Bias on a 93 Blues DeVille

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by bluesbirdaaa, Aug 22, 2008.

  1. bluesbirdaaa

    bluesbirdaaa Member

    Aug 22, 2008
    Atlanta, Ga
    I have a 1993 Fender Blues Deville. Through much research I have decided to choose JJ-electronics. I understand that my amp has a fixed bias and is not adjustable. It has 3 12Ax7a vacuum tubes and 2 6l6WGC 5881 power tubes. My question is, without having to bias, what perameters do I have to stay in as far as brand, voltage, etc......... does anyone happen to know the plate volatage on these? I want tubes with a breakup/headroom as I am going to be running a couple of pedals. Any help would be much appreciated.
  2. colecutter

    colecutter Member

    Feb 12, 2009
    I have the exact same issue and question so anybody who can enlighten us on tthis?
  3. glaswerks

    glaswerks Gold Supporting Member

    Jul 3, 2006
    Afton, MN (St Croix River Valley)
    Per the fender schematic the plate voltage is around 470 volts.

    As tubes (even within the same brand) very greatly on the required bias voltage to obtain the proper bias current. I would suggest have a local tech (or if you have the skiils) modify the bias circuit to be similar to the one in the Hot Rod Deluxe. The only change I would make in that circuit is to drop the 10K to around 4.7K as most of the HRD's I have worked on did not have enough bias range.

    My 2 cents.
  4. tlpruitt

    tlpruitt Member

    Mar 13, 2006
    Just west of Baltimore, MD
    Install a bias pot like the Hot Rod Deville and Hot Rod Deluxe have but use a smaller resistor to get more range. That is what I did.
  5. steve f

    steve f Member

    Jan 12, 2009
    If you want JJs, I'd contact Bob at Eurotubes, he'll be familiar with what you need. I've asked him for tubes for Mesas and Peaveys which do not have bias controls, and he's sent tubes that had the proper current draw so they'd work in those particular amps. It's something that he handles on a regular basis.

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