You are sort of right. Yes you can use the stereo headphone jack and split it to left and right and plug it into a sound system. However, the headphone jack is not the same as line outputs. It will not be quite as clean of sound as using line outs. The levels are a little different.
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George Kaye
Kaye's Music Scene
Reseda, California
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George Kaye
Kaye's Music Scene (Closed after 51 years)
West Hills, California
(Retired 2021)