The final part of this three part series on making a replica of Brian May’s Deacy amplifier covers the design and construction of a replica of the vintage loudspeaker cabinet. I also cover final assembly of the all the component parts.
Launched in 2003 and retailing at US$199/£149, the Vox VBM-1 Brian May Special amplifier remains a popular choice for guitarists seeking to replicate Brian May’s signature tones at low volumes and on a limited budget despite being discontinued in 2005. It was designed to fulfil a specific purpose: to replicate the distinctive sounds of the legendary Deacy amp. Check out my latest musical equipment section article on this unit:
https://dsgb.net/gear/vox_vbm-1/
Check out the third article in the musical equipment section of this website which covers the Brian May Deacy Amp replica made by Knight Audio Technologies (KAT):
https://dsgb.net/gear/deacyamp/
It contains the original pictures shown below, technical specifications for the amplifier, hyperlinks and four embedded YouTube videos, including Jamie Humphries‘ review for Guitar Interactive magazine and some demonstrations recorded by Martin Pitcher at the 2018 and 2019 Brian May Red Special enthusiast meets.
I have created a new website section to cover musical equipment, including amplifiers and effects. The first article for it covers the story of how I acquired a classic JMI era copper top Vox AC30/6 with some history and provenance. I have included a review of the top three publications on the subject including the bible for Vox Amplifiers compiled by Jim Elyea who runs the History For Hire prop rental company in Hollywood.
https://dsgb.net/gear/voxac30/
Following up on the recent story of the KAT Studio-One all-valve practice amplifier, Nigel Knight has released details of the other part of his R&D endeavour over the past few years. Nigel recently announced:
Brian was never happy that we had to discontinue the production of the Deacy Amp replica, but the decision to do so was based purely on the fact that we could no longer source transistors with the correct characteristics that matched the original, either locally or globally and certainly not in the numbers we needed to extend production. So from the point that Deacy Amp replica serial number 0150 rolled out the door, I was on a bit of a mission to design its replacement.
This then, is the Studio-D. It is germanium Deacy’s silicon brother if you will. After years of trawling through transistor specifications, we finally found a set that could be configured to provide the same responses as the original AC125, AC126 and AC128 transistors. We are still using the original Deacy circuit, transformers and components albeit with the odd bias-tweak here and there and it still fires into a single 6.5″ twin-cone speaker. The resulting amplifier sounds magnificent and we’re really pleased with it.
The Studio-D is equipped with an adjustable battery simulator (DABS Unit), HF tone trim pot (that mimics the tone dulling effect of putting a tea-towel over the amplifier) and a built-in attenuator that has been optimised to the speaker and Deacy responses and, like the Studio-One, allows you to dial-down the volume.
Nigel Knight recently revealed a prototype 1 W (max), all-valve 2 x 6.5″ bedroom/studio combo amplifier. The styling and overall cosmetic appearance pays homage to the legendary Vox AC30 used by Brian May.
The valves (vacuum tubes) are biased such that at each stage, the grid starts to go positive at exactly the same point that a Vox AC30 would at full volume.
The KAT Studio-One guitar amplifier features:
• Two newly developed KAT DSP 6.5 TC speakers which have an on-board filter network that tailors the frequency response to give the full bodied mids of Brian’s Deacy amplifer but without the high frequency fizz audible in many 6.5″ twin-cone drivers.
• A built-in attenuator that has been developed in-line with the speakers to ensure the same tone is produced at all output levels. -24 dB attenuation brings it down to almost whisper level whilst still producing jangly cleans and smooth full-on distortion.
• Plywood cabinet construction.
Nigel has deployed all his electronics design expertise and experience producing and maintaining Brian May’s gear to offer the holy grail that amateur Queen players have been seeking for some years: the full on Wembley ’86 tone in your home, or Project BMIB (Brian May in your Bedroom) as I’m calling it. [Other Vox AC30 + Deacy amplifier emulation BMIB solutions are available, such as the Fryer Guitars Mayday effects pedal.]
Nigel has recorded a short demonstration video in the link below using a KAT STB Stomper and Retro Sonic chorus pedal. The amplifier is still at the prototype stage and is not available for general sale yet. Note that corner protectors have been made but are not fitted to the prototype illustrated in these three images (photo credit Nigel Knight).
Update as of 25 September 2022. I recently bought three units and have released a brief (6m 43s) YouTube video in which I unbox them and show you around the inside and outside as well as a quick demonstration through my KAT Brian May rig. Please also check out my gear page for this amplifier here:
https://dsgb.net/gear/studio-one
Knight Audio Technologies (KAT) has developed a “drop-in” speaker upgrade for the popular, discontinued Vox VBM-1 Brian May Special amplifier. It costs £35.00 + shipping direct.
An alternative upgrade option which some people have carried out involves buying a Dai Ichi brand DC65-30 speaker (still available from Wagner Online in Australia at the time of writing) and fitting a 390 microH 1.3A ELC16B radial inductor (choke), RS part no. 6755576 and a 2.2 microF capacitor, RS part no. 7270473.
However, this original option is ultimately more expensive and involves soldering. Check out the product on the KAT website and view the straightforward installation video on Nigel’s YouTube channel.
http://www.deacyamp.com/index.php?route=product%2Fproduct&product_id=51
Text from the KAT website:
“This is a brand new speaker/filter combination enabling VBM-1 users and Deacy Amplifier-style project builders to get their amps closer in tone to the real Deacy Amp.
The KAT DSP 6.5 TC has been developed primarily as a replacement for the Celestion G6 unit that is sadly no longer in production. It has an on-board filter network that tailors the frequency response to give the full-bodied mid range tones of the real Deacy but without the HF ‘fizz’ that seems to dominate most 6.5″ twin-cone drivers.
A by-product of this development was the realisation that this unit could be dropped straight into the Vox VBM-1 giving immediate results. The Vox VBM-1 is a great amplifier, but, it is a little let-down by its stock speaker unit that tends to suck-out the precious mid range tones and enhance the unwanted high frequency ‘fizz’. The KAT DSP 6.5 TC is a straight swap-out with the stock VBM-1 unit with no soldering required to undertake the works. Just 11 screws and 6 minutes will have the works completed and the tone of the amplifier improved many-fold!
The KAT DSP 6.5 TC can also be used in your own Deacy amplifier-style projects to give your amplifier that great Deacy ‘honk’!”
In autumn 2019, Mike Hill passed away. Readers with only a casual interest in guitars and amplification might not be aware that his technical expertise was valued by a client list that literally read like an A to Z of rock and pop including AC/DC, Eric Clapton, Brian May, Dave Gilmour, Iron Maiden, Oasis and many others. Starting off as an apprentice at the age of 18 for Marshall Amplification, Mike worked his way up through the company to eventually become joint Managing Director.
In 1995 Mike formed his own company, Mike Hill Services, which started out offering amplifier modification and repair services then expanded into provision of products and systems including bespoke pedal boards, custom switching units and variable power supplies.
“Due to the importance of high quality and reliability in all aspects of his work, Mike has always had to source and select the highest quality valves. During his inspection process there has always been a high percentage of rejection. The Elite Collection – all which live up to the Mike Hill Services standard.”
https://www.facebook.com/mikehillservices/
https://mikehillservices.com/
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