EMT JSD
 
Old TSD

EMT pick-up's

The history of EMT cartridges is nearly as old as the EMT turntables. And it is still going on. Develloped for broadcast and recording studios the EMT cartridges had been more an insider tip for music lovers and have been used "naked" outside their shells. In the course of time EMT decided to offer the pick-up's in an SME compatible shell (XSD15) and later on launched a typical 1/2" pick-up with the HSD6.

After the Barco era, when EMT worked on its own again as "EMT-Studiotechnik" the range of products on offer was enlarged by two high grade cartridges for home use: JSD5 and JSD6. Each of which is also available in a "gold" version.

In the meantime the offer to play modern records was widened by special versions of the TSD15 and XSD15 which are compatible to the well known SPU cartridges in weight and level: They are called LZ version.

For older records as a standard EMT cartridges with 25µ and 65µ diameter are available in a pure mono version as OF-type (with sapphire as well as with diamond) and T-type (being compatible with the TSD15 in level, weight and tracking force).

Please find here the technical data and hints for using.

 

A little bit of historie:

The early pick-up's were bought from Ortofon, until they were superseded by own developments. First of all the O-series. Working with a high tracking force they were made only for mono reproduction. It's the typical mono reproduction, which only takes the horizontal movement.

The descriptions of the two versions OFS and OFD already point out the stylus type: S = Sapphire and D = Diamond. The figure behind that (e.g.: OFS 25) tells the stylus diameter. Available as standard are OFS as well as OFD with 25µ and 65µ stylus diameter. On request there are also available other stylus diameters as 80µ, 90µ, 100µ and 120µ.

With the beginning of the stereo sound a huge development lead to the conception of the studio cartridges TSD15: A Moving-Coil-System, the transducer of which moves in a permanent magnetic field. Mainly the pick-up consists of a mounting part, the magnet, the polarity shoes, the polarity cylinder and the transducer with the coils and the damping.

As with the O-systems, TSD15 is also just plugged onto the tone arm and locked with a bayonet connection. The connection with the locking pin on the bottom side and the contacts, which look like a rectangle on it's tip, was specially made for the professional EMT tone arm. To be used with tone arms with SME connection the special version XSD15 followed later.

When using EMT arms (on EMT turntables or modified foreign drives) it is not possible nor is it necessary to adjust the overhang. Also the weights of the single units are calibrated so exactly, that the pick-up's are interchangeable without recalibrating the tracking force. The cause was the usage by the pro's, who needed a fast replacement with different stylus diamaters, but is still offered today.

The 15 in the description shows the stylus diameter of the initially used spherical diamond in µm. To meet the requirements of other stylus diameters, as standard are available also TMD25 and TND65 with diamonds of 25µ und 65µ diameter. Other diameters (80µ, 90µ, 120µ) are available on request. Although some versions like SuperFineLine, GygerS and van den Hul have smaller diameters, the name is still TSD15.

New shell
Since 1970 the TSD15 is not longer delivered in the initial bakelite shell, but in a light metal housing. In the meantime also the O-systems are delivered in that shell. But the old shells are highly desired by collectors.

With the new shell TSD15 becomes more user friendly. The mounting part is on the outside constructed like a large white reflector. If illuminated (most of the EMT turntables own a cartridge illumination), it reflects the light to the records surface, thus making it easy to find a certain groove with the built-in magnifying glass. An additional help is the small handle.

Diamond types
With growing quality of the reproduction units and the records too, the demand for smaller diameters growed too. Very often in this case there is used a comparism with the style of the cutting diamond.

Some people like to have the needle in the shape of the cutting diamond, but they oversee, that cutting and reproduction are different tasks. The shape of the cutting stylus derives from the tool technic. For the exact shape also the material to be cutted plays a role. So the cutting stylus' for lacquer foil and metal foils are different in their angles. In each case the cutting forces should be as small as possible.

For the reproduction diamond e.g. the demand for low loss of amplitude when reproducing high frequencies and for less worn-out grooves has to be fullfilled.

A reproduction stylus will normally rest on both sides of the groove and distorts the grooves walls elastically depending on shape and pressure. To make calculations easier, one assumes, a diamond with a conically shape and a spherical tip diameter produces impressions with an area of a circle. With an elastical distortion limit of the records material of 40kp/mm² one can give a relation between the stylus diameter and the allowed tracking force. For the tracking force of 25mN, which is used in studios due to reliability, a smallest diameter of 15µm is the result. Thus, the diameter lays in a range of the wave length (approx. 14µm) which results of a frequenzy in the inner grooves of a record.

Without describing here the way of calculation, it can be shown, that the diameter in every case should be max. 3.6µm. That would demand tracking forces smaller than 3.5mN, which also cannot be realized in the HiFi-Area.

Among others one solution was the elliptical shape. Seen from the groove's square diameter, it has nearly the same dimensions as a spherical diamond and is carried by the groove's sides. Caused by the reduction of the diameter in the moving direction the result is a diameter for the sides in the desired order of magnitude. Nevertheless this does not change the too large pressure per area. This is only possible by reducing the tracking force.

During the time of quadrophonia records with 38kHz subcarrier, the "Shibata" shape was developped. This changed the touched area from an area of a circle to a more longish area. The principle of that shape was also overtaken for the conventional stereo record, optimised and used in different pick-up's.

By reasons, which result of the professional usage of the TSD15 (reliability with high tracking force; compatibility with records, cutted with vertical pre-emphasis), the initiation of another shape by EMT lasts a bit longer. The finally found solution meets the demands for low distortions also of high frequencies with a high level in the inner grooves, low signs of wear caused by low pressure and low distortions also for records cutted with pre-emphasis.

The only change in the outer appearance, when the new diamond was introduced in 1985, was the gold coloured lable, which points out the "Super-Fineline-Diamond". On request a spherical diamond can be put in at any time.

Manufacturing
The parts used to manufacture the pick-up's are mainly selfmade or finished off for the special demands.

Due to the small dimensions, most of the work is done with the help of a microscope. In no production stage machines are used and the coil of the transducer is wrapped by hand winding after winding on the plate of 2x2mm. Precision is only natural. Only 1° deviation of the rectangular direction of the stereo winding degrades the crosstalk damping about 5dB.

After assembling of the parts, the system becomes magnetised and is checked carefully a first time. The following storage of appox. 10 days leads to a good long term constancy. At the final check each unit becomes individually aligned and fullfills the guaranteed technical data.

Technical data
Due to historical evolution, the small limited frequency response (+/-2dB) is given only up to 12,5 kHz. The really frequency response, which leads high upon the aural limits is enclosed with every pick-up as a paper document. This also showing the crosstalk damping, which is normally much higher than the guaranteed 25 dB.

The output voltage depends on the peak velocity while cutting the record and thus is not figured out here. It can be easily calculated with the given transducing factor of 0,21mV*s cm-1 and is normally said to be about 1mV.

Now there's only left to give the value of the frequency intermodulation (FIM), which is less than 0.5%. The impedance is approx. 2 x 24Ohms. As terminating resistance 200 Ohms are told.

During manufacturing all guaranteed data are kept exactly.

Of course, I can deliver all EMT cartridges.

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