PS Audio Begins Shipping New Analog/Digital Hybrid Class A Amplifier

1-Apr-02

PS Audio announced that it is shipping its new PS Hybrid Class A (HCA-2) power amplifier, featuring a proprietary input voltage gain stage, and new technology for the output stage. The two-channel PS Hybrid Class A employs hybrid analog/digital technology, making it the first amplifier to use this approach since the Infinity Hybrid Class A power amp, introduced nearly 30 years ago. However, the HCA-2 uses a zero-feedback, fully-differential/balanced analog input stage, unlike the Infinity, which used tubes for the front end and a solid-state output stage. For the output stage, the HCA-2 relies on Super Digital Amplifier Technologyô (SDATô), newly developed by PS Audio to solve the difficult problem of varying load response. SDAT blends analog and digital topologies. The SDAT output stage runs at 95 percent efficiency. It is claimed to run smoothly even when the chassis is very cold, and is said to require little or no ventilation.The Hybrid Class A delivers 150 watts per channel of high current power into an 8-ohm load. It can output 250 watts per channel into a 4-ohm load. The input stage is an fully-balanced/differential Class A JFET with common mode characteristics that are claimed to exceed 70 dB in balanced mode. The HCA-2's input stage is balanced from input to output, and boasts zero feedback and low distortion. All amplifiers include input and output stages that contribute to overall performance. PS Audio discovered through their research that the input voltage gain stage and the output current gain stage perform best when they are absolutely isolated and independent from each other. They said that once separation is achieved, their topology becomes less important, as long as it meets design goals. The key element, according to PS Audio, is to establish the independent nature of the two stages.The SDAT circuit, in development for more than a year, uses a modular Pulse Width Modulated (PWM) design that is ""super linearized"" as a gain block. Super linearization is achieved by incorporating the output filtering stage of the SDAT in the audio feedback loop. PS Audio says that this patented technique overcomes the problem of varying load response.PS Audio thus claims that SDAT's super linearization technology completely eliminates the need for the output filter to work into a fixed load.The PS Hybrid Class A amplifier is available as of April at a suggested price of $1,695. For more information, visit www.psaudio.com.

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