Monday Mar 19

Build a great little amp

How would you like a compact, clean, bullet-proof 10 watt per channel power amplifier?  Think of the possible applications.  Use it with a portable CD player and a couple of small speakers for a transportable system that you could take on vacation or on business trips.  Add an FM tuner with a volume control and a couple of larger speakers for a nice bedroom, office, or workshop system.  Or set it up as an auxiliary headphone amp.

The amplifier I have in mind is one I put together myself using a very simple to work with K4003 stereo amplifier module made by Velleman ( and purchased from Jameco ( along with the required power transformer.

After receiving those, I picked up an enclosure, input and output connectors, power switch, power cord, power lamp, and fuse holder. Not all of those are totally necessary, but considering that the module and transformer cost under $40, I didn't hesitate to dress up the project a little.

I found that Radio Shack's #270-253 vented project case was a perfect fit and I grabbed a set of dual-banana binding post speaker connectors and gold plated input jacks there, too.  Other parts came from raiding a junk chassis from the Salvation Army as-is shop, and from local electronics outlet.

Building the amp was a breeze.  The process involves mounting and soldering the capacitors, resistors, connectors, and IC to the circuit board, locating and drilling appropriate holes in the enclosure (definitely the trickiest part), mounting the module, heat sink, and hardware, and finally making the various input and output connections to the board.

Once it was all together, all there was to do was plug it in, hook it to a pair of speakers, turn it on, and listen.  Unfortunately what I heard instead of music was a really nasty buzz.  It turned out that I had made a significant error in placing the power supply parts.  It seemed serious enough that I figured I'd fried the thing.  But the built-in protective circuits worked.  I corrected my mistake and the little thing sang quite sweetly.