100V PA system - volume controled by Arduino

Hello,
i have working 100v installation for audio public address system, which have 4 branches, each one has 1x 25W speaker. Now i need make wireless volume control for each one branch, because speakers are on hard to reach places and i cant install more wires. I have experience with arduino and NRF24L1 and i am planning to try ESP8266. How is my options? Is there something like arduino controled voltage divider? Thank you for replies and sorry for my broken english.

It depends what the system voltages for the preamp or power amp input - a digital potentiometer
can only work for voltages within its power supply range.

Details of your public address system are needed...

You would normally use a 100volt rotary switch volume control per branch (near the amplifier).
Those volume controls work by selecting a secondary tap of an audio transformer.
Switching could be done with a relay module
Leo..

MarkT:
It depends what the system voltages for the preamp or power amp input - a digital potentiometer
can only work for voltages within its power supply range.

Thank you for reply.
I dont need modify my amp, i need add volume control to each one branch, like Wava wrote below.

Wawa:
You would normally use a 100volt rotary switch volume control per branch (near the amplifier).

Yes, you mean this?

But question is, how i can achieve this function with wirelessly controlled Arduino? Thanks!

Yes, a transformer based switch.
Read the datasheet. Power is important.
You said 25watt per branch.
Leo..

If you only have the full power 100V signal to play with there is no easier way. Normally you'd look to
control the signal before the power amplifier in an audio system, but it seems you have a single power
amp.

Four branches on a 100watt amp could be four 25watt volume switches.
It all depends on the layout of the venue.
A main/mixing 100volt amp and several slave amps could be cheaper than volume switches.
Leo..