Analogue Control in this context refers to a method of controlling dimmers from a lighting desk via a simple varying control voltage.

The most common version utilises a 0 to 10V signal. The control desk has a separate output line (ie 1 wire!) for every dimmer channel. A signal of 0V represents "off" and +10V represents "full on", with intermediate values representing corresponding outputs.

These control signals are then presented to the dimmer packs which vary the output to the lanterns in a corresponding way.

This is a very simple system, both logically and electrically. One disadvantage is that a large number of connections would be required between the board and dimmers - eg a 72 channel unit would have 72 control lines, plus ground etc.

These would often be grouped in banks of 6 channels, with an 8-pin connector - often a DIN Connector or Bleecon - used to link between the desk and dimmer. The additional 2 lines are used to provide a signal reference ground, and sometimes a desk power supply. Socapex connectors (37 pin variant) are also used to bundle more control channels into one connector.

While 0 to +10V control was the most common format, many Strand Lighting units use 0 to -10V, and some proprietory systems used other voltages. Some older systems use current control (as opposed to voltage control).

While analogue control surfaces have largely been superceded by DMX devices, there are many analogue dimmers still in service. These would typically use a Demux (demultiplexer) to decode from DMX to analogue control voltages.

Historical Survey of Analogue Control Connectors

Small channel counts (up to 6 channels)

The need for connectors began with the introduction of the Strand Mini 2, which was probably the first portable dimmer unit. Strand used the 8 pin Octal Connector, which, in chassis socket version, was a common valve and relay base. This connector was also available as in chassis plug and cable-mounted plug and socket versions. It is also likely that no other reasonably-priced and readily-available 8 way connectors were available at that time. The Mini 2 system had the analogue outputs from the desk on short flying leads fitted with Octal plugs, and the dimmer packs were fitted with a chassis mounted Octal socket. Hence plug to socket Octal cables could be used to extend the desk-dimmer connection, with the benefit that multiple cables could be daisy-chained if needed.

Some Eltec equipment has also been observed using the Octal connector.

The 8 pin Bleecon connector was used by Strand on the Tempus range of control desks and dimmers, which replaced the Mini 2. Strand continued their convention of the desk outputs being on short flying leads with plugs, and hence plug to socket 8 pin Bleecon cables are used for Tempus control connectors. Green Ginger also used the Bleecon on their range of equipment. However both 6 pin and 8 pin versions were employed, the former for four-channel desks and dimmers. Green Ginger did not use flying leads for their desk outputs and their desks typically have chassis mounted Bleecon sockets. Hence a plug to plug cable is used for desk-dimmer connection, but a plug to socket cable is needed to extend an existing connection - a more complicated arrangement than that adopted by Strand. It is not known which of Strand or Green Ginger was first to make use of the Bleecon.

Pulsar probably pioneered the use of the ring-locking DIN connector. Initally, 5 pin connectors were used for three channels of control plus ground and desk supply. Then 8 pin connectors were added for the more usual six channels of control. As a 5 pin plug can be inserted into an 8 pin socket, Pulsar adopted a wiring scheme giving compatibility between their 5 pin and 8 pin connectors, but this was incompatible with the scheme used by other manufacturers.

Zero 88 initially chose to use 7 pin XLR connectors for their equipment. The pins were used for the six control channels and desk supply, with the shell of the connector as ground. This ground connection was often found to be unreliable and some users added a loose 4mm plug for the ground. Desk outputs were on XLR chassis sockets and dimmer control inputs on XLR chassis plugs. The XLR system had the advantage that all cables were plug to socket and could therefore be daisy-chained. However, in addition to the earth's unreliability, the 7 pin XLRs were also expensive and difficult to obtain, so in the 1980s Zero 88 changed to using the 8 pin ring-locking DIN connectors.

MJL Lighting used a non-standard screw locking 8 pin connector (the same style as used for microphones on CB radios) on their equipment.

Strand continued to use Bleecons on the first generation of their Act range of dimmers, which replaced Tempus. However, by this time the Bleecon was also expensive and difficult to obtain and later generations of Strand equipment adopted the 8 pin ring-locking DIN connector.

Large channel counts

As systems grew larger, there was a need for an analogue control connector capable of handling more than six channels.

Avolites and Celco began to use the 37 pin Socapex connector to carry 30 channels of control plus ground. Early Celco desks were 30, 60, or 90 channels. Avo dimmer racks of this period were 30 or 60 channels and contained 10 channel dimmer modules. This fitted neatly into three-phase electrical supplies - for example, a 30 channel dimmer contained three 10 channel modules, each fed from a single phase. Zero 88 also used the 37 pin socapex, although most commonly just to carry 24 channels of control.

Green Ginger had initially based their equipment around multiples of four channels. A popular larger Green Ginger desk was the Discoset 20, which is believed to have been a 20 channel three preset desk with chaser. The author has a faint memory of a 20 channel multicore connector of circular military style being used with this desk, which also had five 6 pin connectors each carrying four channels.

Pulsar had based their equipment around multiples of three and six channels, and used a 23 pin circular plastic connector made by BICC to carry 18 channels of control, three separate desk supplies, plus two grounds. This connector is found on their 18 channel rock desks as well as their 12 and 18 channel two preset desks of the time.

A 25 way D connector was used by Zero 88 and Strand to carry 24 channels of control plus ground. Strand only used the connector on Demultiplexers as they had pioneered Multiplexed Control technology and this was used on all their larger lighting desks.

Current Situation

The 8 pin ring locking DIN connector is the current industry standard for analogue control. The 25 way D connector continues to be used on some demultiplexers. All other connectors are effectively obsolete but still found in theatres and hire company inventories.

See Also

• Dimmer Laws
• Topic on DIY voltage inverters to use +ve demuxes with -ve dimmers (and possibly vice versa).