I just recieved my SVS 20-39 pci sub. The problem is that I have to turn up the volume on my reciever to get output from the sub. I have my sub level on my reciever at 0. (It ranges from -12 to 12) The master volume is set at -40 (It ranges from -60 to I thinlk 20?) I normally listen to movies at -20to -40 depending on the movie. I have the sub volume on the sub amp at 3/4 volume. I have a rca cable from the sub pre-out to the input of the amp. I am using a denon 3600 reciever. Is this normal or do I have something I need to adjust.