Mark, here is what I know about the control knob on Criterion.. . .
The knob first of all has 2 distinct ways of operating. . .
turning the knob adjusts volume for primary and secondary zones, right to left balance, input offsets, output offsets, menu scroll.
Pressing the volume knob utilizes the knob as a selector for entering menu mode and activating a selection.
I do not know what chip/module the volume control is based on, (it may be an HP part but I am not sure(, but it is an optically encoded system, therefore the knob can be rotated continuously clockwise and counterclockwise without ever reaching a stop position. When Criterion is turned on, volume is always at 0dB. The volume is speed sensitive: turning the knob slowly or pressing single taps on the remote control volume buttons changes volume in 0.5dB increments. . . rotating the volume control faster or holding down remote volume buttons changes volume in 1.5dB increments. . . the loudness range is 0dB to 99.5dB. Per my notes, precision/stability is said to be within 0.01dB. Furthermore, the volume control is said to cause the audio bandwidth to remain unrestricted at all gain levels, without the volume becoming a bandpass filter at low SPLs. Also when using the volume to change offset values, balance, and volume for secondary zone, the volume knob remains velocity sensitive.
It is my understanding that the volume control does not act on the audio section directly. . . The volume control is in the control chassis.. . it communicates with a microprocessor controller in the same chassis. . . when a volume change is requested, the microprocessor awakens a communication bus. . . sends appropriate control codes to the audio circuit in the audio chassis that alters the gain of the OPA1632, then powers down the data bus until new controls are required. So the controller is always offline, unless it is needed to change a preamplification parameter. . . and the change takes place in a fraction of a second.
From an experience point of view the volume control is extremely quiet. it turns with a little less friction than on Capri. I can hear very soft volume change clicks only when rotating the knob quickly beyond the 93dB mark on the display. . . which is something that I do only if no music is playing. The background noise is essentially completely quiet up to the top of the gain scale.
Let me know if you need more information. . . but this is all I know up to now. Guido
