VidBlasterX is intended to be used with an external audio mixer, although it can be used in a basic way with a single microphone. The most common reason that beginners have a problem with not getting audio, is not understanding the need for an external audio mixer. VidBlasterX is primarily a video control system, and its audio functionality is limited to input and output. In some ways this is no bad thing because a PC's user interface only allows so much control input from a keyboard and mouse, so trying to control the vision side of things whilst simultaneously controlling the audio could easily become an impossible task. Also, the hardware that's required to look after the audio is fairly cheap compared to the video kit that VidBlasterX emulates, so it's not going to bump up the overall cost by a huge amount. However, it does require some understanding of audio engineering to set it up.
VidBlasterX Audio Input
The audio that VidBlasterX uses for streaming or recording must come from an audio recording device with a standard Windows driver, such that it appears in Windows as a recording device. Typical input devices include most audio chips built onto motherboards, add-on PCIe soundcards and some (but not all) of the audio inputs on video capture cards.
Where an audio input is required for a module, like the Recorder & Streamer, the right-click menu includes an option for Audio Device selection. The device is chosen from a list of software device names associated with physical audio input connections, like a Line-In mini-jack on a plug-in soundcard or as part of the motherboard's built-in audio device.
There is no "global" setting for the input Audio Device. It has to be set as required within each module (Streamer & Recorder) so each module can have its own (independant) audio source. This allows scenarios like having multiple streamer modules, each with the same visuals but different language audio commentary.
The Recorder & Streamer modules have similar audio features. They both have an audio bar-graph level meter overlaid on their video display, which uses a dBFS scale. Each segment represents 2 dB, with the yellow region starting at -18 dBFS, red at -10 dBFS. A good target when setting the level is for the audio peaks to be in the range between -20 and -10 (dBFS). Neither module has a volume control, but the selected audio device can have its level controlled via Windows' recording mixer panel. Of course, proper level control can be achieved using an external mixer.
When you connect an external audio feed to the PC as a module's source, you will not necessarily hear the sound coming through the PC's speaker output, even though you might see the meter display moving in the module. If you do want to monitor a particular input via the PC speakers, read the section on PC Audio Input Monitoring.
VidBlasterX Audio Outputs
There are some modules in VidBlasterX which can generate an audio output, like the IP Decoder and Player. Typically these will play through the PC's default audio device - the one that normally plays sound from other Windows programs - although they can be set to play through any available audio output device on the PC. That may mean you can hear the sound on your speakers, but it doesn't mean it's connected to any other VidBlasterX module. Because the Recorder and Streamer modules take their input from an audio input device like a line input (as selected in their popup menu), the audio output (which feeds the speakers) will need connecting to that input device, usually via a mixer or a simpler splitter cable/adaptor, as illustrated below.
Note that when using a Blackmagic Decklink card or USB3 device as a Output device, it is possible to embed audio into the SDI or HDMI output by selecting this in Windows' playback mixer. A similar method can be used to embed audio into the HDMI output of most graphics cards.