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Xaudia offer microphone re-ribboning and repair services.

2013/03/03

GEC Ribbon Microphone Evolution

Some time ago I posted about GEC models BCS 2370 and 2373, and how they were essentially the same design in different body shapes for different applications.

Left to right - unknown, unknown. GEC BCS2370 and 2373 mics. All have the same motor.

Since then I have come across some other ribbon microphones which may be earlier GEC models, prototypes. They are perhaps rather ugly in style, but I find their functional utilitarian style rather charming.


The two unbadged mics share some parts including a twinaxial connector at the base and rubber yoke mounts. The mic on the left is made of folded steel, whereas the one on the right is brass, with a more open grill.


All four mics are essentially the same design inside. The mic on the far left has a smaller transformer and different brand of magnet, but the pole pieces and ribbon assembly are the same. The mic in the middle of the photograph above is identical inside to the known GEC mics - with the same magnet and transformer and crumbling plastic ribbon mounts.


Remarkably, both of these mics are still working with a nice tone, although a little noisy. A good clean and service should sort that out.

The mics look very similar to the drawing in a patent by GEC and Thomas Julian, from 1947.

Drawing from a ribbon mic patent by GEC and Thomas Julian, 1947 

Which in turn is obviously inspired by the BBC-Marconi type AX ribbon mic...

Drawing from BBC-Marconi type AX ribbon mic manual.

As an aside, the GEC patent is slightly odd, in that the major innovation is that the pole pieces are held in place by the magnetic field alone, with no mechanical fasteners. That is to say the major innovation is something that they have left out, rather than something they have added to the system. The implication being that other manufacturers MUST use a screw, bolt or other fastener, or else risk infringing the patent.  It would have been interesting to see how that one would stand up in court!