Pre/Power Amplifiers

The Ultima 2 is the more powerful of two new monoblocks to be inspired by Chord's massive flagship amplifier, all sharing proprietary technologies. 'All our full-sized amplifiers are designed to be scaleable with many common design parts being the same', confirmed Chord Electronics' MD and Chief Designer John Franks. 'Our Ultima amplifiers use in-house designed ultra low noise HF (switchmode) PSUs. They distribute the instantaneous output current across the main power rails keeping them balanced and the centre ground point free from loop distortion.

'We have made 600W, 2kW and 4kW [peak] PSU modules – each built into a metal frame of precisely the same dimensions, so they can be incorporated into any of the amplifiers. We designed them to operate in pairs, but in practice any number can be wired in parallel giving great power and flexibility.

'The Ultima 2 has three of our 4kW PSUs working in parallel in each mono amplifier. This is the same number we use in the Ultima flagship although the Ultima 2 has 32 lateral metal-on-silicon MOSFET power transistors, half that deployed in our larger Ultima Amp.'

The cool-running of these amplifiers is achieved by reducing the standing current down to just a few mA in each N- and P-channel pair of output devices. 'And', says John, 'this is combined with our dual feedforward transconductance error correction circuit, based on a paper by Prof. Malcolm Hawksford and work by Bob Cordell of Bell labs'.