I had my guitar cord still plugged in (but laying loose on the floor) when I had noise like that. So...... I always leave the mic cable plugged in(48v off), but the guitar cable is out when not in use.

charlyg
I had my guitar cord still plugged in (but laying loose on the floor) when I had noise like that. So...... I always leave the mic cable plugged in(48v off), but the guitar cable is out when not in use.

So are you saying that disconnecting the guitar cord from the interface resolves the issue? If so, it may be acting as an antenna.

Hello Again,
 
I have nothing plugged into to my interface and I still get the hum.
 
Regards,
John

OK you are saying it only happens with Sonar and so are you thinking that something in Sonar is causing the "hum?" It is pretty difficult to imagine Sonar as a particular application generating a hum. Have you tried your outside the box setup with another application that is capable of recording and monitoring audio? You could download Audacity for free, and try that. A lot of work to figure out that Sonar is not the culprit, but it is a useful Audio editor in its own right. Or you could try describing how your setup (hardware and software and project track by track) is set up exactly and precisely and in enough detail that someone who has no idea what your system looks like could set theirs up the same way. That will probably take you a fair amount of time, but doing so may reveal the problem source to you, and would certainly help people here. Or you could set up a minimal test configuration in Sonar with just a single track, no effects and see if the problem persists. Or you could take our best guesses one at a time, implementing them each one at a time until someone hits the diagnosis by accident. 

It can't be SONAR because the program does not generate any sound on its own. It has to be something related to SONAR interacting with hardware.
 
Maybe it's USB picking up "hash" from the USB bus, which usually has all kinds of crap on it. I assume you're not using a hub, powered or otherwise. If so, try a direct connect to the motherboard.
 
I've had enough issues with some older interfaces that I bit the bullet and installed a USB PCI card in my computer and use it only for devices that pass audio. That solved a bunch of problems. The "dirty" USB devices, like hard drives, go to the motherboard's ports.
 
Finally, try connect a wire between the interface ground and the computer's ground to determine if there's a change in the character or level of the hum. Also, by hum I assume you mean sine wave 60 Hz hum, not something with harmonics. 

A MIDI loop will create such a hum, and there are plugins which make noise even with the transport stopped (iZotope's "Vinyl"). Amp sims (if echoed) will also do this, and on some settings even with no input.

Best troubleshooting may be to start a new project and pull tracks from the problematic one until you find the issue. Another possibility is sound card settings in Windows, when doing music you should not share drivers (especially since Windows itself will get first dibs on the interface).

Hi All, and thanks once more for all your replies.
 
Problem Solved............... It seems that it was a dimmer switch in my studio.
 
It was the first thing I tried when the hum started. However I did not realize that I had to have the switch off when I turned on the Computer. I originally checked by turning the switch off while the computer was on.....and that did not help. But if I turn the computer on with the dimmer off I have no hum.
 
I have confirmed that by checking a few times to be sure and that seems to be it.
 
Sweet....Silent.....no Hum.....Speakers.
 
Thanks to you all.
 
John