Massive ammounts of hiss with condenser mics

[MindMunch]

I recorded a test here with just one condenser capturing vocals and guitar at the same time to show how it sounds: http://dl.dropbox.com/u/17053397/sexual healing ruido).mp3

When I plug a condenser mic and turn the interface´s phantom power on, it works fine for about 3 seconds, then the input signal becomes very weak and a MASSIVE hiss emmerges. When I turn a second condenser mic, the hiss continues at the same massive level but the input signal of both mics decreases even more. Dynamic mics work fine.

I´ve tried, with the same results:
-Different USB ports
-Different USB cables
-External powered USB HUB
-Notebook running on battery
-Different computers

An external phantom power supply to the mics should solve the issue, right?
Probably a dumb question, but as I don´t know shit about electronics I figured I'd ask this here before ordering one.

 

[StefTD]

do you power the interface via usb or with exteranl power? I don't know shit, too, but if you only power
it through usb there might be not enough power, no clue

but an external phantom power supply should help.

 

[MindMunch]

do you power the interface via usb or with exteranl power?

The interface is powered though USB 2.0

 

[Notuern]

USB doesnt give you more then 5v.. you need 48v for phantom power.
Most cards have an extra powersupply to use when you need phantom power.

 

[Erratic]

my interface is powered through USB 2.0 and I've been using a condenser mic since forever, never had problems, what's your mic ?

EDIT: Damn, I thought it was a small hiss, that one is massive!

Bad cables maybe?

 

[TheWinterSnow]

USB doesnt give you more then 5v.. you need 48v for phantom power.
Most cards have an extra powersupply to use when you need phantom power.

Its called a step-up circuit, how do you think a 2Kv stun gun/taser can run off two AA batteries?

Regardless though, due to the fact that you would be stepping up and the amount of current that USB is limited to, if you don't have the current needed for the 48v the available voltage would drop to something less, thus increasing the chance of clipping the mic's preamp and drastically increasing the noise floor.

 

[MindMunch]

USB doesnt give you more then 5v.. you need 48v for phantom power.
Most cards have an extra powersupply to use when you need phantom power.

Those 5v turns into 48v by a process that I have no clue at all to talk about.:Spin: The phantom power button is labelled 48V and I´ve recorded stereo condensers in the past using phantom power from other USB interfaces. As my interface doesn´t have an extra powersupply I´m pretty sure that an external phantom power supply is the only way to go. :/

Damn, I thought it was a small hiss, that one is massive!

Bad cables maybe?

I´ve tried with other cables and even other mics. The fact that when I turn the phantom power on it works fine for a few seconds is the clue that the problem lies there. I´ve isolated all the variables so I guess I just want to hear it from someone else before spend the dough on an external phantom power supply.

 

[LeSedna]

Just a 2c :

You can create 48V out of 5V, by decreasing the associated current, using what we call in my language a "tension bridge", using basic electricity laws. And so that's why you can survive 10 000 V for instance, cause current and not tension does kills you (the current is the actual measure of "how many electrons pass during an interval of time" while tension is just a difference of potential). That doesn't mean you can create a decent 48V phantom power out of any 5V source (cause of the current and therfore power), I'm not quite sure about the standard of a phantom power, so a dedicated power supply is always a good idea. That was my 2c !

 

[AudioGeekZine]

WHAT INTERFACE?

Try turning on phantom power, then connect to the computer. I remember the mbox2 had some stupid bullshit like that because the computer wouldn't be able to suddenly supply enough power for the mic.

If you're going to buy an external phantom power supply, you may as well buy a preamp

 

[Notuern]

I can't remember ever seeing a USB/Firewire soundcard that DIDN'T use an external transformer for phantom powering.

Just a 2c :

You can create 48V out of 5V, by decreasing the associated current, using what we call in my language a "tension bridge", using basic electricity laws. And so that's why you can survive 10 000 V for instance, cause current and not tension does kills you (the current is the actual measure of "how many electrons pass during an interval of time" while tension is just a difference of potential). That doesn't mean you can create a decent 48V phantom power out of any 5V source (cause of the current and therfore power), I'm not quite sure about the standard of a phantom power, so a dedicated power supply is always a good idea. That was my 2c !

Exactly.
What happens when using a step up circuit is that you increase the voltage but loose amperage.
Essentially, you have more electricity but with equally less power(Same amount of wattage.).
I think a USB-port supplies 5v @ 500mA, and when you start slicing that up to run all of the electronics within the sound card AND running a phantom powered microphone, i think you're pushing the limits.

 

[MindMunch]

Thanks for all the info guys. Always learning on ths board!
Just ordered a 3 channel 48v phantom power external supply : )

 

[AudioGeekZine]

I can't remember ever seeing a USB/Firewire soundcard that DIDN'T use an external transformer for phantom powering.

my TC Electronic Impact twin (firewire) can run bus powered with two condensers at 192kHz.
The M-Audio Fast Track Pro (USB1) works fine with phantom power and no external power supply. There are many others.

Its most often the super cheap crap interfaces USB1 that can't do phantom power. If it's a feature on the device, it should work without noise.

dude still hasn't told us which interface.

 

[MindMunch]

dude still hasn't told us which interface.

Oh, sorry about that. It´s a Native Instruments Komplete Audio 6. Nice and very portable interface. I´ve checked more people with the same problem with this model, so I won´t return it. Besides this phantom power thing I´m very happy with it. Nicely built, bunch of great features for phone and monitoring.