Interference? What is that?

Brian Maurer · February 11th, 2012, 04:38 PM

Quote:

Originally Posted by Greg Miller

Brian:
Plug in the condensor mic again, turn on phantom power, and make two more files: one on battery, one on AC. If we're lucky, the birdie will be absent from the AC-powered recording, even with the mic connected.

Some inconsistent test results, but could have just been... hell I have no idea what it could have been, but here's what I've got.

Greg Miller · February 11th, 2012, 05:27 PM

Man, that is shocking!

I did expect to hear some sort of oscillation with the phantom/mic combination, simply because that's what was bothering you in the first place.

I rather expected it to occur with battery power, because that's when we heard it with no mic connected; but in fact your battery file was clean. Very odd, because that's when you had the initial problem.

I can't say I was surprised that the AC power file was clean, because it was clean with no mic.

But I was blown away to hear the low frequency really ugly oscillation in the "AC2" test. Of course the phantom power is on, and that's when we expected trouble. But AC with no mic was quiet; why did AC with mic turn out to be the worst of all the tests?

And why the discrepancy between AC(#1) and AC2? Were there any variables whatsoever between AC(#1) and AC2? Different mic position? Different situation in the room? Different anything that you can think of?

What's the headphone situation when you run the tests? Any phones plugged in, or not? What's the monitor gain setting? Where is the headphone cable (if any) relative to the mic jack and mic cable (if any)? {This is a long shot, in case it might be some strange feedback or crosstalk. In reality, I think it's the phantom power supply. But I guess the PS oscillator might be leaking out on the headphone jack... anything is possible.}

If you borrow the other Zoom again, and repeat at least these last few tests on that recorder, it might help to narrow this down, as to whether it's typical of this model, or just a glitch with your particular machine. (It's going to get confusing keeping track of all the variables and all the test results. Sigh.)

February 11th, 2012, 05:27 PM	#32
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Re: Interference? What is that? Man, that is shocking! I did expect to hear some sort of oscillation with the phantom/mic combination, simply because that's what was bothering you in the first place. I rather expected it to occur with battery power, because that's when we heard it with no mic connected; but in fact your battery file was clean. Very odd, because that's when you had the initial problem. I can't say I was surprised that the AC power file was clean, because it was clean with no mic. But I was blown away to hear the low frequency really ugly oscillation in the "AC2" test. Of course the phantom power is on, and that's when we expected trouble. But AC with no mic was quiet; why did AC with mic turn out to be the worst of all the tests? And why the discrepancy between AC(#1) and AC2? Were there any variables whatsoever between AC(#1) and AC2? Different mic position? Different situation in the room? Different anything that you can think of? What's the headphone situation when you run the tests? Any phones plugged in, or not? What's the monitor gain setting? Where is the headphone cable (if any) relative to the mic jack and mic cable (if any)? {This is a long shot, in case it might be some strange feedback or crosstalk. In reality, I think it's the phantom power supply. But I guess the PS oscillator might be leaking out on the headphone jack... anything is possible.} If you borrow the other Zoom again, and repeat at least these last few tests on that recorder, it might help to narrow this down, as to whether it's typical of this model, or just a glitch with your particular machine. (It's going to get confusing keeping track of all the variables and all the test results. Sigh.)