Intellivison Stereo


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I came across an intv-1 schematic on the web one day, Intellivision Master Component and saw that the three intellivision sound channels were connected up to a common-base transistor amplifier (funny, you don't see common-base that often). I duplicated the circuit, then tried it out on an intv2 by lifting one of the three pins and connecting to it the the circuit input, and sent it to the "to mod" output to my stereo. The sound came through no problem. This means you can modify an intv for stereo sound (2 signals on one side, 1 on the other), or three-channel sound (stereo + tv speaker). Unfortunately, I have no idea which of the many possible arrangements would sound the best, the games weren't really programmed for that behavior.

 
 ,----------------------------,
 |                            |
 |        AY-3-8914           |
 |                            |
 |                            |
 |                  A   B   C | 
 `----------------------------'
                   4|  3| 38| 
                    |   |   | 
                    |   |   | 
     ,--------------+---+---'
     |
     |
     |
     |        ,--------+-- +12V
     |        |        |
     |        |        |
     |        /        /
     |        \ 4.7k   \ 9.1k
     |        /        /
     |        \        \          680pf
     |        |        |      ,----|(-----,
     |        |        |      |           |
     |        +---------------|           |------ to
     |        |        |      |           |  modulator 
     |        |        |      |           |   
     |         \c      |      |           |   
     |          \ | b  |      |   110k    |   
     |     3904  \|----+      `---/\/\----'
     |           /|    |
     |          v |    |
     |         /e      |
     `--------|        |
              |        |
              /        /
              \ 470    \ 1.2k
              /        /
              \        \
              |        |
              `---+----'
                  |
                --+-- 
                 ---
                  -

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