Which digital connection standard is mentioned as less common in digital mixers?

In the context of digital mixers, the mentioned connection standard that is considered less common is Serial. Serial connections, while still used in some applications, tend to be more limited in terms of bandwidth and flexibility when compared to other digital connection standards like USB, Firewire, and HDMI.

USB has become a popular standard because it supports a wide range of devices and allows for high-speed data transfer, making it convenient for connecting audio interfaces and mixers to computers. Firewire, although less prevalent than USB today, was historically significant in connecting audio equipment due to its ability to handle multiple audio channels simultaneously with low latency. HDMI is commonly associated with video but can also transmit audio; it is increasingly used in various multimedia applications, including some professional audio scenarios.

Serial connections, however, often have constraints related to speed and the number of channels that can be transmitted simultaneously, which makes them less favored in modern digital audio environments where higher data rates and flexibility are crucial. This is why Serial is considered the less common standard among the options listed when it comes to digital mixers.