An elegant discrete transistor design rather than the more common op-amp circuit is at the heart of the simplex, operating in class A and using local feedback rather than global feedback to ensure high linearity, wide bandwidth and low noise. The product of over twenty years of phonostage design experience - the first Rothwell outboard phonostage was on the market in the early 1990s - this inherently simple circuit is one which sounds detailed, spacious and musical. When the music gets busy and complex, the Simplex always reveals all the individual strands of the music and never sounds confused or harsh.
Accurate RIAA equalisation to within 0.5dB is achieved by combining multiple audiophile polypropylene capacitors. Using several capacitors where a single capacitor is more usually employed in lesser phonostages not only achieves greater accuracy but has the added benefit that the capacitors act as mutual bypasses for each other, minimising the dissipation factor and the effects of parasitic elements such as dielectric absorption.
Noise is minimised and signal integrity preserved by careful track routing on the printed circuit board, with star earthing and the use of components on both sides of the board to achieve a compact circuit with minimum loop area for low inductance. The resulting eerily quiet circuit has noise levels way below the surface noise and vinyl roar of even the best pressings, allowing the listener to enjoy recordings without the distraction of electronic circuit noise or other intrusions such as hum or buzz. Multiple stages of power supply filtering ensure that power supply noise is eliminated, and having the power supply in an external unit well away from the audio circuit prevents direct cross coupling of noise..