AKAI 250D
¥ 98,000 (around the late 1960 s?)
Commentary
4-head 3-motor auto-reverse tape deck.
Equipped with a Oatley berth mechanism using sensing pins. This allows continuous reverse playback by attaching sensing tapes to both ends of the tape. Also equipped with a manual reverse button for manual reverse playback.
With these reverse mechanisms, the capstan automatically moves away from the pinch roller when the reverse motion begins, and the motor rotates in the opposite direction. The tape runs only after the motor reaches the set tape speed, so there is no unnatural sound or noise that can occur when reversing.
Newly designed 3-speed outer rotor motor with servo circuit for capstan drive is adopted.
This motor combines an eddy current outer rotor motor, a control winding and a speed detection gear into an integrated structure. It is designed to detect and amplify the motor speed purely electrically and compensate for changes in rotational speed by means of a servo circuit and a frequency generator. This ensures stable rotation without being affected by the power supply frequency.
Two eddy current outer rotor motors are used for the reel motors.
A 4-head configuration with separate heads dedicated to recording, playback, reverse playback, and erasing.
An automatic tape lifter mechanism is incorporated to prevent the tape from touching the head surface during fast forward and rewind, thereby preventing unpleasant sound and adverse effects on the head surface.
Micro switches and relays are used for the control part to improve operability.
Equipped with a 4-digit index counter with reset button.
Equipped with a reel presser mechanism, the reel can be firmly fixed by pulling the reel presser attached to the tip of the reel shaft toward you and turning it to the right or left.
Equipped with an auto-stop / auto-shutoff mechanism. When the tape is fully wound and reaches the end, the tape stops running with the auto-shutoff lever. If you press the auto-shutoff button, the entire unit is powered off when the auto-shutoff lever returns.
Equipped with a lockable temporary stop button.
Sound on sound recording is possible.
First, record by pressing the Track Selector button "1-4" on the front control panel, rewind the tape, then record by pressing the Sound On Sound button and the "3-2" button while monitoring the first recording, so that the two recordings are superimposed on a 3-2 track.
Mixing recording by line and microphone input is possible.
A silicon transistor is used for the preamplifier section.
Equipped with a large VU meter.
Equipped with a stereo headphone jack.
Equipped with a DIN jack.
The wood cabinet is finished with oil.
Remote control unit of accessories sold separately allows operation from a remote location.
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Model Rating
| Type | Tape deck |
| Track format | 4-track 2-channel, stereo / mono |
| Maximum reel used | Reel 7 |
| Tape Speed | 19cm/s, 9.5cm/s, 4.75cm/s |
| Tape speed deviation | 0.5% or Less (19cm/s) 1.0% or Less (9.5cm/s) 1.0% or Less (4.75cm/s) |
| Wow and flutter | 0.10% RMS or less (19cm/s) 0.12% RMS or less (9.5cm/s) 0.20% RMS or less (4.75cm/s) |
| Frequency characteristic | 30 Hz ~ 22 kHz ± 3 dB (19cm/s) 30 Hz ~ 13 kHz ± 3 dB (9.5cm/s) 50 Hz ~ 6 kHz ± 3 dB (4.75cm/s) |
| Signal-to-noise ratio | 50 dB or More (19cm/s) 48 dB or More (9.5cm/s) 46 dB or More (4.75cm/s) |
| Distortion factor | 2% or less at 19cm/s, 1 kHz, 0 VU |
| Crosstalk | Mono : 70 dB or higher Stereo : 50 dB or more |
| Erasure rate | 70 dB or more |
| Recording (playback) compensation characteristics | NAB characteristics |
| Recording bias frequency | 100kHz |
| Recording level display | 2 VU meters |
| Heads | 4-track, 2-channel recording, playback, reverse playback, and erase |
| Fast-forward rewind time | 75 seconds (1,200 ft tape, 50 Hz) 60 seconds (1,200 ft tape, 60 Hz) |
| Output Level / Impedance | Line : 1.23 V (0 VU) / 100 ohm DIN:0.4V Headset : 30 mv ~ 40mV/8 Ω |
| Input Level / Impedance | Line : 0.1V/150k Ω Din : 50 mV (High), 5 mV (Low) / 68k Ω Mic : 0.3mV/10k Ω |
| Monitoring method | Stereo headphone, 8 Ω |
| Recording time | 4-hour stereo recording (4.75cm/s, 1,200 ft tape) |
| Motor | For Capstan : Outer Rotor 3 Speed Servo Motor x1 For Reel : 6 Pole Eddy Current Outer Rotor Motor x2 |
| Semiconductor used | Transistor : 34 Diode : 18 pcs IC : 2 |
| Pwer | 100 / 110 / 120 / 200 / 220 / 240 V AC, 50Hz/60Hz |
| Power consumption | 33W ~ 130W |
| External dimensions | Width 435x Height 460x Depth 260 mm |
| Weight | 20kg |
| Attachment | 1 x 7 Empty Reel One DR-110 type connection code 2 spare fuses |
| Sold Separately | Wired Remote Control RC-16 |