Here are the questions:
- What is the reason that you want to regulate via voltage? 3-pin fan? Just curious XD
- At the aquabus or at a fan output? Jumper set correctly?
>> If on the aquabus, I would change it. If necessary, connect it to the motherboard if you can regulate the voltage there.
- Is a fan plugged into the RPM slot?
- Is the speed just not displayed correctly or do the fans not regulate themselves down physically (5V - 7V off)? >> Have you ever measured the voltage?
- If a 4-pin fan is plugged in, does the regulation work via PWM?

Actually, regulation via voltage should work in any case, at least the fans should go out.

So I have now tested it and can report the following:

- Connection to the input shows no effect
- Connection to the RPM works

This means that the Splitty9 Active can also be used as a passive hub, but with the restriction that the RPMs cannot be reported back.

So thanks again to you for the help.

Greetings
Walter