Profiling with a dummy load ( hotplate ) problems

  • Hi, So I tried to profile one of my amps for the first time today. It's a 1979 Marshall Jmp. I hooked everything up
    (guitar--->kemper input-----kemper direct out(send) ---->amp input---->hotplate in---->hoplate line out---->Kemper return )

    I then selected a similar marshall amp profile in the browser and started the profiling process. It was nothing near the reference amp. I redid it again and try to match the kemper and reference amp volumes. Nothing near reference... I did the refining process 3 times playing chords. Was not sounding near the reference amp. I could totally hear a major difference through headphones ( Ath-m50s )
    I tried redoing the same process, but with '' cab off '' in the marshall profile to get the sound a little bit closer to the reference amp...Still was not close. The reference sound is bright and large sounding in the headphones, while the '' kemper '' sound is dull, darker and just not the same.


    Am I doing something wrong ? Is it suppose to be that inaccurate when not using speakers ?
    Is it because it automatically adds some kind of '' speaker simulation '' ?

  • No, I mean if you physically disconntected the speaker from the Marshall in order to avoid hearing it while you compare with Headphones.

    "Music is enough for a lifetime, but a lifetime is not enough for music" Serghei Rachmaninoff


  • can you take a profile from the amp's send (if it has one)?


    nevermind... 1979 JMP hehe...


    I have no personal experience with the hotplate, but your best bet would be to connect a speaker (even if you're going for a DI profile) and take the profile from a direct box between the speaker and the amp.


    p.s.
    you were monitoring a distorted DI signal over headphones? ouch, that must hurt...


    p.p.s.
    even better: start profiling a 'traditional' setup amp -> speaker - > mic to get the hang of it

  • The hotplate is an attenuator, but is also a dummy load ( which replaces the cabs speakers resistance by another resistor ). A speaker would be require just to not break the amp, no ? and in this case would not be require...

    Doing the d.i thing with the hotplate is the same as with doing it with a direct box and speaker, it takes the amp signal and converts it into an ajustable line level signal. That's what I want to profile. Again, the reference amp signal is right, but the kemper signal after profiling is nothing near the reference amp signal even after refining...

  • right.


    I'm just saying that since the Profiler has proven countless times to work in a amp -> speaker -> mic setup and even in a Amp -> DI setup to replicate the amp's sound flawlessly, the unknown in this equation is the Hotplate.


    If you want a DI profile (and this seems to be the case) I'd try to use the amp with a speaker connected and with a simple DI box (or the Hotplate without attenuation?) in between the amp and the speaker, this has been proven to work, and we even released a Rig Pack with profiles created this way.

  • Thats what I'm trying to say haha. The hotplate is the same thing as a d.i when taking the line out. It takes the signal and put it into a line level, which is exactly what a direct box does.


    The signal that the kemper receives ( the reference amp ) is perfectly fine ( it is monitored via the kemper, via the headphones ) So the signal chain is alright. What is weird, is that when it's profiling, the '' kemper amp sound '' that is supposed to be identical to the '' reference sound '' is not.


    There's not attenuation with the hotplate going on, that's only for the speaker out on the hotplate, which is not even being used.

  • Hi Maxime,
    Is there some kind of speaker simulation (low pass filter) in the Hot Plate line out? Did you turn it on or off?


    I had problems profiling a clean amp and DI-box without speaker simulation. See this post.
    Profiling worked with speaker sim enabled only. My suspicion is the KPA can't handle high frequencies usually cut off by speaker or speaker simulation.

  • Yes, this would be an explanation.It's exactly what's going on. No, theres no cab simulation on a hotplate. It's really only the sound of the preamp + sound of the poweramp.


    The kemper sound is similar, but not even close to '' exactly the same ''.

    I
    guess you're right about kemper not beeing able to capture the sound without cab simulation. But then how did everyone else are able to profile preamps with the d.i's ?

  • Try to profile it with a speaker simulation on and the remove the speaker part by switching off the cab section later for a DI signal.
    Then add a little bass and high frequencies with the studio EQ's shelf filters in the X slot - try 1,5 to 3 db at 130-100 Hz and 1,5 to 4,5 db at 6,5 to 8k.
    Telling from my experiences this gives better results.


