I am encountering a faint but persistent high pitch noise through my Yamaha HS-50M monitors when my Edirol FA-66 interface is plugged into my computer via firewire ca ble.
I've read all these threads which sound very similar to my issue and have tried all the pertinent recommendations presented so far:
Just to be clear, my problem is similar but not identical to the problems listed in the threads above. Mouse movement or computer activity doesn't effect the monitor noise I'm hearing at all, it is merely a constant sustained high frequency tone that's emitted from my monitors when my FA-66 interface is plugged into my MacPro via firewire cable. My speakers are silent (aside from their own self noise) so long as my FA-66 isn't connected directly to my computer. Even when my FA-66 is powered on via its AC adaptor but not connected to my computer via firewire cable there is no added noise in my monitors. It's just when I make the firewire connection between my interface and my computer that the high pitch noise appears in my monitors.
I used to run my Edirol off of my older MacBook and never had this issue. I just recently upgraded to a new MacPro and am encountering this issue for the first time.
Since the noise is eliminated when I disconnect the firewire cable from my interface, I believe the sound is being caused by interference from my computer, which is then transmitted through my firewire cable into my interface.
My setup is this:
Grounded Wall Outlet > Furman Power Conditioner > MacPro Desktop Machine > Edirol FA-66 > Monitors
I am using TRS-XLR Mogami Speaker cables to connect my interface to my monitors and am using Mogami cables throughout my system.
All of my audio gear is being powered through my Furman power conditioner: my computer, my FA-66 interface via its AC adaptor (not firewire bus powered), my speaker monitors, and all my other audio equipment.
I don't believe I'm picking up interference from any of my other cables and wiring and this doesn't seem like a grounding issue. Like I mentioned, the noise is gone when I disconnect the firewire cable from my FA-66 interface.
I do have some other hardware in my setup (my computer screen monitor, a USB hub, AC power supplies and cords to power external hard drives, a lamp) that are receiving power from a separate surge protector strip plugged directly into a different wall outlet than the one my Furman conditioner is plugged into. I don't believe any of these other devices are the cause of the interference noise because when I unplug all these items from their respective wall outlet, I still hear the exact same noise when my FA-66 is plugged into my computer via firewire cable.
All signs seem to point to my firewire cable and/or my computer.
Originally I started with a different firewire cable and swapped it out for a newer and higher quality, gold-plated firewire cable meant to cut down on interference. This cable swap did help reduce some of the noise my monitors were picking up, but did not eliminate it entirely.
I then invested in some ferrite core clamps and placed those around each end of my firewire cable (one right by my computer's firewire port & one right by my FA-66's firewire port). This helped a little more but did not eliminate the high pitched sound entirely, just made it even quieter. The hole diameter of the ferrite core clamps is slightly larger than the diameter of my firewire cable, however, and I'm going to order more clamps with a smaller hole diameter that will ensure a snugger fit around my firewire cable. Do you think this may help things more?
I also lifted the grounding pin in my Edirol, tied a copper grounding wire around it and connected the other end to my MacPro's metal case with alligator clamps in an effort to better ground the two suspect pieces in the chain. This seemed to have little to no effect beyond what the ferrite cores were able to clean up. (I got this idea from the GS thread contained in the first link above.) I don't know much about hardware electronics but thought I would try this out just to see if it would help. The fact that it didn't help, to me, seems to reaffirm that the system is grounded properly, because if it weren't I would have possibly noticed an improvement by making a grounded connection between my interface and computer. Please correct me if I'm wrong about this.
I even tried plugging my Furman power conditioner into an entirely different wall outlet, but this didn't change things at all. I do have one more unused wall outlet I can try but don't think this will make much of a difference because I'm 99.99% sure this isn't a grounding problem and that the sockets I'm using are properly grounded. My Furman isn't registering anything abnormal and seems to be functioning properly.
As of right now I've been able to make significant improvement to the noise problem and have eliminated it by 90%. The high pitch noise through my monitors is virtually eliminated but I still notice a faint bit of added noise when interface is powered on and connected to my computer via firewire versus when the firewire cable is disconnected.
Could my MacPro be outputting some kind of interference which is being picked up by my firewire cable and transmitted to interface and monitors? I've read that sometimes a computer's power supply unit can output a large amount of EMI or dirty electrical interference. It seems surprising to me that Mac's professional desktop machine would cause a fundamental issue like this though, especially since it is designed for being able to work in a professional audio recording setup.
Any other ideas people can provide as to what may be causing my added interference and how to treat it would be greatly appreciated. Thanks in advance for your help!