How to Setup Virtual Audio Cable (VAC) 4.0x with PowerSDR 1.x ...

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1. Obtain and install VAC 4.0x on the same computer that is running PowerSDR 2. Configure VAC "cables" 3. Configure PowerSDR to utilize VAC Step 1. Install VAC 4.0x as per the installation directions. If VAC was previously loaded, you must first uninstall all versions before installing a new version of VAC 4.0x Step 2. Once installed, set up a pair of VAC audio "cables" for use with PowerSDR by opening the VAC Control Panel. Figure 1 - VAC Console Step 3. By default only one audio cable is defined. You will need to create two cables by changing the driver parameters to 2 cables then click SET and Restart. Highlight the appropriate cable and change the values to match the figure above. In the "Ms per int" box enter a value between 1 and 20 ms. The lower the value, the smaller the VAC audio buffer. In the example above, 7 ms was selected. Depending on your computer setup you may have to adjust this value to prevent the audio from dropping out or "popping". You can choose two different Stream limit formats; cable format and cable range. Since PowerSDR defines both audio cables' format when VAC support is enabled, using the Cable Format is recommended. If you decide to use the Cable Range stream format, one thing to consider, when a format conversion occurs, it takes significant CPU resources and it may noticeably slow your applications causing audio drops outs. Therefore using Cable Format as the stream format may help with audio drop outs. In the example above, I am using Cable Range because it provides the most flexibility and does not adversely affect the performance of PowerSDR on the computer I am using. After completing all of the necessary changes, click on Set for each cable when completed. NOTE: Repeat these changes for the second audio cable as well. NOTE: Do NOT check the Volume Control box in the VAC control panel. This enables the Windows Mixer and can cause unpredictable results. Step 4. Start up PowerSDR version 1.6.0 (or higher). Click Setup on the Menu Bar. The PowerSDR Setup program is displayed. See example below. Figure 2 - PowerSDR Setup (default page) Step 5. Click on the Audio tab and then click on the VAC tab. Figure 3 - VAC Setup
Step 6. In the "Virtual Audio Cable Setup" section, set the "Driver" to MME using the drop down box (other driver options, such as Windows WDM-KS are supported but may work depending on the sound card application being used. For this article, MME is used because it is the most compatible. Once you have VAC working, you can experiment with the other drivers. Their advantage is that they have less inherent latency for audio transfer). In the "Input" drop down box, select Virtual Cable 1. In the "Output" drop down box, select Virtual Cable 2. In the "Auto Enable" section, select this option if you want VAC to automatically engage when any of the digital modes (DIGIx or DRM) are selected on the PowerSDR console. This is the preferred setting. In the "Buffer Size" section, select a buffer size from the drop down box. Depending on your computer setup you may have to adjust this value to prevent the audio from dropping out or "popping". In the "Sample Rate" section, select a higher sampling rate from the drop down box option that exceeds the sampling rate of the sound card program you are using. Using a sampling rate of 48K provides the best audio quality and produces the fewest drop outs. Troubleshooting Technique: In some cases the sound card program can not handle format down conversion very well resulting in no or poor audio processing. If this is the case, change the Sample rate to exactly match that of the sound card program you are using. If the soundcard program uses a stereo mode, such as DReaM, then select the Stereo option in the "Mono/Stereo" section. And finally, the "Gain (dB)" section is the place where you adjust the AF gain of the VAC cable. Since the Volume Control was not checked on the VAC Control Panel (step #3) the Windows Mixer is not available for VAC cables. Use only the adjustments in PowerSDR to increase or decrease the volume (AF gain) going to and from the sound card application. NOTE: Always start PowerSDR with VAC enabled before starting the sound card program so that PowerSDR can define the VAC cable format Setp 7. To check to see if VAC is properly working, Select a digital mode in PowerSDR and make sure the radio is "On" and not in "Stand By" mode. The Open the VAC Control panel and you should see the audio cables active. Figure 4 - VAC Control Panel As displayed above, the VAC channels are active, but only for PowerSDR. If you look at Cable 1, you will see that the number of "Pb streams" is 0 (zero) and the "Rc streams" for Cable 2 is also 0. VAC 4.0x automatically sets up both ends of the audio cable even if the client (sound card) program is not configured or even running. Step 8. When setting up VAC with two audio programs, the audio output of one program uses the same audio cable as the input of the other. Conversely, the audio input of the first program uses the same audio cable as the output of the other.
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How to Setup Virtual Audio Cable (VAC) 4.0x with PowerSDR 1.x ...

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