As i search the internet there are some items about the mod for the HM133 to upgrade the low tone in the audio.

There are many ways to do this mod. The first one i posted on the web is very tricky. If you heat it up to much your HM133 will fail.

Resent i discovered a new way to provide the mod on the HM133. This one is very easy to do.

Just take a 10uF tantaal and set this on mic and position 6 of the RJ45 pinout. Just check the diagram.

4513_HM_133_wire-3 IMG_1382 IMG_1384 IMG_1383

See the difference between Mod 1 and Mod 2. Mod 2 is very good to setup. Mod 1 is tricky enough.