Mofi Electronics UltraPhono

Two years of prototyping, carefully selected components, and a circuit designed by Tim de Paravicini: the UltraPhono is a compact MM/MC phono preamp that incorporates a Class A headphone amplifier. Manufactured in the United States at MoFi’s Michigan factory, it draws on the principles of the Gain2 Ultra Analog analog cutting system used by Mobile Fidelity Sound Lab’s mastering engineers in Sebastopol, California.

A circuit born in the mastering studio

Tim de Paravicini, the British engineer who designed Mobile Fidelity’s Gain2™ cutting system, also designed the UltraPhono’s circuit. This is not a marketing detail: the sonic kinship between the UltraPhono and De Paravicini’s EAR-Yoshino creations is audible, with a three-dimensional presentation, tight bass, and a musicality reminiscent of his tube designs, transposed here into an all-transistor format. The signal follows a streamlined, low-distortion path (THD below 0.006% in MM, below 0.055% in MC), with a low noise floor that lets the micro-details of carefully pressed records come through.

Fine adjustment for MM and MC cartridges

The UltraPhono supports moving magnet (MM) and moving coil (MC) cartridges, with a set of adjustments that covers almost all cartridges on the market. Gain is adjustable in four steps: 40 dB and 46 dB for MM, 60 dB and 66 dB for MC. Input impedance is fixed at 47 kΩ in MM; in MC, six values are available (75 Ω, 100 Ω, 500 Ω, 1 kΩ, 10 kΩ, and 47 kΩ). Input capacitance is 100 pF.

All of these settings are adjusted via small switches located underneath the chassis. No tool is required: turn the unit over, flip the switches, and it’s set. The trade-off is that you won’t change configuration mid-listening the way you would with front-panel controls. It’s a coherent choice for a device you configure once, when installing a new cartridge, and then forget about.

Mono mode and infrasonic filter

On top of the chassis, two buttons provide access to mono mode and the infrasonic (“subsonic”) filter. Mono mode does more than simply combine the two channels: it improves image stability and tonal density on mono records, whether they are period pressings or recent reissues. Anyone who owns a few original mono records from the 1950s or 1960s will hear the difference.

The infrasonic filter, for its part, cuts very low parasitic frequencies. Its usefulness is twofold: it corrects the effects of warped records, which cause excessive woofer excursion, and it compensates for the mechanical isolation shortcomings of certain turntables. In a system where the turntable sits on the same piece of furniture as the speakers, this filter avoids the vicious circle of vibrations → resonance → distortion.

A headphone amplifier that is no mere extra

The integrated headphone amplifier operates in Class A, with a 6.35 mm jack output on the front panel. Its specifications are far from incidental: 8 V RMS maximum output voltage, 1.5 W per channel into 62 Ω, compatibility with headphones above 10 Ω impedance. These values are sufficient to comfortably drive planar magnetic headphones or high-impedance models.

Volume is adjusted via a 31-position stepped potentiometer, with 2 dB steps over a 62 dB range. This step-by-step system provides smooth progression, without abrupt jumps at low levels. Pressing the volume knob activates the mute function (90 dB attenuation), handy for answering the phone or listening to what’s happening around you without removing your headphones.

In practical terms, the UltraPhono allows complete vinyl listening with only a turntable and headphones, without an amplifier or speakers. This is a real advantage for nighttime listening or in an office.

Compared with the StudioPhono

The UltraPhono sits one notch above the StudioPhono in the MoFi range. Both share the same basic circuit designed by Tim de Paravicini, but the UltraPhono stands out with higher-quality components, a lower noise floor, and, according to MoFi, better MC performance. The sound is more neutral and more analytical, whereas the StudioPhono tends toward a warmer signature. The UltraPhono also adds the Class A headphone amplifier, absent from the StudioPhono.

FAQ

Does the UltraPhono work with all phono cartridges? It supports MM and MC cartridges thanks to its four gain levels (40, 46, 60, 66 dB) and six MC impedance values (from 75 Ω to 47 kΩ). The fixed 100 pF input capacitance suits most MM cartridges. A few MM cartridges with a high recommended capacitance (200 pF and above) may require additional capacitance via the interconnect cable.

Can the UltraPhono be used only as a headphone amplifier, without an amplifier or speakers? Yes. Simply connect the turntable to the input and headphones to the front panel. Volume is adjusted directly on the unit. It is a complete, self-contained vinyl listening system.

Are the gain and impedance settings easy to change? The switches are located underneath the chassis and can be operated by hand, without a screwdriver. It’s simple, but you do have to turn the unit over, which means unplugging it or at least moving it. Not a problem if you rarely change cartridges.

Does the infrasonic filter degrade the audio signal? The filter acts only on very low frequencies, below the audible musical spectrum. It does not affect the useful audio content. It can be disabled with a press of the front-panel button.

Is the UltraPhono suitable for very low-output MC cartridges? With a maximum gain of 66 dB, it works well with the majority of MC cartridges. Very low-output models (below 0.2 mV), however, may lack headroom, especially with insensitive headphones.

What type of headphones can be used? Any headphones with an impedance above 10 Ω. The 1.5 W per channel power output and 8 V RMS output voltage allow it to drive planar magnetic headphones or high-impedance models such as the Sennheiser HD 600/650/800 or the Beyerdynamic DT 880/990 without difficulty.

Technical Features

Design and Circuitry

• Circuit developed with the expertise of Tim De Paravicini
• Inspired by MoFi Gain2 Ultra Analog mastering standards
• High transparency and low distortion
• Optimized for MM and MC cartridges
• Mastering-grade audio design

Advanced MM / MC Settings

• Selectable gain: 40 dB, 46 dB, 60 dB, 66 dB
• Adjustable load: 75 Ω, 100 Ω, 500 Ω, 1 kΩ, 10 kΩ, 47 kΩ
• Input capacitance: 100 pF
• Settings accessible via switches under the unit, no tools required

Integrated Audio Functions

• Mono Mode
  • Improves playback of mono records
  • Stabilizes the soundstage on older vinyl or reissues
• Subsonic Filter
  • Removes unwanted infrasonic low frequencies
  • Improves bass stability and protects speakers

Integrated Class A Headphone Amplifier

• Dedicated Class A amplification
• High-voltage headphone output up to 8 V RMS
• Power: 1.5 W per channel into 62 Ω
• 31-position volume control, 2 dB steps
• Adjustment range: 62 dB
• Mute function at -90 dB
• Compatible with headphones above 10 Ω
• Enables high-end vinyl listening directly through headphones

Sound Signature

• Great transparency and neutrality
• Very low noise floor
• Excellent dynamics
• Precise and stable stereo image
• Faithful reproduction of micro-details
• Very clean and immersive headphone listening

Technical Specifications

• Gain: 40 dB to 66 dB, selectable
• THD: < 0.006% in MM, < 0.055% in MC
• MM impedance: 47 kΩ
• MC impedance: 75 Ω, 100 Ω, 500 Ω, 1 kΩ, 10 kΩ, 47 kΩ
• Capacitance: 100 pF

Key Strengths

• High-end MM / MC phono preamp
• Integrated Class A headphone amplifier
• Very precise gain and load settings
• Mono mode and subsonic filter
• Direct headphone listening without a hi-fi system

Target Audience

• Demanding audiophiles with or without a speaker system
• High-end headphone users
• Advanced MM / MC vinyl systems
• Listeners who appreciate neutral and analytical reproduction
• Nighttime listening or personal studio use