"Ho hum - for those prices I could construct my own."

Hi Will, if you check the paragraph at the bottom of eartrumpetlabs "Bricolage" page:

"We are committed to supporting the DIY community. I plan on posting more information here with advice and detailed instructions on how to construct your own mics for other bricoleurs-at-heart. For now, the schematic of our most common microphone circuit is here. This is essentially a variation on the venerable, versatile, and extremely clever transformerless FET Schoeps circuit widely used by commercial manufacturers and home builders alike, as well as for upgrades and mods of lesser commercial mics."