Digital Harmonic Overtones

    I'm encountering a strange problem where sometimes my KPA will add a harmonic to the notes I'm playing. It sounds like something happening digitally, possibly aliasing? It happens no matter what rig I choose and with/without effects / stomps. If I plug my guitar into a preamp directly, the tone is clean. Any ideas about whats going on here?


    Example (totally clean, no effects, noise gate at 0): https://soundcloud.com/noiseco…r-harmonics/s-dwZLKEyq6uj


    External Content soundcloud.com
    Content embedded from external sources will not be displayed without your consent.
    Through the activation of external content, you agree that personal data may be transferred to third party platforms. We have provided more information on this in our privacy policy.

    That is definitely strange. It sound like it could be either some fret buzz that is getting into the pickups or a slightly over driven signal within your recording chain. That is just a first thought. Of course, there are probably many other things that it could be.


    I just listened to it again and had another thought. It also sounds like it could be some hum, like a 60 cycle hum that is in your signal chain that comes through when the guitar sound comes through. Do you have a gate in the track? If you do, turn the gate off and see if you have a hum.

    Quote from wiegersma

    Does this also happen when you use another guitar?

    Yeah, it does.

    Quote from JEverly

    That is definitely strange. It sound like it could be either some fret buzz that is getting into the pickups or a slightly over driven signal within your recording chain. That is just a first thought. Of course, there are probably many other things that it could be.


    I just listened to it again and had another thought. It also sounds like it could be some hum, like a 60 cycle hum that is in your signal chain that comes through when the guitar sound comes through. Do you have a gate in the track? If you do, turn the gate off and see if you have a hum.

    The example I posted was with the gate at 0 / off.


    The weird part is that it'll come and go and I can't figure out if there is any pattern. This morning I fired up the kemper, same profile, signal chain, and it's totally clean. Yesterday I couldn't get it to go away for most of the day, even after multiple resets / power cycles.

    Quote from noisecoalition

    Yeah, it does.

    The example I posted was with the gate at 0 / off.


    The weird part is that it'll come and go and I can't figure out if there is any pattern. This morning I fired up the kemper, same profile, signal chain, and it's totally clean. Yesterday I couldn't get it to go away for most of the day, even after multiple resets / power cycles.

    I wonder if it is interference coming in through your power somehow? Maybe fluorescent lighting or some sort of transformer that is near a cable or power cord? The fact that it comes and goes is what is leading me down that road.

    I had a very similar thing that would happen in my last house. That noise is so reminiscent. It was the mains being polluted. We were the last house the furthest away from the substation and the mains was dirty by the time it got to me. Some days it was ok. By 11 pm at night, I couldn’t record anything as it had that noise on it.


    I never got it sorted out. My friend was in charge of the substations for the electricity supplier. He tested my mains. Sent sine waves from the substation. All kind of tests. He got the company to dig up part of the street to replace the cables. In the end, nothing helped. I was looking into balanced power supplies and everything at the time but then we moved anyway to where I am now.


    Simplest thing is to go to friends house and listen there. After hearing your clip, I am 99% convinced this isn’t the Kemper and is actually the mains supply

    Quote from Vinny Burns

    I had a very similar thing that would happen in my last house. That noise is so reminiscent. It was the mains being polluted. We were the last house the furthest away from the substation and the mains was dirty by the time it got to me. Some days it was ok. By 11 pm at night, I couldn’t record anything as it had that noise on it.


    I never got it sorted out. My friend was in charge of the substations for the electricity supplier. He tested my mains. Sent sine waves from the substation. All kind of tests. He got the company to dig up part of the street to replace the cables. In the end, nothing helped. I was looking into balanced power supplies and everything at the time but then we moved anyway to where I am now.


    Simplest thing is to go to friends house and listen there. After hearing your clip, I am 99% convinced this isn’t the Kemper and is actually the mains supply

    Interesting! Did you have problems with all your gear when your power was being fussy? I was able to record a clean signal into the DI of my preamp while the Kemper was giving me that weird harmonic content which led me to believe that the problem was with the Kemper.

    Quote from JEverly

    I wonder if it is interference coming in through your power somehow? Maybe fluorescent lighting or some sort of transformer that is near a cable or power cord? The fact that it comes and goes is what is leading me down that road.

    I'm going to try to switch the power source the next time it happens and see if that fixes it!

    Quote from noisecoalition

    Interesting! Did you have problems with all your gear when your power was being fussy? I was able to record a clean signal into the DI of my preamp while the Kemper was giving me that weird harmonic content which led me to believe that the problem was with the Kemper.

    I'm going to try to switch the power source the next time it happens and see if that fixes it!

    It was on all my valve amps in that room. SLO100, Rectoverb combo, CAE3+SE/Mesa295 and a Marshall TSL122 combo.


