1. Really cool looking and useful, but those thumb screws have to go. They're too big.

Posted at 10:36PM on Jul 9th 2007 by Chris

2. I'd love to work with more SMD components, but it is usually either very difficult or very expensive for the average hobbyist, unless you have a way to fabricate your own printed circuit boards. Can anybody out there recommend a relatively cheap and accurate way to do good PCB etching and drilling? I'd like to experiment with it, but am interested in what other people use and like.

Posted at 11:59AM on Jul 10th 2007 by Greg

3. a well-designed (and layed out) smps regulator would be a lot more efficient, with minimal audio issues. however, this is definitely beyond the (typical) hobbyist. a multi-layered PCB would be required with ground plane layers and tight, small surface mount (0603 and such) components. plus, a shielded power smd inductor would be needed. most switchers nowadays switch way above the audio level, but you'd want to make sure that the closed loop error amplifiers also crossover above 40 kHz to minimize audio issues. possible, but a big project in and of itself.

Posted at 12:07PM on Jul 10th 2007 by carlton

4. In response to #2, greg I have not done surface mount yet but have had good luck with the toner transfer method of PCB etching. Just google for laserjet pcb etch and you should find plenty of examples. Here is a project of mine where I used this technique: http://workbench.freetcp.com/projects/odbii-scantool

Posted at 1:28PM on Jul 10th 2007 by william

5. A few nimh AA's would be better from a cost and environmental aspect.

carlton: I think you make it sound harder than it is (0603's). And you seem to be describing a full out smps psu, where a simpler boost converter would be adequate. But I agree its not for the average headphone enthusiast to attempt a design (although assembly could be possible).


greg: toner transfer or photoresist are the two main hobby methods. If you've got a laser printer, go w/ toner imo (http://www.fullnet.com/~tomg/gooteepc.htm). I would recommend buying if you require many vias, or value your time :P: http://claymore.engineer.gvsu.edu/egr326/PCBManufacturing

Posted at 2:05PM on Jul 10th 2007 by japroach

6. Forget about a switching power supply. If you don't know yet, headwize is a community of hardcore diy audiophiles, and any sort of switching power supply is total blasphemy. Inefficiency is rarely a concern.

I've been in the headphone diy audio community for a while--generally, the mini^3 board will probably be sold by AMB, the guy who created it. Contact him via headwize for more info. I think he has an online shop somewhere--he gets a load of them professionally made, and redistributes the boards. You'll probably also need to go through him for the ad8397, which, iirc, is not available in small quantities via digikey.

You might also require a bit of experience to build this particular amp--the main opamp chip here seems to have a pretty nasty reputation for oscillating like hell when you're not careful with the soldering. Also don't attempt to build this circuit without amb's board (i.e. on protoboard or whatnot)--you're almost guaranteed to have a fried opamp due to oscillations unless you know what you're doing.

On PCB etching--look up inkjet pcb printer. There are published results of people consistently getting 3mils resolution. I'm actually building one right now--I've completely given up on the toner transfer method, as it hasn't been working very well at all for me.

Posted at 7:14PM on Jul 10th 2007 by threepointone

7. you don't need pcbs for smt: http://home.arcor.de/henning.paul/gallery/cs4331.jpg
http://home.arcor.de/henning.paul/gallery/cypress2.jpg

prototype board and laquer isolated copper wire will do very well.

Posted at 6:20AM on Jul 12th 2007 by hnch

8. More and better pictures of the Mini³ amp can be found here:
http://www.amb.org/audio/mini3/

Posted at 1:32PM on Jul 20th 2007 by amb

9. the DIY community is great. really supportive and you get designs that are refined by many many eyes. much appreciation to anyone who contributes.
you guys should check out

http://www.amb.org/

Posted at 7:38AM on Sep 4th 2007 by Russ