Noise problem

Ya know one thing I remember about that particular board if that's the one from the 90's ,does it have that add on pod on the back/ bottom?  and not sure if this would cause your issue but I'm not sure if your aware of this' We had installed one in a church back then and the system sounded flat. Upon reading the Mackie Manual I discovered they choose to switch the XLR ( and TRS)  pin assignment. It was so pin 2 was neg and 3 was + , The Yorkville power amp was wired standard so the system was out of Phase!!.  They called it the "American" configuration as apposed to British or Japanese.  We ended up getting them a Yamaha board. Not only that issue but because some found the Mackie confusing to run.
I liked that board, great sound, I ended up putting it in my studio and mostly used the direct outputs to a 8 track deck. I made a special set of cables to switch the polarity.
Your issue sounds like my trouble shooting at the aquatic center a week or so ago. The minute we hooked up the cable vision to the PA system there was a hum. We tryed a filter, but in the end it was a pure fluke that solved the issue when I swapped out a module in the Peavey unit ( 70 volt stuff) I mention this as I immediately thought it was a grounding issue with the AC but in the end it was the Pre amp gone bad.
Things I would try,
A different USB cable.
Different inputs on the board.
Swap for standard patch cables, If the Yamaha does not have TRS output jacks, which I doubt,  you could cause a shielding leak.
Test the Yamaha in another mixer or direct to your interface inputs. Take the Mackie out of the picture.
Plug the Mackie and the computer into the same outlet ( if not already)

Does your interface plug in? Wall wart, USB powered? Ground lift it?

Johnny - yes, the CR-1604 is an older one from the 90's with the pod on the back, but yes, I already knew about what you're talking about.  

I built cables long ago specifically for the MAINS on this board and those cables stay with this board's main outs only just to resolve that problem you're describing.

I'll try a different USB cable, but I suspect it's more of a ground loop problem of some kind for the hum - I'm not sure what the 1kHz tone is tho.
different inputs to the board had no affect - same thing happens.
I believe you're right - I don't think the MM6 has balanced outputs, I'll double check that and try changing out the cables to instrument cables.
haven't tried taking the mixer out - I'll try that.
mackie and computer are already on the same circuit.

thanks for the tips

Junski - that's a good suggestion - I'll try that if the things above don't work.

I wondered why you had 2 logins, but you weren't doing anything malicious with it so I didn't care.

I think maybe you're right.  I found something else out (though I haven't gotten far on the other suggestions above yet).  I have a digital piano connected as well, but for MIDI I connect it via MIDI cables and not USB.  so I connected it up with a different USB cable and connected it to a different USB port.  I left the MM6 OFF and left the USB cable to it disconnected and the 1kHz tone happens with the digital piano as well.

so I'm thinking this has something to do with USB specifically.

if I disconnect the USB cable from the MM6 to the computer then BOTH noises go away!

 
I had that exact same issue with a MOTIF ES7.
Swap out the USB cable... and I'll bet the problem goes away.
It's a grounding related issue (bad USB cable).

thanks Jim - I did use a different USB cable for the digital piano and had the same problem, but I'll definitely try another cable on the MM6 and see what happens.

the noise was LESS on the DP than it was on the MM6, but it was still the same hum and 1kHz tone.

I have a Profire 610 and it is connected to m-audio monitors and they are completely quiet. However, when I plug the outputs of the 610 into my mixer/eq/pa, it hums and I can hear digital noise that corresponds to the display. That is, when the display refreshes, it makes the digital noise. The mixer/eq/pa is plugged into the same outlet (through a power strip) as the computer that is connected to the Profire 610.

I unplugged the display, both AC and data cable and it still makes the noise. I think the noise is radiating from the video card into the firewire card. I moved the firewire card as far from the video card as I could and built a grounded shield in between the two cards. The noise is still there.

Today, I got this in the mail: http://www.amazon.com/gp/product/B000KUD2G4

It sits in between the Profire and mixer. No more hum and no more digital noise! For $29.99, it works great!

Just wanted to share in case this could help anyone else.

well, I've tried a different USB cable but no go.  I have not tried to measure the potential difference between grounds.  I just simply haven't had the time to work on it in that depth.

losguy and maximumpower - thanks for the suggestions.  I was considering a DI box if I can't resolve it another way. 

I'm also going to take the mixer out of the equation and see if it's still a problem that way and I will  also try lifting the grounds and see what happens.

thanks for your suggestions.

losguy


You bet, Beagle. The ground-lifter is $0.69 at the hardware store, if you don't have one handy. But please do remember, it's just for sussing out the problem, never intended as a permament solution.

I understand that (I'm an EE by day and singer/keyboardist by weekend!)