Figured that @Donald North deserved some recognition on SBAF for his exemplary handiwork. I own the original Sonett, and have feelings toward it that are distinctly, ahem, inappropriate for a piece of audio equipment. To date, it's the most perfect amplifier that I've ever heard with the HD 600. Simplicity, midcentury modern, minimalist... each of these descriptors can be applied to Don's unique design aesthetic with equal veracity. I know that I'm not the only person with an abiding affection for these beautifully retro headphone amps. Who else is out there? Here's a daytime shot of Sonett #27 for your enjoyment. Captures the "Holy f**k, that's blue" quality. It shifts with the light. Edit: Newly arrived Sonett 2, serial #15.