I can’t verify a hi-fi brand called Plus Audio with high confidence from the provided results. The search results point instead to PS Audio, a separate American company founded in 1973 in Boulder, Colorado, by Paul McGowan and Stan Warren.
PS Audio is known for high-end audio electronics, especially DACs, amplifiers, preamplifiers, power conditioners, and speakers. Its product line is oriented toward serious two-channel listeners rather than mass-market buyers, with an emphasis on performance-focused source and amplification components.
In the market, PS Audio sits firmly in the high-end segment, with a reputation built on long-running engineering-led product development and a direct-to-enthusiast identity. If you meant a different brand named Plus Audio, I’d need a more specific identifier to describe it accurately.