Technics RS-670U
¥ 89,800 (released in 1975)
Commentary
A stereo cassette deck designed to improve and stabilize performance by adopting an easy-to-use horizontal drive.
We have achieved stable performance by adopting a front operation system that can be used with amplifiers and tuners, and a horizontal drive system that installs the cassette horizontally.
A belt drive system is adopted for the mechanism, and 80 mm diameter flywheel (dynamic balance of 1gm-cm or less), thick (3 mm) capstan with high accuracy (roundness of 0.15 μ or less), electronically controlled DC motor, etc. are used for the stable running system.
Although the mechanism of the tape hold is horizontally driven, it is slightly tilted to the front so as not to degrade the performance in consideration of the operability. The mirror structure allows the tape to be monitored and mounted naturally.
The switches are operated using the 2-motor electronic control system that has been used since RS-275U.
The RS 670 u has been improved. In order to improve reliability, a power transistor has been introduced as a switch element to control the plunger. This solves problems caused by poor contact of the relay and eliminates sparks and noise generated from the contact. There are four plungers and they are used for Play, FF/REW, auto-stop, and recording / playback switching.
In addition, in order to improve operability, a slide switch is adopted and a soft touch lock system is adopted.
Equipped with an automatic stop device. When the tape is wound, the automatic stop circuit works and the mechanism is released.
This automatic stopping device uses a reed switch and an electronic control system that detects rotation from a multi-pole 4-pole magnet that rotates in conjunction with the reel base.
The amplifier section uses 18 transistors per channel to achieve low noise.
A PNP type transistor (2SA721) is placed at the first stage of the reproduction equalizer amplifier to suppress the noise level fluctuation caused by the impedance change of the signal source, thereby reducing the audible noise.
In the next stage, a high-gain NPN type transistor (2SC1327) is arranged to ensure sufficient linearity to constitute a 2-stage direct connection circuit.
We have also adopted a carefully selected low-noise carbon resistor to improve SN.
A dedicated muting circuit and a mono-multi-muting circuit are combined to eliminate noise generated when switching a switch.
This automatically mutes for approximately 4 seconds when the power is turned on, and for 0.3 seconds when switching between recording and playback or turning the power off to suppress noise.
To further reduce noise, the erase head and the oscillation circuit block are shielded by a metal case, which also protects the tuner and receiver from radiation noise.
In addition, the printed circuit board is enlarged and the output terminals and volume are directly connected to each other, eliminating the deterioration of characteristics due to stray capacitance of the shield wire and improving reliability.
A series control type stabilized power supply is adopted for the power supply section to supply a stable power supply of 18 v to each part.
An HPF head has been adopted for the head.
The core material of this head is hot pressed ferrite and the hardness of the material is equal to that of hard glass. It is finished with precision by processing with jewel-like precision diamond tool.
Equipped with Dolby NR, noise on the tape is suppressed.
This device is IN-OUT capable. When it is switched to IN, an MPX filter is inserted to prevent the influence of the pilot signal of the FM stereo broadcast transmission.
Built-in meters have a dedicated circuit and can be used by switching between normal level meters and peak check.
Equipped with a dedicated microphone amplifier and volume for mixing. A high power supply of 18 v is supplied to the microphone amplifier to ensure linearity of 40B or more.
Built-in memory rewind function by counter.
Equipped with output level adjustment knob.
There was a special wood case sold separately.
Model Rating
| Type | Cassette stereo tape deck |
| Heads | Recording : HPF head Erasing : double-gap ferrite |
| Motor | For Capstan : Electronically Controlled DC Motor For Reel : DC Motor |
| Recording bias system | AC bias system, 85 kHz |
| Erasing method | AC erasing method |
| Track system | 4-track 2-channel stereo |
| Tape speed | 4.8cm/sec |
| Recording time | 1 hour round trip (when using RT-60 tape) |
| Frequency characteristic | Normal : 20 Hz to 15 kHz CrO2: 20 Hz to 17 kHz |
| Signal-to-noise ratio | Dolby Out:52dB Dolby In:60dB |
| Wow and flutter | 0.07%(Wrms) |
| Input Sensitivity / Impedance | Mic : 0.3 mV (-70dB) / 600 Ω ~ 20k Ω Line In:60mV(-24dB) |
| Output Level / Impedance | Line Out : 420mV/22k Ω or more Headphones : 65mV/8 Ω Din connector Rec/PB : EIAJ-compliant |
| Semiconductor used | Transistor : 51 Diode : 33 pcs Rectifier : 3 pcs |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 20W |
| External dimensions | Width 450x Height 173x Depth 330 mm |
| Weight | Approx. 9.8 kg |
| Sold Separately | Wood Case RP-9670 (¥ 4,000) |