Andy Barnett

Andy Barnett's Audio Routing and Midi Switching Doodah! and Smudge's Wireless Switcher!

We were asked by Andy Barnett to design and build him a rugged Midi-Switcher for his G-Major Effects unit, similar to the one we had already built for Brian May. However, this unit also had to provide additional effects routing and switching along with discrete amp mute functions. Unlike Brian’s unit, which was designed as a hand operated unit, this version was to include a floor mounted foot-board that would be able access all functions.

Foot Panel

This unit has been built to take the rigours of top-end touring. Constructed out of folded and welded 1.2mm thick mild steel, it features three folded internal braces that provide total support for the main switch panel above. You could literally stand on this unit without damaging it!

The finish is black satin powder coat with silk-screened artwork. 

What's inside?

The unit features 24 footswitches each with their own status LED’s and a single multi-core output connector.

Inside are two circuit boards. The blue one on the right is the Midi encoder that sends the Midi Program Change commands to the two G-Majors, the green one on the left is a basic sequencer that allows the three effects footswitches to be cascaded such that the next button press cancels the previous.

The Foot Board derives its power from the main Audio Routing Rack unit via the multi-core cable. The Foot Board and multi-core cable have no audio running through them at all. This is handled by the rack unit.

Audio Router and Midi Controller Rack Unit

This unit is the nerve centre of the system. Built into a light-weight 19” aluminium enclosure, it stands only 2U high and contains all the audio and midi interfaces as well as power supplies and status LED's.

Front Panel

The front of the unit features the obligatory power on-off switch to the right hand side. Tracking left from there and you come to a vertical bank of three status LED's. These indicate the health of the three power supply rails. Next bank of LED’s provide an indication of which effect has been selected. Further left and you find a stack of five LED's showing the status of the system mutes. These glow green when audio is routed, and change to red when a mute has been engaged on that line, so in essence, via individual foot switches you can independently mute the AC30 Left amplifier, AC30 Centre amplifier, AC30 Right amplifier or Deacy amplifier. In addition, there is a 'Global Mute' switch that kills all signals!

To the left of the unit there is a small toggle switch and two further LED’s. This switch allows the user to 'Hot Swap' live between the two G-Major effects units which are constantly pushed to the same settings via Midi. So, if a fault appears on one of the G-Majors, a quick flick of the switch will allow you to carry on with all effects selected as before! The two LED's next to the toggle switch provide visual indication as to which G-Major is currently selected.

Rear Panel

The rear panel provides all the I/O for the system. On the far right is the system input. This is a high impedance unbalanced instrument level input that is currently fed directly from the CryBaby. To the immediate left is a bank of three effects sends and returns. These are buffered, unblanced and again, instrument level. Further to the left are the two blocks of I/O for the two G-Major units. They include individual Midi outs and Balanced audio I/O for both units.

Then to the quad of jacks next to the Foot Board multi-core connector. These are the system output connectors and are all transformer isolated and balanced. The 'Left' and 'Right' amplifier outputs each have the option of grounding the screen to earth via a pair of small toggle switches. The Deacy output requires a special transformer circuit that applies the correct source impedance to the Deacy amplifier in order to emulate the output stages of a treble booster.

What's Inside?

Well, lots really! The unit utilises three circuit boards. These are not printed circuit boards, but 2mm thick FR4 boards' hand-wired point-to-point between turret pins. The main board includes the power-supply, audio switching relays, op-amp buffers and drivers and audio transformers. The medium size board mounted to the back of the front panel supports the status LED’s and their respective drive circuits! (Yes, you can see a bank of AC128 transistors there! They are just as good at switching as their modern equivalent). The small board on the right is the Deacy Amp driver board.

Smudge's Wireless Switcher!

Named in honour of Andy’s cat as it was fed-up of its previous switching duties, this unit provides Andy with a foot controllable way to switch between two guitars.

Front Panel

Minimal controls are required for this unit to perform its function. The front panel features a Power on-off switch and power-supply rail status LED’s to the right hand side. Centre in the panel is the ‘Foot Switch Live’ LED. (We’ll come back to that one shortly). To the left is a small toggle switch and two further LED’s. With no external footswitch connected, the ‘Live’ LED will be extinguished and the front panel switch will be able to switch between the two radio receiver inputs. The selected status being shown by the two LED’s. However, once the footswitch unit is connected, the ‘Live’ LED illuminates and the footswitch takes control such that the two radio receivers can be selected from the stage. The front panel switch is disabled, yet, the two LED’s continue to show the selected status.

Rear Panel

Again, very basic. To the left is the power-in IEC connector. Next to that is the footswitch connector. In the middle are the two line-level balanced inputs that are fed from the Radio receivers and on the right is the output jack.

What's inside?

Based on a two-board set-up, again point-to-point hard-wired between turret pins for reliability. The main board includes the power-supply in addition to the balanced I/O and switching. The small board on the rear of the front panel supports the status LED’s and footswitch change-over relay.

Testing the system!

When your client lives the other side of London some 190 miles round-trip, it made good sense to test and set-up the system locally before it was delivered.

We do not own the necessary three AC30's and radio systems required to test the system fully, but we do know a man who does!

So, round to Brian's to set-up a suitable system in order to check, set-up and fully test the new system!

I got Pete to put it through its paces, so he whipped out the old lady and started jumping on the Foot-Board! Believe me, Three AC30’s at full chat in Brian's lock-up is deafening! Remember Brian does not use attenuators! It does, however, allow the system to reveal even the smallest of problems, which it duly did. A slight hum on all channels caused by a dodgy capacitor. A quick change of cap and that was resolved.

Ears now mopped clean of blood, and AC30's packed back away in their flight cases, it was time to head back home. System passed!

I have to say a big thank you to both Pete and Brian for helping out here! That’s another bottle of J.D. I owe him!

System Delivery!

Andy very kindly booked a rehearsal room a little closer to the M25 so that I could get there and back within a reasonable time! He had also stripped out his rack in readiness for the new arrivals, so my job of installing it and wiring it was made a damn sight easier. I had already pre-made all the interconnecting cables, so it was a simple case of bolting the units in, plugging them up and switching on!

The Finished System

The Rack

The Floor Board

We even got chance to program-up 7 of the 16 presets for him! Just how close they are to Brian’s actual settings, only Pete knows as I left him to it! No point in asking Andy for the presets either as he is sworn to secrecy on pain of slow and very painful death!..........

So, another happy client (and cat)!....................... We like those!..........

Knight Audio Technologies Ltd © 2019