C12 HA Console Speech Input Assembly
(Audio Mixing Panel)

Description: Built by Canadian Marconi under licence from Collins Radio.
Type: C-12 HA 78247A
Spec: 84070-A
End Use: Broadcasting industry.

Basic features: 7 separate amplifiers, 14 tubes and 16 transformers.
Inputs: Up to four microphones
            Up to two turntables
            Up to six incoming lines.
Outputs:   All module outputs used a 600 ohm termination.
Tube lineup: 7 x 6J7, 2 x 6C5, 2 x 2A3, 2 x 41, 1 x 5Z3

DImensions:   Width - 35 in.
                       Height - 11 in.
                       Depth:- 15.5 in.

Power input: 110 VAC 50/60 Hz  1.7 amps  100 watts
Circa: 1937

C12HA front panel.  The meter opening was widened by hand to reduce the effect of the front panel steel on the meter movement. This modification was likely done  by a previous owner.
Right side view. The Hammond transformer was not likely part of the original design. It was probably added boy one of the mixer's previous owners. 
Self test meter detail. 
Left side view. It is normally covered by a lid. 
Rear view.
Chassis top view
Chassis bottom view
THis view illustrates the outboard power supply used with the C12.
 Name plate.
Download any image to enlarge. All photos in this table by J  Douglas Hensley

/c12_technical_notes_s.jpg Technical specifications for the C12HA can be found in this brochure. Click on the image to launch the PDF file. (Courtesy Collins Radio) 
c12_13_sept1937_ad_s.jpg This marketing brochure from Collins Radio describes other variants in the Model 12 Speech Input family. Click on image to enlarge. (Courtesy Collins Radio) 


Here is the C12HA audio mixer in its native habitat. Taken in 1937, this was the control room for AM radio CKUA in Edmonton, Alberta. (Photo courtesy CKUA radio archives) 

A C-12 at KPQ in Washington state.  A young Mark Sorley is at the helm. (Photo courtesy of the  Jerry Lee Lewis photo archive section of the Library of American Broadcasters)
The NBC affiliate WMBG during their 1380 Show. (Photo courtesy of the  Jerry Lee Lewis photo archive section of the Library of American Broadcasters)


Contributors and Credits:

1) J Douglas Hensley, W5JV,   <doug.hensley(at)gmail.com>
2) http://www.ckua.com/about/history-2/

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Apr 28/16