John Harvey
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Hauptwerk Project 2

This is a project to repurpose a defunct 1983 four manual Makin electronic organ from the Methodist Church in Bishop Auckland, County Durham UK, to a Hauptwerk virtual pipe organ.



Makin Organs

Makin Organs Ltd. has its roots in the John Compton Organ Company of Acton, West London. Formed in 1902 to build church pipe organs, Compton moved into making cinema organs in the 1920s and 1930s alongside Wurlitzer and Christie. In the 1950s Compton developed the Electrone range of electronic organs using their proprietary spinning electrostatic tone-wheels. John Compton died in 1957 and the pipe organ department was sold to Rushworth and Dreaper in 1964. The remaining electronic department folded in 1970 and was bought by John Pilling, a Lancashire industrialist and organ enthusiast, becoming Makin Organs of Rochdale. A history of Makin Organs from 1972-1992 has been written by Hugh Banton, one time engineer and technical director. The Bishop Auckland organ is mentioned on page 24.

The Bishop Auckland Makin Organ

Bishop Auckland had two Methodist churches in close proximity near the town centre. The Primitive Methodist church was completed in 1905 and a 2-manual pipe organ was installed by Binns of Leeds. The Wesleyan church was completed in 1914 and a 3-manual pipe organ was installed by Vincent of Sunderland.

In 1982 the Vincent organ in the Wesleyan church was damaged beyond repair by a leaking roof, and John Hart, the organist, took the opportunity to replace it with a large electronic 4-manual Makin organ with a stop list copying that of nearby Durham Cathedral, although with a few extra reeds thrown in for good measure. See here for a stop list comparison of the Henry Willis / Harrison & Harrison organ at Durham Cathedral and the Bishop Auckland Makin.

In 1993 the Wesleyan and Primitive (now called the Central) churches in Bishop Auckland combined at the Central site and the Wesleyan building was sold (now the Four Clocks Community Hub). The Makin organ was moved to the Central church and became the regular service instrument, since the 1905 Binns organ while still playable was not in good condition and in need of attention after nearly 90 years' use. The Binns organ was in fact refurbished in 2014, which was just as well since the Makin blew up with a loud bang during a service in 2017 and was judged to be beyond economic repair.

The Makin Installation

While smaller electronic organs of the period could be entirely contained within the console, an organ of this size and complexity necessitated not only the loudspeakers but the power amplifiers and Rotofon unit to be installed outside the console, the rear of one even as big as this being completely filled with the sound generation circuit boards and the large low voltage power supply for the motorised draw stops. The early 1980s design predates the use of microprocessors.



Located near the console were the Rotofon unit, mounted in the Binns organ chamber directly behind the display pipes (this photo is from another organ), and the bass column, both described in the Makin history. Separately there was a large speaker cabinet high above the west galley which could be switched in or out from the console.

Mosfet Power Amplifiers



Makin used Mosfet based power amplifiers of their own design, assembled in either three (as in the photo) or five board units. Each unit was independently mains powered from a nearby wall socket and switched on and off via a relay board (top left) controlled from the console. A 20-way cable conveyed both multi-channel audio and relay control signals. Mosfet transistors became available in the early 1980s and proved popular in audio amplifier designs (see here and this electronics magazine article), not least because of their ruggedness in unforgiving environments. The circuit design uses a balanced power supply thus avoiding the need for a large electrolytic output capacitor.

Keyboards



The four manuals are well made wood cored keyboards, still in generally good condition apart from some lifting of the white key coverings, no longer ivory of course by the 1980s, perhaps due to damp over the years. Keyboard scanning is achieved using a pair of 0.35mm diameter silver plated spring wires for each note, electrically shorted by a silver plated wire on the note body when a key is depressed.



Digital conversion is done by reading the state of all 61 keys together and then clocking the data out serially using a number of CD4014 CMOS 8-stage static shift registers with synchronous parallel inputs in series, in effect forming a 61-bit shift register (see circuit).



All the contact silver plating is open to air and thoroughly blackened with tarnish after a third of a century, and the scanner boards will need removing from each keyboard, both to clean the delicate contact wires and give access to the key mounted contact wires.

There are about the same number of thumb pistons as the Durham Cathedral organ console, but laid out and annotated differently. The majority are double touch, additional pressure engaging a second contact; some of the contacts are intermittent.

Pedal Board

The pedal board is a standard 32 note radiating concave RCO specification. The contacts are open to air silver plated pins mounted on the pedals and sprung wires on the frame, and like the keyboards they were heavily tarnished. In addition each note uses a very thin braided copper wire to connect the moving pedal pin and handle the repeated pedal movement without snapping after a short while, and many of these were on the point of going open circuit after several decades - interestingly all in the bottom half of the pedal board, reflecting the concentration of pedal playing in this region.



Digital conversion is done in the same way as for the keyboards, reading the state of all 32 keys together and then clocking the data out serially (see circuit). The photo also shows an Arduino board mounted on the pedal board frame, handling the MIDI encoding and USB interfacing.



There are about the same number of toe pistons as the Durham Cathedral organ console, but again laid out and annotated differently. Some of them are double touch.

MIDI Conversion

Since keyboard and pedal data is available in serial form these could be entirely MIDI-fied with a single Arduino Uno processor board, there being ample digital I/O and sufficient processing power to scan the keys at an acceptably fast rate. However given the very low cost of these boards (under £10, $10) it is convenient to use separate Arduinos for each keyboard and the pedal board, keeping wiring runs to a minimum and allowing digital input and reserve processing capacity to handle contact debouncing and thumb/toe piston inputs.

Sample code for keyboards and pedal board is given below - this will be refined in due course. Contacts are scanned twice with a gap of several milliseconds and both sets of keystate data compared in order to achieve reliable debounce of contacts subject to silver tarnish over time.

Keyboard Code

Pedal board Code

The draw stops could be similarly digitally encoded using Arduino boards and the diode matrix scanning method more commonly used on keyboards - there are sufficient digital I/O pins on two Arduinos to scan all the draw stops. The analogue inputs on an Arduino could encode the four swell pedals. Note that excluding the ability to drive the motorised draw stops the entire console could be MIDI-fied and interfaced to a computer entirely powered by the computer USB ports, with no mains power required to the console itself.

That's the state of play as of 7 July 2019 - watch this space for further progress.