Success with adding filament virtual center tap to reduce hum..

Discussion in 'Amp Tech Center' started by JackL, May 23, 2020.

  1. JackL

    JackL Tele-Meister Silver Supporter

    Posts:
    205
    Joined:
    Oct 17, 2004
    Location:
    Monroeville, PA
    Worked on my Lafayette PA622 conversion to guitar Amp today again.

    Installed the Filament Virtual Center Tap(2 - 100 ohm resistors to ground of the heater wires).

    It totally eliminated the hum I was getting when Amp was powered on.

    I still have more work to do but it's progressing to be more of a playable guitar amp.

    18watts and it has a good volume.

    The tone control doesn't have a very good range yet. I did reverse the Cap to the other side of the

    pot and that corrected the bass to treble when turning the tone control clockwise.

    I drew a schematic of where I'm at with the conversion.

    Jack
    20200523_062326.jpg
     
    Jlwctn likes this.
  2. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    7,784
    Joined:
    Dec 29, 2012
    Location:
    United States
    Did the amp have no 6.3v center tap and no artificial center tap?
     
  3. JackL

    JackL Tele-Meister Silver Supporter

    Posts:
    205
    Joined:
    Oct 17, 2004
    Location:
    Monroeville, PA
    No Center tap for the 6.3 v lines. They had it grounded on the 12ax7 on pin4. I took out the ground and added the 100 ohm resistors. What a difference, super quiet!
     
  4. JackL

    JackL Tele-Meister Silver Supporter

    Posts:
    205
    Joined:
    Oct 17, 2004
    Location:
    Monroeville, PA
    New drawing of changes I want to implement into the Amp. I'm going to try changing the Tone stack. What do you think of the new drawing?
    Jack
    524Lafayette.jpg
     
    robrob likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.