Audacity Forum

Hi I just bought the ART dual pre and an inexpensive dynamic microphone. I am making some youtube videos for my students.

ART dual pre amp
http://www.bhphotovideo.com/c/product/6 ... _Pre_.html

Microphone
http://www.amazon.com/Behringer-XM1800S ... B000NJ2TIE

I have a laptop with windows 7 and I have followed the FAQ on the ART website for setup. Everything works pretty well except I can hear a hiss, (feedback?) in my voice recordings. Nothing really awful, I can fix it with noise removal in Audacity 1.3 beta but I wonder if I am doing something wrong?
(It is on USB power and the back knob is set to preamp.)

I have included a before noise removal and after noise removal soundbite. Any advice would be appreciated!

Thanks
Stuart

Did you buy the external power supply? That's not normal preamplfier noise. There is a very pronounced peak in the noise at 121Hz and the frying sound in the show is "gritty," not smooth like normal amplifier noise.

I think you're listening to something "digital" in your system. Like the battery supply from the USB connection is noisy, "dirty" or poor.

Can you make signal level? The voice is very low in the clip.

Koz

It sounds like you are picking up some electrical interference from somewhere.
Try moving your laptop to another room (or another house), run the laptop on battery power and see if the noise becomes less (or more).
The recording volume could do with being about 10 dB higher (adjust the level on the pre-amp).

If you look at the harmonics in the noise they are at approximately 1000Hz intervals ...
If the noise was mains electricity the harmonics would be at 60Hz intervals (in USA).

It does sound like exogenous interference (EMI), but it wouldn't hurt to make sure Audacity and the pre-amp are set to the same sampling rate ...

ART USB Dual Pre - USB 1.1 Digital Audio Interface with Dual Microphone
Sample Rates 44.1 and 48kHz

http://www.bhphotovideo.com/c/product/6 ... _Pre_.html

Maybe if the sample rates aren't the same an artifact tone (noise) could be generated.

BTW The default sample rate for Audacity is 44100Hz, i.e. 44.1KHz (displayed in the bottom left corner) .

BTW#2 make sure Audacity is only recording from the USB device,
If another recording device is enabled you will be recording that as well and it could contribute some noise.
Look in Windows recording devices and disable everything except the USB input ...


http://wiki.audacityteam.org/wiki/Mixer ... trol_Panel

Thanks for all the help!

I have the preamp on usb power. I will try an external power system tonight. I have tried the setup in my living room but I still get the feedback(?).
(Currently the setup is in a room full of computers so that could be the problem. i will move it tonight.) I have the usb codec as the only recording device. I have audacity and windows set to 44.1 and 16 bit. I love the "idea" of the art pre amp. Very easy to use and just what I need but I wish I was better at this.....

Thanks again for all the help. I will try some of these suggestions tonight and I will post my progress.

Stuart

The "hiss" is not "feedback".
"Feedback" is when output sound (for example from the speakers, or any other output route) leaks back into the input (for example the microphone or any other input route). The effect is very distinctive as it causes a loud howl.

Good luck with your testing.

Thanks! I am new to this but I am learning a lot. It is kinda of addicting!

The noise sounds like too much power in the system? Not sure what to call it?

S

Microphone or any audio amplifier produces internal noise. It's usually smooth hiss like rain-in-the-trees with no emphasis on any pitch or frequency.
That's not what you have. You have hash generated (probably) by some digital process in or around the computer. Analyze > Spectrum gives you a comb or spiky display instead of generally smooth hills and slopes.

Historically, inexpensive USB sound devices do not filter the power they're getting from the computer. Filtering is large and expensive (relatively). Most of the time and on most computers that works OK. But if you have a computer that uses the raw five volts both for the powerful computer chips and the USB connection, the voltage becomes "dirty" with digital disturbances in addition to the power. The danger is the dirt becomes part of the show.

It's moons and stars lining up. If the computer filters the power it doesn't happen and if the USB device filters the power it doesn't happen. If neither filters it, you get what you have.

Koz

tallbridgeguy wrote:Not sure what to call it?

Your noise sounds and looks like interference from a computer {EMI}, e.g. ...
It may even be interference from a mobile (cell) telephone, although its 1KHz peaks are exact multiples ...

tallbridgeguy wrote:The noise sounds like too much power in the system? Not sure what to call it?

It is probably some sort of electrical interference, though I can't tell where it is coming from. It could be from other nearby electrical equipment. Try some tests during the daytime so that you don't have any electric lights on, and turn off all other electrical equipment. Interference can come from the most surprising places - I had an old fridge that would cause loud clicks on recordings that were made anywhere in the house.

The evenly spaced spikes are quite unusual - perhaps some sort of switching regulator? Do you have dimmer switches or low voltage lighting?