I’ve had the Zoom H4n for close to a year now, and I’ve been incredibly happy with it on so many levels.
As a portable recorder, it works incredibly well. The built-in microphones are solid and incredibly convenient. The phantom power and line-in inputs might not be what you find in devices that cost three or more times its price.. but I’d peg them at being pretty close. I made some tests against the Apogee Duet, and while it placed behind it, it was a close second.
The H4n also serves as a USB audio interface for both the PC and the Mac. I’ve used it on both platforms, and in terms of driver and system support it’s been consistently top notch.
So what was my problem? On my PC, when I would use the device as an audio interface, I’d get a rather high pitch whine in my monitors which I hadn’t experienced on my battery-powered MacBook Pro. I tried disconnecting other devices, moving cables all over and in different configurations, but nothing seemed to do the trick. I searched the Googles tirelessly, trying to find other people with the same problem.
Eventually, I found out the solution: power up the device on battery/AC power before connecting the USB cable. Then, once the device is powered up, go through the menu items and connect the cable up to the system. No noise, no problems.
Previously, I was relying on the USB power of the system to run the device as an audio interface. In theory, this works rather well: connect the cable when the H4n is off, and it starts up, offering you USB connection options. When you disconnect the device, the H4n immediately shuts off. It seems as though the fundamental problem is that the USB power is a bit dirty; or, at the very least, is injecting some kind of noise into the system.
It is a bit more work to make sure that I don’t leave the H4n on after I shut the computer down, etc., though the benefits are well worth it. In certain cases, the high pitched sound may not be all that apparent; and in others, it may disappear entirely. My feeling is that the laptop, being battery powered, did not have the same kind of electrical signals running through the system, thereby making the USB power a bit more clean.
In any case, I hope this tip helps some other people; it certainly caused me some trouble and aggravation before I got it solved.