Pardon my typos. Please see my tech sheet entry. 1973 sounds right. This is a very powerful keyboard, designed to run on two Roland Cube amps.YOU MUST NOT Y THE TWO CHANNELS TOGETHER. It is true stereo and instruments are weighted according to onstage placement of symphonic orchestra. I left mine at someone else's house too long and can't find the Yamaha power supply. I used to run on six D cell batteries but now I can't get all six in, so there may be an old one stuck down inside, don't know yet. If it will run I will be very happy even though I have a newer keyboard. This thing kicks butt onstage and the sampling is largely very nice. As usual, some horn sounds are a bit lacking in quality, but Yamaha was a leader in sampling in that era. Hang on to your original power supply and don't Y the two channels together. Run them separately into your sound board channels or use two amps. You can adjust the dispersion with the knobs left and right. If you can get a new one with the power supply, it's a good bet for the money. Saving arrangements may not be it's forte but it works really well for live performance.
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