Wednesday, June 27, 2007
RCA 77DX Late Foil Style
The so-called foil versions of the RCA 77DX ribbon microphone were fitted with a stuck-on, printed foil, circumferential emblem in a shallow recess on the acoustic labyrinth, while the older ring style mics had a heavy chrome plated brass ring fitted into a deeper recess.
Externally, that is the only major difference between the old style and new style 77DX mics.
But inside there are numerous differences that I have noted. The way the motor unit is welded, how the wires run to it and how they are held in place with a kind of connector vary greatly from old to new. Other changes through production appear in cast parts, switches, the screws that vary the shutter, and apparently the transformer and reactor, perhaps small differences there. And they sound different too, no matter what ribbon is in, original or not.
I have been listening to the 77DX in the cardioid setting with the shutter partly closed. It sounds blocky to me that way. I can't really say that it is bad, but it lacks the openness and spatial feel we are accustomed to in the figure 8 mode. Another mic that has a hypercardioid response is the Shure 330 ribbon mic, same as that used on Carson's desk for years. It uses a side port system that basically makes up for having the back blocked off, which works at the higher frequencies to create a good deal of rear rejection.
Posted by Bob Crowley at 12:05 PM