The SPU Mono CG 25 Di MkII is for the playback of early 25 µm mono recordings.
The Mono CG 25 Di MkII is an SPU-style Moving Coil cartridge with a spherical stylus profile, for the playback of early 25 µm mono recordings. The CG 25 Di MkII provides an authentic method of playing back these early vinyl recordings with a remarkable level of sonic accuracy.
This cartridge features a 1.5mV output, which makes it suitable for use with a variety of medium-gain moving coil transformers. Ortofon ST-M25 moving coil transformer is designed exclusively for the SPU Mono CG 25 Di MkII.
Available on backorder
Output voltage at 1000 Hz, 5cm/sec. – 1.5 mV
Frequency response – 20-15.000 Hz + 3/- 1 dB
Tracking ability at 315Hz at recommended tracking force *) > 60 µm
Compliance, dynamic, lateral – 7 µm/mN
Stylus type – Spherical
Stylus tip radius – R 25 µm
Tracking force range – 3.0-4.0 g (30-40 mN)
Tracking force, recommended – 3.5 g (35 mN)
Tracking angle – 20°
Internal impedance, DC resistance – 6 ohm
Recommended load impedance > 100 ohm
*) Typical value
Cartridge body material – Ground wood and resin composite
Coilwire material – High Purity Copper (OFC)
Cartridge colour – Black matte
Cartridge weight – 35 g
No other company has ever retained a phono cartridge model in their product range for so many years. The SPU was used by early broadcasting companies among whom the Ortofon brand name was already well known from the first moving coil system – the Ortofon mono system in the small black A-housing. The so-called “Ortofon sound“ became synonymous with the sound from the SPU, at an early stage.
The sound of the SPU cartridge is characterized by a rich bass and a transparent treble range plus those extra qualities which are so hard to define, but so easy to appreciate when they are realized.
Back in 1958 the Ortofon SPU sounded like no other cartridge because it was way ahead of its competition. Today the SPU still has a sound that is definitely its own and it enjoys a remarkable following – in particular among audiophiles whose systems are comprised of vintage valve equipment and horn or reflex speakers.
But with no other cartridge over the course of half a century, have we ever had to take so much care in respecting this original sound when improving technical data, as with the SPU model. As a result and in order to show considerations for this goal, you will after 60 years still find the basic visuals, the original design, as well as the original elements in the construction of the magnetic circuit kept fully intact.
Evidently the product has changed throughout its evolution. New possibilities in regards to housing materials, diamonds and magnetic system have been employed to improve the SPU and its performance whilst at the same time we remain faithful to the original concept. It is also clear that in a period of 60 years certain components will be changed as the suppliers no longer make them and replacements must be found.
But let us for a moment return to where it all began, when the SPU was launched back in 1958.
The term “SPU” stands for “stereo pick-up” as phono cartridges were called “pick-ups” in the 1950s and 1960s. The original SPU was introduced in response to the demand for cartridges to reproduce the new stereo records. Based on Ortofon’s already 10 year old technology and experience in mono cartridges, the SPU immediately set the standard for professional and audiophile applications.
Mr. Gudmandsen, one of Ortofon’s then leading engineers took a principal part in developing this cartridge. 10 years before, Mr. Gudmandsen had been deeply involved in the basic Ortofon Mono MC system. At that time Mr. Gudmandsen of course did not have the elaborate facilities that now make up the company’s development. Nevertheless his flair for a musical sound reproduction and the touch of a genius enabled him to create THE CARTRIDGE to survive all others.
Parallel to this development, Ortofon developed a stereo cutter head for mastering records, and the Ortofon expertise and development activities in making transducers for analogue reproduction equipment made new standards for the area in those days. It is also important to remember that Ortofon during and after the second world war had specialized in making silver spraying of lacquer discs and equipment for high speed nickel electroplating of matrices for gramophone record production.
A very important element based on technologies from said nickel painting process was right from the beginning incorporated into the SPU as a very fundamental part, responsible for the suspension of the oscillating system. This element consisting of cantilever and armature has never been surpassed by any cartridge manufacturer, and we are convinced, that the aforementioned “Ortofon Sound“ to a great extent was influenced by this element. Because of the very low impedance and the very low output, the first SPU cartridge, the SPU-GT, had a small transformer integrated with the cartridge units in the GM- housing, yielding about 7mVolt at 5cm/sec suitable for an MM input sockets with 50kOhm loading.
The SPU cartridge unit was also available without transformer in the original A-housing from the mono-systems. For the two different A and G housings Ortofon developed a program of tonearms among which the RMA/RMG 212 and 309 became very well known.
For more than 20 years the SPU cartridge models were kept unchanged.
In 1980 however, a luxury model for connoisseur, the SPU Gold, was introduced in a mahogany box with a 24 carat gold plated name plate inside the box. The cartridge was featured a gold plated finger lift and Ortofon logo. Silver windings were used on the armature as well as for the terminal leads. The system was awarded in Japan with “the component of the year prize” for best foreign product. But still, nothing that could change the performance and “Sound” from the basic image was made.
In 1989 the SPU Gold Reference was introduced, and the first step of improving the “sound” by utilizing the modern Ortofon developed Replicant stylus was taken. This stylus shape, very close in cross section and radii to the cutting sapphire, reproduced the modulations in the groove with an unheard amount of details in the sound.
In 1992 Ortofon wanted to celebrate Mr. Gudmandsen, because of his 50 years of work for the Ortofon. At that time he had already got the nickname Mr. SPU in Japan, because of his basic and innovative work on the mono moving coil and later stereo cartridges.
