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TechTalk: Why you can’t combine multiple sound cards on the Pi
A frequently asked question is: “Can I combine card X and card Y on my Raspberry Pi?” In most cases, the answer is a simple no.
Why Not?
Unlike conventional PCs that use general-purpose bus systems like PCI Express to connect devices via GPIO, the Raspberry Pi employs an interface called Inter-IC Sound (I2S). The name itself indicates its intended purpose: enabling communication between integrated circuits.
- Designed for Two Devices: I2S is engineered specifically for linking two integrated circuits, not as a bus to accommodate multiple devices.
- No Universal Standard: There isn’t a one-fits-all I2S standard. Both devices must be configured to work together. I2S comprises several signals where each side can act as a sender or receiver, but there is no automatic protocol to negotiate these roles.
- Critical Parameter Matching: Other parameters—such as the audio frame length—must match perfectly. These settings can vary (for instance, if a player requests 16-bit audio instead of 24-bit audio), and managing these differences reliably is the job of a dedicated Linux sound card driver.
For more insights into I2S, please check out our I2S Techtalk article.
What Happens with a Third Device?
- Best case: Nothing happens.
- Usual case: The existing setup stops functioning correctly.
- Worst case: One of the devices may even be damaged.
Are Any Combinations Compatible?
Yes, we offer a select few combinations that are engineered to work together. For example, the ADX8x add-on is designed to pair with the DAC8x. In this configuration, the entire circuit is built from the ground up to operate harmoniously. These add-ons are not standalone sound cards; rather, they connect to an existing sound card, and the corresponding drivers are specifically designed to support this integrated setup.
March 19, 2025
