ONKYO TA-680

Commentary

Stereo cassette deck for metal tape.

The mechanism uses a dual capstan system that uses two pairs of pinch rollers and capstan.
In this method, large windows on both the left and right sides of the cassette half are used for drives. Therefore, it was considered impossible to use a head that can handle metal tapes with strong hysteresis loops due to space considerations. To solve this problem, we developed a small erasing head for small windows in the TA-680.

The head uses a double-gap head that combines ferrite and Dynaloy with a Sendust core.
The Sendust Combination Head consists of a narrow head for playback and a wide head for recording.

The erase head is an FX ferrite junction metal compatible erase head.

In order to bring out the characteristics of the tape, it is equipped with auto accubias.
In this circuit, the outputs of two oscillators, a low-frequency (400 Hz) and a high-frequency (10 kHz), are mixed, recorded while changing the bias current, played back simultaneously taking advantage of the three heads, compared between the low-frequency and high-frequency levels of the reproduced signal, and the bias current is fixed when the two levels become equal.
During tuning, it can be confirmed by flashing green indicator.

The fade-out function allows you to fade out and erase unwanted parts of a recorded tape while playing it back. The fade-out circuit erases the recorded content while maintaining an appropriate time constant (approximately 3 seconds).
This circuit is also equipped with a safety mechanism to prevent accidental erasure.

In order to prevent the tape from becoming painful, if you press FF to REW continuously, the function will be switched to the next function via the STOP position. In addition, with the full auto-stop system, the mechanism will be surely free at the tape end, so that no excessive force is applied to the motor or tape.

Operability has been improved by adoption of feathertouch electromagnetic operation logic control circuit.

A PLL servo motor is used to drive the capstan of the drive section.

Equipped with a logarithmic compression type VU meter and 10-stage left / right independent peak indicators, memory play and rewind, timer recording and playback mechanism, equalizer / bias 3-stage independent switching, Dolby circuit with Rec level carriage, Rec Mute, microphone mixing circuit, microphone jack with automatic mode (stereo / mono) switching, headphone output terminal for high impedance, and soft eject mechanism.

Model Rating

Type	Stereo cassette deck
Track format	4-track 2-channel stereo
Recording system	AC bias
Erasing method	AC Erase
Tape speed	4.8cm/s
Wow flutter	0.035%(W.R.M.S.)
Frequency characteristic	20 Hz ~ 20 kHz (Metal Tape) 20 Hz ~ 18 kHz (High Position Tape) 20 Hz ~ 16 kHz (Normal Tape)
Signal-to-noise ratio	62 dB (Metal Tape)
Minimum input level	Microphone : 0.3mv/600 Ω Line : 50 mV
Input impedance	Microphone : 5k Ω (Compatible impedance 200 Ω ~ 50k Ω) Line : 100k Ω
Reference output	Line : 0.775 V (0 VU)
Load impedance	Line : 50k Ω or more Stereo headphones : 8 Ω ~ 200 Ω
Motor	For Capstan : PLL Servo DC Motor For Reel Drive : DC Motor
Heads	Recording : Sendust Combihead Erasing : FX ferrite junction head
Pwer	100 VAC, 50Hz/60Hz
Power consumption	45W
External dimensions	Width 438x Height 160x Depth 365 mm
Weight	10.2kg