Ribbon Mic Transformer Upgrade

Last year, I bought a pair of MXL R40 ribbon microphones for the studio. These mics aren't the most amazing mics ever, but they were cheep enough that I decided to get a couple to play around with. After experimenting with them for a while, I discovered that they actually worked quite well for some things. I really like them as drum room mics, and they blend well with other mics on guitar amps. But unfortunately, these mics have a pretty big limitation which is they have a pretty poor signal to noise ratio and their output is really, really low. This meant that if I tried to record anything quiet with these mics the result wasn't always very usable since the mics have a high self noise and then extra noise is introduced when adding a lot of gain on a preamp to compensate for the low output. 

A couple months ago I came across an article online about a simple modification for these mics. It said that by replacing the low quality, made in China, transformer, with a higher quality transformer that is made in the US, the mics would have less self noise, a higher output, and a better frequency response. Naturally, I was very interested, so I ordered two of the higher quality transformers.

I finally got the transformers last week and I got to work. It was a pretty easy process. I just had to open them up, unsolder the old transformer from the ribbon and the output, pull it out, and then solder the new one in.

Once I was done, they did indeed sound better than before. It seems like they capture more "airy" high frequencies and have a little less noise. So I'm really happy about that. Unfortunately, the overall output level did not increase as much as I would like. I think I got about additional 2-3 decibels of output, which is nice, but the article I read claimed that the output increased by about 5 decibels.

My original hope for this modification was that increased output would enable me to use them on really quiet sources (such as a few feet away from an acoustic guitar,) but they still have too low of an output to really make this practical since ribbon microphones in general have very low outputs and require a lot of gain from a preamp. I'm not too disappointed though, I will continue to use them in the same way as drum room mics and on guitar amps and the better frequency response will definitely be beneficial in those applications. And besides, I just got an amazing acoustic guitar tone during a session this week by using the Lewitt LCT 940 and Rode NTK in the way that I was hoping to use R40s.

Overall this was a fun project and it will make some tracks in my recordings sound a little better. I guess I'll still have to get an Audio Technica AT4081 for the studio someday :)

-Peter Duff

Head Engineer