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Pokey chips for Atari 8-bit computers are very rare these days and extremely hard to buy, but since there are many programs out there which utilising second Pokey chip to play stereo sound or 8 channels music, Lotharek and AcidMaker created together a ACID STEREO upgrade for all Atari 8-bit systems!

This upgrade utilizes the original Pokey chip and adds extra functionality implemented inside the FPGA - a perfect marriage of old-school and modern electronics.

MAIN FEATURES

  • Uses the original Pokey chip for SIO operations, potentiometers (POTs) and keyboard functions
  • Integrates extra 2 Pokeys and 4 Covox chips inside the FPGA
  • Dedicated 32-bit, 384 kHz DAC for superior sound output
  • Proper audio source mixing:
    • PBI and SIO audio are converted from analog to digital via two ADCs
    • Mixed digitally inside the FPGA
    • Output sent to the DAC for crystal-clear sound
  • 2-layers PCB, slightly larger than the original Pokey chip
  • Mono productions are played in stereo mode with channel interpolation (2 selectable modes) - check out the videos above to hear it yourself
  • Stereo productions sound exactly as intended - but with one major improvement: no humming in the speakers from your Atari!

 PINOUT

ACID Stereo pinout

  • Output:
    • AL - audio left (1)
    • GND - ground (2)
    • AR - audio right (3)
    • GND - ground (4)
    • MONO output (5) - can be used to connect to monitor port inside Atari
    • GND - ground (6)
  • Inputs:
    • A4 - address line (present in many places at the Atari motherboard, for example CPU pin 13) - this the only wire that needs to be connected for basic functionality, however it is recommended to connect the rest of the signals below for best experience
    • Bell - analog input from GTIA to get keyboard sounds
    • Dxx - address page for COVOX (connect to 74LS138 on Atari motherboard: pin 9 for $D6xx or pin 7 for $D7xx)
    • Di2,Di1 - digital inputs (more info soon)
    • SIO - SIO bus audio input 
    • PBI - PBI bus audio input
    • GND - common ground

Please note: pin 31 in the ACID Stereo is intentionally not connected! Please double-check that it is isolated from the Atari motherboard.