Ribbon mic tone

Dan,

Any microphone works as a system with all parameters closely related to each other. Like for any designer for me the most important part is to get all the right parameters to work together, first. Any system is only as good as its weakest link, so I’d say, all of those components are equally important.

Let's look at the 4038, you mentioned--it has short ribbon (1"), which is much more prone to resonances. To compensate, they used a thin ribbon (the thinner the ribbon, the less resonances). But, thinner ribbon has higher DCR (0.25Ω), so to get a standard output impedance they needed to use the transformer with lower ratio. At the same time, higher DCR also means higher noise, so the transformer has to be very efficient (toroidal type), with minimum copper resistance.

The 4038 perforated body serves as a resonator system to extend the high frequency content. Together with ribbon screens (to reduce afore-mentioned ribbon resonances) it damps the low end response quite a bit, so they use a trick—another set of screens to bring it back.

Overall, it is a very clever and thought through design, where every component is carefully matched to work together…

>And similarly, a vintage RCA ribbon transformer compared to a modern high end transformer

While there were some excellent vintage condenser (and audio) transformers, in general vintage ribbon transformers were not as good and efficient. Many of them used low Ni (some even steel) cores and not much attention was put into their construction. Also, many cores were way too big, which is not the best for such a low signal application (there is saying: “you need to wake up the core”).

As such, many of the ribbon transformers were inefficient, had very high copper resistance (equivalent to higher noise), and sonically… less than stellar.

With modern materials and use of toroidal cores it is possible to make by far more efficient, low noise/low losses/low distortions transformer. Many even better vintage ribbons could probably benefit from transformer upgrade, but on the other hand, lots of folks actually, prefer those “imperfections” of the vintage microphones for some special sonic effect…

Best, M