Kingsley Amplifiers was founded by Simon Jarrett, a professional guitarist originally from the UK who settled in Maple Ridge, British Columbia, Canada. The company designs and hand-builds tube guitar amplifiers and pedals, with all products featuring hand-wired circuits on tag boards and tag strips. Jarrett developed his craft through years of repairing and modifying classic tube amps before building his own designs, initially drawing on vintage Vox and Fender circuits while incorporating original engineering with an emphasis on simplicity and tonal quality. The Kingsley Deluxe 30 amplifier received a Guitar Player Magazine Editor's Pick Award in 2001.

In 2008, Kingsley expanded into the pedal market with the Jester, an overdrive and boost pedal using two 12AX7 tubes running at high voltage. The pedal lineup has since grown to include the Page (a transparent tube boost and mild overdrive), the Harlot (a higher-gain tube overdrive), the Minstrel, the Constable valve preamplifier, and the Maiden preamp, among others. All Kingsley pedals share the same philosophy as their amplifiers: tubes operating at high voltage with hand-wired audio circuits on tag board, targeting players seeking the dynamic response and character of a tube amplifier in stompbox format.

Kingsley's tube-driven approach has earned a devoted following among boutique gear enthusiasts and working professionals alike. Their pedals are frequently praised for their ability to interact with an amplifier's natural voice rather than impose a fixed tonal character — functioning more as extensions of the amp than traditional effect pedals. Guitarists including Noel Gallagher, Johnny Marr, and Carl Broemel of My Morning Jacket have been noted as users of Kingsley products.

Kingsley has 38 products cataloged on Equipboard, including Overdrive Effects Pedals, Boost Effects Pedals, and Guitar Preamp Pedals. Their gear is featured by 11 artists, with the strongest followings in Rock, Blues, and Pop. Notable users include Noel Gallagher, Eric Johnson, and Ed O'Brien. Most Kingsley products sit firmly in the high-end, boutique range.