Complex sentence: Early wireless systems, the Schaffer-Vega Diversity System that he would begin using in 1977, was also used as a compressor and a booster in his signal to "fatten up" his tone.
Split into simpler sentences: Early wireless systems, the Schaffer-Vega Diversity System, gave Young extra boost and compression. Not only was it used as the intended wireless unit, but it was also used as a compressor and a booster in his signal to "fatten up" his tone.