From the links and your description, I assume that you have an Amatuerradiokits case with the audio amplifier. If that is correct, then the data that I have shows a TA4225 (not a TA4425) audio amp IC as the audio amp. That is a 5 terminal device, not 3. That board is very cramped, so it could be that the silk screening is really pointing out the TA4225 5 pin socket and not the 3 holes that are close by.
Attached are the 2 pdf files that I have for the audio amp.
My guess is that the 3 hole location is for the onboard "volume" control that is really a maximum volume control as the front panel volume control is used to adjust the volume in operation. You should have a blue 3 terminal variable resistor that goes into that location.
Please verify the above before you start any modifications or soldering. If you need more help, I would suggest that you post a picture of the board and the location so that we can better help you.