YAMAHA K-750a
¥ 79,800 (around 1987)
Commentary
Reverse deck equipped with Dolby HX Pro and dbx.
Equipped with Dolby HX-PRO which prevents degradation of characteristics by automatically adjusting bias.
The Dolby HX-PRO operates so that the dynamic bias is constant, greatly reducing changes in frequency characteristics due to sensitivity changes. In addition, the operation is completely independent on the left and right sides, and each side is provided with optimal bias servo.
Also, it works only when recording, so recorded tapes can be played on other decks without any problem.
As a noise reduction system, dbx is installed in addition to Dolby B/C.
With dbx, the dynamic range of the original sound is reproduced by compressing the sound signal to exactly 1/2 during recording and expanding it to 2 times during playback. In addition, the noise level is also equivalently reduced at this time so that the tape noise can be pushed out of the audible band and has a noise reduction effect of 30 to 40 dB over the entire band.
Yamaha uses a low-impedance pure Sendust head manufactured by Yamaha's proprietary high-vacuum centrifugal casting method.
In the high-vacuum centrifugal casting method, high-purity Sendust is melted in a capsule and pressed into a ceramic mold rotating at high speed to produce a high-purity Sendust core material. Pure Sendust produced by this method is made into a multi-layer laminate and used as a core material to obtain excellent characteristics. In addition, Yamaha's unique low-impedance configuration greatly improves high-frequency characteristics, phase characteristics, bias current efficiency, and separation.
The erasing head uses a ferrite head that is resistant to wear and has excellent high-frequency characteristics.
The amplifier section uses Yamaha's original pure current dam method.
This is a system in which a constant current is always supplied from the power supply to the amplifier, so that no signal current flows into the ground line or power supply line, so that a clean power supply current can be obtained without being affected by non-linears inevitably present in the ground line or power supply line or by non-linears inside the power supply.
In addition, a low-noise operational amplifier is used for the recording amplifier, and a ± power supply is used to enable recording with a wide dynamic range.
It is equipped with a function to display the remaining amount of the unrecorded portion of the tape. This function finds out the unrecorded portion of the tape, displays the remaining amount of the tape on the counter for time, and enters a standby state at the head of the recordable portion.
It has a program recording function that allows you to record specified songs from records or CDs in the order in which they were programmed.
Equipped with monitor speaker out function.
Equipped with an auto-fade out / in function that automatically adjusts the volume when it reaches the tape end during recording.
It is also equipped with an auto-fader that can fade in and out with one touch during recording.
Equipped with an automatic source change function that automatically switches to another source after deck operation is completed.
Equipped with a memory stop function.
It has a repeat function that allows you to repeatedly play the same program up to 16 times.
Built-in program playback function.
It is equipped with a REC return function, and if you perform a direct rewind operation during recording, it returns to the recording start point and stops.
It is equipped with an intro-scan function that plays the head of a song one after another for about 15 seconds.
It is equipped with a music search that allows you to find the beginning of one song before and after.
It is equipped with a skip function that automatically fast-forwards to the next song when the unrecorded portion continues for approximately 15 seconds during playback.
Model Rating
| Type | Cassette deck |
| Tape rerecording system | Auto-reverse stereo |
| Heads | Integrated Mount Rotary Type with SENDUST Recorder / Ferrite Erasure |
| Motor | For Capstan : DC Servo Motor For Reel : Flat Torque DC Motor Mechanical : DC Motor |
| Mechanism | 2 + 1 separate drive |
| Wow flutter | 0.04% or Less (JIS, W. RMS) |
| Signal-to-noise ratio | 90 dB (dbx on, metal tape) |
| Frequency characteristic | 30 Hz ~ 17 kHz ± 3 dB (Normal) 30 Hz ~ 19 kHz ± 3 dB (Chrome) 30 Hz ~ 20 kHz ± 3 dB (metal) |
| Overall strain rate | 1% |
| Channel separation | 35dB |
| Crosstalk | 60dB |
| Meter | 2-Color 12-Point Peak FL Meter (-20dB to + 18 db) |
| Input Sensitivity / Impedance | Line : 45mV/47k Ω Mic : 0.25mV/5.6k Ω |
| Output Level / Impedance | Line : 360mV/2.7k Ω Headphone : 0.6mW/8 Ω |
| Early winding time | Approximately 70 Seconds (C-60) |
| Power consumption | 18W |
| External dimensions | Width 435x Height 114x Depth 303 mm |
| Weight | 5.7kg |