Pro-Ject Phono Box MM
Pro-Ject Phono Box MM: the phono preamp that sticks to the essentials
Many current amplifiers no longer have a phono input. The Pro-Ject Phono Box MM addresses this issue in the most straightforward way possible: a compact phono preamp, made in Europe, that amplifies and equalizes the signal from an MM (moving magnet) cartridge to make it compatible with any line input. No settings, no menu, nothing superfluous. Plug it in, and it works.
Circuits designed for silence
The internal design is based on a dual-mono topology: each channel has its own amplification and equalization circuit, which promotes stereo separation and the precision of the soundstage. The integrated circuits were selected for their low noise, and the figures confirm it: the noise floor is specified at −88 dB, total harmonic distortion (THD) remains below 0.04%. For a device in this range, these measurements are remarkable.
The power supply is external, in 18 V DC. This design choice keeps the mains transformer away from sensitive electronics, reducing the risk of hum induced by the electrical network. Standby power consumption is less than 1 watt.
RIAA equalization and cartridge compatibility
The Phono Box MM applies the RIAA equalization curve with an accuracy of ±0.5 dB across the entire 20 Hz – 20 kHz band. This curve is essential for properly reproducing a vinyl record: during cutting, bass is attenuated and treble is boosted; the phono preamp reverses this process. Inaccurate equalization results in an audible tonal imbalance, and the Phono Box MM’s ±0.5 dB tolerance remains tight for this price range.
The input impedance is fixed at 47 kilohms with a capacitance of 120 pF, which corresponds to the standard load for moving magnet (MM) cartridges. Gain is 40 dB, with an output voltage of 500 mV for an input signal of 5 mV at 1 kHz. No adjustment is available: no gain selector, no adjustable loading. This simplicity is deliberate and consistent with the product’s positioning.
Low-impedance output stage
A technical detail often left unmentioned on entry-level phono preamps: the Phono Box MM features a low-impedance output stage. In practice, this means the signal tolerates long interconnect cables between the preamp and the amplifier better, with less signal degradation. In a setup where the turntable is located far from the amplifier, this is a concrete advantage.
Its place in the Pro-Ject range
The Phono Box MM is the first step in Pro-Ject’s phono preamp range. Above it, the Phono Box DC adds MC compatibility (with a selector on the back of the unit). The Phono Box S2 goes a step further, with an aluminum chassis, adjustable gain across four levels, and load and capacitance settings to fine-tune the preamp to the cartridge in use. Each model meets a different need: the Phono Box MM is the one that gets the job done without asking questions.
Documentation
Technical specifications
Key features
- Compatible with MM (Moving Magnet) cartridges
- Precise RIAA equalization
- Dual-mono circuit for optimized channel separation
- Low-noise integrated circuits
- Gold-plated RCA inputs and outputs
- Metal housing protecting against vibrations and electromagnetic interference
- Black lacquered finish
Electrical specifications
- Input impedance: 47 kohms
- Capacitance: 120 pF
- MM gain: 40 dB
- Output voltage: 500 mV at 1 kHz (with an input voltage of 5 mV at 1 kHz)
- Noise floor: −88 dB
- Total harmonic distortion (THD): < 0.04%
- RIAA equalization curve accuracy: within 0.5 dB / 20 Hz - 20 kHz
Connectivity
- Input: RCA
- Output: RCA
Power supply
- Power supply: 18 V / 500 mA DC; 220 - 240 V, 50 Hz
- Consumption: 20 mA DC, < 1 watt in standby
Dimensions and weight
- Dimensions (w × h × d): 10.7 × 3 × 7.5 cm
- Weight: 280 g (without power supply)
Frequently Asked Questions
Does the Phono Box MM have a ground terminal?
Yes. A screw terminal is located on the back of the unit, next to the RCA sockets. If you hear a low hum during playback, connect the ground wire from your turntable’s tonearm to this terminal. Most turntables provide this cable.
Can it be used with an MC cartridge?
No. The Phono Box MM is designed exclusively for moving magnet (MM) cartridges. MC cartridges, whether high-output or low-output, require a suitable preamp. In the Pro-Ject range, the Phono Box DC or the Phono Box S2 support MC cartridges.
Is the mains power supply included?
Yes. The Phono Box MM comes with an 18 V / 500 mA power adapter suitable for the electrical network of the country of sale (220 – 240 V, 50 Hz for Europe).
Do you need an RCA cable between the turntable and the preamp?
Most turntables come with an integrated or supplied RCA interconnect cable. If not, a standard stereo RCA cable will do. The Phono Box MM accepts RCA plugs only.
Can it be left on all the time?
The device does not have an on/off button: it operates as soon as the power supply is connected. Its standby power consumption is less than 1 watt (20 mA DC), which makes continuous operation entirely feasible.
Is the 120 pF capacitance suitable for all MM cartridges?
The total capacitance seen by the cartridge includes that of the preamp (120 pF) and that of the interconnect cable (variable depending on the cable). Some MM cartridges recommend a precise total capacitance (often between 150 and 300 pF). If the cartridge specifies a high value, the turntable cable will often provide the remainder. If it requires a very low value, the total may exceed the recommended range. Check your cartridge’s specifications.
- Eco-contribution of €0.12 included in the sale price.
