Interesting insights about the Spectral Audio Super Fader Technology and their research into the uncompromising attenuation. Back in 2015 I've had a great opportunity to share an in depth discussion with Richard Fryer about Spectral Audio inner workings, R & D and the advantage of being in the hearth of the Silicon Valley, where resides wast array of ultra specialized small companies working for military and NASA. Some of the things Richard brought up during the talk like Spectral Audio Super Fader Technology materialized in DMC-30SV Reference Preamplifier.
To solve the problems of existing gain control systems Spectral engineers work with a leading aerospace contractor. Out of a multi-year design effort comes an extraordinary ultra-precision gain control. The Spectral ‘Super Fader’ combines mechanical precision, advanced materials science and unrestricted use of exotic materials to create a level control that behaves like an infinite number of theoretically ideal resistors. Inside, the critical moving parts are precision machined from solid precious metals. These wipers have many surfaces that contact micro-polished optically flat resistance elements.
Exemplary mechanical design and alignment is used to prevent localized heating from circulating currents. Ultra-pure contact metal eliminates solid-state or junction distortions which occur from plated parts in other controls. When such precision and material commitment are combined, noise and error is unmeasurable and performance is very near to ideal thermal accuracy limits. The ‘Super Fader’ potentiometer outperforms all existing gain control systems with virtually infinite service life. We hear a transparency, as if a wire has been substituted for the control
The Case for Uncompromising Attenuation
Certain devices in a high-end preamplifier fundamentally determine the ultimate performance possible in the component. Since a preamplifier basically amounts to an adjustable line amplifier, the role of the volume control or gain attenuator system is especially critical and will have a strong influence over the final sonics of the component. Most of today’s high-end preamps incorporate various digital and IC based attenuator systems to control gain, while a minority still use mechanical controls, potentiometers, switches or relay arrays. In our experience all of these approaches have serious compromises which limit signal transparency, dynamic range, step resolution or reliability. Today, digital based IC attenuators are ubiquitous in modern audio design. But even the most exotic of these digital and solid-state attenuators color the sound in various ways. Spectral engineers have long experience researching digital and DAC attenuators and find that none of these gain controls are really up to the demands of high-end preamp use, let alone for critical recording applications. We find the best relay and switch based resistor attenuators to be much better sonically than any digital control. Unfortunately, they in turn suffer from dynamic range and contact life limitations, more importantly they are not a realistic option when continuous gain adjustment is required. Since digital attenuators are not sonically transparent and stepped resistor attenuator controls have step size, contact life and dynamic range limitation, the ultimate gain control would have to be a continuously variable potentiometer or fader. Unfortunately, no pot or fader currently available is transparent or linear enough for the most critical gain adjustment applications in audio.