Thorens - SPU 124 MC Phono Cartridge

Thorens and Ortofon’s modern reading of the SPU, built for the TD 124 DD and its TP 124 arm: an SPU-bodied low-output moving coil, 0.5mV into a 2Ω source impedance, tracking at 3 grams.

The Ortofon SPU has been in production since 1959 and it is not really a cartridge in the modern sense. It is a cartridge and a headshell built as one object, mounting to the arm on a bayonet rather than to a headshell on two screws. That construction is why SPUs weigh what they do — this one is 30 grams — and why they need an arm designed to carry them.

The SPU 124 is a joint Thorens and Ortofon product, described on Thorens’ own datasheet as a special version of the famous Ortofon SPU, made for the TD 124 DD. Thorens supplies a second counterweight with that turntable specifically to balance it. Note that the datasheet names the TP 124 arm, not the TP 160 — this is not a general-purpose cartridge to hang on any deck.

The generator has been revised. Output is 0.5mV at 5cm/sec from a 2Ω internal impedance, and Thorens’ wording is that this “reduces the demands on high-gain step-up transformers.” Read that carefully, because it is doing precise work: it says the transformer’s job is easier, not that you can do without one. At 0.5mV and 2Ω this is a classic low-output moving coil, and it expects either a step-up transformer or a very quiet high-gain MC stage. Thorens nowhere says a transformer is unnecessary, and we are not going to tell you it is.

The stylus is a nude elliptical with 8/18µm radii, on a cantilever whose material Thorens does not publish. Recommended tracking force is 3.0 grams, which is heavy by modern standards and entirely normal for an SPU. Compliance is 8µm/mN — low, as the weight and the tracking force imply, and a good match for the 18g effective mass of the TP 124.

Load it between 10 and 50 ohms.

Features

• Thorens and Ortofon collaboration in classic SPU form — integrated body and bayonet mount
• Developed for the Thorens TD 124 DD and its TP 124 tonearm
• Low-output moving coil, 0.5mV at 5cm/sec, 2Ω internal impedance
• Nude elliptical stylus, 8/18µm radii
• Tracking ability better than 70µm at 315Hz
• Recommended load 10–50Ω
• 3.0g recommended tracking force

Specifications

• Type: Moving coil, low output, SPU-bodied with a bayonet mount
• Manufacturer: Listed on the datasheet as Thorens / Ortofon — a joint product. Thorens does not state which company physically builds it
• Designed for: The Thorens TD 124 DD turntable and TP 124 tonearm. Thorens supplies a dedicated second counterweight with the TD 124 DD to balance it
• Output voltage: 0.5mV at 5cm/sec, measured at 1,000Hz
• Internal impedance: 2Ω DC resistance
• Inductance: Not published
• Recommended load impedance: 10–50Ω
• Recommended load capacitance: Not published
• Step-up transformer: Thorens states the revised generator “reduces the demands on high-gain step-up transformers.” That says a transformer’s job is easier, not that one is unnecessary. At 0.5mV from 2Ω this is a low-output moving coil and expects a step-up transformer or a very quiet high-gain MC stage. Thorens nowhere states that a transformer can be dispensed with
• Frequency response: 20Hz–20,000Hz, ±2dB
• Channel separation: Greater than 23dB at 1kHz; greater than 15dB at 15kHz
• Channel balance: Less than 1.5dB at 1kHz
• Stylus: Nude elliptical, tip radii 8/18µm
• Cantilever material: Not published
• Coil former, coil wire and magnet material: Not published
• Compliance: 8µm/mN dynamic lateral. Thorens does not publish the measurement frequency
• Recommended tracking force: 3.0g
• Permissible tracking force range: 2.5–3.5g
• Tracking ability: Greater than 70µm at 315Hz
• Weight: 30g
• Stylus replacement: Not published. SPU-bodied cartridges are traditionally rebuilt at the factory rather than re-tipped by the user, but Thorens does not state a policy and publishes no exchange programme or expected stylus life
• Country of manufacture: Not published. Thorens prints no country-of-manufacture statement for this product — only the company address in Bergisch Gladbach, Germany, which is a registered office and not a factory.