Ortofon OM PRO S

A DJ cartridge is judged first by how it handles everyday movements: lowering the tonearm mid-track, pulling the record back to cue a start, holding the vinyl under your fingers. The OM PRO S meets these demands with a spherical stylus, a robust moving assembly and a generous output signal, in the half-inch format that mounts on most headshells. It is the entry-level model in Ortofon’s DJ range.

A spherical stylus that tolerates handling

The stylus tip is ground to a spherical shape, with a radius of 18 µm. This rounded profile rests against the groove walls with a simple, uniform contact area, making it more stable than an elliptical profile when the record is pushed, pulled or stopped abruptly: the stylus stays in its groove instead of skipping. The trade-off is well known: a spherical tip tracks the tightest groove modulations less precisely, and the OM PRO S’s frequency response stops at 18 kHz. For playback in a club or at home, this limit takes a back seat to reliable tracking.

The stylus is supported by an aluminium lever (the cantilever, the fine rod that transmits groove vibrations to the generator) rigid enough to withstand the jolts of energetic handling. The suspension follows the same approach: its compliance, meaning its flexibility, is 7 µm/mN, a low value that corresponds to a firm moving assembly, well suited to the heavy tonearms of DJ turntables and relatively insensitive to shocks and vibrations transmitted by a booth or a moving floor.

The recommended tracking force is 4 g, within a range of 3 to 5 g, roughly twice what typical hi-fi cartridges require. This weight holds the stylus down in the groove and largely explains its secure tracking during back-cueing. It also wears the vinyl and stylus a little faster than a light tracking force, a deliberate compromise for DJ use.

A 5 mV signal for the mixer’s phono input

The OM PRO S works on the moving-magnet principle: a small magnet attached to the cantilever moves relative to fixed coils, generating the electrical signal in them. Its output voltage reaches 5 mV, a high level for this family of cartridges. The mixer’s phono preamp needs to provide less gain, hiss remains less noticeable relative to the music, and two turntables fitted with the same cartridge deliver a consistent level, making transitions easier.

The recommended load values (47 kΩ and 200 to 600 pF) are those of any standard MM phono input, whether on a mixer, an amplifier or a separate phono preamp: no special adjustment is required. Channel separation, at 20 dB at 1 kHz and 15 dB at 15 kHz, remains modest and produces a narrower stereo image than a home-listening cartridge, with no consequence when mixing, where the signal often ends up on a front-of-house PA system.

An OM body for mounting on a half-inch headshell

The black, 5 g body attaches with two screws to any standard half-inch headshell, as on turntables with an S-shaped tonearm and a removable headshell such as the Technics SL-1200. The front leaves the tip clearly visible, a detail that helps place the stylus at the exact starting point on the record. The vertical tracking angle is 20°.

Setup simply involves aligning the cartridge on the headshell, balancing the tonearm, then setting the counterweight to 4 g. The replacement stylus, the Stylus PRO S, is removed and refitted from the front without removing the cartridge, allowing the body to remain in place and only the stylus to be replaced when it wears out.

The foundation of the Ortofon DJ range

The OM PRO S shares its stylus with the Concorde PRO S, a version of the same cartridge integrated into a one-piece headshell. Both formats use the same replacement Stylus PRO S. Further up, the OM range offers more specialised models, such as the OM Scratch or the OM Q.Bert, whose higher output and stiffer suspension are aimed at intensive turntablism. The OM PRO S remains the family’s versatile cartridge, comfortable with mixing, headphone cueing and occasional scratching.

On a hi-fi turntable, under what conditions

The OM PRO S can also be fitted to a home turntable, on two conditions: the tonearm must accommodate a tracking force of 4 g, and its mass must remain compatible with a firm suspension. A light tonearm designed for high-compliance cartridges will be a poor match. On a medium- to high-mass tonearm, it tracks without difficulty and is forgiving of worn second-hand records, with the spherical tip resting on a part of the groove less affected by previous playback. In return, treble reproduction and stereo image precision remain below those of hi-fi cartridges with an elliptical profile, making the cartridge better suited to a secondary turntable, family listening or a crate of bargain finds than to a high-resolution system.

Technical specifications

Design and use

• Type: professional moving magnet DJ cartridge
• Mounting: standard headshell system
• Suitable for hi-fi use
• Robust and reliable construction for intensive use
• Color: black

Stylus and tracking parameters

• Stylus profile: spherical
• Clearly visible stylus tip
• Replacement stylus: PRO S
• Tracking force:
  • Allowable range: 3 – 5 g
  • Recommended value: 4 g
• Tracking angle: 20°
• Lateral compliance: 7 µm/mN
• Equivalent mass: 0.5 mg
• Tracking ability at 315 Hz, at the recommended tracking force: 70 µm
• Intermodulation distortion at the recommended tracking force, according to DIN 45.542: < 1%

Audio performance

• Output voltage at 1 kHz, at a velocity of 5 cm/s: 5 mV
• Channel balance at 1 kHz: 2 dB
• Channel separation:
  • At 1 kHz: 20 dB
  • At 15 kHz: 15 dB
• Frequency response: 20 – 18000 Hz, +3 / −1 dB

Electrical specifications

• Internal impedance: 1 kΩ
• Internal inductance: 750 mH
• Recommended load impedance: 47 kΩ
• Recommended load capacitance: 200 – 600 pF

Weight

• Cartridge weight: 5 g