According to Benchmark, this is a common phenomenon due to the way that the DAC 1 is calibrated and built but there are some things you can do to adjust these levels.

The DAC 1 output attenuator jumpers might need to be changed, or the preamp or power amp gain might need to be reduced. You can adjust the internal jumpers to better adjust the outputs of the DAC 1. (see owners manual)

Benchmark recommends operating the volume control between 10:00 and full CW. If a normal listening level is reached before the volume control reaches 10:00, then there is too much gain following the DAC1.

The balance is precisely trimmed at a 1:00 rotation. The rotation between 10:00 and full off should not be used for normal listening levels as balance is less accurate at these settings. All analog stereo volume controls suffer from L/R imbalance as they approach full off. The DAC1 has pot shunt resistors and a multi-turn L/R balance trimmer to reduce L/R imbalance over most of the control range. It is much better
than most analog volume controls. Nevertheless, proper gain-staging is essential.

•NOTE•The headphone outputs of the DAC 1 are not effected by the adjustment of the internal jumpers, only the main outs are effected by these adjustments.