Fidelity-Research FR-7f

Commentary

Shell-integrated MC cartridge, an improved version of FR-7.

It uses a unique push-pull power generation system with a magnetic circuit consisting of two magnets and four poles.
In this system, power is generated at four locations, so that a sufficiently large output voltage can be obtained even with a low-impedance coil. In addition, while the general system generates a cancellation current in the power generation circuit, the FR-7f magnetic circuit can be obtained as a positive output even in the conventional cancellation current generation region. This improves the phase and crosstalk characteristics, greatly increases the electrical conversion efficiency, and improves the output power.

Samarium-cobalt magnets are used as magnetic circuit materials. These magnets have superior characteristics such as high coercive force and resistance to self-demagnetization compared with ordinary alnico magnets, and retain the initial characteristics of the magnetic circuit over a long period of time.

A fully air-core coil without a winding frame is used for the power generation coil, and unnecessary magnetic materials do not move in the power generation magnetic field, and distortion of the reproduced signal is fundamentally removed. The effective mass of the vibrator can also be reduced to approximately 2/3, and high-frequency mechanical impedance is reduced.

The needle tip uses a unique refined contact needle with special polishing of solid 0.15 mm square solid diamond.
The Refined Contact Needle is a new method that combines the advantages of the line contact needle with the advantages of the elliptical needle. It is less susceptible to adverse effects (noise, etc.) from disc sleds and dust in the sound groove. It also produces very little scratch noise or surface noise, so you can enjoy sound reproduction with good clarity and no fatigue.

Special aluminum alloy cantilever is used for the cantilever.
This is a straight cantilever made of highly corrosion-resistant special aluminum alloy and subjected to an optimum heat-curing treatment (ceramic treatment). It is made to minimize moment of inertia and deflection during high-speed motion.

By adopting a structure in which the head part of the string holder extends to the front of the damper B, the position of the supporting point is made more clear. By this, the position of the cantilever vibration supporting point is made more clear, and the change in the vibration distance of the cantilever at each frequency is minimized.
In addition, the string wire that applies tension to the cantilever is made of a material with a high spring coefficient and little aging, which contributes to the improvement of the square wave characteristics.

It adopts a double damper system, and by adopting a damper structure of two layers with different rubber coefficients, it effectively dumps both middle and low frequencies of vibration, making it possible to make an ideal trace over the entire reproduction frequency.
In addition, the rubber coefficients of damper A and damper B are different, so that the effect of temperature on trace performance, mechanical impedance characteristics, and playback sound is totally reduced.

In order to solve the problem that the coil lead wire vibrates with the cantilever, the coil lead wire is inserted between the damper A and B and press-bonded to eliminate unnecessary power generation caused by the lead wire.

The head shell part is designed to completely eliminate dead space which causes parasitic vibration harmful to sound quality. In addition, the shell part is made of special aluminum alloy. By impact processing (cold forging), rigidity is further increased and generation of split resonance is proposed.

The cartridge body is made of epoxy resin that has been selected through careful audibility testing.

In order to improve the insufficient strength due to the looseness of the arm and connector part, a special stainless steel lock plate is adopted instead of the conventional guide pin. By this, the connection with the arm can be more integrated, and the horizontal level can be maintained correctly.

Model Rating

Type	MC Type Cartridge
Output voltage	0.15 mv (3.54cm/sec., 45 °) 0.2 mV (5cm/sec., 45 °)
Output power	2x10-8W (5cm/sec. 45 °)
Needle pressure	2g ~ 3g
Coil impedance	2 Ω
Load impedance	3 Ω
Playback frequency range	10 Hz to 45 kHz
Channel balance	1dB(1kHz)
Channel separation	-28dB(1kHz)
Compliance	7x10-6Cm / dyne (100 Hz, 20 ° C)
Needle tip	0.15 mm Square Refined Contact Solid Diamond Needle
Dead weight	30g
Exchange needle	Replacement of internal unit (¥ 54,000)