"High-fidelity system" is a term that is often used in the context of audio and sound technology. There are a number of synonyms that can be used to describe such systems, including "hi-fi," "high-quality," "quality sound," "high-resolution," "high-performance," "premium sound," "audiophile-grade," and "top-of-the-line." These terms all convey the same general meaning: that the sound produced by the system is of a very high quality and faithfully reproduces the original audio source. Whether you're shopping for a new audio system or simply looking to describe the quality of a particular sound system, these synonyms can help convey the desired meaning.