Name: ST-M25
Brand: Ortofon
SKU: 4571106661724
Price: 699.0 EUR
Availability: InStock

Presentation of the Ortofon ST-M25 Transformer

The ST-M25 transformer from Ortofon is a device specifically designed for turntables. It is a moving coil (MC) transformer intended to enhance the sound quality of low-output phono cartridges, particularly the SPU Mono CG 25 Di MkII and SPU Mono CG 65 Di MkII models. This transformer is essential for audiophiles looking to optimize their monophonic vinyl listening experience.

Technical Specifications

Its wide bandwidth of 10 Hz to 100 kHz allows it to faithfully reproduce the entire audio spectrum with perfectly consistent gain. The input impedance of 5 to 50 Ω is ideal for very low-output MC cartridges like Ortofon’s SPU Mono. The high output impedance of 47 kΩ, typical of an MM cartridge, allows for direct interfacing with the MM phono input of any amplifier or preamplifier.

Interest and Positioning

The Ortofon SPU Mono CG 25 Di MkII and CG 65 Di MkII cartridges deliver an output signal of about 1.5 mV, which is too low to directly drive a standard MM phono input. This would result in significantly insufficient volume. Additional gain is therefore necessary.

This is precisely the role of the ST-M25, which, thanks to its 12 dB gain, raises the voltage to an adequate level, comparable to that of an MM cartridge. This ensures total compatibility with the MM phono stages of amplifiers and preamplifiers on the market, without the need for an expensive dedicated MC preamplifier.

The ST-M25 is thus the ideal solution to fully exploit the potential of Ortofon’s SPU Mono CG 25 and CG 65 cartridges, models renowned for their dynamic and musical reproduction of old monophonic recordings. Paired with these cartridges, it offers powerful and authentic sound, in the pure spirit of the early days of vinyl records.

Implementation

Implementing the ST-M25 transformer is very simple. Just connect the two output channels of the cartridge to the transformer’s RCA inputs, then connect its RCA output to the MM phono input of the amplifier or preamplifier.

Since the SPU Mono CG 25 and CG 65 cartridges are monophonic, they deliver exactly the same signal on both channels. The ST-M25 sums these two channels into a single mono signal, which it outputs simultaneously on its left and right RCA outputs. This results in true monophonic sound on both speakers.

Thanks to its compact size and robust construction, the ST-M25 easily finds its place close to the turntable, protected from vibrations. Its gold-plated RCA connectors ensure optimal signal transfer, without loss or distortion. Its entirely passive operation protects it from any interference with other devices.