YAMAHA P-850

Commentary

A record player announced as a refined version of the P-650.

Equipped with 2-size, pure electronic full auto function, when playing a record, place the record on the turntable, select the size with the Disc Size button, and press the Play button to auto-lead-in to the beginning of the first song just by pressing the Play button.
The P-850 is operated by a photosensor consisting of three photointerrupters fixed to the cabinet and a logic shutter fixed to the tone arm. The built-in microcomputer processes the 3-bit signal from the photointerrupter regardless of the position of the tone arm, and smoothly controls the tone arm to the specified position. The photosensor also detects the rest position and return zone of the arm.
All detection operations of this full-auto function are optical, so it is non-contact and does not adversely affect sound quality.

Micro computer enables up / down, Oatley turn, Oatley peat, and auto-cut operation.
If you want to stop playing in the middle of a song, press the cut button. The motor for the arm lifter is turned on by a signal from the microcomputer and the arm is raised. When it is finished, the horizontal control starts and the tone arm returns to the rest position.
Auto Return uses a speed detection type that takes advantage of the wide pitch of the lead-out groove of the record. The speed signal generated by the speed detection coil built into the tone arm drive motor is always sent to the microcomputer. However, when the speed of the arm increases in the return zone, it is detected and the return operation is automatically started.
The repeat operation repeats the operation of auto lead in again after the Oatley turn.

Equipped with a muting circuit.

The P-850 is capable of manual operation in addition to full-auto operation, which is controlled by a microcomputer.
The horizontal access is 2-speed access in the same way as the PX-2. Depending on the stroke of the button with center click, you can use either fast access or slow access.
In addition, when the arm is moved up and down, a microcomputer controls the system at the time of full automatic operation with a signal from an external button.

The tone arm uses an ARS (Anti Resonance Straight) arm developed by Yamaha to reduce any resonance of the arm itself.
The ARS arm has a symmetrical structure with a straight pipe so that torsional vibration hardly occurs. In addition, a large rectangular balance weight placed as close as possible to the fulcrum, a span between pivots that is more than twice the normal size, and a rubber damper for the angular contact bearing of the bearing are used to improve sensitivity and eliminate resonance due to backlash. In addition, the pipe holder is large and robust, and a double structure 30 mm from the fulcrum is used to deal with flexural vibration at the front and back of the pipe.
The low-pass resonance frequency of the arm was determined to be 12 Hz from the result of measuring the reproduction spectrum of the direct cut record, and the effective mass of the arm was determined by calculating the average mass and compliance of 30 typical MM/MC type cartridge models.

The P-850 uses a coreless direct drive motor in the drive system of the tone arm.
Structurally, two coreless rotor coils are symmetrically fixed at the bottom of the straight-tone arm and work together with the tone arm, and a two pole-magnetized stator magnet is fixed to the cabinet slightly away from this coil. One of the two coils is for the arm drive. The tone arm is controlled by controlling the magnitude and direction of the current flowing in the coil using the rotational force of the coil based on the Fleming left hand rule when current is applied to the coil.
The other coil is used to detect the speed of the tone arm. When the arm rotates, the flux density across the coil changes so that a voltage proportional to the speed is generated in the coil. This speed signal is fed back to the servo circuit to control the rotational speed of the arm.
This makes it possible to keep the lead-in error within an extremely narrow range, and the movement of the arm is also smooth. It is a non-contact drive system, and since there are no gears or pulleys in the driving force transmission part, there is no mechanical noise and maintenance free.

Equipped with fail-safe function by microcomputer.
When the arms sent left and right are stopped by external force, it automatically stops after 0.5 seconds to prevent damage to the mechanism.
When two or more buttons are pressed, the microcomputer gives priority to safer operation. The priority is Cut <Left/Right <Up/Down <Play.

When the power is ON, 33rpm/30cm is set automatically. When the power is 45rpm/17cm, the size can be set by simply switching the speed to 45 rpm.
In exceptional cases such as 33rpm/17cm or 45rpm/30cm, you can respond by pressing the size button after setting the speed.

The head shell part uses an insertion type that is highly reliable and easy to replace the cartridge. In addition, the needle pressure adjustment is a sliding weight type.

A DC4-phase 8-pole coreless Hall motor is used as the drive motor.
This motor has no cogging in principle, and is a non-contact type using a Hall element, so mechanical and electrical noise is minimized.

The servo circuit uses a quartz PLL servo that controls with the accuracy of the crystal.
In this circuit, the rotation speed of the turntable is detected by an all-around integration type FG (frequency generator), and highly accurate rotation is obtained by comparing the phase with the signal from the crystal oscillator.

The cabinet is made of BMC material and uses a 3-mm-thick acrylic resin dust cover and a special rubber W-shaped fold-back insulator to improve the howling margin.

Model Rating

Type	Record player
Signal-to-noise ratio	77 dB (DIN-B, IEC 98A weighted)
Wow flutter	0.015% (FG Direct) 0.025% (test record method)
Arm Total Length	290mm
Effective arm length	222mm
Effective mass	Needle Pressure Proportional Type (Needle Pressure 1.5g : 11g)
Arm lifter	Operation by dedicated motor
Muting	Arm lifter interlock
Anti-skating	Rotary Operated Spring Lever Type
Compatible Cartridge	2.5g ~ 10g
Head shell	Attachment
PU cable	Capacity : 100 pf Reciprocating resistance : 1 Ω
Full automatic control	Microcomputer control (manual operation possible)
Horizontal drive of the arm	Microcomputer-controlled DC coreless motor DD
Rotating system	DC4-phase 8-pole coreless Hall motor DD
Servo system	Quartz rock
Number of revolutions	33 1/3rpm, 45 rpm, with LED lock indicator
Turntable	30 cm Aluminum Die Cast, 1.6 kg (Including Rubber Sheet)
Cabinet	BMC(Bulk Molding Compound)
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	10W
External dimensions	Width 440x Height 132x Depth 376 mm
Weight	7.5kg