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CA/BA-F1 Questions From a Newbie

Discussion in 'Exclusively Sansui' started by P.Bear, Jul 3, 2018.

  1. Hipocrates

    Hipocrates Anti-Muppet Subscriber

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    NP0/C0G disc ceramic capacitors. you can find them in mouser and digi-key
     

     

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  2. P.Bear

    P.Bear New Member

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    Thanks, but I checked both Mouser and Digi-Key and neither one seems to carry 2,3, or 22 pF 125 volt C0G (NP0) caps. They only seem to have much higher pF values and at lower or much higher voltages. For instance 3 and 22 pF 1000 volt 5% C0G (NP0), but no 2 pF caps at Mouser.

    I've noticed that they are available in 1%, 5%, and 10% tolerances. There doesn't seem to be any mention of the original Black Flag cap's tolerances in the Sansui Schematics. I assume the tighter the tolerance the better?

    Any other possibilities for sources [particularly the 2 pF size]?
     
    Last edited: Jul 7, 2018
  3. Hyperion

    Hyperion Roobarb & Custard Subscriber

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  4. P.Bear

    P.Bear New Member

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  5. P.Bear

    P.Bear New Member

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    If 100 volts is safe to use these look like the best available:
     

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  6. P.Bear

    P.Bear New Member

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    Also, any thoughts on the questions in post #3 and #4?
     

     

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  7. kevzep

    kevzep Its all about the Music Subscriber

  8. kevzep

    kevzep Its all about the Music Subscriber

    No, DC offset does not need to be done under load.
    With this pair I would be using DC.
     
  9. kevzep

    kevzep Its all about the Music Subscriber

    Don't worry about the EQ for now, you'll find you probably dont need it.
    Due to the nature of EQ filters, you'll be adding colouration and distortion to the performance of this system.
    Most if not all domestic type EQ's are designed to run in the Tape Loops, this is how their sensitivity is set up, if you put it in line with the pre-amp power-amp you will run out of headroom in the EQ and system will be noisy.
    Most Professional EQ's are designed around +4dbu standard, so in this case you could use one between the Pre-amp/Power-amp, some have a -10dbu option on them too....
    But like I said, don't worry about EQ at this point, I hate graphic EQ's, they are crude, noisy, and rarely improve a system.
    That one with the cheap analyser mic, forget it, it doesn't work that well. To do it properly you need a professional setup with FFT which runs into thousands of dollars....
    In my opinion those SE-9 type things are toys...
     
  10. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Yep, they'll be fine.
    You don't need close tolerance capacitors for this purpose, in a tuner you do, but these are for audio amplifier stability purposes.

    Silver mica 1% or 0.5% capacitors are expensive and unnecessary in this application.
     
  11. kevzep

    kevzep Its all about the Music Subscriber

    Well, carry on then......I will take my unnecessary silver Mica caps somewhere else.....
     

     

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  12. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    I still have Silver Mica capacitors in my AU-919, and I won't be taking them out anytime soon. On the advice and guidance of some of the luminaries of AK, for subsequent restores including a BA-F1, I have realised that for a number of reasons, not the least being price, that ceramic NP0/COG are better.
     
  13. kevzep

    kevzep Its all about the Music Subscriber

    I went that way, because in those Crown Macro-Tech's which occupy a lot of my time, they use 1 and 0.5% Silver mica for that exact application, I figured there was a reason they chose that particular dielectric....
    But, yes they are not the cheapest....
     
  14. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    That's an understandable and good reason to use Silver Mica 1% or 0.5% (10x6mm) with maybe 1pf or 2pF of strays, as compared to Ceramic NP0/COG, 12.5%, (2x2mm) and virtually '0' strays, at about 20% of the price.
     
    Last edited: Jul 7, 2018
  15. kevzep

    kevzep Its all about the Music Subscriber

    I realised after the exercise I could have done it that way!! That damned Hindsight thing again!!
     
  16. P.Bear

    P.Bear New Member

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    Location:
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    Thanks again Kevzep and Hyperion. I gather that after the Black Flag caps are replaced there needs to be some sort of re-calibration of both the CA & Ba-F1? Is that a DIY thing or something to be done at a tech shop?
     

     

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  17. kevzep

    kevzep Its all about the Music Subscriber

    No you can just fit them and you are good to go....
     
  18. P.Bear

    P.Bear New Member

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    Location:
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    Well, that will certainly save a lot of hassle.

    I've had to order a step down transformer from 120 volts to 100 volts [1000 watts] to accommodate these units and was wondering how likely it will be to introduce electrical noise into the system. I have some fairly good AC line noise filters but they are designed for 120 volts and I'm not sure if I can use them between the step down transformer and the CA & Ba-F1 on the 100 volt side.
     
  19. kevzep

    kevzep Its all about the Music Subscriber

    Just try it and see how it is.....
    Might be okay....there's a lot of filtering in the amplifier...
     
  20. Overundr1

    Overundr1 AK Subscriber Subscriber

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    I used npo/cog's in my AU-919 even though my heart said silver mica's due to a mean old billfold that refused to pay for the top shelf parts, no harm no foul and the amp sounds great.
    Either way the comments to get the old black flag caps out of the amp is very very sound advice, as you start to go through things you may find them to be soft gooey falling apart disasters in waiting.
    -Lee
     

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