HELP! High Pitched Hum Using Protools

[daviddewolfe]

Hey... I am Using protools 8 with Mbox mini on my Imac. I Keep getting a hum from my inputs whenever I try to record. I get nothing bad when using my mic, but I have 2 1/4 " patch cables running from input 1 and 2 into my Roland rd-700 gx keyboard. the second I plug my cables into my m-box I get a hum, which only gets worse if I raise my volume levels. I have tried using Balanced cable's, I just bought a Power conditioner with a EMI/RF killer... But I am still having the problem... The only way to stop the hum is to unplug the cables from my mbox... Here is the utube link so you can hear the interference I am having... http://www.youtube.com/watch?v=-1qbEbKP2OI PLEASE help me.... I am about to burn my house down!

[Darryl Ramm]

Originally Posted by daviddewolfe

Hey... I am Using protools 8 with Mbox mini on my Imac. I Keep getting a hum from my inputs whenever I try to record. I get nothing bad when using my mic, but I have 2 1/4 " patch cables running from input 1 and 2 into my Roland rd-700 gx keyboard. the second I plug my cables into my m-box I get a hum, which only gets worse if I raise my volume levels. I have tried using Balanced cable's, I just bought a Power conditioner with a EMI/RF killer... But I am still having the problem... The only way to stop the hum is to unplug the cables from my mbox... Here is the utube link so you can hear the interference I am having... http://www.youtube.com/watch?v=-1qbEbKP2OI PLEASE help me.... I am about to burn my house down!

Burning down the house should stop the hum.

What generation Mbox mini? If you ignore the noise, what does the keyboard sound like when you play.

How do you know the cables are wired correctly? What exact balanced cables did you try - they ran from the XLRs on the keyboard to 1/4" TRS plugged into your Mbox line-in 1/4 TRS connections? Or did you try plugging in 1/4 balanced TRS connectors to the 1/4 jacks on the keyboard (that won't work).

You can try either of Line or DI input settings and see what happens. Try only using either the L or R cable from the keyboard - is it noisy into each channel separately?

Worse case you may want to try to lift the ground on the keyboard or even better/safer try an isolating transformer/DI box.

Darryl

[daviddewolfe]

Hey Darryl, I used Ballanced XLR cables. I have A Digidesign Mbox2 Mini. I still get the keyboard if I play it but both channels are picking up that hum.... Even when my keyboard is off... I have Also a phantom and Kronos and when plugged into those with either power on or off I still get the same hum

[Top Jimmy]

That noise is fairly typical of USB ground noise getting coupling with the signal input. This happens when you use 1/4" TS plugs in the 1/4" TRS input jacks.

First, try a pair of 1/4" TRS cables instead. If that works, you're good. Keyboards don't have balanced outs so the ring will be left floating.

If it doesn't work, try using a passive DI. Use a 1/4" TS cable into the DI and then an XLR to TRS from the DI into the Mbox 2 Mini.

[daviddewolfe]

THanks Jimmy, I'll run to the music store this week and try that out! Will keep you posted!

[Darryl Ramm]

Originally Posted by daviddewolfe

Hey Darryl, I used Ballanced XLR cables. I have A Digidesign Mbox2 Mini. I still get the keyboard if I play it but both channels are picking up that hum.... Even when my keyboard is off... I have Also a phantom and Kronos and when plugged into those with either power on or off I still get the same hum

Balanced XLR cables (meaning XLR on each end?). The Mbox 2 Mini does not have any XLR line/DI inputs. But you could also try an XLR cable to TRS and see if that works (or is that what you did?). If not, then as said you may end up with a DI box. Top Jimmy has already explained this better than I did.

Darryl

[albee1952]

I burned down the house.....then found the hum was all in my head. Anyway, sounds like maybe dirty power, or a ground loop. When I had my Motif plugged into the 003 by itself, all was quiet, but when I added a cable from the phones out(Motif) to another set of inputs on my Central Station, I would get 60Hz hum. Any local music retailers that might let you "audition" a power conditioner? Furman and Monster make some good ones. While they are not cheap(300-400 dollars) if they solve the issue, then it may be worth it. Personally, I would try to trade up to the larger Mboxes with dual inputs that offer both mic and DI ins as you can use good direct boxes, which also may solve hums as they(passive models) have isolation transformers.

[DigiTechSupt]

There are some other suggestions in the General Troubleshooting thread for eliminating/diagnosing ground loop hum and other hum issues.