When we listen back to those great early AC/DC albums like Back In Black and Highway To Hell we think of what may be the epitome of hard rock guitar sounds. While on the surface you’d look at Angus Young’s fingers on a Gibson SG into a JMP 100 Marshall amp and think that was the sound (and surely it’s a big part of it), there’s actually another major component that’s almost always overlooked – his onstage wireless rig, which he actually used in the studio for those projects.
At the time Angus was using on of the first wireless guitar systems called a Shaffer-Vega Diversity System (SVDS for short), which was quite popular at the time with widespread use by the likes of Ace Frehley of KISS, Van Halen, The Stones and Frank Zappa, among others. It was the way that the SVDS worked that really set it apart from any wireless system to come afterwards though.
The SVDS used a compander circuit to keep down the noise, which mean that it compressed the signal during transmission and expanded it upon reception before feeding it into the amp. Along the way though, it also boosted some of the mid-range that became lost in the process, and unintentionally added some pleasing distortion of its own to the signal. Essentially, it acted as an overdrive for the amp! When Angus couldn’t get the same great sound that he got on stage while recording in the studio, producer Mutt Lange suggested he revert to his on-stage setup, and the rest is AC/DC history.
Sadly, Shaffer-Vega stopped making the units in 1982 after the FCC changed the wireless regulations, making the frequencies it used illegal. That said, the device has been resurrected by a company called SoloDallas using one of Schaffer’s original units as a model to create the “Schaffer Replica.” The unit uses only the audio circuitry from the original SVDS, but it’s just what you want for that original AC/DC sound.
Another interesting twist to the story is that SDVS creator Ken Shaffer was indirectly responsible for being named in a big R.E.M. hit, being the subject of “What’s The Frequency, Kenneth?” which revolves around a mugging of news anchor Dan Rather. I know, the story’s hard to follow, but there’s a great article that covers it nicely on Dangerous Minds that’s worth reading.