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Can bias be that low?

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  • Can bias be that low?

    Hi guys,

    I just bought a Tweed Pro kind of amp. It sounds great but stays extremly clean and the distortion is a little bit more "ratty" than I would like. I listened to that amp in a store and the breakup was more pleasent and way earlier.
    So I tought I might just measure the bias cause I know this kind of sound from my Deluxe Reverb. Plate Voltage is 450V. But the bias I measured is just 8ma with 6L6. This seems really strange to me. I measured like I do every time with the resistor method. When turning up the bias pot I got a maximum of about 18mA. The amp has fixed bias.

    Regards Jens
    Last edited by shocki; 02-20-2013, 05:56 PM.

  • #2
    About 8 watts of dissipation, there is a problem.What voltage can give the bias pot (measure on the grid pin) ?

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    • #3
      The strange thing is the amp sounds really really loud and not really broken.

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      • #4
        I removed the tube an measreud the grid pin. -42V.

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        • #5
          Sorry guys. Not my day today. I measured mA not mV. It shows 32mV I turned the bias pot to 40mV which should give me 40mA. So everything is OK.

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