In 1975 American inventor Ken Schaffer created the first dependable, beautiful sounding wireless system for electric guitar and bass. Little did he know he was also creating a circuit that would transform the sound of rock and roll.

Schaffer’s design incorporated ingenious pre-processing circuits to preserve the integrity of the wireless signal. Notably, a mirror-image paired compressor and expander increased the radio circuit’s dynamic range to over 100 dB, 35 dB greater than the theoretical maximum that could otherwise previously be achieved within the bandwidth limits covering wireless systems by the US FCC.

This unit changed the way Angus Young sounded and played.

But there was a side-effect: beyond the staging freedom afforded by Schaffer’s wireless, many A-list players discovered something unintended: the sonic result was pure magic! The wireless design’s unique preprocessing enriched their signal with copious amounts of harmonic content unlike anything they’d ever heard. News traveled fast. Schaffer’s wireless units became the system of choice for nearly every major artist of the mid-70s to mid-80s.

Schaffer ceased producing his wireless system – the “Schaffer-Vega Diversity System” (SVDS) – in 1982 to pursue other interests. Soon, new, stricter FCC regulations on wireless specifications prohibited fully-analog wireless systems of its caliber from being used. SVDS artists – including AC/DC – were forced to move on… the legendary “Schaffer Sound” slipped into obscurity.


Across the world, in Rome, renowned AC/DC aficionado Fil “SoloDallas” Olivieri had been obsessed by Angus Young’s signature tone for more than 30 years. In pursuit of that sound for more than 30 years, Olivieri had bought and duplicated every piece of equipment Angus was known to use. But something was missing…


But eventually, he happened onto a 1984 interview with Angus Young in Guitar Player magazine (“Angus Young: Seriously”, Guitar Player, February 1984). A specific question was asked, during the recording of AC/DC’s iconic Back in Black album: “Do you use any effects?” Young’s reply was “I just have a Schaffer-Vega wireless system.” That next month, in Guitar World Magazine, he elaborated: “Yeah, I use the Schaffer-Vega. I’ve been using that since ’77. On the receiver you’ve got like a monitor switch you can boost the signal and in the transmitter you’ve got the same sort of thing. But good.”

What? Why had he never heard mention of this before? Olivieri scoured the globe trying to find one of these elusive 40 year old units. (Only 1000-odd were ever made.)

A year later, Fil finally reached Ken Schaffer – pleading for Schaffer’s help in getting his hands on one of these magical units. Awestruck by Fil’s 30 year dedication and perseverance, Ken’s last two remaining “souvenir” units were on their way from the back of his closet to a “better home,” Fil’s, in Rome.

Moments after Fil plugged one of his numerous SG’s into the 37 year old SVDS transmitter, ran the receiver into his Plexi… instant Angus!

It took only a few demos before the 15,000 member SoloDallas blog’s community of tone-hunters began scrambling to get one of these magical units. It was then that Fil asked and received Schaffer’s permission to re-create the audio circuitry of the original unit. “The Schaffer Replica®” (TSR™) was born.

Recipient of unit #1 was Angus Young himself, who used it throughout “Rock or Bust,” AC/DC’s first album in eight years. He’d rediscovered the secret to the best tone he’d ever had! Angus got his sound back.

The circuit that transformed the sound of rock and roll is back to do it all over… Again.


Guitar Player Magazine February 1984

What could be there in a wireless system that would have caused Angus Young to use it even in the studio, just feet from his amps?

The Schaffer-Vega (SVDS) had already succeeded in its raison d’être: revolutionizing rock ‘n roll staging. Less known is the fact that many SVDS users took their units into the studio with them and recorded with it. The Schaffer-Vega system introduced a process called “companding.” Angus used the SVDS’ processing and companding to shape his sound and create his unmistakable signature.

Based on his intuition that the Schaffer-Vega must be the missing link, Olivieri finally contacted Schaffer directly and acquired Schaffer’s long-shelved 2 remaining units.

Olivieri: “Finally getting these units was a dream come true for me, as that sound had been haunting me almost all of my life. Indeed, once the Schaffer-Vega was in connected, there, for the first time in 30 years, were those pure tones sought after by everyone. Schaffer’s system was the secret ingredient in creating these sounds.”

The Schaffer Replica

Soon, Olivieri asked Schaffer to condone his producing a replica – an audio replica, not a wireless – of the SVDS to be used for those – like himself – in love with that iconic sound. A team of electrical engineers in Rome and Vienna were retained to retroengineer the SVDS –requiring, too, a worldwide search to procure components that had been discontinued decades earlier. Early prototypes of the Replica were introduced, quietly at NAMM, in January, 2014, certification completed, and production begun in Vienna in March, and fulfillment to SoloDallas blog preorders commenced in May.

Scores of the Replicas’ initial users found that both versions of the Replica indeed contributed the SVDS’s legendary character through a wide variety of amplifiers – not only tube, but also cheap solid state – and even emulation software. Its signature tone still makes the difference, being recognizable as that sound: a definitive replication of the audio effect of the original SVDS.

Olivieri: “The Replica can be easily considered as having Angus Young in a box. It really delivers “that” sound – and, considering the multitude of top artists that owned it and recorded with it at the time, several more definitive A-list players’ signatures.”

Two versions, one, “The Schaffer Replica® Tower,” ($999 MSRP) is housed, “for authenticity’s sake,” in a cabinet nearly the same as the original SVDS, to totally replicate the look and feel of the 1970s Schaffer-Vega Model 63EX receiver. The second version, also a faithful 1:1 replica of the original SVDS’s audio circuits, is called “The Schaffer Replica® Pedal,” ($399 MSRP). With no advertising or publicity, user reviews of the sold-out first production run of both replicas leave no doubt that the most ardent followers of AC/DC’s and 70’s rock in general have been convinced.