Biasing a Peavey C30??

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by nemp, Jun 10, 2003.


  1. nemp

    nemp Member

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    Do Peavey Classic 30s need biasing? How hard is this?
     
  2. John Phillips

    John Phillips Member

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    No. They're cathode (self) biased.

    (well strictly, yes you could change the bias if you wanted to, but that would entail replacing the cathode resistor, and there is probably no point anyway - they seem to work reliably with most types of EL84s)
     
  3. Troy Baer

    Troy Baer Member

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  4. John Phillips

    John Phillips Member

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    OOPS! :eek: Yes, Troy is absolutely right. It's fixed bias.

    I have worked on these amps too (admittedly as rarely as I can, they're a complete pain to get into), and I really was sure they were cathode-biased...

    You could adjust it, although you'd have to change a fixed resistor (R63 or R64, which are the voltage-divider network for it).

    I never have though - I've replaced tubes on these many times too. But that just proves what Randall Smith says, and I agree with - a well-designed amp (which I think the Peavey is, circuit-wise, even though I'm not impressed by the build quality) does not need adjustable bias. Looking at the circuit the bias appears to be -14V, which is quite a conservative (cool) setting at a plate voltage of 332V. I have certainly never had trouble with any type of tubes from the cheapest junk to NOS Mullards.
     
  5. JamesPeters

    JamesPeters Member

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    As long as you don't mind crossover distortion, I agree with you. And FWIW, I'm not even being sarcastic...a lot of people don't realize how much of their amp's distortion is crossover distortion until they get it modded for a bias pot and have it adjusted.

    When it comes to the Classic 30--I haven't heard one yet that hasn't sounded good enough to me the way it was.
     
  6. nemp

    nemp Member

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    So that means I have to bias it? When and how do I do this? What if I don't do it will I have problems?
     
  7. nemp

    nemp Member

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    Thanks John, and Troy. Glad to hear that as I don't know what the hell I'm doing when it comes to amp mantainence.
     
  8. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    Maybe most Peavey products but a lot of folks (myself included) have a soft spot in their hearts for teh Classic series.
     
  9. nemp

    nemp Member

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    Well its either Peavey C or a Crate TV 60. Help me decide
     

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