Williams compatible ATMEGA based soundboard

The main board

ATMEGA8 micro-controller, audio amp, voltage reg., 14.318MHz crysal, R2R array and test switch.
 

It's based on an Atmel ATMEGA microcontroller so hence the name "Megasound"

Comparison with an original board

 
Quick Notes:

• The ATMEGA8 contains a simulator for the 6800, 6821 PIA, 6810 SRAM and the 4K of sounboard ROM.
• Could use almost any of the ATMega family of micro-controllers. A highly available and modern part.
• System clocking is at 14.318MHz, which is exactly 4x the original clock, and 16x faster than the minimum cycle
  for the MC6808/6802 CPU on the original.
• The simulator was written in AVR assembler and all op-codes are coded to be cycle identical to the original 6808/2.
• The current output DAC is replaced by a R2R ladder nework array on the Megasound board.
• LM380 audio amp was used for the demo board. That will probably change to a TDA2003 or TDA1517.
• 5v current requirements is only 24mA (!) So a small 5v regulator was used with no additional heatsinking required.
• Plug in replacement for the original sound board.
• No support for the speech board.. well not yet at least..
  But seeing as Defender, Joust, Robotron, Stargate, Bubbles and Splat don't need speech that's not really a limitation for those games.
• Sounds perfect :)