Random static when recording through USB mixer

I’m recording on a Mac Book pro, using OSX 10.4.11

I’m using an Alesis Multimix 4 USB mixer

I installed the latest version of Audacity from the zip download

When recording every now and then random static/distortion will appear, rendering a portion of the recording useless. If I stop the recording and start again, the static is usually gone. It doesn’t always happen, and can appear at random times, which makes this particularly frustrating to trouble shoot. After doing a bit of googling it seems that other people have had similar problems in the past, although I can’t seem to find any mentions of a definite fix.

At the moment, the only thing I can think to do is check the software play through box while recording. This makes everything strange and echo-y in my headset while recording, but at least allows me to catch the static if and when it appears.

Is there a conflict with older version of OSX or older macbooks? I’m open to purchasing new equipment or new operating software, or even recording using something else other than audacity, although I’d like to be relatively certain that the aforementioned purchase(s) would solve my issue.

Thanks for reading.

A very common problem is trying to run USB audio equipment through a USB hub with something else. That only works if the USB device is the only thing plugged in and is a valid way to extend the cable length assuming the hub is wall powered. No fair running the hub with keyboard and mouse. That will create distortions and dropouts.

OS-X 10.4 is Tiger. We stopped using the last Tiger machine about three years ago. How old is the MBP?

Does it have two USB ports? Random erratic blasts of trash can mean the USB connection is on it’s last days – physically. Try the other one.

Not likely, but how full is your system drive – assuming you’re recording to the internal drive. If you’re not recording to the system drive, you need to be recording to an external FireWire drive, not USB.

Did I hit anything in there?


Thanks so much for the reply Koz.

My MBP is quite old, circa 2007-2008. Perhaps I just need to update my software, at the very least?

I’m not running through a hub or any type of extension. I’ve tried both USB ports and have received the static both ways.

I’ve been assuming it’s some kind of software issue/conflict since starting and stopping the recording seems to eliminate the presence of the static.

If the USB connection is disrupted even for a brief moment it can lose synchronization and the audio data turns into garbage (static / noise).
Stopping the connection and restarting it can allow the audio data stream to be restarted “in sync”.
There are a lot of things that can cause the momentary disruption - some scenarios and solutions can be found in this topic: http://wiki.audacityteam.org/wiki/Managing_Computer_Resources_and_Drivers

Chances are good it’s not a hardware problem because it does the same thing for both USB ports. Unless there is a serious USB Manager problem, that’s not it.

That’s why I wanted to know the age of the machine. Portable machines wear out. My touchpad is nearing the End of Life.

As a first responder condition. Stop all other programs. If you have Skype, for one example, lurking in the background, stop it. Disconnect the network, turn off BlueTooth and shut down Airport.

Go > Utilities > Terminal. Open a terminal and type
top [enter].

That’s a list of everything running on your computer in rough priority of activity. Run Audacity and see if there isn’t anything else soaking up significant %CPU (processor) cycles.

Press Control-C to get out.


Thanks, I’ll definitely be giving this a try tonight.

Software play through allows me to hear the glitch when it starts(and thus stop the recording in time). Do you know if hardware play through will inform me in the same way? There is no distracting echo and delay when I monitor the recording using hardware play through, so obviously that would be preferable. I realize experimenting will yield the answer in due time, but thought if anyone knew off hand it might save me some heart ache. . .

Thanks again.

If you have Playthrough selected and you hear problems, it could be happening on either playback or record. Playthrough is stressing your machine because it has to run both directions in real time. Is the actual show becoming damaged?


Yes the actual show/recording is being damaged. I’ve got playthrough activated only to catch the static so I don’t waste time recording something I can’t use. The static appears regardless of wether playthrough is selected or not.

As an update: I recorded last night without any trouble. I shut down blue tooth, airport etc. and ensured all other applications were closed. Because I’m just recording people speaking, I switched to Mono as well. I recorded for just over an hour. I’m reluctant to kick my heels in victory, since the static appears randomly and without any real pattern as far as I can tell, but for the time being things are working well.