They are supposed to be 4 volts, but the subout sure isn't. I've got the MRD-M301 and this is how I have it set up. First my normal listening volume on the 9835 is around 22-24, but I can go all the way to 35 without any distortion. If you don't keep the volume level around this level on the hu you will never get much sub output. Front and rear outputs are much stronger, and require a very low gain on my 4 channel. It just doesn't put out any voltage on the subout until the upper levels on the HU. My amp is set on 4 volt, input set to 0, gain 0, LPF 80/24, sub sonic off(sealed box), bass comp off, EQ off. Make sure you save you settings at the last memo category.
Bill3508