A New/Old Way to Upgrade Your MC

Low output MC cartridges send an output that’s about a tenth the output of MM cartridges. This means they require a specialty phono preamp with more gain & different electrical parameters… unless you add a step-up transformer to prep the signal for your MM phono stage!

The MC Step-Up Box DS3 B works very differently from a phono preamplifier. The windings ratio of the transformer determines the gain factor. As it’s a passive device that doesn’t require a power supply, no additional power can be produced. The increase in voltage is achieved by a corresponding decrease in current.

As there is no amplification, the MC Step-Up Box DS3 B is remarkably low in noise & distortion with a lively, dynamic & natural sonic signature.

Lundahl LL 1678 Transformer – Balanced Capability

For the MC Step Up Box DS3 B we use high quality Lundahl LL 1678 audio transformers to ensure that all musical detail passes through. You can set the transformer ratio with a push of a button on the back panel. Use single-ended RCA or go balanced with the XLR input & output to benefit from low-noise, interference-free signal transmission. Select the input & output with the buttons on the front. Additionally you can adjust the gain level at 24 or 30dB.

Why Use a Step-Up Transformer?

Once upon a time, step-up transformers were all but required for the optimal handling of a low output MC cartridge’s signal. Active amplification technology was simply too noisy back then (defeating the purpose of the low output design). A step-up transformer removes active amplification from the equation & passively boosts the signal the old-fashioned way. Operating entirely apart from mains power, it’s an opportunity to silently add 24 or 30dB, which amounts to an output that’s comparable to MM cartridges (this is why a step-up transformer’s output is connected to an MM phono preamp input). Needless to say, modern active amplification has improved by leaps & bounds. MC phono preamps can apply all the necessary gain without inducing excessive noise levels… yet there remains a niche population of critical listeners who continue to swear by the performance of the step-up transformer. It’s just a different approach that, pending your low output cartridge and MM preamp, may be just what you’re after!

Designed & Handmade in Europe

The Step-Up Box DS3 B is carefully designed and handmade in Europe. Our goal is to develop a technically flawless device in a housing that is only as big as necessary. Due to the timeless design & rigid aluminum chassis, the MC Step-Up Box DS3 B is built to last an eternity. With high-quality materials and components and a well-thought-out design, Pro-Ject brings the concept of MC step-up transformers back into the conversation.

Additional information
Weight 1.74 kg
Dimensions 20.9 × 20.6 × 7.9 cm



  • Enjoy your MC cartridge with an MM phono preamp
  • Lundahl LL1678 high-quality audio transformer
  • Balanced inputs and outputs
  • Fully passive signal path (no power supply!)
  • 1:16 or 1:32 selectable transformer ratio
  • Superior sound quality
  • Transformer with Mu-metal shielding
  • Dual-mono design principle
  • Ultra-low noise
  • High channel separation
  • Gold-plated RCA terminals
  • Solid aluminum chassis shields RF/EMI
  • Available in silver or black


  • Frequency response: 10Hz – 55kHz (+/- 1dB)
  • Gain at 10-40 ohm: 21dB at 1kHz
  • Gain at 40-150 ohm: 24dB at 1kHz
  • Recommended load: 47k ohm / 100pF
  • Input: XLR , RCA
  • Output: XLR, RCA
  • Dimensions (WxHxD): 206 x 79 x 209mm
  • Dimensions (standard): 8.11 x 3.11 x 8.23″
  • Mass (weight): 1740g (3.84 lbs)