what's the high and low DC ampres (bias adjustment) for EH 6V6 tubes

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Denny, Jun 17, 2006.

  1. Denny

    Denny Member

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    I've installed some new Electro Harmonics 6V6 tubes in my DRRI (a pair) and set the bias to 25.0 ma. It sounds great but I've read elsewhere that I can still go even higher to get more breakup and sooner. I definatel want to keep the voltage within safe operating levels. I've contacted EH with no response (figures). Is there a link that has some kind of a chart that shows the low and high limits of different power tubes by different manufacturers?

    Thanks

    Denny
     
  2. slider313

    slider313 Silver Supporting Member

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    I just installed a set of EH 6V6's in a reissue deluxe reverb at 25ma and 410 plate volts. If your plate voltage is in the same range you could go higher with the milliamps which would in fact lower the plate voltage.
     
  3. Denny

    Denny Member

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    Well.........I've been told by a reputable source that these EH power tubes are known as "firecrackers" to amp techs around the country, and that he wouldn't trust them at 20mA. That's what is making me a little worried. Seems I can't get the same answer twice. Why do different tubes take different bias? Isn't there a chart somewhere that someone can get that says - JJ - Tubes - set to this , EH tubes - set to this, RCA tubes - set to this? Why all the mystery and suspense? LOL! I'm just getting a bit overwhelmed about NOS, thick plates, black glass, military specs, plate voltages, bias adjustments. I don't know who to listen to as far as what is considered "best practice" in the amp industry. Some say this, others disagree and say this. I just want to be able to change the tubes in my amp and set the bias so it sounds best and doesn't explode! This stuff is not rocket science but it seems like everyon's making it out to be. "Back in the day" - we just put new tubes in the amps and that was that! We never seemed to have any major problems - maybe that's because the tubes "back then" were made well (Oh - maybe that's why there's so much talk about NOS tubes)! Pop 'em in, plug it in and play. Beam me up Scotty.......!!! LOL!

    D.
     
  4. Texasamp

    Texasamp Member

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    For one thing, you do not want to get them to where the are redplating. The final judge of a good bias range is done by your ears. If you like it, leave it alone. If you want more saturation up the mV a few. This will also lower your plate voltages. Amps that are biased to cold sound brittle. Hotter biasing will have shorter tube life. 6V6 are all rated at a certain wattage (I forgot what it is for the 6V6). The 6L6GC is rated at 30 watts. We try to get our amps to idle without buring the tubes up. As I said in a previous post, 70% plate dissipation of what your tubes are rated at is a rule of thumb. It is all in what your ear likes.

    Regards,
    Darrell S.
    Texas Amplification
     
  5. Denny

    Denny Member

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    Thank you . That was written so boobs like me can even understand. So if I'm hearing you right, as long as the tube is not glowing that hot red that looks like it's gonna explode, wwe should be ok? I do know that there needs to be some red. Thanks again for unraveling the mystery
     
  6. Texasamp

    Texasamp Member

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    There needs to be no red on the plates. The only red you should see is the heater filament. If you see redplates, back the bias down. Meaning less negative voltage applied to the grids. Good luck.

    Darrell-
     

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