Mofi Electronics MasterPhono black

The result of two years of development with engineer Peter Madnick (Audio Alchemy, Constellation Audio), the MasterPhono crowns MoFi Electronics’ range of phono preamplifiers. Where the StudioPhono and UltraPhono, designed by the late Tim de Paravicini, covered the entry-level and mid-range segments, the MasterPhono aims for reference status: a fully analog and discrete circuit, rare versatility in cartridge matching, and American manufacturing. The black version dresses the sides of the enclosure with black panels (a walnut variant also exists).

Two chassis in a single enclosure

The MasterPhono adopts an uncommon structure for a phono preamp: two distinct compartments housed in a single enclosure, linked together by three copper tubes. The front compartment houses the power supply and the control microprocessor. The rear compartment, galvanically isolated from the first, contains the amplification circuits and RIAA equalization. This physical separation keeps noise sources (transformer, digital control circuits) away from the audio signal path, without imposing the extra cost of an external power supply with an umbilical cable.

The input stage is based on discrete JFET transistors, enclosed in a copper housing that provides both electromagnetic shielding and thermal stability. The entire amplification stage is discrete and symmetrical, and the RIAA equalization uses a passive circuit fed by NOS polystyrene and polypropylene capacitors, components chosen for their precision and long-term stability.

Current input: transimpedance serving MC cartridges

Most phono preamps operate in voltage mode: they measure the voltage produced by the cartridge and amplify it. The MasterPhono also offers a current input (transimpedance), available in RCA and XLR. The principle: the input impedance is nearly zero, which effectively short-circuits the cartridge. The preamp then measures the current flowing through the coils rather than the voltage across their terminals.

The advantage is twofold. On the one hand, the issue of load impedance adjustment disappears: since the input presents an impedance close to zero, there is no longer any interaction between the cartridge impedance and that of the preamp. On the other hand, cartridge damping is automatic, which reduces parasitic cantilever resonances. According to MoFi’s observations, the sonic result tends toward tighter bass, crisper transients, and a more open midrange.

This mode works well with low-impedance MC cartridges (typically below 10 ohms). Moving magnet (MM) cartridges and high-impedance MC cartridges are not compatible with this input and must use the conventional voltage inputs.

Three inputs, ten loads, four gains

The rear panel offers three inputs switchable from the front panel:

• one transimpedance (current) input, in RCA or XLR, for low-impedance MC cartridges
• one balanced XLR voltage input
• one unbalanced RCA voltage input

Each input stores its gain and load settings. Switching from one to another automatically recalls the saved configuration, which makes life easier when using multiple tonearms or multiple cartridges.

Gain is adjustable to four levels (40, 50, 60 and 70 dB), covering both high-output MM cartridges and the quietest MCs. Loading offers ten fixed positions (15, 30, 50, 75, 100, 500 ohms, 1 kΩ, 10 kΩ, 47 kΩ + 150 pF) plus a “Custom” position that routes to a pair of RCA jacks on the rear, where you can install the resistor or capacitor of your choice. Switching is done by relay, which eliminates mechanical potentiometers from the signal path. The slight delay when changing position protects the speakers against popping noises.

VU meters and azimuth adjustment

The two orange-backlit analog meters are more than just an aesthetic nod to Japanese amplifiers of the 1970s. In normal mode, they display the signal level. A long press on the “Meter” button switches to a three-step calibration mode, which lets you set the reference level, then adjust cartridge azimuth using a test record (a signal in opposite phase between the two channels: the lower the displayed level, the better the adjustment). This is a rare function on a phono preamp in this price range, and it avoids the need to use an oscilloscope or third-party software for this operation.

Measurements and specifications

Total harmonic distortion drops to 0.005% in MM mode and remains between 0.010% and 0.013% in MC mode. Frequency response extends from 10 Hz to 50 kHz with a tolerance of ±0.20 dB, and RIAA curve accuracy reaches ±0.05 dB. Maximum output is 10 V RMS at 1% THD.

A startup period to plan for

One point to note: the MasterPhono requires a break-in period. According to consistent observations from several users and MoFi, the unit sounds rather flat and dull when first powered on. After about three days of continuous operation, the sound opens up and gains in dynamics and transparency. After that, the MasterPhono proves sensitive to mechanical vibrations transmitted by the furniture: using it on an isolated support or with damping feet can reduce slight residual hiss.

