Nice, simple, very quiet circuit by Roger Shores, employing an OPA 1641 instead of a JFET. Therefore - low self noise & no fuss with JFET biasing.

This board is designed to fit into Takstar CM-60 body and be used with an electret 22 mm capsule from Aliexpress.

It will not work with the original capsule!

As electret capsules have better moisture resistance than externally polarised (or biased) capsules, you'll get a quiet, mosture resistant mic, perfect for field recording.

While microphones with externally polarised capsules usually die after 10-20 mins in humid environment, my electret mics happily record during a rain (not direct exposure though!).

After the PCB is populated it needs to be meticulously cleaned from flux and the high impedance area needs to be covered in conformal coating, insulating lacquer or, at the very least - clear nail polish.

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TECHNICAL NOTES:

• When ordering the PCB choose thickness of 1 mm or, at most 1,2 mm. Otherwise it will not fit between tne XLR connector pins.
• Due to height constraints the capacitors C1, C2, C3, C4 (47uF) are SMD. They need to be slightly modified: the legs need to be straightened (unbent to vertical) and the plastic base removed.
• In two instances (C7, C8 and R1) I provided footprints for alternate use of THT or SMD components, BOM provides for THT components only.
• I also used the nose cone and the XLR connector taken from the original CM-60's board. One may use 3D printed cone (for example see: Jan Postma's project) or comercially available connector should one find it difficult to dismantle these or want to keep the original PCBA intact.

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Roger's page:

https://www.opic.jp137.com/index-fet.html

The capsule:

https://pl.aliexpress.com/item/1005009197656792.html

Note: Due to shifts and changes on Aliexpress this llink may become obsolete at one time or other. There are other vendors as well.

In spite of a low price this capsule is decent and good sounding.