Best Microphone Mods

It all started out as experiments with microphone parts, diy microphone kits and k47 capsules, and turned into the microphone mod service! Here are some of the best mics to modify from work I’ve done over the past year. Read on to see how we customize a microphone.

MXL 990 Mod

mxl 990 mod

MXL 990s are everywhere. Mechanically, it’s a well-built studio condenser microphone with some great weight to it. The internal frame is sturdy and nothing feels cheesy about it – except the sound. To hit this price point, MXL uses a small diameter capsule and a mass-produced circuit board.

I replace the circuit with my jaSb-990 board which is specifically designed for the MXL 990. It’s a Schoeps-derived circuit build with high grade components, hand-biased FET, hand-matched output driver transistors and optional internal pattern switch. The jaSb circuit has an extra-robust voltage regulator so it works perfectly on low phantom power voltages (as found in some low-end audio and video gear).

The capsule is normally replaced with a k47-style LDC although we could certainly do a CK12-style in these as well for a little bit brighter tone.

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Most customers have opted for the improved headbasket from mic-parts. It definitely gives the mic a more pro look and theoretically better sonic performance because of reduced interference, resonance and standing waves. The one downside of 990s for me, is that as far as I know, mic-parts is the only source on the planet for an improved 990 headbasket so that’s a bit of a supply chain risk.

The short video gives an idea of the improvement after the mod. The results are similar for most low cost Transformerless Mics after the rebuild.

MXL 910 Mod

ck12 mic capsule build

The MXL 910 is a popular tall cylindrical mic from MXL. It’s got a standard MXL internal frame which my jaSb-800 (Transformerless) or BFM-800 (Transformer-Coupled) boards fit. It’s another SDC that looks like an LDC. The headbasket is actually quite nice on these with a dual layer (dual gauge) mesh and lots of room for an LDC capsule. It is one of the few MXLs where they actually put a cardioid emblem on the headbasket itself. It has all the usual cut-corners from MXL to make the price point: mass-produced circuit board and small capsule. The body cylinder is on the light side (but not the lightest from MXL).

For a Transformerless rebuild, I replace the MXL board with the jaSb-800. For Transformer-Coupled Rebuilds, it gets a BFM-800 and a transformer mounting board. The capsule can be either a K47-style or CK12-style. In both cases, I replace the entire MXL pedestal/cradle system with my own pedestal which gets the Capsule nicely centered in the grill.

Overall, I like these a lot and I’ve done quite a few in all configurations

MXL v250 “stupid deal” Mic Mod

v25o mod

Every once in a while these show up as the stupid deal of the day on Musicians Friend – for $69 and free shipping. You can imagine the corners being cut to make that happen! The v250 is one of MXLs “BM800” footprint mics. It’s got the usual Small Capsule and very minimal mass-produced Schoeps style circuit. It’s quite awful frankly. But this has been one of my favorite rebuilds to do because the improvement is so huge!

I’ve done transformerless (TL) and transformer-coupled (TC) rebuilds of these using either the jaSb-800 or BFM-800 boards. The headbasket is pretty good on these. The body cylinder is very thin/light material so the mic will not have a real substantial weight to it.

Sterling Audio ST55 Mod

sterling st55 mic mod

Also sold as the Groove Tubes GT55, this transformer-coupled mic has a lot up its sleeve. The original capsule in the ST55 Sterling uses a “resonator disk” to increase the high frequency response of the mic. This seems to counteract the high end that is lost in the transformer and circuit they use. The result is a so-so tone that has lots of room for improvement. The extra tricks consist of separate hi-pass and pad switches. The internal footprint of the mic is unique so I designed a version of the BFM specifically for it: the BFM-T-55. This circuit supports the pad and filter switches and adds the internal pattern switch. So after the mod, it has even one more trick.

It was this mic that first got me into transformer coupled designs and the development of the BFM (Big F’n Microphone) boards. The BFM is derived from the Neumann KM48 circuit design but adapted for an LDC. KM stands for Klein Mikrofon (Small Microphone) hence my twist on the name. I’ve built four of these so far with both low-cost chinese transformers and CineMags. The CineMag 5722w is perfect for the BFM circuit because it is actually a recreation of the BV107 tranny that was in the KM84!

BM800 Cheap-o Amazon Mic Mod

bm800 mod

I include this one because like Rodney Dangerfield, this mic gets no respect. This particular one was a craigslist rescue. It was non-functional but I cared not about that. BM800s are all over amazon and other retail outlets for incredibly cheap prices. I’ve seen them as low as $15 including a cord and shockmount! BM800 isn’t so much a model as it is a standard. This is why the jaSb-800 board will fit in just about any common cylindrical mic.

This one got the usual treatment of jaSb-800 circuit with optional pattern switch and a k47-style capsule. When finished, this throw-away mic was transformed to perform equally with any other transformerless builds I do. The body is lightweight and a bit wimpy feeling, but the headbasket has a good size and mesh to it. I gave it a paint job and it’s now got a home with a happy customer. He even left a nice review saying “This mic has a wonderfully low noise floor and beautiful, soft detail on the high end.

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