What sort of noise? Can you post a clip on Soundcloud?

If it does that only with condensers, it might be a phantom power problem. Like Boswell, it'll be helpfull to have a sample.

Hi guys... I went to record the noise just now and held the mic in my hand and there was no noise! Forgive the newbie move, now I know what happened. My shockmounts became a bloody mess and I didn't put them back together again, so the noise was propably just vibration from the surface I had put the microphones on to record. I could have made further tests and figured this out myself... Thank you for the help anyways! you guys rock!

What mathers is that it's now workin !! ;)

Hi guys,
Who would've known: I wish I had been stupid all along... I was tracking great vocals when the electricity went out and I hadn't saved. Today I tried to record those vocals again and guess what? THE NOISE CAME BACK! I'm posting a sample of the noise... I was making my voice peak at -12db (this particular song has soft vocals) and the noise was peaking at about -24db... impossible to track anything decently. I tried with the power plug on and off, and I've tried other channels. What to do, what to do...
Please shed a light if you can,
João
[MEDIA=soundcloud]johnverb/micnoise24bits

track unavailable...

This sounds like an unstable phantom power rail.

Wow... yeah, that's nasty. I'm inclined to go with Bos on this, not because I know myself, but because Bos is a bad-ass with this type of analysis and diagnosis. ;)

I've heard this sound before (at least a very similar sound), about 6 months ago, when I was using my AKG SolidTube mic... I thought it was the power supply - it turned out to be , of all things, the tube. I replaced the tube with a new one and the noise disappeared. But, I understand that you aren't using tube mics, so I'd default to Boswell's diagnosis.

Which mic did you have connected when you heard the noise you posted? Or, is this noise apparent regardless of which mic you have plugged in?

Hi Donny, I haven't tested it with many different mics, but it's the same noise on both my condensers (as posted above an mxl and a behringer). It really makes sense for it to be the phantom power, because I don't get any sort of unwanted noise with dynamic mics or the direct input. The solution then would be to buy an external source of phantom power? How important is the quality of the device in this case? Can I get the job done on the cheap?

Hmmm.. what preamp are you currently using? You may be better off just replacing your current preamp/ i-o with another model entirely...

How many input channels do you require?

USB or Firewire?

Budget?

The fact that the noise comes and goes makes me wonder if you have an intermittent connection either at the mic jack, in the mic itself, or with the source of power for the interface.

You say you've replaced and tested different combinations of mics and cables, that's good. Did you put any pressure on the other connections? Repeated stress on the mic jacks can weaken/break the internal solder joints.

Was anything different? In particular the cabling - as others say, it sounds like a power supply issue, if it impacts on both mics. First thing I would do is try a different cable. If you don't have one, then at the mic end get out the digital meter - pin one to pin two should show you some volts. Ideally it should be 48v, but it's often less - which is normally fine. If you repeat the measurement on pin one to pin three, it should be EXACTLY the same. If it's not, repeat the test at the preamp/interface end and compare the readings. again, they should be the same. If they aren't, it's a cable issue. If the readings coming out of the preamp are wrong - then it's a proper fault in the phantom supply.

Hey guys,
Yes I have tried changing cables and changing mics. Donny, I use the interface's built-in preamps. It's a 4-channel interface and the phantom power can be fed to two channels at a time... I've tried using either one of the four channels with the phantom power on with either of my two condensers, with either of my four xlr cables in different combinations... same thing always. On the other hand, I get no noise with dynamic mics or the two direct inputs, even when I leave the phantom power on. I'm wondering at this point if getting a separate phantom power device would solve the problem. Would it?

It still certainly sounds like an issue with the phantom power to me. It seems unlikely you have 4 bad cables, so it almost has to be phantom power, or the mics themselves. Do you have any friends who could let you try your mics and cables through their mixer and/or interface? That should be the final clue.

Even though your phantom power is switchable on/off 2-channels at a time, they are all fed from the same section of the Fast Track's primary power supply - which could be where your problem lies. Using the external power supply, the Fast Track runs on a 5VDC input voltage (2A), so there has to be circuitry in there to step that up to 48V for the phantom power, and still provide enough additional power to run the pre-amps / converters / headphone amps / displays / etc., (presumably mostly at 5V or they would have picked a different input voltage.)

You should use the power supply whenever possible. The USB power option really cuts back on the available current, and hobbles the Fast Track's performance. And you should definitely avoid connecting it to any kind of USB hub, that would rob it of power too. The manual specifically tells you what functions suffer running from USB power - including this about Phantom Power:

"If the interface is using USB bus power, analog inputs 3/4 are disabled and Fast Track C600 can provide up to 4mA of current on channels 1 and 2, or up to 8mA if only one channel is used. This is more than sufficient for most modern microphones, as well as many vintage microphones."

You don't specify which Be*#%nger mic you have, but as we found in another thread the C1, for example, requires 2.5mA of between 36V - 52Volts
The MXL v57M lists these specs, Current Consumption:

So if you can test the mics through other known-working-equipment, and find they don't make the offending noise - you can be pretty sure it's the phantom power in the Fast Track. You could

I'm still concerned that it comes and goes, which would make me wonder about a bad solder connection on the phantom power section power supply.

I agree that this is mostly comming from a phantom power problem and DvdHawk has a good point talking about how the unit is powered. But the OP says that you tried the external power and the usb (which would be last resort for me the reasons already discusted unless using a usb infuser)

Regarding getting external phantom power, I'd advice against it. At this point, you would be better off buying a new audio interface with fonctionnal power and better preamps. Starting with presonus or focusrite

Just my two cents ;)

Guys,
Thanks a lot for the input. I do deserve a spankin' new interface... but for the moment I can still track drums with the TASCAM DR40. But hey, It's the device bangin' with the drumsticks, those flappy ruppery things on either side of my head, and the parts of my brain that aren't Magic: The Gathering and vagina that truly matter. I hope you have a swell time keeping those sound waves in line. The sneaky little bastards!
Catch you on the flipside,
João