I've been working on a clone of the Pass HPA-1. Jam gave a general overview of the topology on DIYAudio, and 6Moons and Hi Fi Knights had a lot of good internal photographs in their reviews. Some of the other guys on DIYAudio also had some good insights, and I exchanged a few more emails with Jam. I now have a schematic and board design. I believe the PSU and audio portions are pretty true to the original, while the control logic is my own as I didn't need remote control and I didn't want to program a PIC controller. I'm doing casework similar to the original, with a few changes to avoid the killer setup charges for anodising one-off parts. Grooving the faceplate: Turning the volume knob insert from Richlite: Boring the hole in the faceplate for the insert: Tapping holes on the back of the faceplate for the PCB that holds the buttons and LEDs: Stuffing the board: That's it for now. Cheers, Jeff.