Is there a volume control KNOB (bluetooth, wifi, usb?) that will work with the Dudu7? That would be a nice accessory. Mostly just curious. I have the controls on the steering wheel but would prefer a dedicated volume knob with push button mute. I do have plans for eventually installing a DSP which will have a volume knob but it still would be nice for many to have an add on master volume knob that works seamlessly. Thanks!