Gorgeous CMoy Pocket Amp Ditches PCB for Resin

By Norman Chan

Mystery electronics project turns out to be awesome headphone amplifier

Last December, electronics tinkerer Rupert Hirst teased the readers of his blog with a few photos of a mystery project, showing a few resistors and capacitors soldered together with copper wire in an elegant arrangement. No PCB or protoboard in sight--which turned out to be the point. Commenter guesses ranged from a battery charger to an LED lighting device, but Hirst revealed it to be a small headphone amp. In fact, it's based on the recognizable low-cost CMoy pocket headphone pre-amp design that you often seen housed in Altoids tins. Building a CMoy amp isn't difficult--you can find detailed instructions at many electronics sites and the parts cost under $25. Ebay is also flush with completed CMoy units for sale if you don't want to build one yourself.

Photo Credit: Rupert Hirst

Hirst's amp project is unique because he chose to build it using point to point wiring instead of a circuit board, largely for aesthetic purposes. The finished project, encased in polished resin, looks stunning. It's not as serviceable as circuits on PCB in a mint tin, but looks great on his desk next to an MP3 player. Hirst's final post on the project addresses heat and signal interference concerns:

I already knew the circuit would not produce any significant heat before I began. If this was a concern I would have embedded a small heat sink on the top of the IC revealing itself on the top surface of the casting.
Although there is no metal shielding as you would have in a conventional chassis/PCB the amplifier exhibits no unwanted noise or RF interference as you may associate with an open chassis design such as this it is dead silent even though it is next to my mobile phone and Wi-Fi router.

Check out the amp's HomeBuiltHiFi project page here.