Another project in the books. This one is my first class A power amplifier build. The circuit itself is actually relatively simple. And the casework wasn’t bad either truth be told. But I’m getting ahead of myself.
The design is from one of the godfathers of the DIY HIFI community, Nelson Pass. He runs a DIY website as well as a commercial and a sort of hybrid enterprise that sells retail items but also provides schematics and articles so the enterprising DIY’er can “roll his own.” He’s also active on the diyaudio.com site and chimes in from time to time.
The specific design I chose is the F5. It’s a push-pull Class A amplifier, utilizing JFETs and MOSFETs in a very simple two stage complementary circuit. It spits out about 180W (most of it in heat) and is one of the more popular designs from Mr. Pass.
For my build, I sourced the PCB from tech-diy.com and most of the little bits from mouser. The heat sinks were from antek and the rest of the chassis was made up of scraps actually. I had spare 1/4″ aluminum for the bottom, African mahogany for the front panel, plywood for the rear, and plexiglass (from an old document holder) for the top. I did buy some 1/4-20 bolts and some new RCA jacks and speaker posts. But all in all, I think I only spent about $300 all told. Some have been known to spend that much just on the front plate!
In any case, pictures are where the fun is so here you go.
It sounds great and doubles as a space heater! I got it biased up to about 580mV and the DC offset is essentially zero on both channels.