Design of High-Performance Balanced Audio Interfaces

The task of transferring an analog audio signal from one system component to another while avoiding audible contamination is anything but trivial. The dynamic range of a system is the ratio, generally measured in dB, of its maximum undistorted output signal to its residual output noise or noise floor. Fielder has shown that up to 120 dB of dynamic range may be required in high-performance sound systems in typical homes. [1] The trend in professional audio systems is toward increasing dynamic range, fueled largely by increasing resolution in available digital converters. Analog signals accumulate noise as they flow through system equipment and cables. Once noise is added to a signal, it's essentially impossible to remove it without altering or degrading the original signal. Therefore, noise and interference must be prevented along the entire signal path. Of course, a predictable amount of random or "white" noise, sometimes called "the eternal hiss," is inherent in all electronic devices and must be expected. Excess random noise is generally a gain structure problem, a topic beyond the scope of this paper.