Here's the rundown on stereo bypass mode on the 950: the left and right analog inputs are passed through volume control and straight to the pre-amp outputs, with no digital processing applied. In addition, if the mains are set to "small", the 950 takes a copy of the inputs, converts the copy to digital, applies bass management, and sends the resulting low-pass data to the sub.

In regular stereo mode, the 950 converts the analog signal to digital, applies bass management (splitting the signal into a high-pass for the mains and a low-pass to the sub), and converts back to analog.