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               Easy 4 channels * 8 bits Covox C/A for Atari 8bit
                                 by: Gumi/Tight
                        mfranczak@ajax.umcs.lublin.pl
              ---------------------------------------------------

List of needed items:
chips:
1 * 74LS138
4 * 74LS574

resistors:
36 * 1.2 kOhm
28 * 2.4 kOhm

capacitors:
4 * 100-220 nF


To pins of chip 74LS138 you must to attach this signals:
pin 1 - A0
pin 2 - A1
pin 3 - R/W
pin 4,5 - $D6 (page $d6 decoder)
pin 6 - o2 (fi2)
pin 8 - 0V - GND
pin 12 - to clock of #4 C/A
pin 13 - to clock of #3 C/A
pin 14 - to clock of #2 C/A
pin 15 - to clock of #1 C/A
pin 16 - +5V
other pins - not connect

You must to do 4 C/A, like this one:

       ---. .---
       |  | |  |
 GND>--|1 '-'20|----|2    19|-->----R1----*          R1 is 1.2 kOhm resistor
       |       |             R2         R2 is 2.4 kOhm resistor
  D1>--|3    18|-->----R1----*           C is 100-220 nF capacitor
       |       |             R2
  D2>--|4    17|-->----R1----*
       |       |             R2
  D3>--|5    16|-->----R1----*
       |       |             R2
  D4>--|6    15|-->----R1----*
       |       |             R2
  D5>--|7    14|-->----R1----*
       |       |             R2
  D6>--|8    13|-->----R1----*
       |       |             R2
  D7>--|9    12|-->----R1----*-----C--->out analog signal
       |       |
 GND>--|10   11|-------*
                |
 out #4--->-----*---------- LEFT channel


 out #2--->-----*---------- RIGHT channel
                |
 out #3--->-----*


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