SFz MC Transformer

Key Features

• Reference passive moving-coil step-up transformer
• Pure 99.99% silver transformer windings
• Balanced multilayer winding architecture
• Two dedicated cartridge-impedance inputs
• 1.5-ohm input for cartridges with 1–10-ohm internal impedance
• 30-ohm input for cartridges with 11–40-ohm internal impedance
• 34 dB or 20 dB step-up gain
• Switchable balanced and unbalanced input operation
• Large Permalloy core made from ultra-thin 0.1 mm laminations
• Frequency response extending to 100 kHz
• Double-layer magnetic and electrostatic shielding
• Permalloy transformer case and pure-copper inner enclosure
• Double-float mechanical damping
• Transformer suspended with damping gel
• Pure-copper outer chassis
• Fixed one-metre Kondo Ls-41 pure-silver RCA output cable
• Minimized internal connection points

Design & Build

The SFz is built around Kondo’s balanced multilayer winding structure using 99.99% pure-silver wire. The winding geometry was developed to maintain a flat response to 100 kHz, with less than 1.5 dB of unloaded secondary peaking when connected to a 47-kohm phono input.

Its large magnetic core is assembled from custom 0.1 mm Permalloy laminations. The thin laminations reduce eddy-current and hysteresis losses, while the core’s large cross-sectional area and short magnetic path support low-frequency extension with minimal distortion.

Each transformer is installed inside a Permalloy case and then enclosed within an inner pure-copper chassis. The Permalloy layer shields against magnetic fields, while the copper layer protects against electrostatic interference. Damping gel and specially selected rubber feet isolate the transformers mechanically.

To preserve the cartridge’s extremely low-level signal, the 1.5-ohm and 30-ohm input terminals connect directly to separate leads from the primary windings. The secondary winding is soldered directly to the permanently attached Kondo Ls-41 pure-silver output cable.

System Pairing

The 1.5-ohm input provides 34 dB of gain and is intended for cartridges with an internal impedance between 1 and 10 ohms. This is the correct connection for Kondo’s 1-ohm IO-XP cartridge.

The 30-ohm input provides 20 dB of gain and is designed for moving-coil cartridges with an internal impedance between 11 and 40 ohms. Only one pair of input terminals should be connected at a time.

A grounding selector allows the primary winding to operate in balanced or unbalanced mode. Balanced mode requires a two-conductor shielded phono cable and cannot be used when the turntable grounds the cable shield internally. The fixed RCA output cable connects to a conventional 47-kohm moving-magnet phono input.