Our Power Amplifier (PAMP) is a great option for driving a speaker, such as our Power Amplifier Accessory Speaker (PAAS-PAMP), or an AC circuit. The Power Amplifier requires a function generator to control it. Whenever possible, we recommend using the built-in function generator in the LabQuest or LabPro (configured via Logger Pro) to drive the Power Amplifier because they were designed specifically with the Power Amplifier’s hardware in mind.
If the Power Amplifier outputs strange or no waveforms, check first that the cable connections are secure and complete (LabQuest and computer use the audio cable, LabPro uses a BTA cable from CH4 to the Power Amplifier). Check that the Power Amplifier is plugged into AC power and is turned on. Next, check that the function generator software you are using is currently running.
We also distribute a free Power Amplifier Function Generator application that will allow you to drive the Power Amplifier from your computer’s sound card. Use the audio cable, provided with the Power Amplifier, to connect it to your computer’s audio port.
When using the Function Generator software on a computer, you may need to make special considerations. Because sound cards vary from manufacturer to manufacturer, and because manufacturer may load audio enhancement software that may alter the sound card’s output, the wave forms produced by your sound card may not match the output selected in the Function Generator application. For instance, the Power Amplifier may only output 2 V when you specified 4 V in the application. In other cases, the waveform generated may be garbled or noisy. Troubleshooting in this situation can be difficult because of the many factors determining what exactly the sound card outputs. Here are some things to try:
- Verify that your headphone/speaker port is identified as audio device 0 in your operating system. Note: Mac computers will often default AirPlay as device 0, even after reassigning the speaker/headphone jack as device 0. The only guaranteed way to prevent this behavior is to turn off Wi-Fi.
- Turn off or disable any audio enhancement software that may be running in the background. It may be necessary to uninstall the current sound card driver and install a generic driver. (On Windows 7, this can be accomplished by selecting “Roll Back Driver” option in the sound card driver properties window. With that option, Windows uninstalls the manufacturer’s sound card driver and replaces it with a generic Windows driver.)
- Check the cable connecting the Power Amplifier to the computer:
- If you use the stereo cable included with the Power Amplifier, it should work as intended. But note that the Function Generator signal is sent differently on the L and R stereo lines. The tip (left channel) carries the waveform. The ring (right channel) is meant for a pulse width modulated signal, used to produce a DC offset signal. Since most sound cards do not know how to deal with this, they could produce garbage that could cause strange behavior of the Power Amplifier. For example, you could get a DC offset, which might not be good for a speaker or other device connected to the output.
- If you use a mono cable, everything will work perfectly, but note that you are shorting out one of the channels of your computer’s audio output. This might not be good for the audio output circuitry of the computer, especially in the long run.
- The best cable would be a stereo cable with the ring and the base of the plug at the Power Amplifier end shorted together.