Mic mods

My love for microphones started when I was doing my degree, and it was a little while after finishing it that I was able to work and afford to build up a collection.

At the time the compromise was to build or modify my own mics and it is still something I do now. About 50% of the mics I own are modified or home made, and the other 50% are yet to be modified.

So, this week I decided to work on two microphones to add to the collection. One I built from scratch, and the other (a mic I had already worked on), I modified.

The first was a  U87 clone, built using the casing and PCB from the Rode NT1-A mic. If I had thought ahead I would have done a before/after sound comparison but as they are fairly common place (I know a few people I can borrow from) I might do one soon.

Røde NT1-A
The mic even looks cheap on top of the Neumann U87 schematic!

The original capsule was swapped out for the RK-87 ‘dual-diaphragm’ capsule from Microphone Parts which costs about £70. The Røde I got second hand off eBay for about £50 and the switch was £1.50. This is the most money I have spent on modding a mic.

I don’t like the headbasket and I’m still looking for a decent one to fit to this but removing the inner mesh opened the sound, although serious pop filtering is required when close miking. Also good to keep it covered when not in use to keep excess dust from gathering on the diaphragm.

I had the mic in a cardioid pattern for months and with the help of a friend fitted a sub-minature switch this week, to add an omni pattern. Although definitely not a Neumann, this modification improved the sound of this mic a lot.

If you are into it, here is the frequency chart for the RK-87 capsule…

image courtesy of microphone-parts.com
image courtesy of microphone-parts.com

And for the Rode NT1-A…

image courtesy of recording hacks.com

And the finished mic!

Finished Røde NT1-A
…with lovely stickers made on a label maker (this is a temporary measure until I find something better)

Mini Mic

The second, was the Mini Mic; a small omni condensor made with an electret mic element, 100K resistor, a 1mF 50v capacitor and some heat shrink tubing, all lovingly stuffed inside a Neutrik XLR male connector.

I stumbled across this looking for omni capsules for my MXL 603’s and came across Henry Spragens site, www.audioimprov.com. The site is a great resource if you are interested in making and ‘modding’ your own mics (and I really love the Apple 2 music section). Full instructions on how to build the mic are here.

Due to it’s size this is a bit fiddly, so use a magnifying glass when soldering.
Hard to see, but I added some heat shrink to the soldered connections for extra strength.
Once the circuit was complete (and tested) I used some more heat shrink to keep it all together and tidy, and to make it easier to get into the XLR connector.
Voila! That went a lot smoother than I had anticipated…
I also used a bit of an old sock (a clean one!) to make a tiny windshield for the mic.

So, the end result is a phantom powered omni electret microphone small enough to fit in your pocket. It took me about 30 minutes to put this together on Saturday and the parts cost about £5 from ESR in Cullercoats.

When I tested them out last night at the studio we were all pretty surprised at the results, and I’m so impressed that I’m going to make another one this week.

Here are the WAV files of an acoustic guitar. Both mics were positioned 6″ from the guitar pointing at the 12th fret. They were recorded through a Soundcraft desk and a pre-Avid M-Audio fast track  into Reaper.