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What is done when an amp is "BALCKFACED"?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Denny, Jun 14, 2006.

  1. Denny

    Denny Member

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    Can someone please explain what is done to a Fender amp when they say it's been blackfaced (other than the obvious cosmetics)? Are the transformers changed? Caps? Resistors? Pots? what are the best brands of materials to use for this procedure? Is there a "standard" that is performed in every mod to call it "blackfaced" or is it just whatever someone feels needs to be done? Thanks

    Denny
     
  2. tmac

    tmac Goldmember Gold Supporting Member

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    Basically the circuit is configured to the earlier "blackface" circuit and layout (see layouts and schematics at http://www.ampwares.com/ffg/).

    Transformers are not changed (unless there's an issue with one), same with pots.

    Best brands? Take a look at Doug Hoffman's site http://www.hoffmanamps.com/
    Lots of info there. His prices are reasonable for parts. Some things you can get a bit cheaper at say Mouser but I like Doug and he has great service and parts specially for tube amps & is pretty much a one stop shop.
     
  3. Mullet Kingdom

    Mullet Kingdom Senior Member

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    It depends largely on the amp.

    Standard operating procedure is changing out the ceramic caps in the preamp section and (if it applies) converting the bias from "fixed" to "adjustable". Sometimes the driver section is also revamped. Transformers are usually only changed out if A) the customer requests it or B) one of the stock transformers isn't working properly because of damage or wear. Again, it all depends on the amp.

    Anyway, if you've got an old silverface you're thinking about modding to pre-CBS specks -- do it. You'll be glad you did -- and wishing you'd done it sooner once you get it back.
     
  4. Blue Strat

    Blue Strat Member

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    It varies from amp to amp. Which amp did you have in mind?

    This almost always involves resistors and sometimes coupling caps, rarely transformers (though upgraded transformers can often make a huge difference).
     
  5. Denny

    Denny Member

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    thanks - you guys have answered my question.

    D.
     
  6. Swarty

    Swarty Member

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    It is typically a half dozen or so resistors in the PI circuit, a rewiring of the bias pot and stripping any caps or power resistors that are hanging off the power tubes.
     
  7. willhutch

    willhutch Supporting Member

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    I'm am about to acquire an early 70's SFPR. I'm planning on doing the stokes mod to get a little more headroom out of the amp. I may also try a 12" speaker to get a bigger sound (and just for the fun of experimenting).

    Who here recommends blackfacing one of these? I have no experience with this process. My understanding is that Blackfacing reduces headroom but sweetens the breakup. Reduced headroom seems undesireable, but sweetened breakup would be good.

    I also hear that the Princeton underwent minimal changes from the BF circuit. So maybe a BF conversion isn't necessary?

    Any input from you knowledgeable cats?
     

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