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Are these tubes too unmatched to use?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by pfrischmann, Feb 4, 2008.

  1. pfrischmann

    pfrischmann Member

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    Hi Guys,
    I got some sylvania STR's from a buddy but all three tubes seem to be pretty far from each other. They seem to be about 10ma away from each other (30ma, 40ma and 50ma) I had always used a rule of 5ma when matching.


    What do you think,
    Are they too far away from each other?

    I gotta tell you, this is one hell of a tube in a super. It's like I added a more knob.

    thanks,
    Paul
     
  2. jbltwin1

    jbltwin1 Member

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    That's not THAT bad. Yeah, it's off but if you bias the HOTTEST one in the normal zone, the other won't be extremely cold. If you wanted, you could split the bias supply and bias them individually. Lot of work for free tubes but then you could use all three. Personally, a little mismatch sounds a little good to me. Back in the day, we never worried about ANYTHING matching. Hell, we didn't even check. Plug it in, fire it up, if it didn't chernobyl, we warmed it up, checked the bias supply volrage and sent it out. Of course, that was a millenium ago and we HAD better tubes.
     
  3. slider313

    slider313 Silver Supporting Member

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    Personally, I like a 5ma or less difference, but up to 10ma isn't that bad. I would pop them in, bias them and give them a listen.
     
  4. HipKitty

    HipKitty Silver Supporting Member

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    Paul, glad to hear of your score!

    Within 5ma (max) to be considered matched....personally, I don't go with anything over 1ma (to many, this is considered picky), however, there is a school of thought about the virtues of mis-matched tubes.

    I'd advise you to bias to the tube with higher voltage if you have any that don't match exactly.
     
  5. pfrischmann

    pfrischmann Member

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    Thanks guys. That's what I did but I didn't know what the long term effects could be. These STR 387's are just amazing! They ate my RCA Black plates alive. Simply amazing punch...
     

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