Biasing an Allen Accomplice (Request for directions)

Discussion in 'Amps and Cabs' started by DJLantz444, Jul 17, 2006.


  1. DJLantz444

    DJLantz444 Senior Member

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    Anyone have the directions that came with their Allen Accomplice (specifically the biasing part)? I have an amp coming in tomorrow that's biased for 6l6 tubes instead of the 6v6s that are coming with it, and I have no idea how to bias the amp. I have a digital multimeter from radioshack, and that's it. I know nothing. So if someone could scan their directions (or that part of the directions) over to me that'd be great. Thanks.

    Edit: Or if someone could explain it here very detailed for someone completely new to biasing that knows absolutely nothing.
     
  2. RichSZ

    RichSZ Member

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    It will be easy. The Accomplice has external bias jacks and an external bias pot.

    Put your tubes in & fire the amp up.

    Stick the red end of the multimeter in one bias jack. Put the black end to ground (I usually use a chassis screw or hole when you remove the back panel).

    Adjust the bias pot to 35ma (or whatever is recommended).

    Repeat process for other bias jack. If you are using a matched set of tubes your bias should be right on for both tubes.

    -Rich
     
  3. bbarnard

    bbarnard Member

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    If you are going from 6L6s to 6V6s I'd also recommend checking to see which rectifier is in it. You may need to change that out too. I believe that is what David Allen recommends.
     
  4. vivalamigra

    vivalamigra Member

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    I believe you will be setting your multimeter to read millivolts. Yes, you should probably adjust the bias pot until you get readings around 35 mv for each tube for 6L6's in that amp. That 35 mv reading corresponds to an approximate 35 milliamp bias.

    I'm pretty sure I'm correct here but some other Allen owners might chime in. David Allen will answer your e-mails pretty quickly if you want to go directly to the source.
     
  5. DJLantz444

    DJLantz444 Senior Member

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    I emailed him and all he told me was that I needed a multimeter, which I assumed, but didn't actually know yesterday (Yes, I am TOTALLY new to this). He said that the seller should supply me with the directions, but I'm not sure he will. I'll be the third owner of the amp, and I've already sent an email with no reply. I might have the directions, but the chances aren't that great. I posted this topic so that I'd be ready to bias it quick when it comes so I can play it.
     
  6. DJLantz444

    DJLantz444 Senior Member

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    What rectifier should be in it?
     
  7. Robertito

    Robertito Member

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  8. DJLantz444

    DJLantz444 Senior Member

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    Thankyou Robert, you're always there with the answers. :AOK

    That's the rectifier that should be in it with 6v6s right?
     
  9. stevieboy

    stevieboy Clouds yell at me Gold Supporting Member

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    It's dead easy, even an idiot can do it. In fact, I've done it several times!

    I have an Accomplice and I don't recall seeing anything from Allen saying you should change rectifiers when you change power tube types.

    It's a great amp, enjoy it!
     
  10. DJLantz444

    DJLantz444 Senior Member

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    Does the accomplice have an external bias jack for the black (ground)? If not, how can I be sure it's grounded? I don't really know much about this.
     
  11. mkg

    mkg Member

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    On my Hot Fudge w/Nuts there's a hex nut with a ground symbol just below and between the bias jacks.
    Touch one probe to the hex nut and use the other to check each bias jack.
    Also on my amp the bias adjust pot is located just behind and to the right of the big black power transformer. It's a shaft so you can turn it by hand, don't need a screwdriver.
    I agree that you should probably email David to find out the details for your particular amp.
     
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  12. DJLantz444

    DJLantz444 Senior Member

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    My multimeter has a milliamp range.. so I use that?
     
  13. mkg

    mkg Member

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    Nope, you want millivolts. The Radio Shack multimeter I've got automatically recallibrates to millivolts once you select V (volts).
    Remember to email David to verify that's the case for your amp.
     
  14. DJLantz444

    DJLantz444 Senior Member

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    Oh, It has volts too of course. So it automatically changes. Thanks.
     
  15. GenoBluzGtr

    GenoBluzGtr Supporting Member

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    READ THE POSTS CAREFULLY!!

    Several folks have kindly (and with good intention) given you voltages to set your new tubes bias voltage to.... BUT THEY SEEM TO HAVE MISREAD your original post... the voltages they have listed are for the 6L6s and NOT the 6V6s that you will have when the amp arrives. Those voltages are MUCH too hot for the 6V6. 35 is a 6L6 bias setting.

    Better info is to adjust the bias to between 22 and 28 volts for 6V6s.

    Refer to the link at: http://www.ampwares.com/bias.html
     
  16. vivalamigra

    vivalamigra Member

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    Genobluzgtr is correct. You want to bias that amp around 25 ma for 6V6's, 35 ma for 6L6's. To do this, you will set your multimeter to DC Millivolts and hook it up to the back of the amp as I have done in this picture (this is an Allen V-18 pictured...). The negative lead has an alligator clip and the positive lead is a probe.

    Locate the bias pot on the bottom of the chassis. It should just be a shaft with no knob on it. You will probably need to take off the panel on your cabinet that partially covers and protects the tubes. This will give you better access to swap the tubes and to find the bias pot. Swap in your new power tubes. Turn all of the amps controls (volume, tone, raw, etc. ) to zero. Fire up the amp on standby and let it warm up for a minute or more. Hook up the multimeter as pictured.

    [​IMG]

    Turn your standby switch to play. The millivolt reading will rise quickly. If it rises above the 25 mv reading you're looking for, turn the bias pot clockwise until it comes down. Now swap the positive probe to the other bias jack and see how close it is. Depending on how close the tubes are matched, you might need to play with it. If I have tubes that are a little mis-matched, I'll go for 25 mv on one tube and 23 on the other, or something like that.

    The Accomplice uses a GZ34 (5AR4) rectifier for either 6L6's or 6V6's. If you were to put 6V6's in an Allen Old Flame you would have to use a 5U4G rectifier, but that is not the case with the Accomplice.

    I'm pretty sure this all correct. If I'm wrong about the clockwise/counterclockwise thing on the bias pot, you'll find out pretty quick....just turn it the other way. If the amp is biased for 6L6's right now, the reading will most likely be way off when you install the 6V6's so be ready to bring it down right away by turning the bias pot clockwise.

    When I'm doing a tube swap, I usually turn the bias pot all the way clockwise before I fire everything up and then I slowly bring up the bias into the correct range.

    I hope this helps. If any other Allen owners notice any glaring errors here, please chime in.
     
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  17. riffmeister

    riffmeister Gold Supporting Member

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    vivalamigra, your instructions are great. lower bias current for 6V6's (around 25 mV reading on the DVM), higher current for 6L6's (around 35 mV reading on the DVM).

    My Accomplice came with 6V6's and the first thing I did was swap them out for 6L6's and rebias. No changing of the rectifier required.

    One final thing.......make sure a speaker is plugged into the amp when doing the rebias.
     
  18. DJLantz444

    DJLantz444 Senior Member

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  19. DJLantz444

    DJLantz444 Senior Member

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    By the way, thankyou to everyone for trying to help someone new to this (and electronic stuff in general). I'm glad you were all patient. Thanks to vivalamigra for the directions that cleared everything I pictured in my mind up.

    I just wanted to make sure I learned all of this the day before I got my amp, so I wouldn't get the new amp and not be able to play it!
     
  20. GenoBluzGtr

    GenoBluzGtr Supporting Member

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    much better to ask how to adjust it properly now than have to ask later how to fix it.

    That's why the gear page is here.... Do me a favor and let me know if you like the Accomplice... I am really gassing for one myself.
     

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