What must "match" on output tubes?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Roodboy, Dec 13, 2004.


  1. Roodboy

    Roodboy Supporting Member

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    I'm sorry if this is a silly question, but I'm hunting EBAY, for some NOS (most likely Mullard/Philips or GE), EL84's for a Marshall DSL201 and I'm confused.
    Sellers list all kind of readings and I'm not sure which one needs to match. Is it milliamps, plate voltage or triodes or something else.
    I really appreciate the help.
    Thanks
     
  2. SeanF

    SeanF Member

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    milliamps. The seller usually measures the current at a given plate voltage + bias voltage, and writes the current in milliamps on the tube box.

    Don't get too hung up on matching power tubes, though; mismatches sound really good sometimes.
     
  3. drbob1

    drbob1 Silver Supporting Member

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    The advantage to matched tubes is that they've been tested for current draw and you know it's possible to bias them to work in an amp. They express the match in a number of different ways (mhos of transconductance, mA for a given bias and plate voltage) but it's just the fact of the bad ones being weeded out thats most useful.
     
  4. Roodboy

    Roodboy Supporting Member

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    Thanks for the help.
     
  5. Roodboy

    Roodboy Supporting Member

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    How close do the numbers have to match for it to be acceptable? I have seen that within 3 millamps is OK.
    Is this correct?
    Thanks
     
  6. Roodboy

    Roodboy Supporting Member

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    The GE EL84's I just got were 23.7 and 22.0 so I'm thinking thats OK.
    Thanks again for the help.
     

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