Do we know whether or not this is 100% true? Are the D/As and analog output stages identical and laid out the same way in all three KPA products?
Well, I meant essentially the same overall. I wasn't trying to assert it was 100% component-for-component. I wouldn't know that at all without taking them both apart and comparing every little component, and even then, I'm not qualified enough to know exactly what to look for. However, I do know that innumerable factors can potentially affect sound. For example, I know that a wire cut in two parts would have a bit more resistance in the longer one, or that there are tolerances in precision of the microscopic sizes within electronic components, but whether any of it ever translates into something audibly perceptible is totally by chance in the aggregate variances of a device.
In any case, my assumption is that the same components. However, comparing toaster vs rack, the rack doesn't have the lights for rig volume. The stage though has several different or missing knobs/features, plus it interacts with a whole network of foot controller electronics, so you would think there's no avoiding some degree of audible difference. None of this I know with a degree of competency, so these are just some of the things I thought about in trying to account for what I'm hearing in my profiler stage.
I've a feeling there are slight differences, SH, but at the level of quality we're talking about here, if there were any, they'd be indiscernible-to-the-ear, you'd think. They'd certainly not constitute the difference between "shrill" and not-so IMHO.
The manual explains it better than I could, MG. I'll quote it here 'cause it covers disabling properly and also the override behaviour depending on settings:
PURE CABINET is available as a global setting in the Output Section and affects all Rigs that you listen to. However, the original sound of each Rig remains unchanged, and you can switch PURE CABINET on or off whenever you like. There are two parameters for PURE CABINET in the Output Section, on the “Output AddOns” page: use the corresponding soft knob to set the desired amount and use the corresponding button to do a quick A/B comparison against the original cabinet sound. To completely disengage the global PURE CABINET, you must uncheck the switch, as it still has an effect even when the controller is at zero.
If you would rather have individual settings of PURE CABINET per Rig or cabinet preset, there is a second parameter in the cabinet module. There is no switch for the local parameter - it is disengaged by setting it to zero. Both values of PURE CABINET interact such that the larger of the two values is always given priority and will be applied as the actual intensity of the PURE CABINET effect.
There is a possibility that your Rack unit had the global PC set to zero, whilst your new Stage in fact had it disabled which technically doesn't disable it, or vice-versa. Given that you found the Stage more-shrill than the Rack, if anything in this context, it'd mean that the Rack was the unit set to zero and the Stage disabled.
The settings are identical in everything as far as I can tell. I don't think anything came turned off or on that's aberrant from factory default.