Well, after a stupid, stupid mistake (frying my WM8741 by soldering it in the wrong orientation
), my gamma-2 is alive and well. To satisfy the DIYer need to "make it my own," I decided to change a few of the capacitors. I have some through-hole 0.1 uF C0G ceramic caps that are small enough to work in some places, and also some surface-mount 0.1 uF C0G caps as well. So, on the gamma-1 and gamma-2 boards, I replaced a number of the X7R caps with C0G ones (bypass on the DACs, opamp, SRC, CS8416 and crystal). I went with LP2985 regulators, since the datasheet specifically states that they are designed to work with low-ESR output caps, which the organic polymer caps certainly are (couldn't find a similar statement in the TPS793xx datasheet, though they do say you can put a ceramic on the output). The datasheet says to use a 1 uF or greater input cap. I have some tiny 2.2 uF Blackgate PK caps, and these have lower ESR than the 1 uF X7R ceramic caps I was considering, so I went with them. For the noise bypass cap on the LP2985, they suggest C0G or PP/PC film caps . I didn't have any in 10 nF size, but I was able to find some PPS surface mount caps for that role. On the Wolfson application notes (WAN-0129), they suggest low ESR caps for the AVDD, DVDD and VMID, so I went with the same organic polymer caps used on the regulator outputs, rather than audio-type capacitors. For the DC blocking caps, I used Silmics on the Gamma-1, and Blackgate NX Hi-Q for the Gamma-2; no film bypass. Here are a few pics:
Gamma-1
Gamma-2
DAC bypassing
Regulator caps
Tight fit with the PK caps! (note that in the second photo, I had to situate cap C6U a little off-center to clear the polymer cap)
I have no idea if these changes made anything better, worse, or different at all. It was just fun to try. Thank you, AMB and MisterX for a great project!
