Iron Pumpkin(s) and other smaller vegetable animals, Tips 'n' Tricks thread

Joined 2011
Paid Member
Just some breakin then test


  • IMG_3376.jpeg
    540.6 KB · Views: 96
  • Like
Reactions: 1 users
Joined 2011
Paid Member
Oh my!….its making the “Bushes” sing!! Running at 4db…
Dead Quiet…just gotta let the music play….very full & open transparent sound.
Can’t imagine every DIY’er not having this gem!
Great job Mr. ZM


  • IMG_3387.jpeg
    487.1 KB · Views: 86
  • IMG_3388.jpeg
    578.3 KB · Views: 86
  • Like
Reactions: 5 users
Whew! This thing slays!

I wrote briefly about my Iron Pumpkin here, but this thread seems like the right place for a picture and additional words.

I’d like to write a few notes about building this thing, because I found it, while rewarding, a little bit stressful. Zen Mod was patient with my questions throughout, but perhaps I can help by attaching a list of all the parts I ordered. I got most stuff from Mouser, but a few things from DigiKey. I

If I had it to do over, I’d:
  • Connect the transformers with some kinda quick connect like Faston 110.
  • Build the power supplies, test and adjust them
  • Build the buffers and set them*
  • Build the logic power supply and test it
  • Attach the turtle
  • Wire up the logic stuff
  • Go bananas

Because I’d soldered all three transformers directly to the board, fixing my inevitable mistake (soldering every accursed BC transistor in the wrong location) was a much bigger PITA than it might have been otherwise. I suppose the flip side is that if I hadn’t made that mistake, it wouldn’t matter. So there we go.

Setting the power supply is pretty easy. Adjust pots 1 and 2 until you get the right V+/- voltage. If you can’t, well, something’s wrong.

Setting the buffer is a tad more involved, but not difficult.
  • If you haven’t installed the turtle, great! If you have, remove the gain jumpers. All of them.
  • Remove all five SE jumpers INXDR/INXDL

Then do this:
  • Measuring across each R131, R137, R231, R237, adjust pots 104, 106, 204, 206 (respectively) to read about 28R
  • Power up.
  • Adjust pot P104 so that voltage across R132 = 20mV
  • Adjust pot P103 so that voltage From AVCR- to AVCRground = 0mv
  • Adjust pot P106 so that voltage across R138 = 20mV
  • Adjust pot P105 so that voltage from AVCR+ to AVCRground = 0mV
  • Do the same thin on the other channel.

The logic unit is not powered by either of the flat connections. You’ve gotta wire ground, 5V and 24V from the big board to the display unit. I’m embarrassed by the amount of time it took me to figure this out.

Once that stuff is done, you can wire up inputs, outputs and fire it up. And grab a chair. And rejoice.


    9.5 KB · Views: 27
  • ipumpkin.jpeg
    1 MB · Views: 70
  • Like
Reactions: 7 users
Official Court Jester
Joined 2003
Paid Member
"how an AVC is actually made"

short and sweet - with brain and some luck

if you need to ask questions as that, you're faaaar from actual starting point of making it

one of the ways, which I certainly did go through - manage to acquire at least 3 different ones, made by reputable manufacturer, then do your own analysis - what are strong and what are weak points of each one

then, with established criteria what Project goals are, work on your own Know How

shorter way is mimicking/cloning someone else's ..... but way is to make original one, isn't it?

of course - all that if you want to make commercial product

if you want just one pair for own use, don't bother ....... too much bother