An elegant lady promotes Philips bi-ampli radios in this vintage poster. The bi-ampli was the first radio to feature two separate output amplifiers for bass and high tones. This technology was extremely successful, and as the bi-ampli logo grew to be synonymous with high sound quality, it became somewhat abused so that consumers had to know the difference between true bi-ampli and false bi-ampli. Today some people assert that their true bi-ampli radios match the sound quality of their modern stereo systems.