Hey hey hey,
I tested the circuit last night with a partially built Mini^3 and a plug board wired with the power supply, and it all checks out. Under steady state conditions, the power supply ends up being around 9.72V which splits between -4.36V and +4.36V with the isolated output rails having the virtual ground connected to USB ground. I realized that after submitting the board, I won't need the switched Alps RK097 pot after all. Since the amplifier's virtual ground is connected to the case, the switch is essentially bypassed because it is connected to USB ground. Alas, that will be something that I will revise in the final production version. In the mean time, one can use one of the smaller unswitched Alps RK097 pots, which will be a way of increasing board space. The offset in my Mini^3 resided in the 2mV range, and I discovered that my BantamDAC that worked on my laptop when it was XP didn't work when I upgraded to Vista. I installed Microsoft's hotfix,
A hotfix rollup for the USB audio driver is available for Windows Vista-based and Windows Server 2008-based computers, so I hope that it will work when I test it later. Compared to my test setup, the opamps will have much more decoupling capacitance than available on the Mini^3 board, so my hope is that the power supply I dreamed up will be sufficient to warrant the Mini^3 name. With the extra space coming from the smaller pot, I think I can use a slightly better filter for the DC/DC converter. I'm quite excited to discover this. This also means I need to rework Tangent's RK097 library. =T
What can I say? I'm ecstatic that the testing confirmed a lot of my suspicions and conclusions, and I look forward to all the magnificent work ahead of me. Further, in honour of this momentous occasion, I have decided to change the name to its final version: Carrie. Yes, I know it's very much in the way of
diyparadise, but I'm going to stick by it
. It's my girlfriend's name, and she's been with me through thick and thin. She's heard it all when it comes to the amp's layout, and she's supported me through its design. I'm dedicating this amp to her, so now you can all call it joneeboi's "Carrie" amp.
That's mostly all I have to report for now. I jumped on MrMajestic2's
thread, and now I have to play the waiting game. I don't want to be presumptuous and just assume that the amp will work fine, but I like what I saw last night. I better make my order to Mouser now. Two weeks in this context is a really long wait.