Introduction: Create a Volume Control for USB Sound Card in Raspberry Pi
After installing the USB Sound Card, I turned the volume knob and i had no effect on the audio level. On further investigation, I discovered that although this particular sound card has a hardware volume contol, the Sound Blaster X-Fi Surround 5.1 Pro sound card does NOT provide any hardware mixer. A solution to this problem is to create a "software" volume control.
This instructable will cover the following:
- Discover whether the sound card provide hardware mixing.
- Create a software volume control for UNSUPPORTED the hardware mixer of the sound card
- Use ALSA utilities to test sound card and sound device
This instructables will NOT cover the following
- Open Sound System (OSS)
My Raspberry Pi:
- Raspberry Pi 2 model Raspbian based on Debian Version 8.0 (a.k.a Jessie)
- Advanced Linux Sound Architecture Driver Version k4.1.10-v7+
- Pulse Audio and OSS are NOT installed
- 2 speakers connected to Raspberry Pi's audio/video 3.5mm socket.
Step 1: Test Whether Sound Card and Speakers Work
Complete the Test Sound Card and Speakers in Raspberry Pi instructable.
Step 2: Check Whether ALSA Creatd a Hardware Volume Control
There is no volume control as shown in the screenshot. That means hardware mixer is not supported by the sound card. Bummer!
Step 3: Create a Software Volume Control
ALSA provides a "software" volume control in our case.
To simplify this step, start with a fresh blank .asoundrc file. Backup the current .asoundrc file if you have them
mv .asoundrc asoundrc.bk
Enter the lines as shown in the screenshot.
Save the file.
Step 4: Test Software Volume Control
speaker-test -twav -c2
Open another terminal:
Refer to screenshot. A new bar called "Master" appears. Use the "UP" and "Down" Arrow key to control the volume.
The loudness of the sound should vary.
This "software" volume control only works in software. The volume knob on my sound card is not able to control the "software" volume control.