Frequently asked questions

Does the current input (transimpedance) work with all MC cartridges? No. This input is optimized for low-impedance MC cartridges, typically below 10 ohms (for example 1 to 5 ohms). MC cartridges with higher impedance (beyond 15-20 ohms) will produce a flatter, less dynamic sound on this input. For these cartridges, the voltage inputs (RCA or XLR) with conventional load adjustment will give better results.

Can the MasterPhono be used with a moving magnet (MM) cartridge? Yes, via the voltage inputs (inputs 2 or 3). The 40 dB gain and 47 kΩ + 150 pF load correspond to the standard values for MM cartridges. The transimpedance input is not suited to MM cartridges.

What is the “Custom” position on the load selector for? It routes the signal to a pair of RCA jacks on the rear of the enclosure. You can insert an RCA connector fitted with the load resistor or capacitor you want. This makes it possible to use a load value not provided among the ten fixed positions, for cartridges with atypical specifications.

Is the MasterPhono compatible with turntables with multiple tonearms? Yes. The three inputs (transimpedance, XLR, RCA) can be connected to three different tonearms, on the same turntable or on separate turntables. Each input independently stores its gain and load settings.

How does azimuth calibration mode work? You need a test record with a track in opposite phase between the left and right channels (for example the Ultimate Analog Test LP by Analogue Productions). In calibration mode, the VU meters display the residual level: the lower it is, the more correct the azimuth. No external equipment is required.

Can the MasterPhono be used in a studio? Yes. MoFi designed the unit to work equally well in a home or professional context. The balanced XLR outputs, the high available gain (up to 70 dB), the azimuth calibration function, and the remote mute make it a suitable tool for a studio or vinyl mastering environment.

Technical Specifications

Philosophy and design

• Radically audiophile approach aimed at reducing losses, noise, and distortion
• Developed in collaboration with Peter Madnick
• Entirely analog high-precision design
• Architecture designed for MFSL vinyl records
• High-end manufacturing and engineering

Amplification architecture

Current-mode input (transimpedance)

• Unique approach for MC cartridges
• Current-mode input (transimpedance)
• Near-zero impedance
• Automatic cartridge damping
• Elimination of manual load adjustment
• Reduced noise and distortion
• Result: tighter bass, open midrange, faster transients

Input flexibility

• RCA and XLR inputs
• Voltage input mode (standard MM / MC)
• Current input mode (low-impedance MC)
• Fully configurable architecture

Settings and customization

• Selectable gain: 40 dB, 50 dB, 60 dB, 70 dB
• Loading:
  • 15 Ω, 30 Ω, 50 Ω, 75 Ω, 100 Ω
  • 500 Ω, 1 kΩ, 10 kΩ, 47 kΩ + 150 pF
  • Custom mode
• 10 matching options and custom adjustment

Audio performance

• THD: up to 0.005% (MM)
• MC THD: up to 0.013%
• Frequency response: 10 Hz – 50 kHz (± 0.20 dB)
• RIAA accuracy: ± 0.05 dB
• Maximum output voltage: 10 V RMS at 1% THD

Advanced features

• Fully discrete balanced circuit
• Dual-chassis architecture (power supply / signal separation)
• Cascaded ultra-low-noise regulation
• Built-in high-pass filter
• Remote control:
  • Gain
  • Mute
  • Mono
  • Input selection
  • Subsonic filter
  • VU meters

VU meters and calibration

• Dual analog VU meter
• Monitoring mode or azimuth calibration
• Precise and audiophile visual interface

Sound signature

• Extreme transparency
• Very low noise floor
• Stable and wide stereo image
• Firm and controlled bass
• Fast and natural transients
• Reproduction very close to the analog master

Key strengths

• High-end reference phono preamplifier
• Innovative transimpedance architecture
• Ultra-low noise and distortion
• Very comprehensive settings (gain and load)
• Isolated dual chassis
• Calibration VU meters
• Full remote control

Target audience

• Ultra high-end vinyl systems
• Audiophiles seeking absolute neutrality
• Users of demanding MC cartridges
• Studios and reference systems
• Enthusiasts of “master tape / master vinyl” reproduction

Dimensions and weight

• Width: 43.18 cm
• Height: 8.89 cm
• Depth: 38.10 cm
• Weight: 6.8 kg