What exactly do you mean by 'two channel'?
Do you mean your sub is hooked up with two cables from the Left/Right front preouts from the Integra (and not using the single subwoofer output)?
Or, do you mean you have the sub hooked up with a single cable to the Integra but when you select the 2-channel only mode the sub is not working?
Many AVRs and Pre/Pros have a "Pure Direct" mode for 2-channel analog connections from CDs or TTs - if this is what you mean, then by the nature of "Pure Direct" and 2-channel - there is no .1 signal for the sub 'cuz the AVR preserves the 2-channel analog only path thru the AVR.
Do you mean your sub is hooked up with two cables from the Left/Right front preouts from the Integra (and not using the single subwoofer output)?
Or, do you mean you have the sub hooked up with a single cable to the Integra but when you select the 2-channel only mode the sub is not working?
Many AVRs and Pre/Pros have a "Pure Direct" mode for 2-channel analog connections from CDs or TTs - if this is what you mean, then by the nature of "Pure Direct" and 2-channel - there is no .1 signal for the sub 'cuz the AVR preserves the 2-channel analog only path thru the AVR.