Integrated Amplifiers

Back in the mists of time, all amplifiers were tube amps but the first hybrid designs – a mix of tubes and transistors – appeared in the early '60s typically involving small-signal transistors driving big bottle output stages. Robust power transistors had yet to be created but once they arrived, in volume and at an agreeable price, then fully-transistorised amplifiers stormed into the ascendant, dominating the audio scene from the late '60s to the present day. Nevertheless audiophiles love a niche, so just as SET triode amps will always have their fervent clique so too has a larger body of enthusiasts sought to combine the sweet sound of tubes with the speaker-driving grunt of a beefy transistor output.

Designer Bascom H King set the ball rolling with his HCA (Hybrid Class A) amplifier in 1979, his combination of industrial-grade triode tubes driving a fan-cooled transistor output stage claimed a rated 150W/8ohm. And with power MOSFETs making their own mark on the high-end hi-fi scene in the early 1980s, the marriage of a high voltage triode line stage driving a high-current FET output achieved a synergy all its own. Not all modern tube/tranny hybrids use traditional FET power amps – some even mix triodes with Class D outputs [see PS Audio's M1200, HFN Jan '21] – but it remains a popular combination, as evidenced here by the collaboration of PrimaLuna with parent company Durob's Floyd Design. Tube/transistor hybrid amps are certainly gaining increased traction with fellow audiophiles – in the last couple of years we've featured the Vinnie Rossi L2i-SE [HFN Jul '20], the Supravox Vouvray [HFN Dec '20], the Copland CSA100 and CSA150 [HFN Aug '20/Jun '21] and BAT VK-3500 [HFN Sept '21]. PM