Two-Box Sutherland Duo MM/MC Phono Preamplifier a Marvel of Smart Engineering and Proven Physics: Super-Quiet Design Evades Dielectric Distress, Eliminates Crosstalk
At heart, the Stereophile Class A Recommended and Editors' Choice/Product of the Year Award-winning Sutherland Duo MM/MC phono preamplifier is a cross between the company's 20/20 and flagship PhonoBlock models. In practice, the two-chassis Duo serves as a knockout analog instrument in its price class – a U.S.A.-made component that borrows much of its design from a $10k cost-no-object product and delivers a level of musicality you will cherish for many years to come, if not forever. Detailed, natural, pure, dimensional, accurate, insightful: A few of the many positive sonic traits that will spring to mind once Duo enters your system and begins to help turn the information embedded in vinyl grooves into reach-out-and-touch-it aural experiences. Duo provides any listener fortunate to own it with superlative performance via perfectionist-minded focus and stunningly quiet operation. It all circles back to founder Ron Sutherland's emphasis on smart engineering and proven physics.
Duo's two-box layout automatically eliminates crosstalk, as each chassis gets its own circuit as well as its own built-in AC power supply and IEC power inlet. The shielded power supply module has one output split into two independently filtered and regulated branches – one for each of the gain stages. There's also more room for the internal parts, which benefits overall reliability. Each channel also features identical electrical and mechanical environments. Duo mitigates circuit-board dielectric properties in the same fashion as PhonoBlock. At twice the industry standard, each 1/8-inch-thick, double-sided FR-4 fiberglass board provides both needed absorption and extreme rigidity for component mounting. Once again, Sutherland refuses to compromise on any attribute. Just lift the cover and see.
Custom-wound 1% polystyrene film capacitors, Wima Polypropylene capacitors, Dale/Vishay 1% metal film resistors, gold-plated Teflon-insulated RCA connectors, and gold-plated configuration headers and shunts speak to the hand-picked quality within each box. Sutherland's trademark, ultra-clean housing – comprised of a 14-gauge cold-rolled steel base, baked epoxy powder-coat finish, and half-inch-thick anodized aluminum panel – complete a phono preamplifier more than prepared to be your daily (and dynamic) Duo. 100% Music Direct Guaranteed.
"The Duo is an incredible product. Ron Sutherland has once again raised his ratio of performance to price. Given the attention it deserves, it well become as much a classic as the original PhD. I can't recommend the Duo more highly."
– Brian Damkroger, Stereophile, Class A Recommended Product
How and Why Duo Skirts Dielectric Distress
Anytime two conductors are at a different voltage potential, an electric field is generated between them. The dielectric (the insulation between conductors) within that field becomes involved in charge storage. If not carefully considered, that extra charge storage can time smear details of a musical signal. Circuit board material is a dielectric. On normal double-sided construction, copper conductors are located on each side of the board. Unintentionally, a new capacitor is introduced into the circuit, formed by top surface copper, bottom surface copper, and the circuit board dielectric sandwiched between the two. It is not the quality of capacitor we want to have in a high-end signal path. Some manufacturers make the situation worse by going to multi-layer boards in the analog audio sections. Instead of two layers of copper, there are four or more. Even worse, the dielectric between layers is much thinner. The undesired capacitive effect is inversely proportional to thickness. At best, some manufacturers make small improvements by using exotic board material. Duo addresses the issue of circuit board dielectric by doubling the thickness of an FR4 fiberglass circuit board. That choice alone reduces electric field strength by one-half. Additionally, the area of copper interacting with board dielectric gets reduced in critical regions. Signal lines are kept narrow. Power lines are extremely wide. The result: refined performance. Good solid advantages based up the application of good solid physics
"It's measured performance reveals the Sutherland Duo to be a superbly quiet, superbly linear, and superbly accurate phono preamplifier."
– John Atkinson, Stereophile, 2017 Product of the Year
From Ron Sutherland:
"In the two-chassis designed Duo, there is the obvious elimination of crosstalk, as it's so much easier to design a mono circuit than one for stereo. Everything is simpler. There is more room to optimize the layout, which ends up improving reliability. Both channels here see identical electrical and mechanical environments, so there are less compromises in performance. Sometimes it actually costs more to optimize the performance of a single-chassis unit than it does to build another chassis and go with a mono circuit design."