Capacitor bleed?
I'm guessing wildly, does it even have caps in it?

Dude, don't ask me questions I can't answer. I seem wildly intelligent, but I'm just a kid, man.

No, but I have no idea what that means. Explain, Mr. Greener, please.

Reading into your mic I haven't found much info on it. I was more guessing for the fun of it than suggesting anything. However, my guess is based on the types of noises broken things make. High pitched squealing is classic failing capacitor action. ;)

Good call, Greenman. Capacitor= condenser. Contact MXL to send the turkey back for repairs. The tiny electronics in that bugger are not easily soldered/replaced...

Ugh, I sent 'er back twice. And they seem to have problems fixing things? I gave up on them. Maybe I'll try again. Hopefully I won't want to punch my phone over and over again.

Of course, that's why I'm a bit worried that it's on my end. I'm relatively sure it's the microphone, I've tested any other variables I can think of, but I assumed Marshall would be able to fix something like that.

14khz Resonance eh? Do you hear it when phantom power is not applied?

Well if it is the mic, it could be a broken Capacitor, it could be a faulty capsule,or it could be a funky transformer. Can you solder SMT?

Well, what did they tell you when you sent the mic to them...TWICE?
Did they say "No trouble found"?
Did they claim that they replaced a component? Did they send you a new mic?
Are you able to take the mic to another system and see how it operates?

Moonbaby has some good points, more info would be helpful.

I've never soldered in my life, but I know I need to learn how eventually.

They said nothing at all. Either time. The first time I got a piece of paper saying "traded cardioid capsule with omni" except I didn't need an omni and I, in fact, needed the cardioid. And testing with the other capsule still created the 14 kHz whine.

The second time, what appeared to be a new microphone came (it was wrapped differently than the previous "fix") but still, the microphone yells at me.

The frequency is affected by both the pre's gain and the phantom power. At lower gain, it's significantly less audible, but, naturally, the good bit of the signal is as well.

I'll find a place to upload and post a sample, yeah?

http://www.soundclick.com/bands/default.cfm?bandID=464100

Okay. There's a bit.

So you hear the whine with no phantom power supplied?

Oh, no. Sorry, I didn't say that. I meant to, swear it. I can only hear it with phantom power supplied.

Hurrah, I'm in an audio class right now. Learning about signal flow.

Also, considering my intricate knowledge of the inner workings of microphones, I'm giving Marshall another shot.

I have not had any consistent luck with the MXL 604. The 603S is much more consistent though it doesn't have the pad. Also, the plating MXL uses on the capsules is not very good. It corrodes causing problems with the function.

Do you have any other condenser microphone to test your set up? Until you try a different mic and/or a different XLR cable then you won't ever know.

Of course. I've tested everything. Different mics (including another 604), different XLRs, different pres, different rooms, and plenty of other different things, I'm sure.

Definitely the mic.

Well I'm really quite curious? Yup, a nasty oscillation around 6400 hertz & 13,000 hertz. So I'm listening to a stereo signal and it's only in the right Channel. What are you using in the left Channel? Does it stay with the right Channel or does it stay with the microphone? It certainly sounds like RF interference. It's not too close to a TV set is it? Hey, Mick Jagger was stupid enough to be watching a football game while cutting his vocal track for their 1976 release of Black & Blue. It was painfully obvious even coming off of vinyl with 15kHz horizontal sync fading in and out with his lead vocal track. So perhaps it is a proximity problem? Many items such as electrostatic air cleaners are also huge sources of problems. You wouldn't believe how many idiots put them in their studios. Then they call me when they have all of these noise problems. You may have other RF producing items nearby? You can't keep going through that many microphones, obviously different, with the same problem. It ain't the microphone. I think it's crappy cables?

And gold sputtered capsules don't corrode. Maybe you live near a volcano? They are effective electrostatic air cleaners when left out, powered up in a hostile environment. But it usually takes years for that to happen.

Most of these problems are usually operator error.
Ms. Remy Ann David

No, that's exactly what I'm saying but not very well. It's just the one microphone. The right channel microphone. One of the MXL 604s gives me that noise and that's it. That's why it's definitely the microphone.

I'm using the other MXL 604 in the left channel. I thought the same thing, probably interference, but it's not near anything. My laptop is probably ten feet away and the only TV is downstairs. That's it. Nothing.

I make no error this time. Usually, but not this time.

OK, if you unplug the cables at the microphones and interchange them, does the whine switch to the other channel? If yes, then it's either (still) a microphone fault, or it's an interaction between that particular microphone and your pre-amp causing an instability.

Mhmm. Even if I switch the cables at the microphones the whine remains in the problematic microphone. It's always the microphone regardless of the cable or the pre I use for that microphone. I got a hold of Marshall again, supposed to talk to the engineer that says he replaced the microphone. Hopefully I'll get my way.

[Q]"And gold sputtered capsules don't corrode. Maybe you live near a volcano?" [/Q]

It isn't the capsule's sputtered diaphragm I'm speaking of. It is the not-really-24karat-plated bottom of the capsule unit. I agree, if it were really gold it would not corrode until after the plating had worn off.

In this particular design the screw off capsule has a spring loaded center pin contact and also electrical contact by way of screw threads. None of which is gold unless I miss my guess. I've seen at least 5 MXL SDC with obvious corrosion marks on either the capsule module or the contact point of the mic body. Regardless, this particular 604 is a bust I think.