Friday, August 04, 2006

Shure 55C Dynamic

Here is an imposing relic and historic mic - the Shure 55C - shown here in restored and rebuilt (as far as we could) condition after being rescued at a ham radio flea market, or "hamfest".

Here is a link to more about the 55C

The 55C is significantly bigger and fatter looking than the present 55S series mics still made by Shure. The 55C was taken apart and found to have lots of internal rubber isolation damping parts that had hardened over the years into a stone-like consistency. We cut new rubber parts by hand, and with some guesswork, because the old rubber crumbled when we took it out. This is an interesting dynamic mic with a large tympanic element attached to a wound voice coil inside a die-cast internal rectangular housing, and with a separate matching transformer mounted adjecent thereto.

I think it looks like a locomotive, or a Hudson Hornet, comin' at ya, and the overhead knuckle mount just adds to the aerodynamic, automotive motif. This, by the way, would not be considered an example of so called "Art Deco", but is I think more correctly categorizable as "Art Moderne" Raymond Loewy style. The mid century modern style, incorporating new materials, plastics and manufacturing methods, and various visual design elements such as those from Bauhaus, artists like Charles and Ray Eames, Saarinen, Loewy and others was and still is reflected in many consumer products.

Shure, Electrovoice and many other manufacturers incorporated dynamic and streamline visual cues such as broad horizontal ribs, inset contrasting colors, shown in this case with the red screen, and rounded off, blended angles which are very nicely represented in the robust knuckle design.

This is made of die cast parts. Die casting is a process in which a molten metal is forced under pressure into a mold. Die casting metals are often a mixture called pot metal, which is comprised of zinc, aluminum and lead. Often the zinc boils and produces zinc oxide, and leaves small holes, or voids. Die cast parts such as this microphone were then chrome plated. The plating often develops pits and flakes as a result of the voids, poor adhesion, and corrosion. Die casting is not used as much to produce decorative items or enclosures today, as plastic injection molding has now become more common, although plenty of die casting is still used where plating and finish are not of primary concern. Die casting has also improved tremendously in recent years. The Japanese bicycle parts manufacturer Shimano, produces high grade, beautifully finished die-cast parts, such as brake levers, that are as strong as single piece machined parts.



Lynn Fuston said...


How difficult is it to find the connector that's on that mic? I know it's not an XLR. Do you know of a good source for connectors for old mics?

Bob Crowley said...


That's an Amphenol MC3M and I think that they still can be ordered, maybe through Digikey or one of the many electronics parts houses.

If you google MC3M I think you will go right to several sources.

Anonymous said...

I have that mic, my parents found it in my Grandpa's basement. I got the cable replaced at Long and McQuade in Calgary for about $50. Most seasoned reparair-ers can do it.

jasztone said...

I am looking for a transformer for that 55c microphone. Can you tell me where I can get one ?


Bob Crowley said...

There are two different transformers for the mic. Hi Z and Lo Z.

You could likely use an SM57 or any other mic transformer in that application. If you don't need a lot of output, you could use no transformer and have a very Lo Z out, same as a loudspeaker.