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The TDA1517P would make a good amplifier for this application since 3 Watts would be more than adequate. And, I was tempted to just drop the Dell board into my enclosure. But, I wanted something unique and maybe a little more cutting edge. So, I went to the T.I. web site and checked out their selection of Class D amplifiers. At first I was a little frustrated since most of their devices require a regulated 5 volt supply. What’s the point of using a Class D amplifier in a battery powered device if you have to add a 5-volt regulator to use it?

I couldn’t find what I wanted so I placed a phone call to Keith, my local Arrow representative. He directed me to the TPA3005D2. Bingo - this device requires a minimum of 8.5 volts and can drive a pair of 8 ohm speakers with up to 6 Watts. And, the best part is, it doesn’t require filters on the output side like most Class D amplifiers. But there was just one catch: the part is a 48-pin quad flat pack with a large pad on the bottom that requires connection to the PCB for optimal thermal performance. I wasn’t looking forward to laying out a board and so was very happy to discover that T.I. makes an evaluation board for the TPA3005D2. After considering the time and expense of designing my own board, I figured that the $50 price was a bargain.

So, this was my plan: I would use six AA batteries to generate 9 volts, the TPA3005D2 evaluation board as an amplifier, and build some small enclosures that would incorporate the Dell speakers. It was time to collect the raw materials.

My first stop was OfficeMax where I bought a Mead Five Star® 1.5" School Ensemble Binder. Then it was to Hobby Town USA where I purchased a 1’ X 2’ piece of 1/8” laminated plywood and some super glue. After drawing a schematic, I went to Austin Electronics, my local emporium where I picked up the discrete components necessary to finish the project. While there, I told the owner, Lloyd, about my project. He directed me to some small preassembled speakers that measured roughly 4” X 4” X 1.5” – perfect! Finally, I went to Home Depot for some small brass hinges, some silicone-based glue, four ¼” spacers, and some ¾” #4 machine screws and nuts. Assembly then began.

First I built a small circuit board to hold the amplifier assembly, the battery contacts, and the dual potentiometer that I scavenged from the Dell amplifier board. The nice thing about this pot is that it has an audio taper and an intrinsic power switch.

• Notebook Amplifier Schematic