AC30s

Information and photos about Greg Fryer’s handmade AC30s:
Brian May Fryer AC30:

This uses the Vox AC30 TBX UK made 1994-2004 series speaker cabinet and integral head chassis as the starting point. All electronics and transformers are discarded from the amp head (some of these, notably the Drake output transfomer, were reasonable quality but were rejected in favour of higher quality components and transformers throughout), and the steel plated head chassis is then cleaned down and drawn up for drilling of mounting holes for valve sockets, larger choke and tagstrip mounts.

The whole amp head is rebuilt from scratch using custom designed handmade mains choke and output transformers, over rated resistors, and preferred coupling and electrolytic capacitors all hand soldered on tagstrips like the best of the 1960s and 70s AC30s were. The circuit is my tweaked version of the AC30 based on my own preferences from the 1960s and 1970s amps along with a few custom touches thrown in.

Version 3 with silicone diode rectifier:

Brian May Fryer AC30 version 3 #1

AF BM Fryer AC30 version 3 with added features

AF BM Fryer AC30 rear view

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Vox AC30BM redesign and rebuild:

In 2011 I designed a new version of my Brian May AC30, the tagstrips and power/preamp sections were designed to fit into the JMI styled chassis of the Chinese made AC30BM amp. The amp also included a new master volume control which was different to the Matchless style ‘drive lines summing’ master volume control that I had been using from 2003-2010 on my We Will Rock You production AC30s and also on Brian May’s own AC30s. (more about the master volume control later)

The first amp was built for Kazutaka Ijuin from Kz Guitar Works in Japan. As with my other WWRY and Brian May handmade AC30s, the whole amp was built from scratch by myself and retained just the metal amp head chassis and speaker cabinet from the original amp. Martin Kell’s and Paul Voller’s custom handmade Australian transformers were used again same as with the WWRY and BM amps from 2003-2010, this time the mains transformer was wound by Martin for the Japanese 100V AC mains power.

Schematics of my rebuild of the AC30BM amp for Kazutaka Ijuin in 2011: (please note that the AC30s that I built for Brian May were different in some respects to this rebuilt design but share many similarities)

AC30BM schematic 2011 rebuild preamp page 1 Kazutaka Ijuin

AC30BM schematic 2011 rebuild preamp page 2 Kazutaka Ijuin

AC30BM schematic 2011 rebuild EL84 power amp Kazutaka Ijuin

AC30BM 2011 rebuild mains tx and rectification stage Kazutaka Ijuin

AC30BM power amp and rectification section #1

AC30BM preamp #1

AC30BM testing November 2012

AC30BM head rear #1

AC30BM testing #2

AC30BM testing #3

The extra hole on the top section was for a mod that Kazutaka was considering adding later. Each push-pull pair of EL84 valves have their own fuse and LED indicator same as per my WWRY and Brian May AC30s.

EL84 cathode fusing:

If an EL84 blows up and trips the fuse (which usually happens when its screen grid starts to fail and begins to pull steadily increasing amounts of current through its screen grid resistor), that push-pull pair is disconnected and its LED lights up. The amp will still continue to work as usual although there will be a slight volume level drop and a little more distortion due to the mismatch of mains tx secondary HT winding driven by just one pair of EL84s.

This function was designed with the We Will Rock You theatrical shows in mind because of their obvious need to get through the show regardless. The EL84 fusing began based on ideas from my Sydney amp tech friend Dave Peach and Kevin O’Connor from Canada’s ‘London Power’.