Studio Monitor Loud Buzzing/Hum

    Hi,

    I purchased some Dynaudio DBM50 studio monitors yesterday, plugged them in to use with the Kemper, and am getting a loud nasty hum/buzz. Anyone know how to solve this? Here are some details:

    • The studio monitors are silent if nothing is plugged in.
    • The buzzing/humming occurs when an XLR cable is plugged into the studio monitors, regardless if the Kemper is on or off.
    • I tried two different XLR cables (brand new), tried in stereo, tried plugging each monitor separately in mono, and had the same result each time. I also tried plugged into multiple different outlets in the house, and turned off the lights (in case a dimmer was causing something).
    • If I crank up the volume of the monitors, they sound great, and will drown of the buzzing sound. If I am playing quietly, the buzzing is very noticeable and distracting.
    • The studio monitors only have a two prong electrical cord, which I thought was odd
    • The monitors and Kemper are all plugged into a surge protector, into the same outlet
    • The buzzing occurs regardless of if I'm using the surge protector or plugging straight into the outlet on the wall

    Any advice would be much appreciated!

    Thanks.

    Thanks - and I think you're right. So I've done some further testing, and think I've isolated the problem, but I still could use some further advice. When I plug one monitor in, the buzz decreases dramatically (almost silent). When I plug both monitors in at the same time (either directly to the outlet, or through a surge protector), I get the nasty hum/buzz. Since the monitors only have the 2 prong cord, I'm assuming it's a grounding issue. Will some sort of isolation transformer fix the problem? Any other suggestions?

    I don't think it's a ground loop, since they have no ground prong. Where would the ground loop occur?

    Maverick, what changes if you:
    connect one monitor only to the Profiler and the latter is on or off?
    Use an 1/4" mono<->XLR adaptor so that the signal line becomes unbalanced?
    Connect the two monitors to two different wall sockets?
    :)

    That's because I didn't want to have to admit that it's was my own stupidity as the cause for the buzzing :) . It helps if I ensure the big red button that says ground lift on the back of the Kemper is on the right setting. Ha! It was set to lift the ground...deselected the button, and problem solved. Guess I didn't need to spend a few hours isolating monitors and cables, and running extension cords to other outlets in the house :) . True newbie here! I do appreciate the support from this forum!

    On a semi-related topic, do you have any suggested best practices for gain staging/output/input settings on the Kemper and my studio monitors, which are directly connected to the main outputs via XLR? For example, my studio monitors have input settings of -10db, 0, and +4db. I've done some experimenting, and it seems that the Kemper runs pretty hot to the studio monitors. For example, with the studio monitors set at 0 db, my main output on the Kemper is set around -30db, and my Aux in with my iphone for jam tracks is set super low at like 0.8. Obviously, if I set the studio monitors at -10db, I can raise the main ouputs and Aux levels on the Kemper. Any suggestions for what the optimal settings are, as I really don't know, and am just guessing? I primarily use a PRS with hot pickups, and have my clean sense set to -4.5 to avoid clipping.

    Glad you solved!
    As for the levels, the "problem" is that your monitors don't seem to have any clipping meter.
    The various sensitivities you can set are meant for adjusting different kinds of devices. since the Profiler can output a strong signal it makes sense to set sensitivity to -10 dB, but since the Profiler's output is largely adjustable it doesn't really makes a difference in terms of gain staging.
    OTOH, -10 dB will reduce the cabs' amp noise, so I'd go for that.