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Dukane PA head into Magnatone 401

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  • Dukane PA head into Magnatone 401

    I thought I would share some pics of my latest project at my home for mistreated amps.
    I had, on my workshop shelves, several messed with amps I got cheaply because they didn't work. I am just learning this stuff, coming from a background that never included electronics.
    I had a Dukane PA head that I almost have working. I was getting help in another thread with this and am nearing completion. It was recently recapped (sort of) and the wiring for the volume and tone controls were completely missing. I have it working now, but it is very very weak so I will be pursuing that in 2012.
    It was in its original very unattractive cabinet.
    I also had a Magnatone 401 which buzzed very nastily. I had tried several ways to correct this with no success. Since it is a power transformerless model, I decided to cut my losses and combine the two.
    After doing some rudimentary work on the sheet metal of both chassis, I got them together fairly neatly and attempted to rewire the volume control. With a 6K11 as the preamp tube and two no longer used inputs, mic and phono, (wiring for these missing also), this is more complex than anything I am familiar with.
    I took the old 6" speaker out and enlarged the baffle hole to take an 8". Not earth shaking but I trust it will sound better. I also had to drill an enlarged hole for the pilot light.
    The old speaker, which was in great shape, is an Alnico Jensen 4 ohm job. I put it in a new Champion 600 and it sounds real good.
    I have here a pic of the old dukane cab. You can see where the EL84s have scorched the metal.
    Also there is a pic of the maggie with her new chassis and speaker. I have to wrap up the unused OT outputs yet.
    If anyone can give me some pointers on wiring the volume control to get more out of this it would be appreciated. I now have one more almost working amp instead of two anchors.
    Attached Files

  • #2
    The amplifier mad scientist strikes again. Surely any person who is brave enough to build this Frankenstein is capable of attaching a volume control.
    Look at any schematic of a tube amp. You must see that the volume circuits are all the same?
    Then why don't you DRAW a schematic and post it?


    • #3
      I have looked at quite a few schematics but none seem to use a 6K11 preamp tube. That is the part that is confusing me.
      I may just have to ignore the third section, which is wired for something that was there previously and treat it like a 12AX7. If you could see the cramped little chassis, you could understand the difficulty in drawing a schematic or a wiring diagram.


      • #4
        You need to start with a schematic. But don't build the 401 stock; its too dangerous. Get a PT with a 190-0-190VAC HT winding and 2 x 6.3VAC heating windings, and use a 12AX7 for the pre-amp tube, an EL84 for the output tube, and an EZ81 rectifier (from one of the 6.3VAC windings)
        Attached Files
        Last edited by tubeswell; 12-25-2011, 07:05 PM.
        Building a better world (one tube amp at a time)

        "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo


        • #5
          Tubeswell, the 401 guts are now gone, and the Dukane guts are in it. I got tired of trying to get the 401 working, and since it didn't have a PT, I was somewhat afraid while fiddling. The Dukane is almost working and fits in there pretty nicely.


          • #6
            Just build an Vox AC15 or an 18 watt Marshall variant. On the chassis using the transformers you have. Quick, easy, and great amps. Don't even try to make the old amp work.


            • #7
              The old amp works. I just need to adjust a few things. I don't wish to build a Vox or Marshall variant, I just want to get this one working.


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