Brian May Deacy Amplifier Build Project


In February 2013, I bought a KAT Deacy amp replica and Deacy amp battery simulator (DABS) in mint condition at a keen price from U.K. eBay. You can find out more about it in my musical equipment (gear) section:

Twenty years earlier, I was undertaking an electronics subsidiary module in my first year at university and, despite not appreciating the art of electronics as much as textbook authors Horowitz & Hill, I have had a passing interest in the subject ever since. Not even the most ardent Brian May enthusiast really needs a second Deacy amp replica (although playing a stereo chorus effect through two units does have a certain appeal), but I got caught up with the intrigue surrounding the special characteristics of this particular circuit board.

Red Special enthusiasts and amateur electronics specialists Mark Reynolds, Lee Speight and Manuel Angelini have built their own exquisite Deacy amp replicas with Mark eventually sourcing all the period correct component parts to make an exact clone of Brian’s original and Manuel building and selling various Deacy related products in France via his website, DoxyWorld: Their work inspired me to begin my own quest to build my own replica for a project, as I did with my Brian May Red Special replica build, to learn more about this legendary amp.

This is the first full project I have carried out with the intention of filming the process to make a series of YouTube videos, having previously dabbled in making informational videos about BHMOHM pickups and Tri-Sonic pickups for the Frequently Asked Questions (FAQ) section of this website in early 2022. I started making YouTube videos about Brian May related topics in spring 2021 to challenge myself to develop a new skill set and to augment the primarily “words and pictures” content of

In part one, I briefly discuss the origins of the Deacy amp circuit (salvaged from a vintage transistor radio that John Deacon found in a London dumpster in 1971) and what Queen tracks Brian used it to record on. I then move on to talk about the new Knight Audio Technologies (KAT) amplifier board kit and the other component parts required including suitable vintage and modern woofer and tweeter loudspeakers and the cabinet itself. I finish by introducing the only official Deacy amplifier replica which was made by Knight Audio Technologies between 2011 and 2019.

Part 2 – Circuit Board Components and Assembly

In part two of the series of three videos, I unbox the Knight Audio Technologies (KAT) custom kit of electronic components and assemble it, discussing the characteristics of key components such as the transformers as I progress. The video duration is 21 minutes.

Part 3 – Making the Cabinet and Final Assembly

Part 3, the final video in the series covers designing and constructing a replica Deacy amplifier loudspeaker cabinet and final assembly of all the component parts. There is a link to a high resolution scan of the original ICI Vynair speaker baffle featured in the introductory video in the downloads section below. The only way of sourcing the original thermoset vinyl plastic material is to salvage it from vintage loudspeaker cabinets so the best option for DIY builders who want the same cosmetic appearance of the original is to get a textile custom screen printed. The image file size is 62 MB and measures 13,742 x 8,607 pixels.

Part 4 – Demonstration (Legendary Tones)


All KAT drawings, files and information on are currently available, or were originally available on the Knight Audio Technologies website (, shared on web forums and/or social media platforms and are mirrored here for your convenience by agreement with Nigel Knight. Please only download it for your personal study. Definitely do not upload it to any file sharing websites or post on forums without consulting Nigel first.

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