MXL 920 Rebuild – An Oddball Becomes My Favorite Donor Body

As I’m always searching around for microphone donor bodies on ebay and Reverb, I see the same usual suspects from MXL and a few others. My jaSb (just another Schopes board) circuit is fabricated in two footprints that can pretty much fit in a wide variety of mics. Until now, the jaSb-990 version was strictly for an MXL-990 while my jaSb-800 version was for everything else.

A few weeks ago an MXL-920 came up in a search. I had never heard of this before but it looked pretty cool. This is what recording hacks has to say about it. It’s got a big fat body similar to a 990 but is about the same height as the more standard shape seen in the 910, 440, 550, etc. It has a great looking headbasket (that even has a Cardioid Emblem on it!). It has this gigantic square circuit board in it which is a form factor that my boards will not fit in. I figured I’d buy it and see what I could cobble together. I offered $30 and my offer was accepted!

A More Serious MXL Mic

What stands out about this mic compared to anything else from MXL I’ve rebuilt (besides how nice it looks), is that it really is an LDC. It features a 32mm K67-style single sided capsule. Unfortunately, it is coupled with a standard edition Schoeps style circuit which will not compensate for the HF boost these capsules have. So I expected it to sound bright and sibilant and I was not disappointed. That said, this LDC really does not sound bad. On acoustic guitar, it brought a nice bit of free top end and didn’t have any weird peaks or notches like the MXL small capsules have. So would my rebuild actually improve this mic? Let’s try and find out. The plan is to use a k47 style capsule and my jaSb board (assuming I can figure out how to mount it).

The Sibilant Theory

Since my theory is that I should be able to really improve the sibilance of this mic, I had my lovely assistant, Linda, do an up-close test with the 920 and what is essentially the future version of itself – one of my RS/47s. I had her read the following: SibilanCe is SometimeS an iSSue with condenSer micS. ESpeCially when the capSule is cloSe to the SourCe. It was pretty clear in this shootout recording that the 920 was way more sibilant. It was even easy to see on the spectrum display in Ozone. I used Identical CAPI vp312 preamps for the test.

Comparing Sibilance of the stock 920 with its “future self” – one of my RS/47s

Off to the Bench

Out with the old board

The first thing to do was get that gigantic board out of there and figure out how to mount one of my boards in its place. I was considering 3-d printing an adapter of some kind to mount my board vertically like the original. I also considered mounting my board to their board and using the mxl board as just a bracket.

Kinda Silly, but I considered using the MXL board as a “bracket”

But then it dawned on me that this mic is the the same diameter as a 990 so my 990 footprint board might just fit the same way it fits in a 990. And it does… sort of.

A Grinding Wheel Solution

Not only does my 990 footprint board fit within the diameter, the two mounting holes line up exactly with the existing screw holes for the headbasket. The only problem is that the side rails will need a little modification at the top end with ye olde grinding wheel.

The rest of the build was fairly straightforward. I put my standard 3d-printed capsule saddle on the MXL pedestal and mounted a jaSb-990 board with optional internal pattern switch and a Brass Ring k47 style capsule. The existing XLR wires were a little too short so I had to pop out the connector and replace them. I had it together, powered up and run through the initial electrical tests in no time.

A New Favorite

This mic came out great. It looks so cool that my brain thinks it sounds even better. I went with the Vintage Green paint on the cylinder. I will do some testing and recording with it, but I will have it available in the shop soon too. I’ve since been on the lookout for more of these but they seem pretty rare. Although I got this one very cheap, I would probably be willing to spend a little more on them because – well I like it. And the other reason is that it comes with a k67 capsule I can sell on ebay.

A little initial testing

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