Recording audio from sound board


Yesterday I played a show with my band at a college, and the show’s sound was taken care of by professional sound techs–all the mic-ing, mixing, everything. I figured I would record the show straight from the sound board, so the guy at the board let my plug into the XLR out port–which he said was where I needed to plug into–and he set up the board so that I could record from it. I then used two adapters to convert the other XLR end to a 1/4", and then to convert the 1/4" to 1/8". I plugged the 1/8" into the line-in port on my Macbook Pro, and set Audacity to record from Line-In. I recorded the entire show through Audacity. However, the recording is complete silence. When I normalize the audio, it’s just a bunch of static, but interestingly the static level increases dramatically when we started to play.

What am I doing wrong here?


Apparently you didn’t record the show…

I can think of 3 possible causes:

  1. you didn’t have the line-in selected as the recording device on audacity

  2. the tech guy wasn’t outputing the right signal to the xlr output, or the xlr output was not a line level signal

  3. the conversion from XLR to 1/4" wasn’t done properly…

What kind was the XLR output? stereo? mono? balanced? unbalanced? Which adapter did you use?

My bet goes to the option #3.

Thanks for your reply bgravato! I did indeed have line-in selected as the recording device in Audacity. I’m not sure what kind the XLR output was, but I recorded in stereo to be safe. I’m not sure if it was balanced or unbalanced. The sound guy was the one who plugged it into the board, so I’m assuming he probably did it right. Here’s how I did the conversion: The XLR cable I used was one that I unplugged from a microphone. So he plugged one end of that into the board, and at the other end I used the adapter that came with the microphone to convert XLR to 1/4". Then I used one of those small 1/4" 1/8" adapters to convert to 1/8".

Maybe the microphone cable wasn’t the proper cable to use? It seemed just like a normal XLR cable though…

There’s a lot of interpretations to what a “normal” XLR cable can be :wink:

Both XLR and stereo jack connectors (1/4" or 1/8") can be used for pretty much the same… both kinds of connectors have 3 pins which usually connect to 3 wires.

On a stereo unbalanced connection, you’ll have the ground on one pin, left channel signal on another and right channel on the other.

On a balanced connection (mono), the one usually used on mic, you have the ground too, but on the other two pins you have the same signal but inverted on one of them. The useful of this is to eliminate the noise added by the cabling, this allows to use very long cables with barely no quality loss to the audio signal.

So if you connect a balanced signal output to an unbalanced input things can go wrong… And you might actually be cancelling the audio signal and getting only the noise :slight_smile: Usually the trick is to shunt one of the signals to the ground and you’ll get just one of the signal (either the positive or the negative) in one of the channels (left or right depending on which one you connect to the ground).

Here’s a good article about this, explaining all that:
Take specially attention on this section:

If you split the stereo track and play just one of the channels do you get any sound?

If I split the stereo track and play just one channel, I still get only static. I talked to a sound guy I know, and he agreed that it is probably the unbalanced/balanced cable issue. Thanks for all your help!

It’s dangerous to adapt the mixer XLR out to a Mac because unless the mixer has very good isolation between all its sound services, the adapter may create distortion or hum in the house.

You also need to know that Audacity gives you very clear indications when it’s recording correctly. It’s not a mystery.

If you don’t get the blue waves or the bouncing red sound meter, you’re not recording anything.

We use these to get in and out of different audio systems.

This allows you to maintain the qualities of each cable system and still get the show through.

That’s usually too rich for single users, so you really need one of these…

That’s the formula how to build it. I’ve never seen one for sale. I made that one. This technique is electrically cheating and can cause problems on some sound mixers.