Ortofon SPU Mono CG 65 DI MKII Moving Coil Cartridge

What makes the SPU Mono CG 65 DI MKII different from a general-purpose cartridge?

The SPU Mono CG 65 DI MKII is an SPU-style moving coil cartridge built specifically for mono replay rather than adapted from a stereo design. It reads only the lateral groove modulation found on mono and 78rpm pressings, which lets it recover the recorded signal with a level of accuracy that a stereo cartridge, picking up both lateral and vertical movement, cannot match on these discs. This mono-only construction carries a firm restriction: the cartridge must never be used on stereo records, since doing so can cause irreversible damage to the generator. Buyers building a dedicated mono playback chain get accuracy in return for that single-purpose design; buyers who need one cartridge for a mixed record collection do not.

Which phono transformers and stages does it suit?

The SPU Mono CG 65 DI MKII is rated at a 1.5mV output at 1kHz, a level that suits a range of medium-gain moving coil transformers rather than requiring a specialist high-gain unit. Its internal impedance is 6 ohm, and Ortofon specifies a recommended load impedance of 100 ohm, figures a buyer needs when checking a transformer or phono stage for a correct electrical match. Ortofon's own ST-M25 moving coil transformer is designed exclusively for this cartridge and its sibling, the SPU Mono CG 25 Di MkII, giving buyers who want a matched, single-source signal path a transformer built around the same electrical specification rather than a generic step-up unit.

How does this cartridge need to be matched to a tonearm before installation?

The SPU Mono CG 65 DI MKII is rated at 7µm/mN compliance, placing it in the low compliance category. Low compliance cartridges pair with moderate mass tonearms, those with an effective mass between 11 and 25 grams, such as the SME IV, V and VI, Triplanar or Graham; a light, low-mass arm is not a good match. Correct pairing matters because the cartridge and tonearm together form a resonant system, and the resonance frequency, calculated from cartridge compliance and total tonearm mass, needs to fall within 7 to 12Hz, with 10Hz recommended, for the stylus to track the groove reliably. Outside that window the system can behave unpredictably, so a buyer should check their arm's effective mass against this compliance figure before ordering.

What tracking force does the SPU Mono CG 65 DI MKII require once fitted?

The SPU Mono CG 65 DI MKII is specified with a tracking force range of 4.0 to 5.0g (40 to 50mN), with 4.5g (45mN) recommended, and a tracking angle of 20°. These figures need setting accurately at installation, since they sit well above the tracking force used by most modern stereo cartridges, reflecting the heavier tracking historically needed to trace 78rpm and early mono grooves cleanly.

Who should choose this mono cartridge?

The SPU Mono CG 65 DI MKII is suited to collectors and archivists who own early 65µm mono and 78rpm pressings and want an authentic playback method regardless of the shellac, vinyl or other materials those discs were pressed from. Because it cannot be used on stereo records, it typically forms part of a dedicated mono setup, often a second arm and headshell alongside a stereo cartridge, rather than a single all-purpose solution. Buyers without a meaningful mono or 78rpm collection gain little from its mono-specific construction and are better served by a general stereo cartridge.

Why does it use a spherical stylus?

The SPU Mono CG 65 DI MKII is fitted with a spherical, or conical, stylus, the simplest diamond profile Ortofon produces, with a tip radius of R65µm on this model. A spherical tip suits the wider, less finely cut grooves of early mono and 78rpm records better than the narrower fine-line or line-contact profiles built for modern stereo microgrooves, because its rounded contact point sits at a groove depth appropriate to that wider cut rather than riding too high or too low in it. Frequency response is specified at 20Hz to 20kHz, ±1dB, and tracking ability at 315Hz is rated at 60µm, indicating the cartridge can handle the more pronounced groove modulations typical of 78rpm cutting without mistracking.

What is the cartridge body made from?

The SPU Mono CG 65 DI MKII is built with a cartridge body of ground wood and resin composite, finished in black matte, and weighs 35g complete. That weight is a direct input into the tonearm resonance calculation covered above, so it needs to be added to headshell and tonearm mass when working out total effective mass. The coil wire is High Purity Copper (OFC), the conductor material carrying the generated signal from the cartridge to the transformer or phono stage.

How does the SPU Mono CG 65 DI MKII compare with other models in Ortofon's SPU range?

The SPU Mono CG 65 DI MKII is positioned within Ortofon's SPU range alongside the SPU Mono CG 25 Di MkII as a mono-specific model at the same price point, while the SPU Classic G MkII and SPU Classic GE MkII serve as the equivalent stereo cartridges for buyers playing a general vinyl collection rather than dedicated mono or 78rpm discs. A buyer choosing between the two ranges should base that decision on what the collection actually contains: mono and 78rpm pressings call for the Di MkII's mono-only generator, while mixed or stereo collections need the Classic range instead. For anyone assembling a mono-specific chain, Ortofon's ST-M25 transformer and a Stylus Guard for the SPU body are the accessories built to match this model.