This little PCB contains an RF Interference filter that has been optimised to suppress cell phone interference in condenser microphones. It will easily slip into almost any SDC or LDC microphone, even into models that have narrowed-down tail sections, such as the Alctron T-02A. This filter will often prove more effective than filters that consist of 10 or 22nF capacitors mounted on the microphone PCB. These may prove effective against lower-frequency interference, but not against cell phone frequencies of 700 MHz or up. If the PCB contains these capacitors, it is recommended to remove them when installing this PCBA. When they are removed, it will also help to reduce THD and IM distortion in the upper octaves.

I have attached a document describing various XLR insert models that are available on the market. Be sure to select the right model before soldering to the PCB! Unfortunately, the best model from RF suppression point of view is also the one that is only available from Alibaba with a minimum order quantity of 100 pieces.

Depending on the XLR insert that you use, you may have to solder a ground wire between the ground tab of the XLR insert and XLR pin 1. This is not shown in the components assembly drawing and the 3D PDF. The XLR inserts from the Alibaba link and the ones with the wing tab already have such a connection.