I had posted this in response to someone elses thread re SPE amps and ALC ... I thought it might also apply here or at least provide some reference and show what appears to be an issue:
This is in response to your statement re using the ALC on the SPE amps and Tim's saying the ALC does work.... I've noted that the SPE says the ALC signal can be as low as -11V whereas the hardware instructions for the Flex 6700 say not to go lower than -4V or damage might ensue... I've no reason to doubt what SPE is saying - so since you connected the two up were you just lucky or does the flex actually have protection against lower levels of ALC coming in? As I understand ALC it is nominally at its lowest level - so when not 'active' the SPE would be outputting -11V!
[its been a couple months since I looked at this in their respective manuals... I'm pretty sure the numbers are accurate... it seems strange that the Flex would say this - its so easy and cost pennies to clamp a signal so that neither the input nor itself is effected detrimentally.]