The most common interface for connecting a computer to an amplifier is the RCA (phono) connector. This interface is widely used due to its simplicity and compatibility with a variety of audio devices. RCA connectors are typically found on both computers and amplifiers, making it a straightforward choice for audio output.

The RCA interface is preferred for several reasons. Firstly, it offers a relatively low signal loss, which is crucial for maintaining audio quality. According to a study by the Audio Engineering Society, RCA connections can achieve signal loss of less than 0.1 dB over short distances, which is negligible for most applications. Secondly, RCA connectors are durable and can withstand frequent plugging and unplugging without degradation in performance. This durability is particularly important for users who frequently change their audio setup.

Another popular interface is the XLR (XLR3 or XLR4) connector, which is often used in professional audio setups. XLR connectors provide balanced audio signals, which help reduce noise and interference. However, XLR interfaces are less common on consumer-grade computers and amplifiers, making them less convenient for general use. Additionally, XLR connectors are more complex and expensive to produce, which can be a barrier for many users.

In conclusion, the RCA interface is the most suitable choice for connecting a computer to an amplifier due to its widespread compatibility, low signal loss, and durability. While XLR connectors offer advantages in terms of noise reduction and professional-grade performance, they are not as practical for everyday use.