A. Can I connect to it a three pedal unit instead of three separate pedals?
B. Does it work only with a computer operating system? What if I want to work with hardware sound module(directly, without a computer)?

Does your three pedal unit just have one output jack? What kind of output jack does it have?

I think that the MIDI Expressions Io  will do the job of not needing the computer. You can research it more.

I have the MIDI Solutions F1, and I use it for gigging, but with just one pedal. The company is good about answering questions.

That won't work. You would need to buy the MIDI Solutions F8 that can handle up to eight pedals.

Better solution:

MIDI Expressions Quattro or Io

http://www.audiofront.net/MIDIExpression.php

Good luck. Larry

A. Can I connect to it a three pedal unit instead of three separate pedals?
B. Does it work only with a computer operating system? What if I want to work with hardware sound module(directly, without a computer)?

Better solution:

MIDI Expressions Quattro or Io

http://www.audiofront.net/MIDIExpression.php

Good luck. Larry

So far I found this:
http://www.sweetwater.com/store/detail/MIDIPC

In the manual it's written "up to three optional additional MIDI channels"
http://www.midisolutions.com/MIDI%20Sol...roller.pdf
Does it mean it should work well with a three pedal unit?
If not, do you know another solution?