KRK Rokit 8 humming problem

[Vibesx]

Hello.

I have a pair of KRK Rokit RP8's G3 monitors, connected through RCA cables to a Numark Mixtrack Pro 3 dj controller, connected to my PC via USB and there is a humming noise coming out of them. From what I've read, it might be a ground loop problem, but I've already tried some things and am running out of ideas:
- changed power cables around to be in different power outlets
- bought a ground loop isolator to no avail(although a pretty cheap one... maybe a better one would have a better outcome?)
- connected the monitors directly to my laptop through a 6.35' -> 3.5' cable; no humming noise
- connected the dj controller to my laptop, both while unplugged and plugged to a power outlet and the humming noise was there
- connected one of the monitors to the DJ controller through an TRS cable, converted to 3.5' through an adapter, connected to a 3.5'(mother) to 2 RCA's(father) splitter; humming was gone, but audio quality obviously changed

What would be next would be DI boxes, DAC's, audio interfaces... but these are kind of expensive solutions that aren't sure to fix my problem, so trying to grab some more ideas. Somebody even suggested some custom balanced RCA cables, although I don't even know how that's possible or how to do it. The problem is that I only have RCA outputs from my dj controller, so using balanced cables would be kind of a problem.

Waiting on your suggestions.

Thank you.

 

[guitaristic]

Hmmm I would guess its some part of your dj controller, maybe just the RCA outputs. Or possibly the RCA cables themselves. You tried swapping those out yet? Also try out other usb ports if you've got them. Since you connected the monitors straight to the laptop and they played (I assume) then that narrows it down some.

 

[RFR]

I had g2 rokit 8s they had hum from the rca jacks. Bad pc board grounding was the issue.
Wiggle the connection. If in certain positions the hum goes away that's what it is.

Build quality on those leaves something to be desired.

 

[Vibesx]

Hmmm I would guess its some part of your dj controller, maybe just the RCA outputs. Or possibly the RCA cables themselves. You tried swapping those out yet? Also try out other usb ports if you've got them. Since you connected the monitors straight to the laptop and they played (I assume) then that narrows it down some.

I've thought about it being from the dj controller, but it's brand new and I think it's pretty improbable. I've also tried some other RCA cables and changing the USB ports... still nothing.

Can you try connecting with the cable above, as well as connecting the RCA's between the Numark and the Rokit's. Zero out the volume that would normally be output from the laptops audio jack. Kinda thinking the ground through the USB to the Numark may not be too good, thus hum finds its way into the Rokit's. The extra cable may provide a ground path between the laptop and the Rokit's and get rid of the hum. The laptop likely isn't grounded well back through it power adapter either.

Unfortunately, I've returned that 6'35 to 3.5 cable, since it didn't quite solve the problem. But I'm thinking of going back to buy another one (longer, since the one I had was really short), since it might have its practices in the future. If I do, I'll try your suggestion and come back with an update. But as a note, I'm going to mainly use my PC, not my laptop, for music production/dj-ing, since I'm still in the learning phase and don't need mobility.

I had g2 rokit 8s they had hum from the rca jacks. Bad pc board grounding was the issue.
Wiggle the connection. If in certain positions the hum goes away that's what it is.

Build quality on those leaves something to be desired.

By wiggling the connection, you're referring to the RCA's? Not sure how that would work, but will try it


By the way, as another symptom, the humming triggers as soon as audio plays in the monitors. If I turn them off and on again, the humming is gone until the first audio signal that goes through them, which triggers it again. Also, humming is affected by the back volume knob. It goes up/down with the volume. If that helps in any way.

Thanks a lot for the replies and hope to get some more suggestions.

 

[ecc83]

If there is not an actual fault try one of these...High Quality Ground Loop Isolator from Rimmers Music

Yes, dirt cheap (also available from Amazon) but they are of very decent audio quality and, more to the point, they really DO isolate the earth.

You can connect with RCA leads and RCA - jack adaptors. I am usually averse to adaptors but that particular type is very reliable.

On another point. Sending cables back causes me to twitch! I cannot do it, NOR can I dismantle and "rob" old cables that I have made up! Something a bit OCD there! But, seriously...COLLECT cables! If you want to progress in the audio field you will need an ever expanding grab-bag of bits!

Worth considering the purchase of a solder iron and associated tools. There will be times when if YOU don't fix it, the show WON'T go on!

And FFS get a digital test meter anyway.

Dave.

 

[DM60]

On another point. Sending cables back causes me to twitch! I cannot do it, NOR can I dismantle and "rob" old cables that I have made up! Something a bit OCD there! But, seriously...COLLECT cables! If you want to progress in the audio field you will need an ever expanding grab-bag of bits!


Dave.

I had to laugh, I rarely throw away cables either.

 

[Vibesx]

Yeah, thing is I'm kind of on a budget after all the acquisitions, and can't really waste money on anything. That's why I've returned them. In the end I've ordered a Focusrite Scarlett 2i2 interface to see if that fixes the problem, it should arrive on Monday. And also, as I've said, I've tried the isolator you've posted. Thanks for the tips will also pile up on cables from now on.

 

[Vibesx]

Ok so I've bought another 2x6.35 to 3.5 jack cable and connected to both my PC and laptop (plugged and unplugged). There is very little noticeable humming, which I can work with (you kind of need to be close to the speakers to really hear it). So the problem must be with the DJ Controller? Any solutions for that?