Bias Test Point installation

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Scott_F, Dec 9, 2005.


  1. Scott_F

    Scott_F Member

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    Quick question, which pin do you connect the 1 ohm resistor to? Thanks.
     
  2. VaughnC

    VaughnC Supporting Member

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    Replace the connection between the cathode and ground with the resistor. With 6L6's or EL34's that would be pin #8. Also, it would be best to install a seperate resistor for each output tube so you can see what each tube is doing individually.
     
  3. Scott_F

    Scott_F Member

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    Done and it works well. Much more convenient than using a Bias Rite. Thanks.
     
  4. deeval

    deeval Supporting Member

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    I just want to Ask,
    Why would you ask a Question like this? if you Build amps for a Living, This is not ment to put you down.I am just kinda wandering how you can build amps and not know this.
    Thanks
    Your amps look nice also:D
     
  5. Scott_F

    Scott_F Member

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    Fair enough question. First of all, I have a great day job which accounts for my delivery times. And, I'm pretty much just getting started in this endeavor, although I've been putting together amps for a while now.

    I build tried and true circuits with a few tweaks here and there. I'm not reinventing any wheels here. I do not claim to possess the expertise of guys like Roccaforte and Aiken. But, I learn from those guys and everyone else on the net that provides such great technical resources. It's a constant learning mission for me and I had a guy ask me for the test point thing, so I figured I'd ask, especially if someone might have a better way of doing it.

    My attention to detail and build quality is incredible, my parts are first rate. My amps are quiet and dependable. The guys that have bought from me are 100% happy. And, I have a waiting list that is getting longer. Time will tell how it goes. But, it is a fair question that I do not shy away from.

    At this point in my amp bulding life, I'm the "six sigma black belt" production guy on the line putting together the BMW. I'm not the engineer that designed the fuel injection system. But, as to anything in life, I"m getting better and better at what I do.

    Thanks for checking out my website. I've got these amps priced to get some attention and judging by my waiting list, it's working. I only accept 2 projects (deposits) at one time. I don't want to get overextended like what happened to another amp guy here in TX.
     
  6. rockstah

    rockstah Member

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    with an el34 amp pin1 and pin 8 are tied together and the 1 ohm resistor can run form either pin1 or pin 8 to ground
     
  7. rockstah

    rockstah Member

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    further more with resistor in place like this your meter set to 1 or 2 not (200mA) for acurate readings black to chassis red to pin side of that resistor mv = ma so if it reads 42mv = 42mA
    remember el34 safe side is 70% max plate disipation with ( max plate is 25 watts ) so .7x 25 = 17.5 / b+( say 400dcv) = 0.04375amps = 43mA
    from there some use their ears and find the sweet spot for their playing remeber going higher ie 45mA is bring the tube closer to cut off and going lower ie 35mA is giving the tube higher plate voltage which in essense is bring the tube closer to its dieing day - have fun
     
  8. Scott_F

    Scott_F Member

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    Thanks. Yeah, I know how to accurately set a bias, just didn't know which pin to hook up the resistor. Over on the Weber forum, there is a lot of information on biasing, including a little calculator for those that are mathematically challenged. Thanks for all the info.
     
  9. Roccaforte Amps

    Roccaforte Amps Member

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    Don't sweat it, doesn't matter who we are in this industry,
    we're always learning something new, and none of us know it all.
     
  10. Scott_F

    Scott_F Member

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    Damn doug, I totally butchered your name, bro. Sorry about that.
     
  11. Scott_F

    Scott_F Member

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  12. deeval

    deeval Supporting Member

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    Very Cool Scott that you didnt take as a Negitive,Hey Man I am still learning every:RoCkIn day also.So just keep a good Thing going,
     
  13. Scott_F

    Scott_F Member

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    Well, after you pointed that out, I got a bit of a chuckle at the irony. It kinda falls under the old "the only stupid question is the one not asked" kind of thing.
     

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