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One of the most famous, legendary and musically inspiring was the TG 12345 series EMI recording\mixing desk. The technical design was carried out by the EMI Studios technical department for studio's equipment development. 

The EMI TG12345 Mixing console was produced by EMI Research Laboratories, Hayes, to a design brief submitted by the engineers at Abbey Road Studios. The requirement was for a Transistorized ("Solid State") 24 channel, 8-track mixing console to replace the 10input/4-track valve (tube) mixers which had been in use at the studios since the early1960's.

Part of the original design brief was for the desk to be "transportable," (as opposed to portable), so that it could be used for location recording, and also the ability to make a simultaneous stereo recording at the same time as a multi-track session.

A specification for the console was drafted in December 1967, and a prototype was delivered to Abbey Road in the fall of 1968 and installed in Studio 2 in December.

Since at this time EMI manufactured it's own recording equipment, there would be a limited production of these consoles to equip it's various studios in Europe, Africa, South America and the Far East.
The construction featured all discrete components and a novel motherboard/daughterboard interconnection between the circuit sub- assemblies.

Technical features of the TG 12345 Recording\Mixing Console


The TG consoles featured the following technical innovations:

1. A Limiter/Compressor on every microphone channel (A first on a large console)

2. All inputs and outputs were balanced using transformers.

3. Almost every rotary control is a stud switch, with precise calibration for repeatability and matching.

4. Each modular section ("Cassette") was dual channel, containing identical left and right signal paths. These could be used as a stereo pair, or two independent mono channels.

5. Each Cassette contained its own local DC power supply, with its own rectification, regulation and decoupling.

 The mixer "Power Unit" was simply a constant voltage transformer, which supplied 50 volts ac to a wiring loom, which fed all the power supplies on the individual cassettes. Keeping the power regulation within the channel meant that much smaller local decoupling capacitors could be used rather than the massive decoupling necessary on a remote DC power supply.


EVOLUTION of the EMI TG 12345 recording\mixing console


The TG series of mixing consoles evolved through several different versions.

Mk I

This was the original spec. version as supplied to Abbey Road. It was only produced as a 24 mic. 8 track + Aux stereo* configuration. Basic EQ. (Bass & Treble on Mic channels, with Presence Controls on the Main and Sub-Groups). It also featured a stereo "spreader" (width control) which could be switched in on the Mic. channels. Finished with light grey front panels, with a blue hammer finish main frame.

*Aux Stereo was a feature of the earlier desks. Intended for use in a "live" situation, it was simply a method of deriving a simultaneous stereo mix from a multi-track recording. There were individual level and pan controls on the eight main output buses and by using these a separate stereo sub-mix could be created. This is why the MkII consoles pictured have ten group faders and meters, the extra pair being the masters for the Aux. Stereo bus. Aux Stereo was not extensively used, and was a feature that was deleted on the later MkIII and Mk4 consoles.


This was still produced in a 24/8 + Aux stereo format, but with modified EQ, and various minor refinements, such as multi-track announce, instead of the individual track buttons of the Mk I.

The simple "shelving" HF equaliser on the Mic. channels was thought to be too basic in operation, and the Abbey Road engineers requested a presence control, as fitted to the Main and Group channels, be fitted to the Mic. channels. The Limiter-Compressor was improved and the spreader control deleted.

Abbey Road also requested a colour change, to dark grey, for the front panels, and the dark grey hammer finish console frame was dressed up with wooden end cheeks.
The two front panel colours were offered as an option, with the result that some overseas versions were supplied with light grey front panels and others dark grey.


The console was further developed by EMI Research Laboratories into the Mk 3 version. This final production version of the TG console was supplied to overseas studios, but never used at Abbey Road.

The basic version of the Mk 3 was a 24 input, 16 track version of the desk, although the frame was produced in various sizes up to 32 input, 16 track. In order to minimise the frame size, the track monitor ("TMC") and Group cassettes were eliminated, although the Group cassettes could still be fitted as an option. The monitor controls (pan, level & echo send) were moved to the area of the main cassettes previously occupied by the Aux Stereo controls. Minor changes to the Cue/Foldback controls.

A dedicated "Echo" cassette was introduced, each of which contained the master level controls and Eq. for two sends, plus a pair of echo returns.

Mark IV / "Mark Q"

Only two Mk 4 consoles were produced, both of which were custom built for Abbey Road (originally in Studios 2 & 3, later the desk from 3 was transferred to Studio 1).

Initially they were built with a combination of Mk II and Mk III cassettes, but they were later upgraded to what was unofficially called the Mark Q.
The Mark Q designation came from the provision to monitor "Quadraphonic" 4- channel surround sound, with the addition of front/back pan controls on the track monitor cassettes, and the incorporation of encoder/decoder switching on the Control Room Monitor cassette, allowing the effects of the "SQ" processing system to be monitored.

The Main and Group channels were eliminated completely and Mic. cassettes from the Mk III were used throughout the desk, supplemented by custom made "auxiliary" Mic. and Main cassettes. The Mk3 Echo Cassettes were also incorporated. The frame also housed a simple 16 channel "sync mixer" to mix the sync replay signals from the tape machine and feed them to the cue (fold back) circuits. Although the basic configuration was 24/16 the possibility of using Mics on the main channel inputs meant it was theoretically possible to have up to 40 mics with 16 group outputs. The flexibility of the configuration also meant that some mic. channels could be used as monitors for tape returns allowing for 24 track operation, and still have up to 32 microphone inputs available. It was this flexibility which allowed the desk to be used well into the 24 track era before it was finally replaced in Abbey Road studio 2, by an SSL 4000E series console in 1983.

The Mark 4 mixer was housed in a substantial wooden console which had a semi-wrap around layout, with the outer wings of the frame angled back towards the operator for easier access. The whole console was a much sturdier construction than the previous versions, and was much better suited to a fixed studio environment.

There was another official Mark "Q" version produced for the Pathe-Marconi studios in Paris. This console had full Left-Right & Front-Back pan controls fitted to every channel.
Housed in a frame based on the TG post-production console, the "quad"modifications meant that Limiter/Compressors were not fitted due to lack of space. This console is now owned by "Vega" studios, in Southern France.

The earlier Mk I and Mk II desks were modified by Abbey Road technical staff to become used mainly as mobile desks at Abbey Road, although one was used in a dedicated remix room, and was later modified for 4 channel "Quadraphonic" mixing.

Despite having been designed from the outset for "transportable" operation, their aluminum frames were inadequate to withstand continual mobile use. As a result the Abbey Road engineers modified the construction of the consoles. The cable forms were split and fitted with mating connectors, whilst the frames were rebuilt in sections constructed of welded tubular steel. The frames were fitted with lockable castors, which made transporting them much easier. Once on location the sections of the frame could be wheeled together and secured, then the cable forms would be plugged together and the desk would be ready for use.

These modified frames were built in various configurations to suit different recording requirements.

There was even a 16 track version built from two 8 track Mk II desks, with full Four Channel ("Quadraphonic") surround monitoring.

The following Studios currently operate or own TG consoles:

2 KHz Studios, London.
Abbey Road Studios, London.
AR Studios, Rio de Janiero, Brazil.
Vega Studios, France.



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