Mofi Electronics MasterPhono walnut

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 chassis 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 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 balanced, 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. First, 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. Second, 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 standard 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 MC cartridges. 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 sockets on the rear, where you can install the resistor or capacitor of your choice. Switching is handled by relays, which eliminates mechanical potentiometers from the signal path. The slight delay when changing positions protects the speakers against pops.

VU meters and azimuth adjustment

The two orange-backlit analog meters are more than just an aesthetic nod to Japanese amplifiers from 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 allows you to set the reference level and 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 tier, and it avoids having to resort to 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 anticipate

One point to note: the MasterPhono requires a break-in period. According to consistent observations from several users and from 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. Thereafter, the MasterPhono proves sensitive to mechanical vibrations transmitted by the furniture: using it on an isolated support or with damping feet can reduce a slight residual hiss.

Technical Specifications

Philosophy and design

• Radically audiophile approach aimed at reducing losses, noise, and distortion
• Developed in collaboration with Peter Madnick
• Fully 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
• Eliminates 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)
• THD MC: 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, controlled bass
• Fast, 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 loading)
• 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