Pro-Ject MC Step-Up Box S3 Passive Step-Up Transformer - Black

Boost Your MC Cartridge, No Power Required

The Pro-Ject MC Step-Up Box S3 is a passive transformer built to raise the output of a moving coil cartridge up to moving magnet levels. That lets you run a low-output MC cartridge into a preamp or receiver that only has an MM phono input.

Unlike an active phono preamp, it uses no external power at all. A pair of transformers inside do all the work, boosting the signal through magnetic coupling rather than electronic gain stages.

The S3 sits below Pro-Ject's MC Step-Up Box DS3 B in the lineup. The DS3 B adds balanced XLR connections and two switchable gain ratios; the S3 keeps things simpler, with RCA only and a single fixed transformer ratio.

It's housed in a solid aluminum case with gold-plated RCA terminals, and it's handmade in Europe. Because it's entirely passive, there's no standby power draw and nothing to switch on.

Some listeners prefer this transformer-based approach specifically because it stays passive. There's no active gain stage adding its own noise or coloration, just magnetic coupling between two windings.

Matched to a Wide Range of MC Cartridges

The transformation ratio is fixed at 1:16. Gain works out to 21dB at 1kHz for cartridges with 10 to 40 ohms of internal impedance, or 24dB at 1kHz for cartridges between 40 and 150 ohms.

A switch on the front lets you pick whichever of those two impedance ranges matches your cartridge. Frequency response is rated at 10Hz to 55kHz, within ±1dB.

The recommended load coming out of the S3 is 47 kOhms in parallel with 100pF, the same standard loading most moving magnet phono inputs already expect.

It measures 206 by 65 by 153mm (164mm with connectors) and weighs 940 grams. Single pairs of RCA input and output sockets handle all the wiring.

Keep the S3 away from power transformers and other sources of magnetic hum where you can. Like any transformer-based device, it can pick up interference if it sits too close to one.

Who Is This Step-Up Transformer Best For?

• Owners of a moving coil cartridge whose amp lacks MC support. It raises MC output up to a level any MM phono input can handle.
• Listeners who prefer a passive signal path. There's no power supply or active circuitry between your cartridge and your amp.
• Anyone whose amplifier or integrated already has a good built-in MM stage. The S3 lets you use that stage with an MC cartridge instead of buying a separate MC preamp.
• Shoppers who don't need balanced XLR connections. The S3 covers RCA-only systems at a lower price than the balanced DS3 B.
• Not the right fit for anyone who wants adjustable gain beyond two settings. Its transformer ratio is fixed; only the impedance matching switches.

How Does It Connect to Your System?

Run your turntable's phono cable into the S3's RCA input, then connect its RCA output to your amplifier or receiver's moving magnet phono input.

Set the front switch to match your cartridge's internal impedance, choosing between the 10-40 ohm and 40-150 ohm ranges. No power connection is needed anywhere in the chain.

Pairs Well With

Building your system? Here are some great companions for the Pro-Ject MC Step-Up Box S3:

• Moving coil phono cartridges matched to its impedance ranges
• Integrated amplifiers with a built-in moving magnet phono stage
• Interconnect cables to connect its input and output

Frequently Asked Questions

Do I still need a phono preamp with this?

Yes, but it can be a moving magnet one. The S3 raises your MC cartridge's signal to MM levels; your amp's or receiver's built-in MM stage handles the rest.

How is this different from the MC Step-Up Box DS3 B?

The DS3 B adds balanced XLR wiring and two switchable gain ratios, in a larger case at a higher price. The S3 covers RCA-only systems with a single fixed ratio.

Does it need a power supply?

No. It's entirely passive, so there's no external power supply or standby draw to worry about.

What's the warranty?

Pro-Ject covers the MC Step-Up Box S3 with a two-year warranty, extendable to three years with product registration.

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Learn More

Want to learn more about matching a step-up transformer to your cartridge, moving coil versus moving magnet phono stages, or getting the most from your vinyl collection? Visit our Learning Center for guides, tips, and expert advice.