This thread is for any and all troubleshooting of PPAS, and to document compatibility with different parts and opamps.
All standard SMD build procedures apply.. opamps and buffers first, then resistors, then build higher.
Also, the PPAS is VERY unfriendly to sloppy soldering.. DieInAFire's prototype failed twice because of sloppy soldering.. be careful and you should be fine..
BUF634U - this part is ALWAYS out of stock, but I have 23 or so left, ask me.
LMH6321 - This part is stocked at digikey.
TLE Railsplitter - There are no alternate parts for this.
SST310 - Ive just been told the SST310 is out of stock.. Currently reccomended subtitute is the BSR-57 from mouser electronics. If you know of any better substitutes, please PM me.
PLEASE make sure you buy the SST 310.. the SST309 was marked in the old revisions of the BoM. The SST309 may be unable to supply enough current..
Silkscreen may be missing at parts.. due to gerber issues our manufactuerer may have left out sections of the silkscreen.. NB that you should use http://apuresound.com/ATAT/PPAS/PPAS...%20Artwork.htm as reference during the build.
NB The tantalum capacitor direction.. the Tantalum cap is polarized.. it is marked on the board artwork link, but NOT on the board (see warning above).
NB Opamp and buffer direction.. Opamp and buffer pin 1 is indicated by the strip on the artwork above.. just for reference here's the directions.. Looking from the top down onto the board, OPA L/R pin 1 is left top, BUFL is right bottom, BUFR is left top.. on the bottom, looking down onto teh bottom of the board, both OPAG and BUFG have their pin 1s on the left top.. (the picture is mirrored)
Configurations/changes that *should* work
Using a larger ELNA sized cap on the rails (capacitor bending) should still fit in MINT tin.
LM6172 / LM6171 / LMH6321.
Warning for those using LMH6321 - The LMH6321 is a great buffer, can output nearly .7A of current and its ridiculously fast.. one problem. Pin 2 is used as current control. Before you solder the LMH6321, cut off Pin #2 (or bend it upwards). Pin 2 is connected to output on the schematic (so that opamps can be used as buffers) but this will prevent sane operation of the LMH6321.
Warning for those using OPA551 or other Opamps. - The PPAS can accomedate using running opamps in closed loop mode as buffer.. There's two things to watch out for. First, bandwith, make sure your opamp is fast, as well as being high power.. if a fast opamp feeds a slow buffer, you'll have some serious issues with the feedback loops (also stability) if using the OPA551, use a slow opamp like the OPA2227. Also, even though the L/R buffers wont have an issue running closed loop, the ground buffer is *finicky* and I'd suggest using the BUF634 or LMH6321 unless you're really feeling lucky.
Currently Tested Configurations -
AD8620 / AD8610 / BUF634 (both bandwiths) (lots of detail on this one)
AD8620 / THS4631 / BUF634 (both bandwiths) (similar to the above, but seems fater, and eats more battery)
LM6172 / LM6171 / BUF634 <-- NOT RECOMMENDED, THROWS HIGH OFFSET AT LOW BATTERY
AD8066 / LM6171 / BUF634 <-- See above
AD8066 / OPA132 / BUF634 (bass beast.. nearly overpowering..)
OPA2701 / LM6171 / LMH6321 (Amazing detail and midrange.. my rec, but KILLS battery)
(by quicksilver )
AD8610 / AD8620 / LMH6321 <-- LMH confirmed working.
OPA2701 / OP627 / BUF634 <-- OPA627 confirmed
A List of Problems encountered
9v Offset on Channel
(fixed)Prototype 1 - Routing problems
One Channel dead
(solved)Final Board (Proto 2) - Soldering issues(happened twice)
Current draw absurd
(solved)Proto 1 - Ground Mistakenly swapped with Left channel (whoops)
Amp clips at all audible volumes
(solved)Proto 1 - Case shorted SST310.
(fixed)Proto 1 - SST309 Used instead of SST310.