    BTW what are you using that DI profile with? poweramp+cabinet?

  • Thats what I'm trying to say haha. The hotplate is the same thing as a d.i when taking the line out. It takes the signal and put it into a line level, which is exactly what a direct box does.


    Actually it's not. The speaker is a nonlinear load. I made many DI profiles (which all turned out quite good) - always got better results with cab + DI box then when I just used a dummy load.

    MJT Strats / PRS Guitars / Many DIY Guitars -- Kemper Profiler Rack / Kemper Remote / InEar

  • Actually it's not. The speaker is a nonlinear load. I made many DI profiles (which all turned out quite good) - always got better results with cab + DI box then when I just used a dummy load.


    That´s right. Attenuators change the sound in most cases. DI Boxes between the amp and cab provide better profiling results imo. Taking DI profiles of tube amps does not require high volumes. Cranking tube Amps has an impact on the speaker but it does not make a better profile.

  • I'm not too sure about that - Maxime wants to profile a Marshall JMP.


    I have never heard any amp that sounded better if you crank it and then attenuate it back. Speaker compression due to high load is a different thing but power amp distortion on its own is one othose great myths everyone is aiming for until they finally hear it... If it really sounds so damn awesome why would anybody build an amp with more than 10 or 20 watts? One of the first amps with integrated power brakes got a huge amount of users stating that their amp seems to be broken :P

  • Yeah - I agree with you with 98% of all amps... but the typical Marshall JMP tone is based on heavy poweramp and PI distortion....
    Let's leave away poweramp distortion - the PI distortion still has a huge impact on sound - dunno if that occurs when profiling on low volume - you'd need a PPIMV for that.


    I agree that poweramp distortion sounds like shit though :D

    MJT Strats / PRS Guitars / Many DIY Guitars -- Kemper Profiler Rack / Kemper Remote / InEar

  • BTW what are you using that DI profile with? poweramp+cabinet?

    Yes, for that and maybe to try and record with different cab impulses later on. Anyway thanks for your advice, I don't have a cab simulator though so I'll try to find that. The torpedo is cool but is expensive, any ideas ?

    Actually it's not. The speaker is a nonlinear load. I made many DI profiles (which all turned out quite good) - always got better results with cab + DI box then when I just used a dummy load.

    Ok, so if I plug the cab and turn off all attenuation, now it's acting exactly like a d.i between speaker and amp, right ? It will give the non-linear load to the amp and therefore the line signal will be acting more like a d.i signal...I'll try that when nobody's home.


    Again, I'm not complaining that the profile doesn't sound like the actual amp in a cab...
    I'm asking if it's normal that the profiling process does not achieve what the reference amp sounds like in the kemper. Linear or non-linear load, I thought the kemper was supposed to replicate the sound it receives from the return input.


    After reading a few forums, I noted that a lot of people were having this similar problem. When '' cab '' is engaged, the sound will be really similar. But when you turn off '' cab '' the reference/profile are not really close anymore.


    I have never heard any amp that sounded better if you crank it and then attenuate it back. Speaker compression due to high load is a different thing but power amp distortion on its own is one othose great myths everyone is aiming for until they finally hear it... If it really sounds so damn awesome why would anybody build an amp with more than 10 or 20 watts? One of the first amps with integrated power brakes got a huge amount of users stating that their amp seems to be broken

    My jmp actually sounds better when the master volume is around 4-5-6. It has to do with speaker saturation, but also with the power amp being cranked a little ( it always sounds better around 4-5-6, even when direct recording ).

  • But when you turn off '' cab '' the reference/profile are not really close anymore.


    Yeah, that's because the KPA tries to remove a cab that isn't there. Doesn't work very well. Just leave cab on for DI profiles (when using them with poweramp and cab).
    There will be a future firmware update where you can switch off the cab while profiling (for DI profiles) - read it somewhere, can't find it now...

    MJT Strats / PRS Guitars / Many DIY Guitars -- Kemper Profiler Rack / Kemper Remote / InEar