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Replacing 10,000uf filter caps with 22,000uf?

Discussion in 'DIY' started by z-adamson, Jul 5, 2017.

  1. Bill Ferris

    Bill Ferris Well-Known Member

    Messages:
    504
    Location:
    NE. FL.
    Also FWIW, on any new to me "music reproducing" power amp in for repair or bench check up, whether tube or SS.

    When driving it to clip during check out, I don`t want to see any ripple riding the top of the waveform at full rated power output(clean thin horizontal clip line on the scope), which if the main PS capacitors are in decent/fresh shape then I interpret that the capacity of the capacitor/s are undersized and depending on the type of gear and ownership, and will usually desire to up the PS caps value/rated voltage..
    How much over design, or current values, will be determined by the device, of course, and it`s use.
    Just enough-- isn`t enough for this old guy..

    Some Sponge in PS`s are "usually" only good on both tube rectified, or not, tube guitar amps IMHO & E, but still should have a clean clip line.
    Because good players can skillfully "work" that PS sponge compression as part of "their expressive tone" and make their amp sing.
    Again, just my $.02`s worth.. Take care, Kind regards, OKB
     
  2. Alan0354

    Alan0354 Super Member

    Messages:
    1,469
    Location:
    Bay Area
    Problem is unless you have regulate supply rail, when you clip, you will see the sawtooth. Just how little is good enough. For tube amp, it's easy to do regulated supply to get rid of the ripple( low current) and you can still get sponge effect. Ha ha, I add a series resistor on the SS rectifier to give the sponge effect in my own designed guitar amp!!!

    For SS, it is harder to do regulate supply unless you go for SMPS. I did a simple attempt on a pass transistor regulated supply and the heat quickly got out of hand. I did not try too hard to redesign, instead I just put a lot of caps. Like 200,000uF worth of filter caps to lower the ripple down. I use C-R-C pi filter to lower the ripple even more.
     
  3. Bill Ferris

    Bill Ferris Well-Known Member

    Messages:
    504
    Location:
    NE. FL.
    No sawtooth here observed on scope across B+/- unless I crank up the scope`s gain into the low millivolt setting with properly filtered buss at full power.. Also never needed to consider regulating rail right after rectification as not practical.. Down stream yes for low noise/high gain circuits or preamp applications..
    And no SMPS in any of my audio gear.
    I prefer CLC pi.
    As to 200,000 uF up capping, read my thread 34 concerning the re cap of my Mac MC 2205 around 4 years ago. DSCN0010.JPG
     
  4. Alan0354

    Alan0354 Super Member

    Messages:
    1,469
    Location:
    Bay Area
    There should always a sawtooth on the rail if you don't have regulated supply no matter how much capacitance you have. I have 50,000uF for each rail of each channel, still have a little over 100mVpp of sawtooth. I have separate filter for the low power section of the power amp, 10ohm resistor followed by 10,000uF for each rail of each channel, I can still see about 10 or 20 mV. Just how much you crank up the scope.

    I tested my circuit using resistor to draw 4A from the rail. Your amps are so big, it likely a class A and draw at least 4A. You should see the sawtooth.

    I don't consider regulated, that's why I did not try that hard. For home audio, you really don't expect the amp to clip much. Power for normal listening level is very very low, unless you have a 20W amp, I don't think clipping is really a problem. More like how the circuit recover from the clip is more of an issue. I am surprised I almost never see any schematic of even high end amp has anti sticking designed into it.
     

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