Alot of stuff :-)
All per-sample code now fast assembly code
Simplified hardware to have separate data and address bus
(saving 1 latch and making also the software faster but needing more i/o
pins on MCU)
Settled from PWM output to use a 12 Bit SPI DAC (MCP4821)
 - Todo - look for 16 Bit DAC: Because it is faster (no need for
   relative complicated 4 bit shifts in software) AND better quality
   (WIN-WIN)
Maybe even more I already forgot about...