    A lot of times during the day, it was OK but as soon as everyone was home from work it worsened. Then after 11pm when things like old storage heaters would come on in other people’s houses, it was just so noticeable and no work could be done. First time I noticed it, I thought one of my amps had broken. Plugged another in and the same thing.

    I was gutted at the time as my previous house was only 5 doors away and I bought this one because of the extensions they had done that would become my studio. That other house 5 doors away, the mains was silent as it ran from a different substation.
    Was so glad when I moved.


    Definitely try it at someone else’s place.

    Quote from deadpan

    I would try to reset the flash memory. Mine did the same or similar years ago.


    Although contact support first.

    Thanks for the tip! Was your problem also intermittent or was it constant once it started happening?

    Quote from DamianGreda

    Sounds like a ring modulator. Certainly something is wrong - unless you are using a ring modulator somewhere in the FX section.

    No effects enabled unfortunately.


    Quote from deadpan

    I bought my unit used and it did it constantly when I first received it.

    I see. So resetting your flash memory fixed it? I submitted a support ticket but I'll note resetting the flash memory as a possible solution. Thanks!

    Hi!

    If you have dimmer switches on your lights and you are using single coils, that can cause noise issues. Also, if a neighbour has an induction loop set up for hearing aids, that can also be a problem. I’ve even had that happen at gigs where the venue has an induction loop. Out came the ladders to unplug the loop microphone to stop it interfering with my guitars. I only found this out because my neighbour had an induction loop years ago and I could hear their TV through my gear!

    I always ask if a venue has an induction loop now as they need to be switched off as they are often left switched on in locked cupboards so anyone can use them when in the venue. No good if you have live music though!
    Cheers

    Pre-Amp

    Edited once, last by Pre-Amp ().

    It sounds like wolf tones from having the pickups too high. I noticed you said it happens with other guitars too though. So unless you habitually set all your pickups very high it's unlikely to be the cause. It should be a very easy exercise to check though. First measure the height of your pickups under both the high and low E strings (so that you can return to the current setup later if you choose). Now lower all pickups significantly. You need to do all pickups even if you are only listening to one of them as the problem is caused by the magnetic pull which still affects the strings when the pickup is bypassed at the selector switch.


    If the noise disappears you have found the culprit and can start raising the pickups gradually until you get a sound you like without any interference. If it doesn't help just put the pickups back to where they were and at least you have ruled out another possible cause.

    Another thought - I used to get "ghosting" when I used my Focusrite into Ableton and it sounded similar.


    Do you get this same issue through headphones? Check that if you haven't...


    Hope you find it soon!

    Quote from Wheresthedug

    It sounds like wolf tones from having the pickups too high. I noticed you said it happens with other guitars too though. So unless you habitually set all your pickups very high it's unlikely to be the cause. It should be a very easy exercise to check though. First measure the height of your pickups under both the high and low E strings (so that you can return to the current setup later if you choose). Now lower all pickups significantly. You need to do all pickups even if you are only listening to one of them as the problem is caused by the magnetic pull which still affects the strings when the pickup is bypassed at the selector switch.


    If the noise disappears you have found the culprit and can start raising the pickups gradually until you get a sound you like without any interference. If it doesn't help just put the pickups back to where they were and at least you have ruled out another possible cause.

    Yeah I considered the guitar as the problem at first but if I plug in my guitar to a real amp or the DI of preamp, its totally clean.

    Quote from V8guitar

    Another thought - I used to get "ghosting" when I used my Focusrite into Ableton and it sounded similar.


    Do you get this same issue through headphones? Check that if you haven't...


    Hope you find it soon!

    It took me a second to test because the Kemper had been clean for a couple days but now the issue is back. I listened to the headphone output and its perfectly clean.

    Quote from noisecoalition

    Yeah I considered the guitar as the problem at first but if I plug in my guitar to a real amp or the DI of preamp, its totally clean.

    It took me a second to test because the Kemper had been clean for a couple days but now the issue is back. I listened to the headphone output and its perfectly clean.

    On this basis, I suspect its not the KPA. For me it was a monitoring issue from my interface.


    Not sure if that helps...

    Quote from noisecoalition

    It took me a second to test because the Kemper had been clean for a couple days but now the issue is back. I listened to the headphone output and its perfectly clean.

    Based on this comment, the next thing I would look at is your cable(s) that you are using for your output from the Kemper. Are they running next to any wall warts (transformers) or power cords? I would look for anything that could cause an electric interference. If you have other cables try a different one to see if that helps at all.

    Quote from JEverly

    Based on this comment, the next thing I would look at is your cable(s) that you are using for your output from the Kemper. Are they running next to any wall warts (transformers) or power cords? I would look for anything that could cause an electric interference. If you have other cables try a different one to see if that helps at all.

    Worth checking but to me it didn't sound like interference, more like ring modulation to me as DamianGreda mentioned, hence I mentioned my "ghosting issue"