Mr. Gudmandsen was also personally awarded by the Danish Queen Margrethe II, and Ortofon decided in honor of Mr. Gudmandsen to launch the SPU Meister cartridge with Mr. Robert Gudmandsen signature printed in both A and G-models.
The new features for the SPU Meister cartridge, again fully respecting the original concept, involved a wooden box of noble tree – a dedication from Mr. Gudmandsen to the owner of the cartridge. An important new technical data was a raise in output of about 75%, by introducing the Neodymium magnetic circuit. Further the very pure 7-Nines copper was now used for the armature windings.
When the SPU Royal N, SPU A and GM models were released in 1998 it was also done not to forget the basic Ortofon product in 40 years among the great number of other successful MC models – all being highly indebted to the original ideas in the SPU cartridge.
The SPU Royal N cartridge with its half inch adaptor has provided a new flexibility and ability for the customers in mounting the unit in headshells, as well as in a wider range of tonearms.
A key SPU feature is an integrated headshell, designed to mount directly into classic tonearms with detachable headshells – tonearms such as the SME 3009 and 3012, and other tonearms with similar “universal” tonearm mounts. Quite simply, there is no finer complement to a classic tonearm with a detachable headshell than an Ortofon SPU.
The faithfulness against the sound from the ancestors is still there, whether it is using a new silver/gold alloy for the armature, using the Replicant stylus, or using Selective Laser Melting manufacturing technique.
The SPU 85, from 2003, was a limited production of 500 units.
SPU 85’s unique characteristics included an outstanding housing made of Japanese Hida Beech wood, famous for its strength and hardness. For the exclusive surface treatment, the 6000 years old Japanese Urushi lacquer method was chosen in order to achieve a hard, resistant and beautiful multilayer surface in dark maroon colour.
In order to influence sound from the motor system, a new wire concept for the armature windings called “AUCURUM” was developed. The basic material here is a specially developed composite consisting of a very pure copper and gold, creating extraordinarily high conductivity and environmental resistivity.
The SPU 90th Anniversary, from 2008 was limited to 500 units.
What makes the SPU 90th Anniversary unique is the combination of following four elements:
– a completely new patent-pending magnetic system
– the inclusion of the renowned Field Stabilizing Element (FSE) system
– the direct connection between the generator system and the wooden housing (ensuring extremely high internal damping)
– and finally the use of the revolutionary Selective Laser Melting (SLM) manufacturing technique.
SPU 90th Anniversary provides reproduction of sound that is unsurpassed in its neutrality, detail and dynamic range.
In 2011 we decided to give our SPU fans around the world an opportunity to get a collection of the four most famous SPUs: SPU Classic, SPU Gold Reference, SPU 85 and SPU A90 – each of them being a very special collector’s item.
These four most famous SPU cartridges represented the diversity of technical solutions and materials, and reflect the continuous technological development thoughout the past 50 years. These 4 cartridges were made exactly as the original models, and are as genuine as the original production units. All materials and techniques have been preserved during the manufacturing process.
The SPU 95th Anniversary from 2014 has gone to the next level by reducing unwanted vibrations in the cartridge. Our extensive knowledge of vibration properties, characteristics in different shapes and materials, competences in magnetism, mechanical design and new technologies has been applied for optimization of the SPU A95.
Being the inventor of the world famous SPU stereo cartridge in 1958, most music lovers, even today, find that there is no name like Ortofon which is more involved in the history of analogue reproduction. The fact that Ortofon has kept the SPU in production for half a century says a lot about the enduring rightness of its design.
Perfect all-rounders for the newcomers to the world of SPU, the SPU #1 E and S were introduced in 2016. The SPU #1 S and SPU #1 E feature respectively Spherical and Elliptical stylus, High Purity Copper armature windings and terminal leads and a housing of grinded wood and resin composite.
With their linearity and full bodies, the SPU #1 models are a perfect solution for the playback of stereo recordings.
Sonically, the SPU #1 models are genuine SPUs, known for their full-bodied and powerful music image, minimum of intermodulation distortion and an impressive channel separation.
A perfect combination of Japanese and Danish craftsmanship and technique, the new SPU Wood A is beautiful in finish and form, as well as in its sonic expression.
The SPU Wood A unique characteristics includes an outstanding housing made of Japanese Beech wood, famous for its strength and hardness. For the exclusive surface treatment, the 6000 years old Japanese Urushi lacquer method was chosen in order to achieve a hard, resistant and beautiful multilayer surface in dark maroon colour.
The wooden housing has a strong influence resulting in a very pleasant, open, dynamic, straightforward and present tone range characteristic for the SPU sound.
The SPU Century is built with the magnetic system based on the concept developed by Robert Gudmandsen to embody the essence of the original design as well as the original elements in the construction of the magnetic circuit.
The SPU Century retains many of the characteristics that put its brethren in a class of their own, while at the same time expounding upon its strengths to provide reproduction of sound that is unsurpassed in its full-bodied, detailed and powerful music range.
• The bottom cover is CNC-milled of stabilized Beechwood by Ortofon.
• The dividing line between the top and the bottom cover is elegantly shaped as a violin-, cello-, bass- or guitar’s curved body – a unique expression of the universal music motif.
• The new absolutely crucial feature is the use of a Nude Shibata diamond, considered one of the best stylus profiles available, mounted on an Aluminum cantilever.