My good friend Bill has some crazy expensive hifi gear. He has also bought some of my home grown goodies to supplement his gorgeous high-end stuff. Also he travels to NZ regularly and has some very classy high-end ear buds. BUT the plane's audio system fails to drive them to their best. CMoy to the rescue!
Bill gave me one solid, immovable mandate in two parts: Small and light. When checking out the specs of most OPAMP chips; LM833 and OPA2134 (my fav.) I discovered they will work down to +/- 2.5V. I'm running this fledgling on a single 9V battery with a differential resistive and capacitive network to give me +/-4.5V. OK not a lot of headroom but I'm working under tough conditions here.
A small Jaycar ABS enclosure houses all parts and battery required. I use prototype brds. I bought from Stiff Dick many years ago. When on the LED just glows to show some one is home. At 152gm with battery and being a little larger than the palm of your hand I think I have met all mandates. Not only that it sounds excellent.
As you can see I work in 3D when it comes to cct. bds. The whole shebang is silver soldered and solid core fine copper wire hooks it all up. The two tone ABS enclosure is lined with bitumanised heavy Al foil for screening and resonance control. It will carry a "retro-thermionic" decal and will be delivered in a black velvet slim fitting bag. What a spoil!