SUT Degaussing service

"Professional core demagnetization service for Clinamen and third-party step-up transformers"

Step-Up Transformer Cores

Step-up transformers for moving coil cartridges use—when properly designed—high-permeability, gapless magnetic cores, typically made of mu-metal, permalloy, Vacoperm, amorphous, or nanocrystalline materials. This is no random choice: it provides high primary inductance, extremely low losses, and a highly linear response with minuscule microvolt-level signals. However, this exact characteristic makes them exceptionally sensitive to unwanted DC components.

These cores are designed to operate strictly on AC signals, oscillating symmetrically around zero magnetic field. Even tiny DC currents—fractions of a milliampere—can shift the core's operating point out of its linear region. The outcome is not obvious saturation, but something far more insidious: the core operates in an asymmetrical region of the hysteresis loop, where permeability shifts alongside the signal. In audio terms, this introduces low-level non-linearity.

How Can a Core Become Magnetized?

Residual magnetization can arise in several ways. One of the most common is simply measuring winding resistance with a standard multimeter: the meter’s test current, though small, is often enough to magnetize a gapless core. Repeated testing, improper connections, or equipment with DC offsets can also contribute over time. Under normal daily use with a pure, symmetrical audio signal, magnetization should not build up significantly; yet in the real world, SUTs often pass through test benches, multiple hands, and less-than-ideal setups. Furthermore, many SUTs we own were bought second-hand, with their past history unknown—a scenario even more relevant for step-ups built around vintage transformers from the golden era (Partridge, Tango, Western Electric...), which have undoubtedly seen many mA pass under the bridge.

How Does a Magnetized SUT Sound?

Sonically, the effects are subtle rather than blatant. You won't hear gross or easily measurable distortion, but rather a progressive loss of micro-detail: less transient delicate precision, a less stable soundstage, and a reduced sense of air and naturalness. In a high-end analog system, these nuances make all the difference between a merely correct listening experience and a truly captivating one.

The Physics of Magnetism and Restoring Pristine Conditions

Restoration involves the controlled removal of residual core magnetization. Physically, the goal is to return the magnetic material to a neutral state by gradually driving the magnetic domains back into a random distribution around zero. This is achieved by applying a controlled AC magnetic field to the primary winding—starting strong enough to trace the full hysteresis loop, then decaying smoothly and progressively. Gradual reduction throughout the entire procedure is essential. This process is known as "demagnetization via decreasing hysteresis loops."

Technical/artistic drawing showing the Clinamen degaussing procedure for SUT cores

The Clinamen Offer for Peak SUT Performance

This procedure is executed using laboratory-grade equipment, incorporating a signal generator and direct control of the magnetizing current without ever subjecting the transformer to stress or deep saturation. The treatment is fully reversible, non-invasive, and involves no electrical or mechanical modifications to the component.

 I am therefore making this residual demagnetization service available upon request, specifically tailored for moving-coil step-up transformers. It is designed as a restoration of the core's ideal operating conditions—not as a "tuning" or sound alteration. The objective is simple and rigorous: to allow the transformer to operate once again within its intended design region, restoring linearity, transparency, and the integrity of the musical information.

 In a high-level analog system, even invisible details matter. Sometimes, resetting everything back to zero is the finest upgrade possible.

 The cost of the service is €60 (shipping excluded). The price includes a certificate documenting the date of the service, the test signal level, and the lowest frequency reached.