Quad have always had a very straightforward engineering view of their products, and insisted that all amplifiers of adequate quality sounded the same when used within their capabilities, and that speaker cable had no sound at all, unless ludicrously long and thin wire is used.
To verify or disprove that amplifiers of adequate quality sound the same, Quad commissioned James Moir to organise and conduct listening tests comparing Quad II, Quad 303 and Quad 405 amplifiers. Statistical analysis of the expert listening panel's scores showed that "the decisions of the panel were no better than might be expected from sheer chance".