Mofi Electronics UltraDeck +

When a label specializing in record pressing since 1977 decides to manufacture its own turntables, it doesn’t come empty-handed. Mobile Fidelity Sound Lab entrusted the design of the UltraDeck to Allen Perkins, founder of Spiral Groove and designer of turntables priced above $30,000. The “+” version comes ready to use with a factory-mounted UltraTracker cartridge, hand-assembled in Japan by My Sonic Lab.

A Turntable Made in Ann Arbor, Michigan

The UltraDeck+ comes out of the MoFi Electronics factory in Ann Arbor, Michigan, less than 50 miles from Detroit. This choice of American production is no coincidence: it allows for direct quality control, from chassis machining to final tonearm adjustment. The plinth rests on an MDF body onto which three aluminum plates of different shapes and sizes are bonded, a multilayer construction known as “constrained layer dampening” that adds mass while absorbing resonances. By comparison, the StudioDeck, MoFi’s entry-level model, uses only a single aluminum plate.

The whole unit weighs 10.5 kg and measures 50 × 15.2 × 36.2 cm, generous dimensions due to the 10-inch tonearm, which requires a wider-than-average plinth. A removable hinged dust cover is included, and a square power button backlit in yellow is reminiscent of the controls found on Studer tape machines used in Mobile Fidelity’s mastering studio in Sebastopol, California.

The Delrin Platter: 33 mm of High-Density Polymer

The UltraDeck+‘s platter is machined from a block of Delrin, a crystalline polymer developed by DuPont. At 33 mm thick and weighing 3.1 kg, it is 75% thicker than the StudioDeck’s platter. Allen Perkins chose this material for a specific reason: its mechanical impedance is close to that of vinyl, which allows parasitic vibrations to be drained away from the stylus rather than reflected back to it. Delrin is easy to machine, an industrial advantage that helps maintain a favorable cost-to-quality ratio without resorting to a more complex composite platter.

The platter’s high inertia promotes stable rotation and a very low noise floor, two measurable parameters: MoFi specifies wow & flutter between 0.017% and 0.025%, and a signal-to-noise ratio of 74 dB.

Isolated Motor and Belt Drive

The motor is an AC synchronous type running at 300 RPM, mechanically decoupled from the rest of the turntable by dampening materials. This isolation prevents motor vibrations from traveling up to the stylus through the plinth, a common problem on turntables where the motor is rigidly fixed to the chassis.

Speed changes between 33 ⅓ and 45 RPM are made manually, by moving the belt (yellow, a distinctive MoFi aesthetic detail) onto the two-step Delrin pulley. The operation does not require removing the platter. Power consumption stays below 5 watts; the power supply is integrated into the chassis and the turntable connects via a standard IEC socket.

The 10-Inch Ultra Tonearm

Most turntables in this price range are fitted with a 9-inch tonearm. The Ultra Tonearm measures 10 inches (approximately 254 mm), a compromise between the standard short arm and the 12-inch arms found on high-end turntables. The advantage of a longer arm is geometric: the arc traced by the stylus across the record is gentler, which reduces tracking error.

The tube is straight aluminum, mounted on ball bearings in both planes (horizontal and vertical). The internal wiring, from the headshell to the gold-plated RCA connectors, uses Cardas Audio wire, a cable manufacturer well known in the hi-fi world. The RCA connectors are shielded with copper foil to limit RF interference. The tonearm offers adjustments for tracking force, height (VTA), azimuth, and anti-skating, the latter being a classic thread-and-counterweight system.

The platter’s main bearing uses a hardened steel inverted spindle with a sapphire thrust pad, a combination usually reserved for far more expensive turntables. The lubricant used is ester-based, chosen for its low-noise properties. The anti-vibration feet were co-developed with Harmonic Resolution Systems (HRS), under the direction of Mike Latvis.

One point to consider: the tonearm’s effective mass is high, around 30 g. This makes it compatible with low-to-medium compliance cartridges (between 5 and 10 g according to MoFi), but very high-compliance cartridges, typical of some lightweight moving magnet models, are not the best match.

