6L6 to el-34 conversion?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by JDW3, Apr 19, 2005.


  1. JDW3

    JDW3 Member

    Messages:
    3,624
    Joined:
    Mar 2, 2005
    Location:
    Below Flint
    A buddy has a 6l6 amp he needs converted to el-34s. I have read about this mod many times, but never done it, although I have done work on amps. Is there a page to directly reference this mod?

    I posted this previously in the amps and cabs column.
     
  2. JDW3

    JDW3 Member

    Messages:
    3,624
    Joined:
    Mar 2, 2005
    Location:
    Below Flint
    Well, Im sure SOMEONE knows what Im talking about. Just a page reference?
     
  3. Igneous

    Igneous Supporting Member

    Messages:
    1,878
    Joined:
    Aug 24, 2004
    Location:
    Mass.
    try just swapping them out and adjusting the bias maybe?
    What kind of amp?
     
  4. wilder

    wilder Supporting Member

    Messages:
    769
    Joined:
    Feb 20, 2004
    Location:
    Denton, TX
    You need to mention what amp you want to do the mod on for me to have any specific info. The issues usually involve having sufficient filament heater current and making sure that pin 1 and pin 8 of the power tube socket are connected and don't have any other components mounted on them. The value of the grid resistors will likely need to be changed.

    Chris
     
  5. JDW3

    JDW3 Member

    Messages:
    3,624
    Joined:
    Mar 2, 2005
    Location:
    Below Flint
    The amp is a Sovtek Mig-50. Model 001. The resistors have no color codes, so this amp is a bit confusing. How do you test to see if the PT is capable of powering the el-34 tubes?
     
  6. mungo

    mungo Member

    Messages:
    43
    Joined:
    Oct 1, 2004
    Location:
    NW Chicago burbs
    FWIW I'd be carefull because if memory serves me correct I had an early Mig 50 that had 500+ volts on the plates (pushing close to 540). I think you'd eat up EL34's pretty quick.

    dug
     
  7. JDW3

    JDW3 Member

    Messages:
    3,624
    Joined:
    Mar 2, 2005
    Location:
    Below Flint
    Well anyway, it's done. The amp sounds much better than with the 6L6s. He even wanted a master vol installed. Post PI, which came out as expected. Everything was easier than I thought.

    I would never buy a Sovtek...
     
  8. WailinGuy

    WailinGuy Supporting Member

    Messages:
    1,268
    Joined:
    Aug 30, 2003
    Location:
    Silver Spring
    EL34's have no problem with high plate voltages. In fact they are spec'd to handle up to 800 volts on the plate. The importaint thing is to not exceed their 25 watts max. plate dissipation rating.
     
  9. glasman

    glasman Guest

    You are going to definately want to up the screen resistors. The MIG50 uses 470 stock. I would say to up this to a 1K to 1K5 5watt resistor. The 34 does pull more screen current.

    Be sure to follow Jim's comment about the plate dissipation.


    Gary


    PS> Jim I like the "Soldering Iron Jockey" byline. Yes, there is nothin' better than the smell of multi-core in the morning!! :)
     
  10. Blue Strat

    Blue Strat Member

    Messages:
    29,924
    Joined:
    Aug 2, 2002
    Location:
    Sterling, VA (not far from Washington DC)
    How about checking the values of the resistors with an ohm meter?

    Compare power specs for 6L6s and EL34s. Therein lies the answer to the transformer question.
     
  11. calieng

    calieng Member

    Messages:
    646
    Joined:
    Nov 21, 2003
    Location:
    San Diego, CA
    This link may be helpful:

    http://www.hoffmanamps.com/images/Ab763.gif

    The power tube sockets are wired for EL34 or 6L6s

    Check around the rest of Doug's site and also his forum for extra help.
     
  12. RJones

    RJones Guest

    I would monitor the power transformer. if it gets sizzlin' hot, stop and put the 6L6s back in.
     
  13. Reeek

    Reeek Member

    Messages:
    1,208
    Joined:
    Feb 1, 2005
    Location:
    Reno, NV
    And don't forget that EL34's REQUIRE pin one be tied to ground or they'll burn up in a flash. Make sure that pin one on the 6L6 amp is tied to a ground point somewhere. Most amp mfg's these days tie pin 1 to pin 8 (ground) on 6L6 amps so that there is never an issue other than trannies, etc. with EL34's since 6L6's don't use pin 1 at all.
     

Share This Page