In 1952, Butts received a request from his friend, guitarist Bill Goldney, who said, "Les Paul was using an echo effect in his live performances, and I want an amplifier that can do that." So Butts created a prototype by embedding a wire recorder in a Gibson amplifier. However, a problem arose where noise would be picked up when crossing the wire joints, so after much trial and error, he settled on using tape.

The resulting amplifier was named "Echo-Sonic." Considering that amplifiers with reverb didn't appear until the early 1960s, this was a very early development. It is said that the Echo-Sonic later served as a reference for the Echoplex.

In 1954, Butts met the legendary guitarist Chet Atkins. Atkins liked the Echo-Sonic and bought it immediately. It is said to have been used in the recording of many famous songs, including "Mr. Sandman." This was the fateful encounter between Ray Butts and Chet Atkins.

In 1954, Gretsch released the 6120 as Chet Atkins' signature model. This 6120 was equipped with the "Gretsch Dualmond Federatone pickup" (later known as the Dynasonic), developed by Dualmond.

In 1957, the 6122 Country Gentleman was released. This model was developed in collaboration with Atkins, and its name is derived from a Chet Atkins song title. This model also featured Butts' newly developed Filter'Tron pickup. The development of the Filter'Tron pickup was heavily influenced by the earlier Echo-Sonic amplifier.

Atkins was troubled by hum noise when using the 6120 and Echo-Sonic combination at the time, so he consulted Butts. This is how Butts, by chance, arrived at the same solution as Gibson: hum cancellation.

The resulting pickup had a humbucker structure and was named "Filter'Tron." Butz pitched the Filter'Tron to Gretsch, and with Atkins' support, it was installed in the 6122. Since then, more and more Gretsch models have come standard with the Filter'Tron, and it has become a representative model of Gretsch pickups.

Filter'Tron pickups, like Gibson pickups, have a humbucker structure, but are smaller in size. This results in narrower spacing between pole pieces compared to Gibson pickups. Furthermore, they use Alnico or ferrite magnets that are approximately twice as thick as those used in Gibson pickups.RecruitAs a result, the pickup was designed to produce clear, crisp high frequencies.