Gravis Ultrasad

« PC to Apple II Joystick Adapter »

Posted on 02 April 2019 21:15 in misc
Last updated on 04 April 2019 19:45

I learned what I needed for this project from here:

However, since that set of instructions is pretty primitive, I had a hard time conceptualizing it in my head, and it requires modifying the joystick - which is both distasteful and limiting. Decent or period-appropriate PC joysticks are beginning to become somewhat rare, and I'd rather not limit myself to just a single stick, when I could have the entire pantheon:

I'd love to hook a racing wheel up to my Apple, so a converter box was the obvious choice.

I should note that this only applies to Apples with the DE-9 joystick plug, such as the IIc and IIgs; the older DIP-socket-style ones I know nothing about, since I don't own one of those machines. As far as I know it's just a change of pinout on the connector.


I'm not much of an EE. This might smoke your Apple II by consuming too much current through the joystick port. I don't think this is likely, since the stock joystick - as far as I can tell from the official system documentation - uses simple switch closures with no extra resistors to limit current. But I don't have one of those (they're $80, fuck ebay and its STEVE JOBS RARE LQQK bullshit) so I don't know for sure.

There are more sophisticated looking prebuilt adapters you can buy for $50 on the internet, which look like they were made by real EEs and are probably safer. Build this at your own risk.

Bill Of Materials

  • 1 perfboard with copper pads, at least 2x2
  • 2 x PNP transistor (I used 2N3906; I think just about anything will work)
  • 2 x 1kohm resistor
  • 1 female DA15 socket (I desoldered one from an old sound card and bent the pins to fit the perfboard)
  • 1 female DE9 plug
  • DE9 male-male cable
  • Assorted bits of wire

I didn't have all this so I just soldered some wires to my board and attached them directly to a DE9 plug. I don't recommend this approach; they will break off the board eventually. Get a DE9 socket, bend the pins to fit the perfboard and you'll have a much more solid unit.


Any "digital" PC stick will be useless here, naturally. You'll need one that just has buttons and potentiometers in it, no chips.

The axes convert over trivially, they're just potentiometers of roughly the same value as the Apple sticks used. If we were just converting axes there'd be no need for circuitry, it'd just be a pin-to-pin converter.

The buttons are what give us trouble. The PC grounds button inputs to activate them, while the Apple II applies 5V to inputs to activate them. There's no easy way to solve this; you need a logic inverter. Fortunately this constitutes a single transistor per button.


The +5 and ground symbols are just representations. Mostly you're just connecting the pins straight through, with the exception that you need to connect from DB15 pin 1 (+5V) to the emitters of the transistors. That's it.

Here's what mine looked like:

As you can see, it's mostly just wires and then four components. To test it, use Apple Cillin II (option 4, then option T.) Good luck!


It works well, but it's a little twitchy. Arkanoid works great (it sure beats console versions with relative instead of absolute inputs) but the paddle skips around a lot.

I feel like adding a trim pot to the X and Y axes to decrease their range might not be a bad idea, though it would only work for games with calibration code.

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