Audacity Forum

Hi all, I'm new to the forum, but I like what I've seen so far.

My question:

I have set up a small home studio. All of our instruments/mikes plug into a behringer board and the board connects to a usb audio connector via 2 male 1/4 inch to male rca cables, and then to the computer. We also use the rca outputs on the usb connector to monitor output through a stereo. We are using Audacity as the recording software.

Playback through this line to the monitors is crystal clear. But as soon as we start monitoring the feed or recording (both in Audacity) there is a noticeable constant high pitched whine. If I disconnect the 2 rcas no whine, if I disconnect the usb no whine.

usb: http://altoedge.com/usbaudio/
board: http://www.behringer.com/EN/Products/1204FX.aspx

Having a hard time determining if this is a software or hardware issue. I can't provide any more detailed specs right now, but if there are any specific questions I can answer them later on tonight when I get home. Thanks for reading-

It sounds like feedback. Everything is fine until you close the loop, and you can break the loop anywhere and it stops. Are you listening to the speaker and microphone getting into each other?

There's a more convoluted path. Are you recording Mix-Out instead of the signal from the USB device? Anything you put into the microphone would form a feedback path inside the computer.

Can you make it worse? That sounds counterproductive, but if you can make it much worse, that tells us where the problem is. Does it change when you move either the microphone or the speaker?

Koz

Thank you for the reply Koz.

Feedback was our original guess (I'll have to look into that internal loop scenario). However, I don't think that's the problem - here's why. When recording we kill the monitor speakers. To take it a step further, I can turn off the power to our board and the whine persists when recording begins, but if i unlink board to usb its gone. In simplest terms, as long as there is a connection between the board and the computer it will be there. There's no way to make worse or better other than turning up or down the monitor volume.

The reason I'm not so quick to blame audacity is with our original set up, we were using the line-in on the computer and there was no problem.

I'm willing to try other setups, but am at a loss at to what.

<<<If I disconnect the 2 rcas no whine,>>>

Let me read this back to you. You have the whole thing set up for recording and the act of removing the two RCAs from the USB device gives you a clean recording? I'm clear that disconnecting the RCAs removes the monitor amplifier and speakers, but does it clean up the live performance recording as well?

Is the USB device powered from a wall plug-in supply, or from the power coming down the USB connection from the computer? I've had some very bad experiences with a cheap sound device called an iMic. If the conditions were appropriate, I could tell when my hard drive was spinning up by the low level whine and clicking in the recorded performance.

Koz

>>Let me read this back to you.

lol, I thought about that after I posted. When I disconnect the board and and hit record no whine, but ALSO no signal either. Now, if I reconnect the board AND it's turned off, hit record there is the whine - but still no signal, obviously.

Now that you mention it, I have noticed before that opening and closing other apps on the computer _sometimes_ causes the whine tone to fluctuate. Also the usb does use the computer's power supply.

At this point my instinct is telling me the usb connector is the culprit - but I have no other way to test this other than using my compy's line in for recording....yeccchh. What are some other ways to get signal to my comp from mixing board? I also have firewire capabilities. I'm willing to spend up to $100, but have no idea what I need. Thanks again for sticking with me.

Laptop PC?

And if you disconnect the laptop PSU and run on batteries?

PC - windows.

You're using the USB device because your built-in sound card is that bad?

Are you sure?

My sister's machine puts a high pitched hiss on one channel only (left) and the other one is clean, so she has troubles with good quality audio. Two of my PCs at home have well-behaved SoundBlaster® sound cards and I record line-level production sound all the time with both.

The way things are going for you, I suspect there are worse things than to go back to Line-In on the computer.

Here's a trick. While the existing system is working, pull the wall power from your USB device. I bet it doesn't stop working.

Koz

Sound card works fine - the only problem is that I thought there would be significant signal degradation taking the stereo out from the board, and condensing to the 1/8inch(?) line in on my computer. I know the line in is stereo but I think the point remains. Maybe if there was some way to get the rca inputs to the computer itself - perhaps there is a board I can install in the comp...off to google-

btw - no power adapter on the usb just runs on power from the computer

<<<btw - no power adapter on the usb just runs on power from the computer>>>

Cast your mind back about three messages ago. That's where your noise is coming from.

<<<significant signal degradation taking the stereo out from the board, and condensing to the 1/8inch(?) line in on my computer.>>>

OK, now you are officially crazy. Of all the places you can have signal damage, that's probably at the bottom of the list. As long as the signal connections don't go over about six feet, I defy anyone to find any damage caused by condensing the signal down to a stereo 3.5mm (1/8") plug.

You do need to keep them clean. Rub the plug with alcohol or spot of vodka on a paper towel and then dry with another towel. Plug in and turn. If you want to be compulsive, pull it and clean it a second time.


Plug everything together and set up for recording, but leave all the volume faders on the sound mixer down. Record a bit in Audacity and I bet the noise level is way down in the -60dB or more range. You may need to change the range of the meters in Preferences to see it.

Koz