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8950 tubes.

Discussion in 'Amplifiers' started by datsun66, Feb 22, 2008.

  1. datsun66

    datsun66 Active Member

    Apr 10, 2005
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    I am looking into replacing the tubes in a amp that is running the 8950. 1x3.
    What tube would be a drop in or something else. Maybe replacing the 4 with 2?
    Just something to kick around. Bob.

  2. AudioShockwav

    AudioShockwav Extraterrestrial Admin Staff Member

    Apr 6, 2005
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    About the only drop in I know of is a M-2057, and it is just as hard to find as the 8950 is.
    The 8950 is a 12 volt version of a 6LF6, the heater runs on 12 volts on the 8950/m-2057 and the heater on the 6lf6 is 6 volt.
    I know the Swan 1200X Amps used the 8950`s ( 4 of them) and many were converted to run 6lf6`s, 6kd6`s and so on.
    So If you can dig up a 6 volt filament transformer, change a few things and re-wire the socket for 6 volt you can get away with a 6lf6,6kd6 or a 6lb6. Another way to go for the 3 tubes is if you can find 3, 40lf6 tubes, you could run the filaments in series, and heat them from a 120 volt line (40+40+40 =120), but you are still stuck with a 8950 driving them.

    Sweep tubes are getting harder and harder to find, and the price just goes up...I remember when you could buy 8950`s from Thrifty Drug stores for around $18 each, they had a box of them in the big tube tester by the front door...If I knew then...... I would have bought a truck load of them.
    I now see 8950`s go for $70 to $80 NOS :glare:
    At times you can find them on E-Bay used in the 25 to 35 dollar range, but that is a toss of the dice.
    There are 5 on E-Bay right now, starting bid is $100

    Or here is a Guy that says he has lots of new ones, $75 Bucks


    I got rid of my last sweep tube amp long ago, and got a Al-811H, tubes are cheap, and easy to find.

    Good Luck.

  3. datsun66

    datsun66 Active Member

    Apr 10, 2005
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    I wonder if the amp will support a ceramic type of tube.? Take out 4 and install 1.
    Just a thought.

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