300B/6SN7 Amplifier Recap

Discussion in 'DIY' started by batriq, May 23, 2016.

Tags:
  1. batriq

    batriq Probably has made you smarter

    Friend
    Joined:
    Oct 31, 2015
    Likes Received:
    656
    Dislikes Received:
    0
    Trophy Points:
    93
    This is an amp I've been slowly working on. I changed almost all the capacitors, the volume pots, a couple of resistors, and generally cleaned things up and re-did some solder joints. The main enhancements came from the power supply capacotpr updates. Originally, the first cap was a pair of capacitors connected in series without balancing resistors. Next after the L was a huge Russian 10uF 400V film cap. The problem is that B+ is >400V (!). I switched the first cap to a Vishay 10uF 500V film cap and the big Russian to a TMC 50uF 600V electrolytic cap. (I was amazed to find the Vishay at Mouser for < $4.) Here are 2 before and 2 after pics:

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    The amp used to be irritating to listen to for a long period and lacked resolution. It became detailed and more focused, and much more enjoyable to listen to (sound is rich without being fuzzy like before).

    I also learned that punching holes through steel with a drill is a loooong process even though I all I needed was 4 of them for the capacitor clamps. Water helped keep the bit cool so that it doesn't deteriorate.
     
    Dino, PoochZag, Wilson and 6 others like this.
  2. HitmanFluffy

    HitmanFluffy Hoping to see real genitals someday!

    Executed Anti-SBAF PSYOPS
    Joined:
    Sep 26, 2015
    Likes Received:
    1,563
    Dislikes Received:
    15
    Trophy Points:
    93
    Location:
    Austin, Texas
    Drilling steel with home tools?! Absolute madman. Neat build.
     
    batriq likes this.
  3. bazelio

    bazelio Friend

    Friend
    Joined:
    Nov 16, 2015
    Likes Received:
    3,447
    Dislikes Received:
    160
    Trophy Points:
    113
    How does it sound? Despite proper orientation, it's hard to believe there wouldn't be any hum with that transformer spacing as it is...
     
  4. batriq

    batriq Probably has made you smarter

    Friend
    Joined:
    Oct 31, 2015
    Likes Received:
    656
    Dislikes Received:
    0
    Trophy Points:
    93
    There is a slight hum when you're close to the speakers and no music is playing. At >3ft, it's inaudible.
     

Share This Page