[details=Fan Hub]It actually works well.
I also updated it a little for PWM compatibility. Or at least that’s the plan, but I gotta test first.
[details=Power Switch]Works perfect. Just need to design a case for it and it should be good to go.
[details=Audio Switch]Updated the layout of the switches so it should be more compatible with a slightly wider variety of switches. Also changed it to a star ground of sorts, although I’m not sure if it would matter much since there seems to be an ongoing debate in whether or not a ground plane or star ground is better for audio purposes.
[details=Headphone Amp]I’ve been tinkering with the idea of making an amp in the spirit of the O2, using slightly better parts and a smaller design. Mainly because it gives me something to do, and with enough updating I think it could be released under a slightly more open license. I just can’t decide what to do with the three “sections” of the amplifier.
- Power Regulation - The O2 has a very simple setup, but it’s not super efficient and requires the use of an AC-AC adapter, not a more common AC-DC adapter. I can’t decide if it would be best to keep the linear regulators and just update parts, or swap to switching regulators like the ADP5071. Switching regulators would make it slightly more efficient and would allow use of the more common AC-DC adapters. There’s an ongoing argument about whether or not switching regulators introduce noise into audio signals or not (I vote no)
- Power Management - The power management circuitry in the O2 works, but it can thump when turning on/off sometimes. The other option would be to use a relay setup, like the Super CMOY.
- Amplifier Section - There are two routes here to match the performance. The first would be to more or less follow the O2’s example and use one opamp for gain, and two others in parallel for the primary amplification. With new opamps like the OPA1688 this would make for an amp that is about as powerful and have an even lower noise floor. The other option would be to go the buffer route with something like the LME49600. This would allow for an absurd amount of power, but would be a bit more expensive. Either way, implementing a SOIC/DIP adapter on the board itself would be nice, that way people could use a wider variety of opamps.
*NwAvGuy used a non-derivative license, so technically you’re not even supposed to change the parts on the board aside from what has been listed in the BOM. The problems arise when those parts go EOL or otherwise out of production, as is the case with the barrel jack and power LED. NwAvGuy seems to have fallen off the face of the planet however, so ehh?[/details]
[details=Keypad]Some people have probably already seen this, but I’ve designed a keypad using a Teensy 3.2 as the brains. This would allow it to either be a numpad or as a 20-key macropad, or both. It’s setup for PCB or plate mount switches, and even though it has places for LEDs, I don’t think the LEDs will stay lit when not pressed. In the future I might tweak the design to completely remove the LEDs and PCB mount compatibility just to simplify things a little before working on a design with persistent LEDs.
I’d need to order what works out to be about $70 in boards though from OSHPark at a minimum, so needless to say I haven’t ordered or tested the design yet.