All about the Amp Created by John Deacon (2023 Edition)

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If you’re curious about the amp created by John Deacon, you’ve come to the right post!


We’re all aware of Brian May’s innovative nature. And this is not only about music writing. We also need to consider the gear he used over the years as well. Aside from his famous Red Special, there’s also an additional custom-made piece of gear that he’s famous for.

No, it’s nothing high-end. We’re looking at a custom-made amplifier by his bandmate, bassist John Deacon. Being an electronics engineer, he created this small guitar amp from scrap. Eventually, it became one of the most important and somewhat mysterious amps in rock music history.

The creation of this amp happened by mere accident. One night in 1972, Deacon stumbled upon wires dangling from a skip in a random street in London. It turned out to be a circuit that he just found to be interesting. The circuit in question was a transistor amplifier, most likely from an old radio or a cassette player.

Deacon was studying electronic engineering at the time. So he used the circuit as a basis for a guitar practice amp. After that, Deacon showed this amp to Brian May. Impressed by its simplicity and possibilities, he eventually began using it in the studio with his Red Special and a treble booster pedal.

The Deacy Amp

What’s interesting about the amp is that it features no controls. As Deacon explained, there might have been a volume knob on it in the early development phase. But what he aimed for was a super-simple amp. It’s a low-power practice amp with a volume set to max all the time.

There were also no other controls. No tone or EQ controls, and not even an on and off switch. It’s simply turned on when you connect a 9-volt PP9 battery to it. What’s even more surprising is that there was no battery compartment. The battery just hangs outside. So all you have to do is power it and plug in the guitar in it.

While the circuitry has been a mystery for a while, it was revealed in 2013 that its main circuit board is from the Supersonic PR80 radio. This was further explored by a man from France named Manuel Angelini. He even makes some very convincing replicas of the Deacy amp.

What’s So Special About It?

The first thing that’s great about it is, obviously, its simplicity. Sure, there was no way to shape the tone. However, this also made it incredibly consistent. We’re talking about the days of predominantly tube-driven amps. And tubes weren’t always consistent with their performance.

This particular issue drove many engineers crazy. But the little Deacy amp always had the same tone. In addition, its output was much warmer compared to solid-state guitar amps of the era.

What’s important to add is that the amp had a distorted tone. It was in a constant clipping mode. While it may seem like an inconvenience, the tone was recognizable.

The only way to change its tone was to use additional effects. This is why Brian May used a treble booster with it. This added even more dirt to it. And since we’re talking about a small amp, this gave it a very specific and somewhat piercing tone.

Popular Uses

By mere chance, the Supersonic PR80 radio found its unexpected use as a guitar amplifier. Of course, the amp on its own may not seem that impressive. However, Brian May was innovative enough to implement it in many ways.

The Deacy amp was predominantly used for lead sections. In particular, May found it useful in settings where he wanted to replicate some orchestral instruments.

One of the best-known uses was for God Save the Queen which you can check out below. Of course, the song also features layered guitar tracks with his regular VOX AC30.

Queen - God Save The Queen [Instrumental] (Official Montage Video)

Mad the Swine, an originally unreleased song from the band’s debut album is another example.

But probably the most popular use was for Good Company from the A Night at The Opera record.

Queen - Good Company (Official Lyric Video)

However, The Fairy Feller’s Master-Stroke and Procession from the Queen II album were the first officially released recordings to feature the Deacy amp. Sure, Mad the Swine is technically the first time he used it in the studio. But the song only resurfaced many years later.

Queen - The Fairy Fellers Master-Stroke (Official Lyric Video)
Queen - Procession (Instrumental) (Official Montage Video)

Commercial Replicas

Knight Audio Deacy Amp Replica | Review | Guitar Interactive

Of course, the Deacy amp is one-of-a-kind. But as years went by, some guitar players yearned for its specific tone. Aside from some minor projects, there was also a bigger commercially successful line by KAT or Knight Audio Technologies.

The KAT project took a lot of time. The whole thing started back in 1998 with a blessing from Brian May himself. However, it was only in 2008 that developers were allowed to analyze the original amp.

In addition, KAT tested many different speakers with their replicas of the circuitry. Nonetheless, they took their time in the pursuit to create the perfect replica of a seemingly simple amp.

The official production commenced back in 2011. Those initial amps sold within just one month. But unfortunately, KAT had to discontinue the Deacy replica amp model. The main reason was that they were unable to get transistors and other components that matched the original amp’s characteristics.

The Amp Created by John Deacon: Conclusion

I hope this article has given you some useful information about the amp created by John Deacon!

And if you want to read more about amps on this blog, then check out:

Lastly, feel free to leave a message in the comments below if you have questions about this or another guitar-related topic!

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