There is not a direct control to adjust sub level. It can be a problem for some, but there are some good tools in the 990 that can allow the sub to be integrated with the mains so that you don't necessarily have to ride the sub trim all the time. Between the adjustable crossovers and the two-channel sub offset (which allows the sub trim to be run up to 8dB lower when in a two-channel mode), you can dial it in pretty well.