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AK-22: New (re)build

Discussion in 'Shock Brother's DIY Amps' started by shortcircuit, Apr 14, 2018.

  1. shortcircuit

    shortcircuit TDPRI Member

    82
    Sep 9, 2017
    North Carolina
    It's a dumb name, but the thing has 2 6AK5's and 2 6AK6's so it adds up to 22. Don't judge me. Anyway, this started life as the first amp that I'd built. It was a 2 tube affair: http://www.frontiernet.net/~jff/pipsqueak_pentode/Pentode_DIY_guitar_amp.html

    Like the original author, I had built it into a dead computer PSU shell. Because of the size constraints, the transformer placement was not optimal and it had a lot of hum, but it was a fun little amp.

    PP.jpg

    Obviously, I can't leave well enough alone, and came up with this, reusing the PT and OT.

    AK-22.jpg

    I want to try my hand on a point-to-point build. Does it count if I used terminal strips? Here's the overview of the internals:

    01 Overview.jpg

    I screwed up on drilling the bolt holes for the tube sockets.

    Close up of the amp part:

    02 Main Amp.jpg

    Power supply section:

    05 Power Supply.jpg

    Outside:

    07 Outer Overall.jpg

    There's 2 Soviet 6J1P-EV's pictured, but I eventually settled on 2 Tung-Sol 6AJ5's--much more mellow.

    The 6AK6's are running at 2W plate dissipation each (75% of max). The measured power output for the amp is 1.45W at 1KHz.

    The tubes are pretty microphonic when tapped, but at this low output, I don't notice it when playing.

    The sound is clean at lower volume, but when cranked up, it goes into a nice fat overdrive. At 1.45W, it's loud enough for the missus to come by to shut the door.
     
    kleydejong and sds1 like this.

  2. shortcircuit

    shortcircuit TDPRI Member

    82
    Sep 9, 2017
    North Carolina
    The amp always had a hum that I had attributed to the poor placement of the transformers. With the rebuild, the hum was less, but still significant. The original Pipsqueak Pentode amp had the screen from the power tube hooked up to the same power node as the plate, which was unfiltered. I realized that the hum was from the screen and switched the screen to the second node. The actual drop in voltage was only a couple of volts, so it made no difference in the tube operation, but the hum was gone. Live and learn.



    AK-22.jpg
     

  3. nasdak

    nasdak Tele-Meister

    177
    Mar 22, 2013
    france
    Great build !
    I built a 6j1 pedal (documented somewhere on this forum),2 wired as triodes, i don't get much OD but a huge boost...
     

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