The Pro-Ject MC Step Up Box S3 is a passive step-up transformer designed to bridge the gap between an MC phono cartridge and a standard MM phono stage. MC cartridges generate a signal roughly ten times lower in voltage than their MM counterparts, which means a standard phono stage often lacks the gain headroom to handle them cleanly. The MC Step Up Box S3 solves this by placing a precision transformer between cartridge and phono stage, amplifying the signal passively and without any active circuitry or external power supply.
Passive Transformer Design
Because the MC Step Up Box S3 uses transformer windings rather than active amplification, it produces no additional noise of its own. The gain is determined entirely by the winding ratio: the secondary coil has more windings than the primary, stepping up voltage while correspondingly reducing current. The result is an exceptionally low noise floor and minimal distortion, qualities that active MC phono stages must work hard to match. Many listeners find the sound character of a good step-up transformer to be more immediate and expressive than active solutions.
Impedance Matching
A rear-panel button allows the user to select between two impedance settings: 10 to 40 ohms and 40 to 150 ohms. This means the MC Step Up Box S3 can be matched accurately to a wide range of MC cartridges, from low-output moving coil designs requiring the lower impedance setting to higher-impedance cartridges benefiting from the upper range. Correct impedance matching is essential for linear frequency response and optimal energy transfer from the cartridge.
Premium Build Quality
The chassis is machined from rigid aluminium with a timeless industrial aesthetic that sits comfortably alongside other Pro-Ject Box S3 components. Gold-plated RCA phono sockets are fitted at both input and output for low-resistance, corrosion-resistant connections. The unit is handmade in Europe, continuing Pro-Ject's tradition of precision craftsmanship in their Austrian-affiliated manufacturing facilities.
Integration with a Phono Stage
The MC Step Up Box S3 is placed between the turntable and a MM phono stage. The output from the cartridge feeds into the step-up's RCA input; the step-up's output then connects to the MM input of the phono preamplifier. The phono stage then applies its RIAA equalisation curve as normal. No additional power supply is needed, and there is no on/off switch to consider.
