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Wombat Amps "Grail" - The lovechild of Merlin and Dumble

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  • Wombat Amps "Grail" - The lovechild of Merlin and Dumble

    Hi all

    I've already been posting shots of the cabinetry over in the cab sub-forum here, I think things are now far enough along circuit-wise to introduce you all properly to my latest project, which is rapidly nearing completion.

    Imagine if you started with what is basically a 80's 100W Dumble overdrive special circuit, then decided to add reverb and a high quality effects loop in as a transparent manner as possible? Been done, you say? Yes, but wait, there's more! On top of that I've added VVR and a regulated power supply (VVR, choke replaced with capacitor multiplier, and preamp stabilized with a Zener regulator). This lends perhaps a bit more of a modern element to the tone (it's still very dumbly however). DC heaters for the preamp tubes as well.

    As you can probably guess, this is, by far the most ambitious DIY amp I've ever attempted, but, By Gum, I think I've pulled it off. There's still some tweaking to put the icing on the cake, but it's already sounding pretty damn glorious IMHO. Everything is up and running except the VVR, which I'll have a stab at this coming weekend.

    Here's the schematic for this beast.

    You can find pics of cabinetry and gutshots on my blog. Note that the layout file posted there was very preliminary and mistake ridden. I'll post complete and corrected layouts once I'm totally finished and satisfied.

    Thoughts? Comments?
    Last edited by Wombaticus; 08-09-2011, 02:39 PM.

  • #2
    neat! I like that way the radial e-lytics are mounted. I bought a ton surplus and I thought about doing the same thing.

    I have an Antek toroid in my main gigging amp. Very solid. Can be problematic at outdoor gigs on a generator though- seems like it doesn't like the dirty generator power.

    How does the big Antek hold up at full power? I've thought about using an antek to build a much larger amp but I'm unsure of how it'll hold up in real world tube amp usage. My little one sags very little but it's only a 100 watt 300 volt model.

    jamie

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    • #3
      Originally posted by imaradiostar View Post
      neat! I like that way the radial e-lytics are mounted. I bought a ton surplus and I thought about doing the same thing.

      I have an Antek toroid in my main gigging amp. Very solid. Can be problematic at outdoor gigs on a generator though- seems like it doesn't like the dirty generator power.

      How does the big Antek hold up at full power? I've thought about using an antek to build a much larger amp but I'm unsure of how it'll hold up in real world tube amp usage. My little one sags very little but it's only a 100 watt 300 volt model.

      jamie
      Jamie,

      The Antek has been pretty great so far, especially considering the very reasonable price (only about $40 for the basic toroid). It's nominally a 325-0-325 unit and I have been getting about 425VDC rectified out of it at the reservoir cap under quiescent load for four 6L6s biased to about 70%. Not bad at all -- certainly less sag than I would expect from most standard transformers. Notably, the 6.3V taps are dead on specified voltage with a 120VAC mains. I wouldn't hesitate to go the toroidal/Antek route again in the future.

      Cheers,

      Paul

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