On that Alpine HU you'll only get 4volts from the sub rca's when it is set to +15...so turn it all the way up and reset your gains...then you should be good to go.
I had the 9831 and that's the way the sub preout worked for some reason
maan i hate caps mine had a short and it jumped up the rca's and burned out the amp in the head unit. i need to buy a 4ch amp to get it playin music. cheapest one i foud was $50 for a boss. any cheaper?
save your money and buy something decent when you can afford it...Boss is crap and you'll get crap out of it..
I'll be selling an Audiobahn 4 channel (150x4) Digital Series ampe here next week...certainly not the best but far better than anything Boss has ever made.