From the get-go, Chord Electronics’ amplifiers pushed the technology envelope. The company was making amplifiers with switch-mode power supplies when every other audio brand had barely even heard of a switch-mode power supply. That ability to see technologies in other fields and turn them into viable high-performance audio devices has seen the company go from a tiny maker of power amps for BBC studios to a world-class maker of high-end, high-performance analogue and digital audio electronics. It’s still a small, precision operation, but in the intervening years Chord Electronics has gone from ‘kitchen-table go-kart’ brand to ‘Formula One Engineering Team,’ and the Étude power amplifier shows precisely why that happened.
If we are being honest, the world of amplifier electronics is getting a little bit stagnant. Yes, there has been the Class D revolution, and let’s not forget the developments made by Devialet in producing a Class A/D hybrid power DAC, but the former is turn-of-the-century technology and the latter has been on the market for 10 years. While this might seem like an eye-blink to those using single-ended triode amplifier circuits from the 1930s, there is still room for growth. But to find that next great innovation in circuit design, Chord Electronics went looking through developments in amplifier designs from the past to create something outstanding for the future.
The Étude circuit is based on a paper by Dr Malcolm J Hawksford’s (emeritus professor at Essex University), and the resultant design was developed by Bob Cordell of Bell Labs. Cordell put forward a design which had an unprecedented 0.001 per cent total harmonic distortion at 20kHz. Chord Electronics looked at Cordell’s work from the 1980s and developed an initial design that incorporated his topology as well as John Franks’ own, which with nested feed-forward and global feedback, allows for Chord Electronics’ custom-designed dual silicon die MOSFET output transistors to perform uniquely well.
The Étude circuit design intelligently adjusts and compensates the individual linearity of the output devices, in this case, two banks of four aforementioned proprietary 250‑watt lateral structure MOSFETs. This makes for a switch-mode driven amplifier that can deliver 150W into four ohms (or 300W in bridged mono mode). In fact, the Étude sports three separate power supply stages inside its small, light chassis: one for the auxiliary rails and the other two feeding the high-current active power rails. The internal architecture of the Étude allows these power supplies to be heavily shielded to prevent their actions influencing the signal path.