Sine

Sine is not a clearly verifiable hi-fi hardware brand in the usual sense. The search results point instead to a London-based audio post-production and sound design company called Sine Audio, operating from Fitzrovia and described as a high-end or boutique facility rather than a consumer-audio manufacturer.

Its focus is sound design and audio post-production for TV commercials, radio, and cinema, with an emphasis on end-to-end audio services from its studio rather than on products such as amplifiers, speakers, DACs, or headphones. The company is said to have been created by founder Phil Bolland, with Julian Marshall serving as MD.

In market terms, Sine appears to sit in the specialist boutique category: professional, premium, and service-led, but not a traditional hi-fi brand sold to consumers. If you were looking for a maker of home audio equipment, the available evidence does not support that identification with high confidence.