Digital potentiometer to replace analog

[ro-alijani]

I have a Logitech z506 speaker and I want to replace the volume with the digital potentiometer so that I can use an Arduino and tv remote to control it.
I have two problems:

1. the analog pot is a 6 pin and I assume that it is a dual-channel one. but the 3 top pins are connected together like the below pic. I want to know why?
2. I got 2 x9c104s digipot to replace the analog one. how can I wire them to the speaker board?
   
   
   
   this is the analog pot:
   https://images.app.goo.gl/BdWFMmRp4M5yg6pf6

[gilshultz]

Assumptions can get us into trouble. It could be that it is being used as a single pot with the other pins used for mechanical support and do nothing. It is also possible the wiper(s) interact with each other. What is the taper of the pot, is it log, audio, linear etc. A schematic would help resolve your question in short order. Will the Arduino add digital noise to the analog section, how will you shield the pot lines, both digital and analog.

[blh64]

I would guess that those 3 pins are all tied to the ground plane. Something a DMM could easily prove/disprove.

[ro-alijani]

Sorry, I have limited electronics knowledge and I was hoping someone could help me draw a schematic I could use. I don't know much about this analog pot. there is just B100k marking on the pot.

[ro-alijani]

I checked it with a DMM and those 3 pins are grounds.
now my question is that should I connect these grounds to the digi pot or a ground from the Arduino suffices?

[blh64]

There is only 1 ground plane and EVERYTHING needs to reference to it. You arduino, your sensors, your power supply, etc.