Nakamichi 660ZX

Commentary

Cassette deck without after-monitor function from 670 zx.

Equipped with an automatic azimuth alignment function that automates the adjustment of the azimuth.
This allows adjustment only by setting the tape to be recorded and turning the calibration switch ON. Adjustment is completed when the indicator of the play button stops blinking.
In actual operation, when the calibration switch is turned ON, the built-in 400Hz0dB test signal is turned ON and recorded. Then, the 400 Hz sine wave signal reproduced immediately is converted into a square wave signal, and the advance (delay) between the left and right channels is detected by a phase discrimination circuit. This phase shift causes a switching circuit to control the output of the operational amplifier. The output of the operational amplifier = the plus or minus voltage applied to the motor terminal changes depending on whether the right channel is advanced or delayed relative to the left channel, and the direction of motor rotation changes. This causes the lever connected to the reduction gear to move and adjust the tilt angle of the recording head.

On the 670 zx, calibration is performed by displaying the playback level on the peak meter.

The mechanism uses a frequency distributed double capstan system.
In this method, the double capstan method, in which the tape is held firmly by two pinch rollers and a capstan, reduces modulation noise and various disturbances. In addition, focusing on the flutter components caused by the correlation between the capstan and the tape, by changing the diameters of the two capstan, overlap of the flutter peaks is avoided and the characteristics are improved.

In the single-capstan type, the contact between the tape and the head is secured by the crimping force of the head pad mounted in the cassette tape. In the double-capstan type, however, the head pad is not necessary because a constant tape tension is always applied between the two capstan. Therefore, a pad lifter is mounted to suppress the characteristic change by eliminating the head pad.

The chassis uses a resonance damping type chassis. Aluminum alloy with large vibration damping characteristics is used, and resin molded parts are combined to absorb microvibration and suppress resonance.

The mechanism is controlled by C-MOS logic control. The control cam linked to the motor drives mechanisms such as the head base and pinch roller, and simultaneously operates the muting circuit. Unlike the method using the plunger, it can operate quietly and smoothly with less mechanical noise.
In addition, the six control buttons of this mechanism drive system allow for operations other than the normal tape control. When the Pause button is pressed from the FF / Dew state, it is used for queuing, when it is pressed again, it is used for RAMM (Automatic Tracking), and when the Rec button is pressed during recording, it is used for Rec mute as long as it is pressed. These operations can also be performed with an optional remote control unit.

The head section uses a discrete three head system in which the recording head, reproducing head, and erasing head are completely independent.

A P-8L type head is used for the playback head.
This head is a 0.6 micron narrow gap reproducing head made of crystal and enables flat reproduction up to ultra-high frequencies. Moreover, by adopting a unique head shape and structure, it eliminates low-frequency waviness called contour effect, and realizes ultra-low frequency reproduction of 10 Hz.
In addition, it has excellent wear resistance, and there is no degradation of characteristics even after 10,000 hours of use.

The R-8L type recording head is used.
This is a 3.5 micron gap head using a crystal, and the core does not saturate even when metal tape, which requires a large bias current, generates a sharp critical zone and enables recording with less distortion.

E-8L type head is used for the erasing head.
It is a direct flux double-gap type and overcomes the signal erasure effect due to poor low-frequency erasure capability during recording and spontaneous magnetization during playback from the material and structure aspects.

In the recording amplifier section, the coupling capacitor connected to the recording head is eliminated to make it directly connected and DC. This reduces distortion during recording and prevents low-frequency phase distortion.

It employs a double NF circuit that applies a negative feedback to the capacitors of the recording and playback equalizers. This reduces the distortion generated by the capacitors, while maintaining high DC stability.

By improving the linearity and setting the clipping level higher, it is possible to record accurately from very small input to very large input.

Equipped with a pointer type level indicator.
This level meter displays the peak level in a wide range from the noise level of -40dB to the saturation level of + 7 dB.

It is equipped with RAMM (Random Access Music Memory) as an automatic cue function.
You can fast-forward or rewind up to a maximum of, up to a maximum of nine tracks, and start tracking or playback. If you count too many tracks due to misreading, press the Rec button to count down.

It is equipped with a manual queuing function. If you press the Pause / Queue button during FF/Rew, the speed will be reduced to about 1/3 and you can listen to the recorded sound. If you then press the FF/Rew button continuously, the speed will be reduced to about 1/5.

It is equipped with a one touch Rec-Mute function. If you press the Record button during recording, the input signal will be cut during that time and the recording will be silent.

Equipped with a Dolby level calibration function, the built-in 400Hz0dB test tone and 3-head configuration allow for one action.

Equipped with timer recording and playback mechanism, it is possible to record absence and play alarm clock by combining with audio timer.

It comes with a rack-mount adapter, 19-inch panel width, 2 1/4-inch mounting screw pitch, EIA-standard rack-size and removable.

Equipped with a 3-position tape selector, it supports EX (normal type), SX (chrome type) and ZX (metal tape). The 120 μ s/70 μ s equalizer can be switched independently.

Equipped with a Dolby NR system as a noise reduction system.

Equipped with a high-output headphone port.

Equipped with a pitch control function, playback speed can be changed by approximately ± 6%.

Equipped with high-speed shut-off function.

Equipped with a tape start memory function.

Equipped with MPX filter.

Equipped with a dedicated power terminal for the Black Box Series (up to 125 ma), peripheral devices for tape decks, amplifiers, and Black Box Series can be used without a dedicated power supply.

Compatible with optional Remote Control Unit RM-200.

Model Rating

Type	Cassette deck
Truck type	4-track, 2-channel stereo system
Tape speed	1-7/8ips(4.8cm/s)
Wow flutter	0.04% or less Wrms 0.08% or less Wpeak
Frequency characteristic	10 Hz ~ 22 kHz ± 3 dB (ZX Tape) 10 Hz ~ 20 kHz ± 3 db (SX, EXII tape)
Overall S/N ratio (400 hz, ZX tape)	60 dB or greater (0 dB, WTD rms) 66 dB or more (3% THD, WTDrms, Dolby NRin, 70 μ s)
Total Distortion Factor (400 Hz, 0 dB)	0.8% or Less (ZX Tape) 1.0% or less (SX/EXII tape)
Erasure rate	60 dB or More (Saturation Level, 1 kHz, ZX Tape)
Channel separation	37 dB or More (1 kHz, 0 dB)
Crosstalk	60 dB or More (1 kHz, 0 dB)
Bias frequency	105kHz
Input	50mV/50k Ω
Output (400 Hz, 0 dB, maximum output level)	Line : 1V/2.2k Ω Headphone : 45mW/8 ohm
DC Output	± 10 V, 125 mW maximum (black box series only)
Pwer	100 V, 50/60Hz
Power consumption	27W max.
External dimensions	Width 482x Height 143x Depth 340 mm
Weight	Approximately 9 kg
Sold Separately	Remote Control Unit RM-200 (¥ 6,000)