A passive step-up transformer for moving-coil cartridges, placed between the turntable and an MM phono input: 1:16 ratio, 21 or 24 dB of gain depending on cartridge impedance, and no power supply at all.
MC Step Up Box S3: how it works
An MC cartridge delivers roughly a tenth of the level of an MM. To raise it to a usable level a phono preamplifier has to amplify far more, and with gain come the risks of added noise and distortion. Pro-Ject's step-up box deals with the matter upstream: it lifts the voltage before the signal enters the phono stage, which then works as it would with an MM. Pro-Ject advises this approach alongside a good MM phono preamplifier, a valve one in particular, in place of an MC phono stage.
It operates differently from an amplifier. Gain depends on the ratio between the windings, 1:16 here, and the unit is wholly passive: it is not plugged into the mains and adds no energy, since the rise in voltage is offset by an equal fall in current. With no active stages involved, noise and distortion stay very low. The two transformers, one per channel, are enclosed in mu-metal shields.
A button on the rear panel suits the input to the cartridge: in the position for impedances of 10 to 40 ohms gain is 21 dB, while in the 40 to 150 ohm position it rises to 24 dB. The advised load downstream is 47 kohms and 100 pF, in other words an ordinary MM input. Input and output are on gold-plated RCA sockets and the enclosure is aluminium throughout.
Specifications
- Type: passive MC step-up transformer
- Turns ratio: 1:16
- Gain for 10 to 40 ohm cartridges: 21 dB at 1 kHz
- Gain for 40 to 150 ohm cartridges: 24 dB at 1 kHz
- Frequency response: from 10 Hz to 55 kHz within 1 dB
- Advised load: 47 kohms and 100 pF
- MC input: one gold-plated RCA pair
- Output: one gold-plated RCA pair
- Power supply: none required, passive circuit
- Size (WxHxD): 206 x 65 x 153 mm, 164 mm including sockets
- Weight: 940 g
- Finishes: black, silver
