Profiling with DI Box and speaker cabinet isn't going well!

  • I have run into my first confusion with my Kemper. I am a two-week owner. Perhaps somebody can recognize this weekend, what I am doing incorrectly.


    * I will call Kemper on this coming Monday. Yesterday was Friday, so no luck.
    * To check my procedure, I called Sweetwater (dealer). They listened to my questions, promised to get back and did not.
    * Checked everywhere I could find, to see if the pad (-15dB) on the Radial PRO DI box should be activated. No mention in manual; conflicting information on a few posts.


    1. Following a successful profiling of an original tweed Fender Champ, I decided to try a DI profile - an original Marshall bass plexi (model 1986).
    2. The plexi has to be dialed into Duane Allman territory. Every knob isn't dimed, but close enough to be very loud. Also bridged both channels.
    3. Connected the speaker output to a Radial PRO DI box Input and Radial Thru to the Marshall 4x12 cabinet.
    4. Connected DI box Line Out XLR to Kemper Return Input XLR. Pad (-15dB) not activated.
    5. Connected Kemper Direct Output / Send to Marshall input.


    As soon as I switch the Kemper to Profile, a tremendous audio feedback loop begins to build and bloom (tremendous in the tsunami-that-obliterates-everything-it-touches sense =O , not the really-nice sense.)


    6. I quickly abort.


    I checked everything and repeated, same results.


    What the heck am I missing? The profiling manual states that I should leave the speaker cab in the loop during the profiling, since the Kemper will perceive the reactions of the amp begin profiled.


    Thanks in advance!
    Frank

  • It might be that the line out level is too high. I would pad it. For large wattage amps I usually have it at -20 db. Once you try that see if you can get your signal working good. You can also try one with a lower volume to see if you have good luck. If it works at lower levels you know its the line level. You should be on a similar amp and then switch to profile and go back and forth to the reference amp so you can level off before the profiling process begins.

  • Good question. I reworded it twice, but It remained ambiguous.


    The Kemper was switched to Browser. I turned the selector switch to Profiler, to initiate the profiling process. Also, I had the speaker output was connected to a guitar speaker cabinet, but I tried to lower this to "minimum" and "off". Yes, this can provide a route for audio feedback, but at the time, I was worried about how to detect dangerously loud signal harming the Kemper unit. I can try headphones, but I decided to first ask these questions. I believe that I have gone down a wrong path, and it is best to stop and verify the procedure.


    Speaking of language, the terms are mixed on the selector switch:


    Tuner : Tune
    Browser : Browse
    Performer : Perform
    Profiler : Profile

  • turn down the Marshall's volume for now


    make sure you have a guitar connected to the cable leading to the Input of the Profiler


    with the cabinet and the guitar in the same room (I assume) and the amp being extremely loud, a building feedback is to be expected


    make sure there are no unwanted stomps active


    make a Direct Amp Profile with a 'normal' setting to insure your setup is o.k. and the levels are working - than increase the gain/volume (slowly) and see/hear what happens.
    You might have to place the cab in another room to stop the amp from feeding back, or use a guitar with humbucking or very quite pickups.


    hth

  • Thank you. I will try these procedural changes.


    Fyi:
    The guitar I was preparing to use (to "refine" the profile) is an old Les Paul with humbucking pickups.
    The guitar was not yet connected to the Kemper Profiler unit.
    There were no effects or stomp boxes in the chain.


    My most critical question:
    Is there any risk, that the signal from the amp being profiled (returning to the Kemper unit), can damage the Kemper unit? My intention, is to profile this vintage Marshall at it's concert level.

  • Hi all,
    Thanks for the suggestions and recommendations. I spoke with Kemper this morning. Here is the scoop, assuming I understood it:


    1. My connections were correct.
    2. Best to use the Kemper DI box. The circuit to the Profiler delivers a line-level signal to the Kemper.
    3. Yes (as the manual states), have the amp being profiled hooked to its speaker cab - this captures and profiles the impedance influences and interaction in the circuit
    4. No, there is no necessary reason, to have the 8-16ohm speaker output connected during the profiling process.