White Noise while recording even when Microphone is unplugge

[GentaX]

For the longest time I've been using a condenser microphone plugged into a Beringer sound board for phantom power. Due to lack of USB cords on the board I used tape out and pluged into a sound card. Unfortunatly I've been getting an annoying hiss in the background. As a means to simply my audio setup I decided to be a smaller usb audio interface but still here the hiss while recording. For diagnostic purposes I unplugged the XLR cable and played back the file and still hear hiss.

Attached is an example of the hiss I'm hearing. At the six second mark I simply unplugged the XLR cable.

What can I do to fix this?

[kozikowski]

Most hiss noise like this comes from the microphone amplifier. On some Mic Amps, if you unplug the microphone, the hiss level goes up. They want to be connected to each other.

Microphone level is vanishingly small. It's a delicate butterfly compared to most other electrical signals. The microphone amplifier's job is to boost your voice signal so it can be mixed and faded with other signals and sent to a recorder, computer, or other equipment.
In your case, of course, it also supplies Phantom Power to run the microphone.

Microphone amplifiers have to be specifically designed to be very much quieter than mic signals and that makes the successful, well behaved ones expensive. The cheap ones hiss.

That's why when you buy a mixer they frequently brag about how well behaved their microphone electronics is. "Now featuring Abbey Road Mic Amps" or "Each sound channel has a Nashville Cash microphone amplifier with Hollywood limiter."

I'd just settle for them being quiet and the higher end units are very quiet. The Shure FP33 field mixer..

http://www.shure.com/americas/products/ ... ereo-mixer

... is a pretty normal if aging sound mixer, but it's reputation is for very quiet microphone amplifiers. I sometimes have to check that the unit is turned on.

I bet if you pot down your mixer -- either the mic channel or the master, the hiss goes away.

Koz

[kozikowski]

Which Behringer mixer?
Koz

[GentaX]

Most hiss noise like this comes from the microphone amplifier. On some Mic Amps, if you unplug the microphone, the hiss level goes up. They want to be connected to each other.

Microphone level is vanishingly small. It's a delicate butterfly compared to most other electrical signals. The microphone amplifier's job is to boost your voice signal so it can be mixed and faded with other signals and sent to a recorder, computer, or other equipment.
In your case, of course, it also supplies Phantom Power to run the microphone.

Microphone amplifiers have to be specifically designed to be very much quieter than mic signals and that makes the successful, well behaved ones expensive. The cheap ones hiss.

That's why when you buy a mixer they frequently brag about how well behaved their microphone electronics is. "Now featuring Abbey Road Mic Amps" or "Each sound channel has a Nashville Cash microphone amplifier with Hollywood limiter."

I'd just settle for them being quiet and the higher end units are very quiet. The Shure FP33 field mixer..

http://www.shure.com/americas/products/ ... ereo-mixer

... is a pretty normal if aging sound mixer, but it's reputation is for very quiet microphone amplifiers. I sometimes have to check that the unit is turned on.

I bet if you pot down your mixer -- either the mic channel or the master, the hiss goes away.

Koz

Thanks a lot for the feedback. By any chance do you have another recommendation that's less than $500. I'm a extreme hobbiest at most so it's a little hard to work up spending 1K for a mixer.

Which Behringer mixer?
Koz

Originally used Xenyx 1204 (got a great deal $60 for the board) which was before they released the USB model. The sample was recorded on a Xenyx 302 which I bought based on reviews and USB connection. Also is there a chance that it's simply my PC being the main problem?

[DVDdoug]

It can also be related to your microphone and the sound level you are recording... i.e. The stronger your signal, the greater your signal-to-noise ratio. The signal tends to drown-out the noise, and you can set the playback-volume (or mix level) lower, which lowers the signal and noise together. (Or, at least you may not have to boost the signal as much digitally). With a weak signal, you have the opposite problem and you'll have to turn-up the signal and noise together.

Since you are using phantom power, I assume you are using a studio-style condenser mic? Usually, these are pretty "hot". If you have a singer (or speaker) a with a strong voice a few inches from the mic, you can usually get a good signal-to-noise ratio, so that the noise/hiss is not noticeable under normal listening conditions. It also helps if you mix several instruments/tracks together for a "dense" sound to cover-up the noise. A quiet single solo-instrument, such as an acoustic guitar can be difficult. And, the same goes for distant or otherwise quiet songs sounds.

