CS Port Analog Disk Player LFT1

Ultra heavy-duty designed that suppresses unnecessary vibration
Turn Table Unit

Thought of vibration isolation

Analog disc is a recording of sound vibration directly on a disk in micron unit.Therefore, it is strictly prohibited to add vibrations other than those recorded in the sound groove.There are two ways to suppress transmission of unnecessary vibration. It is shielding and damping.
High frequency vibration can be damped by vibration isolating materials, but low frequency vibration can not be shielded or attenuated with vibration isolating material alone.Therefore, it suppresses vibration by adding weight as a so-called thick walled concrete wall which has both functions together.

Stable heavy granite base

On the base of the turntable, we use 40 kg of granite (granite) stabilized over 5 million years. Unnecessary vibration transmitted from the floor surface is suppressed by this weight and vibration damping characteristics of granite. Granite is used as a reference for making a mother machine (machine tool) as a stone surface plate, it is processed to the highest grade JIS 0 grade flatness of 5 microns, and a distance of several tens of microns on top of it While keeping the floating platters are spinning.

Air floated ultra heavyweight platter

In order to obtain stable rotation, a platter with a large moment of inertia is required, but in the case of a mechanical bearing, a large force is applied to one point and wear progresses, unnecessary vibration is generated and a signal of sound I will miss it.
In LFT 1, a platter with a high inertia moment of 344 mm in diameter and 27 kg in weight made of stainless steel of super bowed bow is rotated. The weight of the platter is handled by the pressure of the air, and only the force of about several hundred grams applied in the lateral direction is handled by the metal bearing, thereby realizing a structure that does not cause unnecessary vibration and long-term reliability.
If you support the platter with one point and hit it, you will hear a metal sound, but if you float it with air it will be a jerky sound. By damping with the air film, integration with the base becomes possible, and unnecessary vibration can not be pulled.

Heavy weight stabilizer for adhesion of analog disk and platter

Place where the platter and the analog disc are in contact are tapered and pressed with a heavyweight stabilizer to get close contact between the record board and the platter, suppressing unnecessary vibration when the needle point traces.

Precise rotation performance to minimize extremely fluctuation
Motor Drive Unit MDU1

Thought of platter drive of LFT1

In order to pick up sound accurately from the analog disc, the rotation of the platter must be rotated at a constant speed without any “fluctuation”. In general, accurate rotation is obtained by servo control by negative feedback, but at the micro level, if it rotates or becomes faster, it detects it and slows it, and repeats the operation to make it faster if it gets slower.

Although this level and cycle are determined by the gain of the control system and the loop speed, the period of the speed control of the platter which is the mechanical system surely comes into the audio band. In general, accurate rotation is obtained by servo control by negative feedback, but at the micro level, if it rotates or becomes faster, it detects it and slows it, and repeats the operation to make it faster if it gets slower. If you try to measure a period with a small level, you can not measure the instantaneous state, so you should measure the average value.Therefore, fine vibration generated by servo control can not be measured by the measuring instrument, it depends on the human ear.

LFT1 hates this vibration and lacks convenience, but in addition to selecting an open loop control that does not apply servo control, it also shuts out noise generated from itself and noise from the outside.

Synchronous motor

In the direct drive as well as the motor speed control it can not escape the vibration caused by the servo control. Although there is no servo control amplifier in the synchronous motor, unnecessary vibration is small, but the permanent magnet of the rotor constantly controls the deviation from the rotating magnetic field, and due to processing precision of the rotor, variation in magnetization, variation in windings Vibrations are occurring.

Non-feedback motor control

In LFT 1, the rotation control is not performed, and the constant speed rotation is left to the high moment of inertia of the 27 kg platter, creating a rotation free from unnecessary vibration caused by the control. Only the positive direction force is applied from the motor, but by using a coreless motor with less moment of inertia, the influence of the vibration is reduced. Motor rotation control with no negative feedback · The XFD method realizes a drive with the minimum fluctuation.

*XFD method:Based on a crystal oscillator with high frequency precision, a direct digital voltage generator is formed to supply a voltage with high precision without fluctuation. It is a system that “CSS port” developed independently by CS Port which drives super-heavy platter with light load bearing with low inertia coreless DC motor.

Adoption of thread drive

There are various methods such as gear drive, rim drive, belt drive, etc. to transmit the power of the motor to the platter, but LFT 1 adopted Kevlar’s yarn drive with four knitting yarns stronger than iron. On the other hand, because it is hard to convey the vibration of the motor and the elongation is small, it plays the platter firmly.

Setting and checking rotational speed by strobe

A strobe set to 33 1/3 and 45 revolutions with a crystal transmitter as a reference places marks engraved with high precision with a laser on one side of the platters.
Adjust the rotation speed with the + and – speed setting buttons, and the rotation accuracy can be judged by the strobe mark.

Stable arm unit supports fine needle tip

LFT1 sound pickup philosophy

In the LP record, sound grooves of 120 micron width are engraved at intervals of 600 or more from the outer circumference to the inner circumference, and the needle traces submicron music signals.

Characteristics required for the arm are not fine movement when the cartridge traces the signal, movement lightly to the adjacent sound groove moves lightly, does not receive unnecessary vibration from the surroundings, vibration generated by the needle is generated only in the generating coil It is to tell. In the production process of analog discs, since the movement of the cutting race becomes a straight line, linear movement is also required for the head. In LFT1, linear tracking was realized by air floating, the fine movement at the time of signal tracing was suppressed by the weight of the arm, and the movement to the adjacent groove slowly moved lightly.

Vibration generated at the tip of the needle is transmitted through the arm and damped by the air layer of the slider part, so it will not be reflected back to the tip of the needle.

Linear tracking arm

Record grooves are not engraved at regular intervals, and where the signal is small, the interval is small, whereas where the signal is large the interval is large, earning the time to be able to reproduce.

In the past, several linear tracking arms that detected the angle of the needle tip and served a serial control were suggested, but since there was a disadvantage of the servo control described above, it disappeared from the market. In LFT 1, the arm can be moved with a force of 0.5 g or less by its own air floating structure, and the irregular record groove is stably traced from the outer periphery to the inner periphery. Also, heavyweight arm units are not swayed by music signals, they trace without missing the fine movements of the needlepoints.

Unnecessary vibration generated at the needle tip

Mechanical vibration traced by the needle point is converted into electric signal by the generating coil, but this mechanical vibration passes through the stylus, cartridge body, shell and arm, it is reflected at the mechanical contact point and returns to the tip of the needle , It adds extra things to the playback signal. LFTl dumps the vibration from the tip of the needle at the air floating part of the slider, as well as the damping effect of unnecessary vibration from the outside, it becomes a performance like a silent forest.

Air Pulse pump flow highly trusted in medical field Pump Unit POU1

Pump Unit

The LFT1 comes with an air pump unit for floating the platters and arms. The air pump is driven by 12 VDC supplied from the motor drive unit, and by adopting a motor type pump used in medical equipment etc., it gave stable operation for a long time.

Because the compressed air coming out of the pump is a pulsating flow, it can be supplied as compressed air with no ripple and vibration by Π type filter.

Furthermore, it adopts a sound leakage prevention system with a double sealed structure, and maintains quietness enough even if it installs in the listening room.