The CKIII is an all-discrete headphone amplifier with no global negative feedback. Output DC offset is kept in-check by a DC servo. Both stereo channels and the split regulated power supply (except the transformer) are all on a single board. It should be relatively inexpensive and easy to build for anyone who has some prior DIY experience.There is no availability date on boards yet, and I would like to conduct a straw poll on how much interest is there for them. So, if you would like to build a CKIII amp, speak up here and be counted. That would help me determine the number of boards to order, at least initially. The more boards ordered, the more economical each would be.
Below is a preliminary PCB layout of the CKIII amp. There are still a couple of minor adjustments I would like to make, but it's pretty close to "final" form. I am also including a 3D rendering of the board with most parts populated (some are not exactly right, but that's the way it comes from Eagle3D), so you could get a better idea what the board looks like.
The board layout is notable in its prominent star-ground near the center. The dimensions are 4.25" x 4.20" (10.8cm x 10.7cm), which is small enough to fit in a compact enclosure. The volume control pot is not board-mounted. You can mount the power transformer in the same case as the amp board (although I would recommend a good distance between the transformer and the board to avoid magnetic interference), or use an external box for the transformer. The recommended transformer is a dual 15V secondary unit rated at least 200mA per secondary (6VA total), or two separate single 15V secondary transformers (3VA each). A center-tapped transformer cannot be used with this layout. Note that this amp is not intended to be "portable" and has no provision for battery power. The output transistors do not need heat-sinking, but if you wish, you may bend the leads a little and bolt them to a case wall. Onboard heatsinks are used for the voltage regulator ICs.
I will do some independent spice simulations of this circuit in the near future and report back on the results.
[Edited by amb on 11-05-2006 at 06:47 PM.]
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posted 11-03-2006 02:44 AM CST (US) 
