Microphone Mods

Microphone Mods, Upgrades & Rebuilds

I do full rebuilds of low cost LDC and SDC mics from MXL and others. LDCs can be Transformerless (TL) or Transformer Coupled (TC). SDCs are TC only. For TC’s, you can choose from several high quality transformers. You can also choose type of capsule for most mics. The TL circuit is a Schoeps style circuit. The TC circuit is a KM-84 style circuit. Both are assembled with care using high quality discrete components and point-to-point capsule wiring. I also maintain a rotating stock of pre-modded mics which are ready to finish to order and ship.

These are not “diy microphone kits”. We do all the builds, testing and verification in-house with our own components and designs. What we ship to you is always a finished, working and awesome microphone.

Upgrade Your Locker!

LDC Flavor Guide

There are no hard rules to this, but below is a general guide to choosing a flavor based on the intended use. The table headings are indicating Transformerless (TL) and Transformer-Coupled (TC) for both K47 and CK12 style capsules. Generally, the K47 builds are more versatile but the CK12 capsules can really shine in some specific applications. The TL builds are more pristine but the TC builds have more harmonic color. Most microphones can be rebuilt in any of the configurations below (with a few exceptions). Please contact us for more specific details.

SourceK47 TLK47 TCCK12 TLCK12 TC
Male Vocal♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥
Female Vocal♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥
Elec Guit Cab♥♥♥♥♥♥♥♥♥
Elec Bass Cab♥♥♥♥♥♥♥♥♥
Acoustic String Instr♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥
Drums / Lo Freq Percussion♥♥♥♥♥♥♥♥♥♥♥♥♥♥
Hi Freq Percussion♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥

Mass Produced vs Not

It’s amazing to think that MXL can build something like a 990 and give it a street price of under 100 bucks. While they do a pretty good job with the mechanical design, they must cut every corner on the electronics and capsule to make that price. For high-volume manufacturers like MXL, this means mass-produced surface-mount Tech (SMT) circuit boards. Most MXL boards are based on the Schoeps design (as is my jaSb board). Our boards are hand-assembled with very high quality discrete thru-hole components including low noise resistors and film capacitors in the audio path. We hand-match the output transistors on each board. We also hand pick and bias the FET on each board. This attention to detail is lost in mass-production mics.

mxl990 circuit
MXL990 Board (L) and our jaSb 990 (R)

LDC Capsule Flavors

mic mod capsules

Our standard configuration is to use a K47-style Center-Terminated LDC Capsule. The k47 design yields a wide, flat frequency response with full low-end, harmonically rich mids and a smooth, non-harsh top end. The K47 paired with our Transformerless jaSb circuit, is extremely versatile. That is the configuration used in every mic on the Mictastrophe video.

Optionally, we can use a CK12-style Edge-Terminated capsule. The CK12s have a little less of that mid-forward energy of the K47 but more of an extended silky top end. They are generally brighter sounding and they pair nicely with our Transformer Coupled circuits. They will put a nice top end sheen on background vocals, or stringed acoustic instruments or percussion.

LDC Circuit Flavors

All of our circuits use a directly coupled FET at the capsule input. But we offer two distinct flavors of circuitry: Tranformerless and Transformer-Coupled. What’s the difference?

Transformerless (TL)

Our all-discrete jaSb (just another Schoeps board) board is a “Schoeps Style” circuit built with high quality, low noise components. This circuit is based on the Schoeps CM-5 which is a elegant microphone amplifier circuit and is the basis for most transformer coupled mics built today. The slightly self-deprecating “just another” in the acronym is because this is a very common approach for transistor coupled mics. Our board uses low noise Vishay/Dale resistors and WIMA capacitors in the audio path. It also has an improved voltage regulator which lets these mics work perfectly on low phantom power voltages (like some Behringer products or video equipment will provide).

Transformer-Coupled (TC)

Our BFM Transformer coupled circuit is based on the Neumann KM84 mic circuit adapted to an LDC. This elegant design yields an incredibly pristine tone with some transformer mojo and very low noise. Neumann’s KM prefix stood for Klein Mikrofone – small microphone – like the KM84 and KM184, etc. Being adapted to a large capsule, we gave our circuit the BFM (Big F’n Microphone) prefix.

The BFM is made in multiple footprints to fit many different mics – including MXL 990s.

We have BFM versions for the Sterling Audio ST55 and MXL 992 which support the Pad and HP Filter switches on those mics. The BFM boards support an optional internal pattern switch. The BFM can be used to rebuild an existing Transformer-Coupled mic (such as MXL2001) or we can transformerize a TL mic!

Transformer Choices

  • 3U Audio GZT-84 7:1. The 3U is a slightly lower cost transformer that has a tiny bit less low end than the other options (we’re talking -0.5dB at 50Hz). It has plenty of transformer mojo with low frequency harmonic distortion and sounds wonderful on vocals, acoustic instruments. Overall, it will sound just a bit brighter than the other options)
  • CineMag 5722w 6.9:1. This is a very high quality transformer yet still moderately priced. It is CineMag’s recreation of the BV107 that was in the KM84 which our circuit is based on. It has better harmonic distortion characteristics and a bit more of that transformer sound than the Chinese one. Overall, this is probably the one to go with for most applications.
  • AMI Tab-Funkenwerk 6.5:1 T12 style. This is the highest price option and is very high quality. It has very full lows and low-mids with lots of great harmonic distortion. It is the definition of fat! It’s an excellent choice for low frequency applications like Kick Drum or Bass Cabs. It’s not dull by any means, but because it is so fat and full in the lows, it can make the overall tone of the mic heavy and slightly less bright. The AMI is also a great choice for CK12 capsule build because the brighter capsule compliments this full bottom end beautifully