EGR 103/DAQ Audio 1

Frequently Asked Questions

How many songs so we need?

You will only need one song; in your group, pick which of the music sources you want to use.

How do we connect our music source?

• If you are using a standalone device - your own MP3 player, for example - connect the black cable that is coming from the back of the DAQ computer to the headphone jack of your device.
• If you are playing a song off a CD or memory stick, use the other computer and plug the black cable from the back of the DAQ computer to the headphone jack at the front of the other computer.

What do you mean by "What was the maximum voltage the DAQ measured...?"

When you figured out the level for the various volume controls, you were looking to make sure the signal peaked at a particular value. What was that prescribed value and why did you want to make sure your signal did not generally exceed that?

What do you mean in Question 5?

Compare the quality and the number of songs for each sampling rate - is it possible that something of CD or iPod quality would store that many songs? For example, if something is very high quality and would store only one song on a CD, that is probably not how files are stored on a CD...

Volume Control

Optiplex 270 / Optiplex 280

If you are on an Optiplex 270 / 280, do the following:

1. Open the Volume Control Panel by right-slicking the Volume icon at the bottom right of the screen and picking Open Volume Control
2. Go to Options, Properties, pick Recording, and make sure all of them are on
   1. Select "Line In"
   2. Set this volume about 80% on
3. Go to Options, Properties, pick Playback, and make sure all of them are on
   1. Mute everything but "Volume Control," "Wave," and "Line In"
   2. Set the "Volume Control," "Wave," and "Line In" volumes to 80%

Optiplex 210 / Optiplex 755

If you are on an Optiplex 210 / Optiplex 755, do the following:

1. Open the Volume Control Panel by right-slicking the Volume icon at the bottom right of the screen and picking Open Volume Control
2. Go to Options, Properties, pick Recording, and make sure all of them are on
   1. Select "Rear Input"
   2. Set this volume about 80% on
3. Go to Options, Properties, pick Playback, and make sure all of them are on
   1. Mute everything but "Master Volume," "Wave," and "Rear Input"
   2. Set the "Master Volume," "Wave," and "Rear Input" volumes to 80%

Note - if the computer is asking you what to do about the rear audio jack, select "Line In."

Others

Let Dr. G or a TA know if you are at a different kind of machine from those desribed above.

Oscilloscope

Sample Screens

Proper Setup

Here is an example of a sound file being played at the right volume:

Too Loud

Here is an example of a sound file being played at too high a volume:

Note that the top of the signal hits 10 divisions above the Ch1 pointer. Basically, the signal may be going above 0.5 V, but the DAQ card is not set up to handle voltages that high, so it "clips" the value to 0.5. This will lead to poor sound quality.

Won't Stop!

If the "stop" button does not seem to work, just close the whole oscilloscope.

Troubleshooting

Values not centered

First, note that the Ch1-> on the left side of the screen points to 0V; because you have two channels on, Channel 1 will show up "centered" in the lower part of the oscilloscope window (see the above picture in the Proper Setup section). If the issue is that one side of the signal is clipping, or the signal has an average that is not at the Ch1-> spot, the most likely problem is that the black and green wires connected to Lines 66 and 32 are either connected to the wrong place on the DAQ card or on the breadboard.

No sound

Several possible causes. Make sure all the wires are plugged in correctly and completely; make sure the Volume Control Panel has all voltages unmuted and set to about 80% voltage. Make sure the red and black clips are connected to metal (not insulation) and also that they are not touching.

Weird Errors

The following have been happening semi-randomly:

• softscope issues:
  • Opening softscope gives an error about the GUI - restart the computer you are on.
  • The "stop" button will not work - close the softscope window. This may lead to the following problem:
  • Closing softscope closes MATLAB - just restart MATLAB. This may happen a couple times... If it keeps happening, just use softscope to get your volumes correct, restart MATLAB, then skip to the next part of the lab without reopening softscope.