Phono Preamplifiers

Using a step-up transformer to fit a moving-coil cartridge to a moving-magnet phono stage originates with the introduction of the first low-output cartridges. A passive component, it sits between the output of the turntable and the input of the MM phono stage to add an extra 20dB of gain. In recent years, the ability to add this level of gain to phono stages without inducing noise has seen step-up transformers become less common, but they do offer some advantages – including much lower distortion.

The Anniversary Custom is at the top of Rothwell’s range and differs from more traditional designs by using two coils per channel to reduce hum. Hum created by a step-up tends to be exacerbated by the bass lift that is part of the RIAA equalisation curve, making it more audible.

It is possible to adjust the impedance load of both the first and second transformer, which means 36 possible load combinations to suit a wide selection of cartridges. Rothwell says that the 10/1 step-up ratio should suit cartridges between 0.3 and 0.5mV – although there is some scope to go slightly outside these measurements.

The Anniversary Custom is built entirely in house at Rothwell, including the winding of its own transformers. The result is a product that looks and feels rather lovely considering the asking price, with high-quality polished metal chassis and wooden side cheeks, combined with excellent spiked feet supplied with protectors. As it needs no mains supply, you can place it out of sight, but it looks so good I’d happily have it on display. It is practical too with well-spaced connections and two easy-to-use load dials.  

Sound quality
Rothwell’s claim of low hum is borne out in practice as this is one of the quietest step-ups I have used, and certainly the quietest under £1,000. Taking a modicum of care with placement, the Anniversary Custom adds no noise to a Cyrus Phono Signature (HFC 408) and the connected Goldring Legacy MC cartridge demonstrates its ability to accommodate the >0.3mV output.

The Rothwell imparts a subtle but worthwhile benefit to the performance and there’s a noticeable improvement to the sweetness of the upper registers with it handling the gain boost with ease. Voices have a bit more richness and warmth, while edgier pressings gain a degree of refinement. Strange Times by The Chameleons sounds slightly more open and is a more refined listen without losing any of the urgency that the album excels at.

At the other end of the frequency spectrum, it’s less clear cut. By the finest of margins, the MC input on the Cyrus has the edge over the Rothwell in terms of outright punch. Putting the Anniversary Custom into the signal path softens the impact of low notes, but not to the extent you’d notice except under the close scrutiny of an attentive A-B listening test. More importantly, it doesn’t affect the timing and sense of agility that the Cyrus possesses and the musical enjoyment remains intact.

Suggestions the Anniversary Custom is simply a tool to help valve users and shares some of the frailties of the medium are wide of the mark. It makes a huge amount of sense in the context of similarly priced phono stages we’ve seen recently. Combining it with the Lindemann Limetree (HFC 441) – which has an excellent moving-magnet performance – results in a truly outstanding combination. If you are a valve phono stage user, this is going to be even more useful still, as good all-valve moving-coil phono stages remain costly. The Rothwell Anniversary Custom is a keenly priced, beautifully executed step-up transformer that uses its unique design thinking to excellent effect. ES

DETAILS
Product: Rothwell Anniversary Custom
Price: £795
Type: Step-up amplifier
Read the full review in April issue 448