Since I moved, my AirDesk-mounted MacBook Pro has become my primary entertainment center. Alas, the MacBook’s tiny speakers are almost useless, so I have finally rigged an external speaker mount for the AirDesk.
I’m using a pair of old Apple Pro speakers that came with my wife’s 17-inch G4 iMac. These speakers came with a “Y” cable and a special stereo plug that only works on the G4 iMac. I simply cut off the “Y” part of the cable so I could wire the speakers separately to an amplifier.
For the amplifier, I used kitsrus.com kit #139 (available here). This is a 1W stereo amplifier module based on the Philips TDA7053A chip. For input voltage, I’m currently using a +12V wall wart. This amp/speaker combination will work with a +5V USB supply, but only at relatively low power. At 12V it puts out all the volume I want, although I should change R3 (as described in the kit instructions) to expand the volume pot’s useful range. The module is supposed to work with up to 18V supply voltage, so later I intend to try eliminating a cord by tapping the MacBook’s power cord. That will be a separate blog entry, if it works!
The mount crosspiece is simply a length of 1″ angle aluminum, cut to size with a hand nibbler. I drilled and tapped the AirDesk’s plexiglass top so I could bolt on the crosspiece. (Some grease on the tap helps it cut the plastic more smoothly.) I used steel 10-32 machine screws because that’s what I had handy, but I would probably get a 1/4-20 tap and matching nylon screws if I were starting from scratch.
To mount the speakers, I drilled and tapped their undersides and bolted them to the crosspiece. To mount the amplifier, I drilled panel and index holes in the crosspiece to accept the volume pot’s shaft mount. I also solidified the pot-to-board joint with a lump of epoxy putty, and encased the board in heat-shrink. The knob for the volume control came out of a junk box.
One watt isn’t a lot of power, but I like the sound of this setup with the 12V supply and Apple Pro speakers. I doubt I could find anything better in a rig this small, but of course you’re welcome to try any alternative that you like. Someday I might try to add an amplified subwoofer of some sort to round out the bass, but probably not anytime soon!