Also, noise reduction can work very-well with low-level backgroiund noise. i.e. Noise reduction works best when you don't really need it.

[GentaX]

It can also be related to your microphone and the sound level you are recording... i.e. The stronger your signal, the greater your signal-to-noise ratio. The signal tends to drown-out the noise, and you can set the playback-volume (or mix level) lower, which lowers the signal and noise together. (Or, at least you may not have to boost the signal as much digitally). With a weak signal, you have the opposite problem and you'll have to turn-up the signal and noise together.

Since you are using phantom power, I assume you are using a studio-style condenser mic? Usually, these are pretty "hot". If you have a singer (or speaker) a with a strong voice a few inches from the mic, you can usually get a good signal-to-noise ratio, so that the noise/hiss is not noticeable under normal listening conditions. It also helps if you mix several instruments/tracks together for a "dense" sound to cover-up the noise. A quiet single solo-instrument, such as an acoustic guitar can be difficult. And, the same goes for distant or otherwise quiet songs sounds.

Also, noise reduction can work very-well with low-level backgroiund noise. i.e. Noise reduction works best when you don't really need it.

I've already ruled out sound levels as I record samples with the volume and gain dial/slider all the way to 0 and I'm still getting the hiss at the levels you hear in the attached file. In addition you can hear the hiss stay the same level between active recording and having the XLR cable unpluged. In addition I am able to listen to the recording in real time by plugging headphones into the sound board and through the playback I hear everything crystal clear. However I do understand that lowering the volume to eliminate the hiss in playback but the only problem is once your turn up the volume of the file in post or simply raising the levels through your headset, it returns as normal. Mixing in other files is a great way to cover things up but the only issue is that I've been relying on this set up to record audio only auditions and thus this hiss sticks out like a sore thumb.

[kozikowski]

It would, yes. OK, let me look at the mixer.... [time passes].

The mixer has three ways to control the volume of the microphone: Gain, Mic (both on the left) and Main Mix. Are any of those all the way up? Gain in particular should never be cranked wide open. Messy things happen when you do that on almost all preamps.

Set up like you normally do with Gain about 3:00 o'clock and the other two where they need to be for natural, normal levels. I was going to send you to the mixer sound meters, but there don't appear to be any. It is required that you keep the Line/USB knob all the way down.

Right-click on the Audacity red recording meters > Start Monitoring. You should see the meters hover around -40 to -45 which is the sample you sent us. It's sucky noise level, yes, I'm clear about that.

Grab the edge of the meters and pull to make them bigger. You'll need that for these tests.

http://kozco.com/tech/audacity/Audacity1_record.jpg

Now turn the Main Mix knob all the way down. What happens to the noise level in Audacity?

Koz

[GentaX]

It would, yes. OK, let me look at the mixer.... [time passes].

The mixer has three ways to control the volume of the microphone: Gain, Mic (both on the left) and Main Mix. Are any of those all the way up? Gain in particular should never be cranked wide open. Messy things happen when you do that on almost all preamps.

Set up like you normally do with Gain about 3:00 o'clock and the other two where they need to be for natural, normal levels. I was going to send you to the mixer sound meters, but there don't appear to be any. It is required that you keep the Line/USB knob all the way down.

Right-click on the Audacity red recording meters > Start Monitoring. You should see the meters hover around -40 to -45 which is the sample you sent us. It's sucky noise level, yes, I'm clear about that.

Grab the edge of the meters and pull to make them bigger. You'll need that for these tests.

http://kozco.com/tech/audacity/Audacity1_record.jpg

Now turn the Main Mix knob all the way down. What happens to the noise level in Audacity?

Koz

I actually JUST fixed the issue. The new soundboard really helped. It's just I decided to lower the microphone boost in downs by 10 dcb then recorded. Everything sounded clear and all I did was to test my findings was I raised the dB in post and sure enough no noise.

[kozikowski]

It's just I decided to lower the microphone boost in downs by 10 dcb then recorded.

Wait, What? The microphone boost in Windows should have nothing at all to do with the mixer if you have it connected with the USB cable. Do you have any other cables between the computer and the mixer? Koz

[GentaX]

It's just I decided to lower the microphone boost in downs by 10 dcb then recorded.

Wait, What? The microphone boost in Windows should have nothing at all to do with the mixer if you have it connected with the USB cable. Do you have any other cables between the computer and the mixer? Koz

I only use the single USB cord from the mixer