The UltraTracker Cartridge: Dual Magnet and Nude Elliptical Stylus

The cartridge supplied with the UltraDeck+ is the UltraTracker, a dual-magnet moving magnet (MM) cartridge. Its “V-Twin” generator places two magnets in a V configuration, parallel to the record grooves, an arrangement that replicates the layout of the cutting head used to create the grooves on the master. Allen Perkins and Mobile Fidelity’s engineers developed this cartridge together; it is hand-assembled in Japan in a body machined from solid aluminum in the United States.

The stylus is a nude elliptical (unbonded), which reduces moving mass and improves tracking ability in complex passages. The recommended tracking force is between 1.8 and 2.2 g, the output voltage is 3.5 mV (compatible with all 47 kΩ MM phono preamplifiers), and the frequency response covers 20 Hz to 25 kHz. The machined aluminum body helps control resonances, resulting in controlled bass and good channel separation.

The UltraTracker’s stylus is not user-replaceable, a MoFi design choice aimed at preserving the factory alignment. Those wishing to mount a different cartridge can opt for the UltraDeck without a cartridge.

Setup and Installation

The UltraDeck+ arrives with the UltraTracker cartridge already mounted and factory pre-set (VTA and azimuth). Getting started simply involves placing the platter, installing the belt, counterweight, and anti-skating thread, then connecting the supplied RCA cables. A mark on the counterweight indicates the correct position for the UltraTracker’s tracking force, eliminating the need for a tracking force gauge, although a finer adjustment with such a tool is still recommended.

The turntable should be placed on a stable surface and leveled using the HRS feet, ideally verified with a spirit level. As the plinth is sensitive to its environment, a dedicated audio rack or wall shelf will improve results compared to a standard open furniture unit subject to floor vibrations.

MoFi’s Recommended Accessory

MoFi offers an optional stabilizer weight, the Super HeavyWeight (367 g, aluminum shell with rubber core), sold separately. On the Delrin platter, records can slide slightly when brushing or in the case of pronounced warps. The weight resolves this issue and further stabilizes playback, an addition that several specialist press reviews consider highly beneficial for this turntable.

Technical specifications

Motor and drive

• Motor: AC synchronous 300 rpm
• AC motor isolated from the chassis
  • Optimal speed stability
  • Reduced mechanical vibrations
  • More precise and stable playback
• Belt drive
• Speeds: 33 ⅓ and 45 rpm

Audio performance

• Wow and flutter: 0.017% – 0.025%
• Signal-to-noise ratio: 74 dB
• Power consumption: < 5 W

Platter

• Solid high-inertia Delrin platter
• Thickness: 1.3” (≈ 33 mm)
• Weight: 3.1 kg
• High-density polymer material
  • High inertia
  • Reduced background noise
  • Better playback stability

Ultra Tonearm tonearm

• 10” straight aluminum tonearm
• Made in the USA
• High-precision low-friction ball bearings
• Internal Cardas Audio wiring for lossless signal transmission
• Gold-plated RCA connectors
• Overhang: 18 mm
• Offset angle: 22.8° (± 2° adjustable)
• Compatible cartridges: 5 g – 10 g

Chassis and isolation

• High-rigidity multilayer construction
• Constrained Layer Dampening (aluminum + MDF)
  • Resonance suppression
  • Sonic neutrality
  • Faithful signal reproduction
• HRS anti-vibration feet developed with Harmonic Resolution Systems
  • Effective mechanical decoupling
  • Reduced unwanted vibrations

Dimensions and weight

• Dimensions (W × H × D): 50.0 × 15.2 × 36.2 cm
• Weight: 10.5 kg

Sound signature

• Very high precision
• Wide and stable soundstage
• Clean and controlled bass
• Detailed and natural midrange
• Transparent highs
• Remarkable background silence

Recommended uses

• Advanced audiophile hi-fi systems
• Critical and immersive listening
• Demanding vinyl collectors
• High-resolution setups