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Tag: mic mod
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New Microphone Footprints Afoot
Since I’ve been building and rebuilding microphones, I’ve only imported one type of body – the so-called BM800 style body. These are what I’ve been using for the RS/ series mics like the RS/47, RS/12t and RS/47t.
I’ve been tempted to try some other shapes and sizes that I see on my various suppliers’ websites and I finally acquired a few samples of some new styles. New shapes mean new Circuit Boards and I’ve finished jaSb (just another Schoeps board) transformerless and BFM (Big F’n Microphone) transformer-coupled board designs for both new bodies.
The Tall Boy Telefunken-ish style
When I ordered this thing, the photo didn’t do justice to how huge it is! First impressions are that it’s a nice quality body with a heavy cylinder and a good quality headbasket. The Internal frame is much bigger than a BM-800 style and so the circuit board is nice and big. The jaSb and BFM boards were very easy to design for this mic given all the space. In both cases, all components can fit on one side and in the case of the BFM, there is actually room for the transformer right on the main board!
jaSb Tall-Boy board 
BFM Tall-Boy Board The TLM 102 Style
I was really excited to find a good source for these. I’ve always loved the look of the “little” Neumanns and I occasionally get asked about rebuilding a TLM mic (or a TLM clone). Until now, I had no circuitry that would fit. The samples arrived and I’m really happy with them. The cylinder is solid and heavy and the headbasket is beautiful.
In terms of size, this is the extreme opposite of the Tall Boy. These are tiny and the the circuit board layouts were very challenging – especially the transformerless jaSb version which has many more parts.
Unlike most of my other builds, these mics are not so straightforward to open. The headbasket is fastened to the body with three hex set-screws. For that reason and because of the limited size of the board, I’m not going to fit the optional internal pattern switch in theses. They will be full-time cardioid (or omni if you wanted). The board is round like an MXL 990 but only 47mm in diameter (with some notches cut out) compared to the 53mm diameter of the 990 board. Besides losing the pattern switch, I had to put some components on the bottom side for both boards.
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CineMag is In The House!
From the beginning of my transformer mic build experiments, I had wanted to use a transformer which was as close to the original BV-107 found in the Neumann KM84 as possible. That’s because my BFM (Big F’n Microphone) board is a modern recreation of the KM84 circuit but adapted to LDC capsules. CineMag makes a BV-107 recreation they call the 5722. It is a 6.9:1 turns ratio hum-bucking transformer which is ideal for the BFM circuit. I contacted them several times early on by email and really didn’t get very far (other than a price quote). They do not really have a web store per-se or a dealer network. Frustrated by that, I started using the low-cost imported Transformers and an expensive one by AMI.
A few weeks ago, I thought I’d go old school and actually call CineMag on the phone (I forgot my phone actually has that feature). David Geren himself answered the phone and took my order for a small batch. Wow!
The Shootout
I had previously done shootouts between the Imported Chinese Transformer and the AMI. I have two RS/47Ts – each with one of those installed. For the CineMag test, I reworked a Sterling ST55 rebuild I had. This one also had the Chinese transformer but I swapped that out for the CineMag. All mics now have the same capsule and circuitry. The only variation is the transformer.
Below is a result of some recordings made with both. In all cases the AMI is first then the CineMag (after a short pause). Shorter and shorter loops let you hear the tonal differences easier.
CineMag Transformers (L) ST55 Test Body (C) Shootout CineMag vs AMI (R) To my ears, the AMI is a bit more mid-forward as the kids like to say. The guitar seems to have a bit more presence with the AMI, but the CineMag has a little more silky of a top-end. It’s that top-end sheen that I felt was missing from the AMI in my previous tests. They both have a beautiful crunch on the hard strums of the guitar. This is why we love transformers!
That’s what it sounds like. What’s it look like?
I ran swept-sine tests on both mics to compare the distortion and frequency response characteristics of the Circuit/Transformer. The differences are subtle but meaningful. The CineMag has a bit more 2nd and 3rd harmonic distortion over most of the spectrum. The AMI has a bit more in the very low frequencies. Interestingly, the fundamental frequency response shows that the CineMag actually has a bit more low end and a subtle drop at the high end. This just goes to show that the distortion characteristics have more of an effect on what we perceive as bright or dark than does the frequency response – at least with transformers.
In-circuit tests of CineMag (L) and AMI (R) showing 2nd, 3rd, 4th Harmonic distortion Conclusions?
Overall, I think the CineMag is going to win the day. It is slightly less expensive than the AMI and I think more versatile. It pairs nicely with the k47 style capsules which have a relatively flat high end. The AMI would win if I wanted a very mid-forward mic with lots of harmonics in the low end. Maybe on kick drum or bass cabinets, upright bass, etc. This is all very subtle stuff and either would work well on just about anything. For that matter, the cheap Chinese transformers really don’t sound all that bad and I will still offer them in the shop.
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Latest Trash to Treasure
I’m always looking for MXL donor mics to upgrade. I saw this beauty on ebay a few weeks ago. Yikes!
Ran over with car? Dropped from 100 feet? Who knows Despite appearances, this mic is actually an ideal donor body for me. I normally replace the headbasket anyway and that was where the primary damage was (I also keep a stock of a few clean 990 headbaskets). The main part I care about is the bottom cylinder and internal frame. These parts in the 990 are built like a tank so even this owner would be hard pressed to ruin those bits. The few minor scratches on the body will be sanded and painted over anyway.
Totally New Inside and Out
As usual, the MXL board and small capsule are removed and replaced with my jaSb900 board and K47 style “Brass Ring” capsule. I already had one in stock with the optional pattern switch so I added one to this mic too – and give it the new pretty blue color.
The Paint Shop 
New Capsule and Circuit 
New Headbasket 
Finished Mic along side the old circuit, capsule and trashed headbasket And now there are two
This new 990 joins one that I already had in stock. Same color, headbasket and capsule; and both have the optional pattern switch. They are tested, burned in, ready to ship and sound amazing!
It’s Twins!
