The CABINET simulation happens before the EFFECTS Session

  • I've seen various posts claiming that the CABINET simulation in the KPA was the last stage in the signal chain, after the EFFECTS session, i.e. not as it looks on the front panel. But the following experiment supports that the signal chain is actually exactly as shown on the front panel.


    Setup: Select any overdrive-type STACK with cab on. Set DELAY in EFFECTS to 'Legacy Delay' with 2 repeats,' Note Value 1' = 8/16, 'Note Value 2' = 16/16. Connect your headphones or a FRFR to MAIN out and listen to the STACK sound including CABINET. When you play a note on yer Guitar, you should hear the note plus 2 repeats: pling ... pling ... pling.


    Preparation: Switch CABINET off and do the same. Now the three plings will sound differently, typically bright/fizzy. If not, select another CABINET, where the presence/absence of the CABINET simulation is very well audible. Switch CABINET on again.


    Experiment: Put a finger on the CABINET button. Play *3* short notes on the Guitar now, quickly switching off CABINET after the 1st note and switching it back on after the 2nd note . The undelayed sound of the 3 notes should then be [normal] - [bright] - [normal]. Now listen to the delay: *both* repeats of the 3 notes will be [normal] - [bright] - [normal], like the original, even if the CABINET sim is back on while the repeats ring.


    This more or less proves that CABINET sim is before EFFECTS, and that the CABINET sim output is fed into EFFECTS, as shown on the front panel.


    Consequence:
    a) there is no way to put simulated stomps into a simulated FX loop of the profiled AMP.
    b) there is no way to put simulated stomps between the AMP and the CABINET. You don't do that in real world either.
    c) "Monitor Cab Off" is rocket science, or uses an additional EFFECTS chain simulation. I do assume the former.


    Additional, simpler evidence by Andrew d'Angelo in facebook: Put a fuzz into the X EFFECT and it will wipe out any differences between different CABINETS selected.

  • EDIT: forgot to cite „If the cab model is a linear transfer function, it doesn't matter whether it is before of after the effects. See, A times B is the same as B times A“


    Indeed. However, I think it is non-linear. Simple test: put the same stomp in A and X, switch everything off except CABINET, then see if stomp - cab sounds the same as cab - stomp for all cab types.

  • Maybe ckemper or someone from staff could enlighten us regarding the matter :) There's indeed lots of posts that suggest that the cab is last one in the chain.

    Right! And just to emphasize, if cab was last in chain, Monitor Cab Off would be a simple thing. However, from my evidence cab is not last and that makes Monitor Cab off a difficult function (wich again partially explains the frequent observations that CABINET off changes the Monitor sound even with Monitor Cab off. @ckemper, I really wonder

  • This is pure speculation, but I think that the cabinet is before the effects so that the cab section doesn't have to be "stereo" or two channels.
    To me this is fine, since I think of those effects as something one would add in studio after the the amp in DAW or in other post-processing.

  • If the cab model is a linear transfer function, it doesn't matter whether it is before of after the effects. See, A times B is the same as B times A.

    This is incorrect. The multiply is a linear transfer function but it’s not on its own, the functions to either side are non linear and the two arguments are amp & cab, not cab & fx.


    To make it clearer imagine that this is the Kemper signal chain from amp signal onwards :


    Amp -> Cab -> FX


    Now the idea proposed is that the cab would come after the FX so :


    Amp -> FX -> Cab


    This is quite different. FX can be anything, they needn’t be multiplying the signal. So let’s substitute some basic functions for each. Let Amp be unit 1, Cab be a multiply by 2 and FX be an addition of 3 :


    1*2+3


    The result is of course 5


    Now if we swap the order of functions to the cab is at the end we get a very different result :


    (1+3)*2


    This gives you 8


    These are all linear transfer functions but that just means that within the function itself the arguments a and b can be swapped and you get the same result, but when you change the order of operations, the order of functions you’re changing the function inputs completely and there’s no guarantee of linearity.

  • Thank you for the correction. The order of the cab and effects is irrelevant only if both of them are linear.

  • Consequence:
    a) there is no way to put simulated stomps into a simulated FX loop of the profiled AMP.

    This isn't correct. Test it with a Loop in the Effects section, but put your guitar directly in to the return input. Try strumming a bit and engaging and disengaging the Cab.


    However, if everything else is correct, then it must mean that Kemper has different routing for the Loop effects when placed in the Effects section. I was interested in this subject as I have a Fender Acoustasonic Telecaster, that is capable of outputting the piezo and magnetic pickups individually. I wanted to be able to put the output of the piezo in a Loop Stomp after the Cab to preserve the acoustic high frequencies, but it turned out it wasn't possible without disengaging the Cab (which would ruin the magnetic pickup sound). I wrote to support and got the reply along the lines of "although the legending on the front of the Profiler suggests otherwise, the Cab is always last in the chain". Interesting indeed...

  • I have a Ditto in the loop in the X slot, record a loop, and it is absolutely effected by the cab block being engaged or not. The fact that after this many years the product has been out that this is still not known, addressed, fixed is insane (IMHO)

  • the manual is wrong, or I have found a bug, or setup my loop using the X slot incorrectly(possible?).

    Wait... Forget I said anything :-)


    The signal INTO the looper should be affected by the cab (if I understand how you've wired it up), but not the signal OUT of the looper.


    If this isn't how it is, I'd advise you to open up a support ticket to make the company aware of this. There's a link in my signature :-)

  • I have a Ditto in the loop in the X slot, record a loop, and it is absolutely effected by the cab block being engaged or not. The fact that after this many years the product has been out that this is still not known, addressed, fixed is insane (IMHO)

    The signal going into the Ditto has the cab in it (or not if you turn it off), so you should expect that. What are you wishing it did?