if there was ever going to be a group buy for boards, I'm in for 5 at least...
There are a couple other people who have expressed interest in some boards, I was going to make another order anyway, but if others want a board that will help keep the price down. I would love to have others try this out.
I have been slowly putting the final touches on the new board, nothing earth shattering, but as it sits the op-amp bypass caps have been moved to the back side of the op amp board. These will be large SMD film caps, however there seems to be a large selection of SMD film type caps, so people should have the option of using large uf polyesters and similar, or ~.1uf high quality polypropylene. Might have too get a little creative mounting smaller sized (1206) caps, but should still work fine. Maybe some more experienced PPA user can weigh in on this, but I think the "standard" 1uf polyester film cap is probably perfectly fine for 99.99% of op-amps.
I have moved the charge connector so that it doesn't interfere with the volume knob, and I revised the op-amp power circuit layout to a much cleaner design, most of the traces are on the top side, thus giving a very nice un-interrupted ground plain on the bottom. I also changed the layout of the buffer daughter board, it is smaller and has a cleaner layout, and no longer requires power and ground internal planes.
All in all i think the new boards will work just fine, and hopefully will work better with more finicky op-amps.
I also think i may have found a way to make the op-amp board(s) removable.
The one thing I would like to do is get a bigger battery! I initially thought that with 20ma for each buffer, and say 8ma for each op-amp, i would have a quiescent current for the amp of 84ma, so round that up to 90 ma, a 900ma battery should last at least 8-9 hours.
what i am finding, is that with 20ma buffer bias, and even lower power op amps (less than 2ma draw each, so figure 3ma with 1ma bias) the amp draws close to 120ma at a dead idle. So battery life is down to 7 hours or so.
of course 20ma bias is not the minimum, but its what i wanted to have. this was never going to be a long battery life amp, but i was hoping for 10 hours.
So, with almost half of the board space reserved for premium quality caps, i am pondering building another layout (in addition to the current one) that would use smaller (but still very good) caps, or even some of the new Panasonic EEH series that were recommended. Doing this It may be possible to use the same case (i love this case) but get a 1250mah battery installed. another option is to go with the 120mm long Hammond case, its a good match for the new iphone, and would allow for a larger battery, i just need to find a battery!
So, there will be board available, hopefully early next month, I hate to put a time line on it, but i have a habit of getting a board 99% done in a few days, then spending weeks on the last 1%..... so maybe if i set a deadline i will focus a but more...