Distortion in Alternative input

  • Hello all, I am attempting to connect a MP3 player to my Kemper using a 1/8" TRS to 2X 1/4" TS cable. It works, and I can change the volume in the headphones using the Aux In/Headphones level control in Main, but the channel coming through the Alternative Input has significant distortion on it. Lowering the source input volume does not seem to help very much. Power cycling the Kemper did not help. The distortion happens with different sources as well. The side going through the Return input seems to be OK. Is this normal? And is there a input level control in the UI anywhere? Thanks for your help.

  • What happens when you connect your guitar to the Alternative input and select it as the input source in the input menu?

    Thanks for the reply. I did not try this last night. I just tried it with a clean profile, and with a guitar it sounded just like the main input, no distortion. I then plugged a mp3 player in its place (so the mp3 played through the profile from the Alt input), and the distortion was not present as before. I then tried the standard mp3 connection where it was distorting last night, and it sounds perfect now. The distortion is gone, even at high signal input levels.

    I understand that some of the signal inputs have gain switching, is this perhaps what the problem was? Maybe the alternative input has to be used as the profile/instrument input before it gets its gain settings correct? I also noticed last night that the cable from the aux input was very microphonic (lots of handling noise), but was not nearly as sensitive today.

    Thanks again for your help.

  • Tonight I tried connecting the MP3 player to the Alt input and the distortion reappeared. I immediately tried switching to the Alt input as a profile input, and heard significant clipping using that input for guitar. The profile sounds normal when using the front panel input. Cycling power on the Kemper did not fix the issue.

    So the problem is back. Any ideas on what I should try next? Thanks for your help.

  • Your rigs and performances will be unaltered but you will need to verify time and date agin and put your username in again. All input and output settings get wiped so it is a good idea to create a local preset for each of them that you can reload after the reset.

  • So tonight I worked with the Kemper on the Alt In distortion issue. I powered up the Kemper and made a backup, but before the system reset I tried the MP3 player; no distortion. I the did the power on system reset, after the reset the distortion in the Alt input came back. After this I tried System/Init Globals, this did not help the distortion problem either.

    Do you think I have a defective Kemper, or maybe it is a software issue as from time to time the distortion isn't there (so the hardware works at that time)?

  • What happens when you restore the backup?

    Thanks for the response. I tried this, and after the unit was on for a half hour or so the distortion reappeared.

    BTW I found that the Kemper was on firmware version 3.0.0, so I upgraded it to the latest version before the backup restore.

    I noticed that the Alt in seems in some cases to sound fine when the unit is turned on after being off for several hours, but after being on for awhile the distortion starts. Maybe there is some sort of thermal issue, or an analog bias drift over time? I will work with the unit a bit more to see if this might be the cause, and if there is a time constant involved.

    Another symptom is that the hiss with the Alt input increases when the distortion is present, and there are noises present between songs being played on the mp3 player (clicks and hiss that are not normally there, like the low level noises between the songs are amplified). This is what is making me think of a biasing drift; for example if the mp3 player has a DC offset at its output and the input analog circuitry in the Alt input is DC coupled, that could perhaps cause such issues. However that probably isn't happening here as the distortion also happens with a guitar with passive electronics.

    Sure wish I had a set of schematics... :)

  • please check if you are getting a clean signal when you connect your guitar to the return and/or alternative input.

    Chances are that your mp3 player is clipping the inputstage of the Profiler if the signal is too hot.
    If you get distorted sound with your guitar too please open a support ticket.

  • what happened with this issue? I am having similar problem with mp3's clipping into aux input.

    After some troubleshooting with Kemper, we unfortunately decided it was a hardware problem and I had to return the unit. But Kemper US treated me right, they put a new in box Kemper in the mail to me as soon as they had a tracking number of the one I returned. The replacement has worked perfectly and I've been a very happy user.