In 1974, American inventor Ken Schaffer introduced the first commercially available wireless system for electric guitar and bass: the Schaffer-Vega Diversity System (SVDS). What he didn’t realize at the time was that he had also created a circuit that would revolutionize rock and roll forever.
How the Schaffer-Vega Diversity System Changed Guitar Tone
A perfectionist at heart, Ken Schaffer designed his wireless system with advanced interactive circuits to preserve signal integrity and enhance dynamic range beyond what had been previously possible.
Key Innovations of the SVDS
Companding Technology – A mirror image compressor and expander in the transmitter and receiver expanded the dynamic range to over 100 dB—35 dB more than previously achieved.
Goalpost EQ & Buffering – Restored lost frequencies and optimized signal clarity.
Monitor Output with Built-in Driver – Featured a ¼” front-panel output designed for headphones, but it had an unexpected effect on guitar tone.
The Accidental Discovery That Changed Everything
Many top-tier guitarists of the 1970s and ‘80s preferred plugging directly into their amps, rather than using the balanced DI out. Instead, they connected their guitars to the ¼” monitor out—and that’s when magic happened.
The monitor driver circuit boosted the signal, adding harmonics and tightening the attack.
The compressor, expander, and line buffer enhanced sustain and saturation.
Amps were pushed into harmonic-rich overdrive, delivering a signature, explosive rock tone.
This accidental "boost" effect made the Schaffer-Vega the secret weapon for some of the biggest names in music.
Rock Legends Who Used the Schaffer Sound
Ken Schaffer’s wireless system quickly became the industry standard, adopted by legendary artists including:
AC/DC, Aerosmith, Black Sabbath, Pink Floyd, The Rolling Stones
Fleetwood Mac, Foreigner, Heart, Kansas, KISS, ZZ Top
Bob Seger, Billy Joel, Peter Frampton, Tom Petty (Mike Campbell)
Bootsy Collins, Earth Wind & Fire, The Beach Boys, The Grateful Dead
Eddie Van Halen, Frank Zappa, Yes, Thin Lizzy, Styx
…and countless others.
The Disappearance of the SVDS (and Its Unexpected Return)
In 1982, due to stricter FCC regulations, the Schaffer-Vega Diversity System was discontinued, forcing many artists—including AC/DC, Aerosmith, and ZZ Top—to abandon their beloved secret weapon.
For nearly 40 years, the Schaffer Sound faded into obscurity—until one day, a passionate AC/DC fan made a groundbreaking discovery.
Fil “SoloDallas” Olivieri and the Return of the Schaffer Sound
Fil “SoloDallas” Olivieri, an AC/DC tone expert, was reading a Guitar Player Magazine interview when he stumbled upon a game-changing quote from Angus Young:
“Only my Schaffer wireless system. Malcolm and I use the boost to push the front end of our amps.” – Angus Young, on the Back in Black album
This one sentence changed everything. Fil tracked down a rare Schaffer unit, plugged his SG into the transmitter, ran the headphone output into his Marshall Plexi, and cranked the driver.
Instant Angus!
Realizing the power of the Schaffer circuit, Fil contacted Ken Schaffer and, with his blessing, began reverse-engineering the legendary design.
The Birth of The Schaffer Replica
The result was the Schaffer Replica—a faithful recreation of the original SVDS receiver (minus the wireless function).
EX Tower – A visual replica of the original SVDS receiver.
The Storm Pedal – A pedalboard-friendly version of the Schaffer circuit.
Bass-X – A version designed for bassists, inspired by Rudy Sarzo (Quiet Riot, Ozzy Osbourne).
And our NEW SVDS Boost which is take from the EX Tower.
Angus Young Reclaims His Tone
When Angus Young received the first Schaffer Replica unit, his guitar tech, Rick St. Pierre, immediately called to order more. Angus has since used The Schaffer Replica exclusively—both live and in the studio—including on the album Rock or Bust.
Now, guitarists and bassists worldwide are rediscovering the secret weapon that shaped rock and roll.
Rediscover the Legendary Schaffer Sound
The Schaffer Sound is back, thanks to Fil Olivieri and SoloDallas. Whether you’re chasing the raw power of AC/DC, the smooth sustain of classic rock, or a harmonically rich bass tone, the SoloDallas lineup delivers.
