serious electricity hum

  • I always use the Monitor output and the Direct output for my own monitor sound. For this I use 2 jack cables with a tip and a sleeve, like for my guitar and they are plugged in into my small 8 channel Soundcraft mixer. Also my XLR mike is plugged in into this mixer and 2 channels are for my guitar.


    The main outs go to the PA with 2 XLR cables.


    The trouble is that this all produces a serious (electric?) hum.This hum stays if I disconnect my mike. so it has to do something with the 2 ring - sleeve jack cables. I checked both of them but the solding is all right. I press both the ground switches at the back but the hum stays...


    What can be wrong here?

  • Assuming you have your Profiler and the Soundcraft mixer plugged in the same powerstrip (on stage), the PA / FOH likely is plugged into a different power source with a different ground potential. Classic ground loop situation.


    What to do:

    Disconnect the Main Out XLRs and see if your own rig (Profiler, microphone, Soundcraft and your monitors) are without hum now.


    If that's the case, you need to electrically isolate your rig from the FOH rig by using (passive) DI boxes for your Main Outs -> FOH desk or stagebox.


    On the other hand, if you still have the same hum, it's likely the (unbalanced) TS cables running a couple of meters across the stage to your Soundcraft catching electrical interference from other gear/power cables on stage. In this case you should keep the unbalanced cables as short as possible and use (passive) DI boxes to convert to balanced connection as early as possible.


    One more bit of info:

    NEVER run audio cables (especially unbalanced ones) side by side (parallel) with power cables! If there are unavoidable power cables on the way, cross them in a + instead of = way.


    Hope this helps :)

  • Is there still hum if you disconnect the guitar?

    Is there still hum, if you disconnect one TS-cable e.g. from the MONITOR OUT?

    I guess the PROFILER's MAIN OUT is connected to the PA (not the Soundscraft's main out). What if you press the MAIN OUT's ground lift?

    What if you disconnect one XLR?

    Can you narrow in, if there is hum, if just PROFILER and PA are connected or if just PROFILER and Soundcraft are connected?

  • Silly question, why are you needing a sub mixer? It's almost certain it's the sub mixer causing the problem but not sure why you need it?


    I never just want my vocals and guitar in my monitor. You are also controlling the levels from the KPA to the PA manually as they will be affected by the mixer i.e. turn up your monitor, you increase signal to the PA, surely?


    Also, I would use XLR's rather than jacks.

  • Silly question, why are you needing a sub mixer? It's almost certain it's the sub mixer causing the problem but not sure why you need it?


    I never just want my vocals and guitar in my monitor. You are also controlling the levels from the KPA to the PA manually as they will be affected by the mixer i.e. turn up your monitor, you increase signal to the PA, surely?


    Also, I would use XLR's rather than jacks.

    No silly question, though. It's quite simple. I need the mixer to play and sing when rehearsing in my studio. All instruments connected to this mixer feed my DAW in the computer. All volumes, gains and EQ are this way easy to control and to balance. I use this mixer for some years now and this works fine.

    Only my mike has XLR . I use Monitor and Direct for stereo reasons so no XLR here.

  • Is there still hum if you disconnect the guitar?

    Is there still hum, if you disconnect one TS-cable e.g. from the MONITOR OUT?

    I guess the PROFILER's MAIN OUT is connected to the PA (not the Soundscraft's main out). What if you press the MAIN OUT's ground lift?

    What if you disconnect one XLR?

    Can you narrow in, if there is hum, if just PROFILER and PA are connected or if just PROFILER and Soundcraft are connected?

    Perhaps some extra details:


    1. I only have described my home situation. So the PA and the stage are not present. The Monitor out and the Direct

    out go straight into the mixer with 2 jack cables. The main outs of the mixer go to my 2 KRK6 100 W monitors in

    my studio.

    2. Profiler and mixer share the same power strip in the room.

    3. Disconnecting the mike (XLR) has no effect.

    4. Distance of jack cables from profiler to mixer is less than 1 meter.

    5. There’s no crossing of audio cables with power cables. The mixer has a power adapter at the back and the profiler’s

    power cable is far from that.

    6. Both Ground buttons (Monitor and Direct) don’t respond to hum.

  • What has an effect?

    Does the hum disappear, if you disconnect the two TS cables?

    Or is it even sufficient to just disconnect one of those two?

    Is it relevant which one?

    Have you tried other channel strips of the Soundcraft?

    What if you disconnect your guitar cable from the PROFILER?

    Can you control the hum via Input Noise Gate?

  • No silly question, though. It's quite simple. I need the mixer to play and sing when rehearsing in my studio. All instruments connected to this mixer feed my DAW in the computer. All volumes, gains and EQ are this way easy to control and to balance. I use this mixer for some years now and this works fine.

    Only my mike has XLR . I use Monitor and Direct for stereo reasons so no XLR here.

    Gotcha. You said going to the PA hence it sounded like your live set up.

  • Ok, so you use this setup exclusively at home ... not for gigs, right?


    First of all, try to find the cause of the problem systematically (by exclusion).


    1. Connect headphones to the Soundcraft to check if the hum is still there after every step below

    2. Disconnect the XLR Main Outs of the Soundcraft

    3. Turn down ALL Level knobs of unused channels on the Soundcraft (like 3, 4, 7/8, 9/10, 11/12)

    4. Disconnect the microphone

    5. Disconnect USB

    6. Disconnect the TS cables coming from your Profiler


    At some point the hum should be gone. If it's gone only after step 6, you will likely have to hook up your Profiler through a balanced connection

    (XLR female ->TRS cables from Profiler Main Outs). If the hum is gone at a different step ... e.g. after disconnecting USB, let us know.


    One of the potential issues is that your Profiler is grounded, your PA speakers are grounded as well and your computer (USB connection) might be grounded as well ... but the Soundcraft isn't because it doesn't have a 3-pin plug.

  • I'm still a bit confused:


    I'm assuming your are feeding MONITOR OUT and DIRECT OUT with "Monitor Stereo" activated into the channels 1 and 2 of your Soundcraft, correct?

    Why is the 100Hz filter activated in channel 2 and not in channel 1?

    Why are the channels not panned left and right?


    Regarding the hum ... is there hum when the PROFILER is shut down or at any time? Is there a way to shut down the phantom power at that Soundcraft desk? I'm asking as sending phantom power reversely into the output amplifiers of sending gear is not a good practice and we have experienced one case, where it caused hum, while the PROFILER was switched off - and only while it was switched off! What if you plug your TS-cables into the line level TS sockets of stereo channel 5/6, which doesn't deliver phantom power?

  • maybe too obvious but, check only the kemper connected only with the headphones. if you have the same noise, you have to work with the profiler. if not. just check adding one by one the cables to isolate and identify the problem

  • The whole setup at home is an exact copy of what I use on stage. The only difference is that I use a 22 channel mixer with a 7000 W QSC PA when I gig with the band. So it's a kind of checking everything in my home setup as a copy for doing this live on stage.


    From what I read now, on stage the hum wouldn't be there because of the 3-pin plug for the 22 channel mixer?


    But first I will check all 6 steps to eliminate possible problems. Thank you!

  • MONITOR OUT and DIRECT OUT are unbalanced, so TS cables are sufficient.

    Yes, I never had any hum problems with the two TS cables for these two outputs. I guess the problem comes from elsewhere so I will systematically try to eliminate this hum by checking all cables and, if necessary, replace them by others.