Kemper sounds all farty/buzzy [solved]

    I was playing my bass with one of the amp factory's excellent profiles. It started to do sounds like a broken speaker cone. But only if I played loud. So it sounded fine when I played it normally (i.e. not slapping etc).


    Then I plugged in my guitar and it's parping and fizzling and sounding weak.


    I thought maybe the speakers are blow, but I played some Morbid Angel and Opeth and they sounded fine.


    Could my speakers be blown? I am using Hi Fi floorstanders through an amp.


    How do I tell what is the matter?

    Ok, so I tried headphones and the fizzing is gone. So I turned the volume down on each profile. If I turn it down enough the fizzing stops.


    That's weird right? The Kemper shouldn't just suddenly start clipping where it wasn't before? And can the output at line level blow speakers?


    :(

    You mentioned you're using hi-fi speakers, how are you amplifying?


    Guitar line level is much hotter than normal line level and can easily blow your speakers, amp input, amp in general or other components in your hi-fi circuit, so I hope you were going from the headphone out to your hi-fi if that's the route you were taking.

    Nope, I was (am) going from main out into the CD input in my amp.


    If I have busted my speakers, why has it taken so long, and why does it sound fine with music?


    I guess I will try headphones out.


    :((

    OK, the good news is that your speakers are most probably fine, the bad news is that you've more than likely blown some caps in the input on your hi-fi. You can test to see what's going on by simply plugging in another input source to the same input and seeing if the result sounds acceptable or not.


    Why would it take this long? Because components wear and don't always immediately burn out due to stress, most electrical components aren't rated for their peak values but their minimum manufacturing quality so there's that little bit of leeway that can be a factor. Then the amount of time that the signal is hot in a soundwave is microseconds and a tiny proportion of the overall wave normally, it may take repeated hitting of that peak voltage before components start to fail and depending on the profile, volume at the KPA end and so on it could take quite a while to do that. You might also have just picked a new profile to play with that you've not used before, raised the volume that little bit too much, started playing particularly aggressive chugging chords and so on. Just because a component doesn't instantly fail is no indicator of the amount of stress it's under or how long it might last,

    Ok, thank you very much for taking the time to explain that.


    So, the best thing to do is to plug the headphone out into my stereo, is that the case? I have it plugged into the same input and it sounds fine. Should I just pick another input?


    Also, does it matter what volume I have the headphone out set to? I guess it might, but I have probably got it on max.


    Thanks again for your help.


    Ah, one thing. When I said I played some music, I just plugged my iPod into the same input the Kemper is plugged into.

    Well there are other possibilities too. For instance you may have simply set a value wrong on the kemper and you can just try to find out what by going through everything and trying stuff out, or you can reset it, instructions are on the kemper wiki (search the forum for links), if you're using a pedal board you might want to check that the midi channels are set up correctly.


    Then you may simply have a dodgy cable. That's easy to check for, just switch out for another one.


    You might also have active pups on your guitar and it may be time to replace the battery.


    There's also always the slim possibility that the out on the KPA may have been damaged too, it is possible when going from high impedance to low for components to get damaged all along the chain. You can test whether your KPA is faulty by simply running the same master out into something designed to take it, e.g. if you have an actual guitar amp try that. If the result sounds messed up you have your culprit.


    To find out exactly what then you need to go through and test each thing in isolation till you hone in on the exact place where problems are occurring.

    Ok, thanks. I hope I haven't broken the Kemper!


    Strange thing, it sounds fine now I have plugged it from the headphone socket. It also sounded fine when I reduced the volume on each rig a fair amount and turned the amp up.


    I will try resetting it, does anyone know if I will lose my performances?


    Anyway, thanks again. :)

    Need to clarify things here...There is no such thing as a "guitar" line level. "Line level" use some different reference/nominal levels, the most common being -10 dBV and +4 dBu. Your Hi Fi uses -10 dBV and the Kemper +4 dBu.


    No, don't use the Kemper headphone out into your preamp's CD input.


    The Kemper's max output is about 8 dB's more than a CD player. Just reduce the main output on the Kemper by 8 dB and unlink it from the master volume control. Control loudness on your Hi Fi.


    Does it still fizzzz...?

    Edited once, last by Trazan ().

    I've always been taught that this is an impedance issue rather than simple voltage one, line level is 10kOhm but unfortunately that's about the same as the pickups on your guitar (instrument level) and you need the input to be at least ten times the output to avoid causing problems (the Kemper input is 1MOhm!).


    According to the spec sheet ( http://www.kemper-amps.com/pag…ier___Specifications.html ) the headphone out on the Kemper is 33Ohm and the other analog outs are +16dBu (as it's u = unspecific impedance that's gonna be high right?), so I'm not sure why you'd advise against using the headphone when that seems to be a closer/safer match.


    Or is this way off the money?

    Ok, all this advice is great.


    I've set it up as suggested, main out -8dB.


    Most patches didn't do the wobbly blown speaker sound. Except a couple of really high gain ones. So I turned the rig volume down and it stopped.


    I think it's sorted.


    I also think I should get a FRFR cab like the Matrix C12 active.

    Quote from Per

    I've always been taught that this is an impedance issue rather than simple voltage one, line level is 10kOhm but unfortunately that's about the same as the pickups on your guitar (instrument level) and you need the input to be at least ten times the output to avoid causing problems (the Kemper input is 1MOhm!).


    According to the spec sheet ( http://www.kemper-amps.com/pag…ier___Specifications.html ) the headphone out on the Kemper is 33Ohm and the other analog outs are +16dBu (as it's u = unspecific impedance that's gonna be high right?), so I'm not sure why you'd advise against using the headphone when that seems to be a closer/safer match.


    Or is this way off the money?


    Yeah, way off the money :)


    What you call "guitar line level" is commonly called "instrument level". The latter (such as the signal from a passive guitar pickup) is high impedance. Outputs on the Kemper, and just about any other preamp, are line level (low impedance).


    Then there's the different voltage outputs that requires the correct input (microphone/instrument/line (-10dBV/+4dBu ++)/headphones/speakers)


    dB is a logarithmic scale, and the V and u in dBV/dBu describes the voltage reference (V=1v, u=0.775v. At 0 dBV/dBu) +16 dBu equals about 5 volt. A CD player puts out max 2 volt.


    OK, good to know, but there's nothing on the spec sheet to indicate that there's any impedance difference between direct, monitor or master outs. They're all just +16dBu, which as you say is near 5 volts, yet direct out is meant to go into a guitar amp.

    Quote from Per


    OK, good to know, but there's nothing on the spec sheet to indicate that there's any impedance difference between direct, monitor or master outs. They're all just +16dBu, which as you say is near 5 volts, yet direct out is meant to go into a guitar amp.


    I'm sure they're all low impedance. Direct out can be used in many ways. Low impedance is no problem into a guitar amp.