The Ortofon ST-M 25 is a moving coil transformer specifically designed for use with the SPU Mono CG 25 Di MkII and SPU Mono CG 65 Di MkII cartridges. These cartridges have a low voltage output, making them unsuitable for direct connection to the MM input terminals of standard amplifiers or phono equalizers, which can lead to inadequate sound volume. The ST-M 25 addresses this issue by increasing the voltage by 12dB at 1 kHz, allowing proper connectivity and amplification for these cartridges. This transformer enables both left and right channels to be connected, facilitating a robust monaural sound experience through standard stereo speakers. The unit is designed to handle a frequency range of 10 to 100 kHz, with an input impedance of 5 Ω to 50 Ω and a load impedance greater than 47 kΩ with a capacitance of 200 pF. The physical dimensions of the transformer are 65mm in width, 39mm in height, and 98mm in depth, with a total weight of 410g.
