Sutherland Engineering Little Loco
Descriptions of the sounds of products from Sutherland Engineering nearly always include “refined.” While that word is certainly justified, it would be more apt to use it as a verb: Ron Sutherland spends more time than any audio designer I’ve known studying and fine-tuning and refining every detail of his work. I have the impression he knows those products so well that when he decides to design a less expensive version of his newest and best models, he knows exactly what to do.
The Sutherland Duo phono preamp I reviewed in August 2017 is a case in point. It sells for $4000 and comes within a hair of matching the performance of the $10,000 Phono-Block Refined. It even betters it in a few ways. So when I heard that Sutherland was introducing a “trickle-down” version of the costno-object Phono Loco phono preamp, I muscled my way to the head of the line for a review sample.
I heard the hall’s ambience in the spaces between the performers.
Transimpedance 101
The Little Loco and the Phono Loco differ from Sutherland’s other models in being current-mode designs, other examples of which include the CH Precision P11 (which Michael Fremer uses as a reference), the Channel D Lino C 2.0, and the Haniwa HEQA03-CI (see this issue’s Analog Corner). But the technology is not as well-known as that of voltage-mode phono preamps, so the distinction bears repeating:
An MC phono cartridge can be modeled as either a voltage source or a current source; conventional phono preamps take the former view: The movement of the cartridge’s coils through its magnetic field creates a small voltage that pushes a current through the internal resistive load of the attached phono preamplifier.
Current-mode phono preamps view the cartridge as a pure current source, ignoring voltage, and aim to impede that current as little as possible. A typical strategy is to use an op-amp to mimic a short between the cartridge’s two terminals; the cartridge thinks current is flowing freely, but it is actually diverted through
