What magic is this?

    So started profiling my mesa roadster tonight. Ran amp to torpedo live (load box/speaker sim), and then took torpedo live line out to Kemper. Made profile. Yay! Then noticed I could deactivate cab (with button on Kemper) or switch to other cabs in the Kemper. How is this possible? It should not be able to subtract the effect of my torpedo live as I never gave it an amp only DI. What magic is this? Does it just subtract some generic cab impulse that it totally just makes up, or am I missing something here? ;(


    Thanks!

    Quote from kempertron

    So started profiling my mesa roadster tonight. Ran amp to torpedo live (load box/speaker sim), and then took torpedo live line out to Kemper. Made profile. Yay! Then noticed I could deactivate cab (with button on Kemper) or switch to other cabs in the Kemper. How is this possible? It should not be able to subtract the effect of my torpedo live as I never gave it an amp only DI. What magic is this? Does it just subtract some generic cab impulse that it totally just makes up, or am I missing something here? ;(


    Thanks!


    Hello Kempertron,


    Doesn't the Torpedo Live also act as a load box? I think that is what is causing the problem. In order to make a Direct Amp profile, you need to use a suitable DI box (such as a Behringer® Ultra-DI DI600P). The load is supposed to be the actual speaker cabinet, which you connect to the DI box via the pass through. The DI box's XLR out goes back to the KPA return.


    What I think is happening in your case, is the KPA is getting confused with the Torpedo Live's active load. Also, I assume you have activated the Cab Sims in the Torpedo Live, so the KPA is getting the Torpedo Cab sims as part of the Profile signal. The KPA is not recognizing this as a Direct Amp profile, and therefore is treating it as if the signal it is receiving is from a mic'd cabinet, so it is making a full Studio Profile. The Cabinet module is activated, because the KPA has recognized it as a Studio profile, and when you deactivate the Cab module, it implements it's CabDriver algorithm, and does it's best to intelligently subtract what it calculates to be the contribution of the cabinet (in this case, the Torpedo Live IR-based cab sim) from the amp signal.


    I don't know if there is a way to force the KPA to recognize that your are making a Direct Amp profile. I believe it auto-detects this. In which case, I am afraid it is the Torpedo Live loadbox that is screwing up the process.


    Hopefully another KPA owner who also is familiar with the Two Notes Torpedo Live Digital Loadbox can chime in on this matter.


    Cheers,
    John

    Quote from Tritium

    The Cabinet module is activated, because the KPA has recognized it as a Studio profile, and when you deactivate the Cab module, it implements it's CabDriver algorithm, and does it's best to intelligently subtract what it calculates to be the contribution of the cabinet (in this case, the Torpedo Live IR-based cab sim) from the amp signal.


    We are on the same page Tritium. For my first attemp, I was just planning to make a studio profile, but I was just surprised that the kemper could "intelligently subtract what it calculates to be the contribution of the cabinet". Seems dubious from an electronics standpoint, but maybe it's just subtracting some default cab response. Anyway, in the future I'll hook up my countryman 10 between amp and speaker and take DIs that way.


    Thanks for your response!

    Yeah, I'm just confused by this. It seems like there would not be a way to deconvolute the cab/mic contribution from the amps natural eq given only the final response. But maybe Christoph Kemper is a wizard! Maybe he's using the time-dependent amplitude decay of physical speaker outputs to infer their contribution or something. Neat to think about anyway, and cool that it works.