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.


craig said...

Why can't someone make an inexpensive USA made ribbon mic? All I see is the foreign made stuff.

Bob Crowley said...

Labor rates in China are about 10 cents an hour. There are no regulations concerning safety, and materials that are prohibited here, such as lead filled brass and exposed cadmium, are used to make those inexpensive mics. Some of the ones in the $150 range you see advertised actually cost about $40-50 at import.

Toothpaste, tires, toys and many other items sold in the US and made in less regulated countries are being examined more closely now, and you can do a google news search and come up with these stories easily.

So a long answer to your question: The imports are artificially low in price for the time being since there is a huge labor pool in some countries where the pay is almost nothing.

Even so, the better low cost units from China still have a price of over $500 if they can get it. Naked Eye is entirely made in the USA, here in Ashland MA, by us. At $745 it is the lowest cost US made ribbon mic. We will keep it low priced as long as we can because we seem to get a lot of repeat business from people who buy one mic, love it, then buy some more.

Hope that answers your question. Today I spent several hours personally going over a table full of Naked Eyes getting ready for a large shipment. Anything that was even remotely blemished was picked out and either fixed or replaced with a perfect one. Slight marks on the finish, a scratch etc. and I will reject a mic. Of course this is AFTER it has passed ALL of the sound tests which are very rigid and strict.

That's why.

craig said...

Guess I'll have to save up my $745.

craig said...

Have you ever experimented with old magnetron magnets for engines? Seems like the Coles are almost as big ! :)

Bob Crowley said...


I have one of those. At the time they were the strongest, but not any more.

Coles is an important early design, and was optimized for output and sound using the materials available at that time. The very thin ribbon material in the 4038 is indeed fragile, and it is a relatively wide ribbon to maintain the output. It is not a modern ribbon mic however so must be treated like an heirloom, but doing so will give a very nice result. I have a little trouble with the Coles, only because it perpetuates the ribbon stigma (fragility wise) which has prevented many from trying ribbon mics. I do hate to term it obsolete, more like a classic car or bike.