I want to say up front that the electronic schematic and parts lists (the important part) of these microphones are essentially a duplication of Scott Helmke's "Alice" microphone. I couldn't have done this without his generous website and willingness to answer email.
I've made a couple changes to the components but overall, the circuit is the same. Scott's schematic is in turn based on a Schoeps Circuit.
The finished product will be a pair of high quality cardioid microphones. They will require preamps capable of balanced input and 48 volts of phantom power. Phantom power less than then 41 volts will not work well. I have no problems with 43 volts. I mention this because some preamps which profess to have "phantom power", don't in fact have the industry standard 48volts (hint: M-Audio products that don't SPECIFICALLY say "48 volts phantom power", like the Audio Buddy) Note: actually it's lack of proper current more than voltage that causes this issue, but the bottom line is the same.
These microphones will be excellent for recording solo instruments, vocals, atmospheric sounds, etc. and compare favorably to microphones costing several hundred dollars. They have low self-noise and fairly high output. However, these microphones are not good for extremely high SPL (loud) sounds. Close mic'ing of drums, for instance, would be better served with something else. A 10 db (or whatever, really) pad could be incorporated into the schematic fairly easily but wasn't needed for my uses. This would allow higher SPL recording.
* I recently made a pair of omni microphones. They use the same circuit, minus a couple parts, but the body and capsules are different. I have found these Omnis to be even better for close mic'ing of the violin and ambient sounds. However, these cardioid microphones seems better for accoustic guitar and other situations. I think having a set of both is the ideal world.
Warnings:
The circuit is very simple, however, you need to have a modicum of electronics knowledge. You don't need to know why the stuff works, but you do need to know how to read a basic schematic. If you don't know, the internet is full of info. A few hours of crash coursing and you should be good to go. Also, you need to know how to use a soldering iron. This circuit, particularly the capsule/JFET/1G resistor area, is fairly delicate stuff, and since audio signals can get nasty very quickly, small, shiny, clean solder joints need to be a matter of course. If you're iffy on this, practice, practice, practice first.
The following parts breakdown is for two (2) microphones. My reasoning is that after you build the first one, you'll be so thrilled, you'll want to match it with a second for stereo. Also, since there are certain supplies where minimum orders are enough to build many microphones and since shipping costs won't change, it makes sense to spend the extra $23 odd dollars on the electronics to build at least two microphones from the start.
If you absolutely insist on building just one, divide all the electronic components by two. Please note also, as written in the 'preface', two microphones capture the sound of a violin more completely than one, even if you mix to mono.
ELECTRONICS
First - the parts that make this possible at all, the sound capsule.
Go to the electrets page, choose the TSB-165A.
Buy two of these at $7.50 per unit, for a total of $15.00 (plus another $3.00 roughly for USPS shipping)
Next, highlight and copy the list below.
At http://www.mouser.com go to > "Project Manager", > select "Import BOM" click "Start new Project. (You may have to register yourself first)
Then, copy and paste the below in. It will create an instant price list ready for checkout. Pretty cool, huh?
781-2N4338
2
610-2N5087 4
512-1N5242BTR
2
660-MF1/4DL6801F
2
660-MF1/4DC1003F
4
660-MF1/4DLT52R3300F 2
660-MF1/4DL2201F 4
588-MOX-750231007F 2
140-MLRL16V10
2
140-PM2A474K
4
140-mlrl16v100
2
502-B3M 2
I have separated the 502-B3M part from the rest because you may want to look around for something less expensive. It is a male XLR plug. At $8.78 per piece, there are cheaper alternatives such as buying a cable ends and modifying them. It's your choice and depending on what you use for a body, you may want something else anyway. Also, after experimenting with a couple different FETS, I just changed the 2n4416A to the 2n4338 listed above. Cost is a couple bucks more, but they are a bit quieter. Any mention you see to the 2n4416a should be the 2n4338.
The Mouser.com order total (as of May 2006) is $35.62 not including USPS shipping (which should be around $3.00-$4.00 in the U.S.)
note: occasionally, Mouser catalog numbers change. If you get any changes, the mouser order will generally help you find the right part and update the b.o.m. However, make sure the quantity of parts is also accurately updated. Always Double check the order before placing it.
At RADIO SHCK, buy 1 perfboard piece (3 odd dollars). This will be enough to build quite a few microphones - certainly more than two.
Your electronics total should be roughly $65.00
Continue to building the microphone body
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