Disc Capacitors 50V 220pF Y5P 10% Tol
    C8 - 80-C430C104M1R5CA - Multilayer Ceramic - Leaded 100volts 0.1uF 20% X7R
    C9 - 140-50P5-103K-RC - Ceramic Disc Capacitors 50V .01uF Y5P 10% Tol
    C10 - 594-D471K20Y5PH6UJ5R - Ceramic Disc Capacitors470pF 100V 10%
    C19 - 594-D203Z59Z5UL63L0R - Ceramic Disc Capacitors.375LS .02UF 500V +80/-20%
    C20 - 140-50P2-102K-RC - Ceramic Disc Capacitors 50V 1000pF Y5P 10% Tol
    C25 - 80-C430C104M1R5CA - Multilayer Ceramic MLCC - Leaded 100volts 0.1uF 20% X7R
    C26 - 594-H472K47X7RL63J7R - Ceramic Disc 4700PF 500V 10%

    This is not an end all be all of list of caps that will work but for a couple of bucks, I wouldn't hesitate to mod a clone/repro and see if I like the change.

    ..Joe L
     
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  15. Washington Soares

    Washington Soares New Member

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    Hello guys
    Sorry if my english seem confusing , I'm from Brazil and I'm using a translator
    Joe, you did some more mod since the last post? could approach the sound of the original jubilee with these mods I'm trying to build one, wanted it to be the most possible near the marshall sound
     
    Last edited: Sep 1, 2016

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