I hear no sound in EDIUS/Premiere/Avid
If you use a Blackmagic or Matrox device to monitor the video when editing then the sound will come out of this device as well. If you only have your speakers plugged in to the speaker socket of your sound card you will not hear the sound in the editing program.
You could do anything out of the following:
1. Plug a second set of speakers into the output of your Blackmagic or Matrox device.
2. Route the sound from the sound card and the sound from the Blackmagic/Matrox device to an audio mixer and switch between the two using the mixer.
3. Listen to the sound through a TV which is connected to the Matrox/Blackmagic device through HDMI
4. (the most common) Take the sound out of the Blackmagic/Matrox device and plug it into the sound card's line in socket (the blue socket which is next to the green speaker connection socket). Now the sound will come out of the Blackmagic/Matrox device, go into the sound card and then through the sound card and off to the speakers.
The most common problem with no 4. is that the line in gets "muted" in the settings. How you fix this depends on the sound card. Below is the most commonly used sound card, called a Realtek sound device, using the version of the software available with Windows 10 in March 2017.
Set the line in volume on the Realtek sound card
This diagram should be self explanatory.
What is the best position for the playback volume slider?
You are basically using an audio mixer. Put this slider too high and the sound will be distorted because the line in volume is too high, not because it is actually distorted. Too low and it will sound quiet even if it is a normal volume. The best position for us has normally been about 22% of the way across but this does change depending on the sound card, video device and software version. So experiment by putting a loud sound on the timeline and playing it. If the audio levels in the editing program do not go into the red it should not be distorted - if it is lower the playback volume slider until it sounds correct.