Tuesday, July 1, 2008

Power in the Pot

Some of you may know that I like to play around with electronics. Sometimes I discover something on the internet that I just have to try. In this case its what is known as a "chipamp" or an audio amplifier where all the circuits are built into a little electronic chip about 3/4" x 1".

After reading up on the nice quality sound from chipamps and the nice specs provided by the manufacturer, I just had to build one. Now my friend, Bob Wilson, was just moving into a new house. Some of you may know that he loves his music, especially the 60's, and although he has very nice stereo equipment, his power amp is his oldest piece, an old Dynaco Stereo 80 which he built from a kit in the 70's.

Putting these two ideas together, I decided to build Bob a new power amp based on chipamp technology. I was able to buy a kit for the National Semiconductor LM3886 chip and assembled the rest of the components to try to match the gain of the old Dynaco amp.

Although most of this was straight forward, I had fun with the enclosure design. You see, torroidal transformer (part of the power supply that turn AC power into DC power for the amp modules) are large and heavy and round. It seemed to me that it would make sense to put a round transformer into a round enclosure. After looking around for appropriate round shapes, I fell on using an aluminum cooking pot. In this case, a 3 quart saucepan, turned upside down with the handle removed. The rest of the power supply is mounted on a circuit board attached to the bottom of the pot which is now the top of the enclosure. There are places for plugs and fuses and switches and even cute little blue and red lights when its turned on.

The power supply provides DC power to two amplifier modules that are small, dominated by their heat sink, and are intended to sit behind the speakers. The whole thing makes more than 50 watts per channel of clean amplified sound.

Now its all in Bob's hands. I'm looking forward to hearing how it sounds.

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