Upgrading Prius V 2013 Aspiration Headset to the JBL version loosing volume control

I just upgraded my standard Prius V 2013 Aspiration Headset to the JBL Business version of the same nav radio. Everything works fine , I now even have dab radio.( still need an antenna ) Problem is I lost volume audio control and settings. I can turn the knob on the radio of press the buttons on the steering wheel , nothings happens. I can however skip songs and control everything.I have bluetooth audio etc. But... The sound stays at the same pretty loud level. I don't have the extra amp that most JBL systems have , can this have something to do with it? I thought sound level / etc is done in the pre amp stage?

thnx marc

This is what i found online myself, maybe someone has a solution :

Some head units don't actually control the volume. When you turn the knob, then send a digital signal to the factory amplifier to turn the volume up/down. If this is the case with your vehicle, you'll need something like the Maestro AR or Metra's AX-DSP.

 

No solution, I will put the JBL headunit on ebay. I don't have the main amp and it will never be a decent solution. Anybody interested in the JBL head unit? send me a pm