KENWOOD KA-990EX
¥ 79,800 (released in 1987)
Commentary
An integrated amplifier designed to provide more pure sound quality with a thorough anti-vibration design.
We have newly developed and adopted a strut air suspension to suppress noise and distortion caused by external vibration.
This suspension is a unique independent suspension vibration absorption system. Vibration from the floor is first absorbed by the special elastic rubber at the grounding section. Furthermore, large amplitude vibration that could not be absorbed by the special elastic rubber is smoothly absorbed by the following coil spring and air damper.
In addition, these main parts are made of aluminum die-cast movable parts with high rigidity, and vibration from the floor is eliminated as much as possible.
In addition, the casing is made of a high-strength vibration-proof casing bonded with iron plates. By increasing the weight and adopting new structures such as logical flow construction, sound quality degradation is prevented.
In order to reduce the effect of sound quality degradation caused by home power supply, we have adopted an independently developed clean cyclone power supply.
By adding a special clean cyclone device to the transformer winding, this technology does not change digital noise in the high-frequency range into secondary voltage. This improves the bare characteristics of the power supply itself and improves the quality.
In addition, by fusing with the DLD circuit that eliminates the interference between the voltage amplification stage and the power stage that occurs through the power supply, and with the NEW VIG circuit that improves the SVR of the amplifier, the influence of the AC power supply and power supply circuit on the amplifier circuit is reduced.
The New VIG / OLD circuit is a circuit system originally developed by Kenwood, in which a VIG circuit, which does not transmit the noise component of the power supply to the power amplifier, is installed between the amplifier and the power supply, and the performance of the DLD circuit is utilized to improve sound quality.
This eliminates the ripple, signal components, and intermodulation distortion components from the power supply, and supplies clean energy to the power amplifier. At the same time, it achieves the same effect as a huge battery. The ripple free large power supply greatly increases the power supply capacity.
The internal structure employs a 5-box logical flow construction. The shield plate completely separates the small signal and large signal, digital signal and analog signal, and each signal processing part and power supply to suppress mutual interference.
In addition, by placing the transformer in the center, the merits of the strut air suspension can be maximized, and vibration damping effect is also improved.
The heat sink uses a chimney type heat sink with excellent heat radiation effect and vibration isolation.
Equipped with a Σ drive circuit that reduces distortion.
In the Σ drive, the NF loop is connected to the speaker terminal of the amplifier, and parts which cause distortion and sound quality degradation are put in the NF loop, and generation of distortion is suppressed.
In addition, all GND lines are concentrated at one point on the speaker terminal of the amplifier to suppress mutual interference caused by ground line patterns and wires, and to prevent digital noise generated by peripheral devices.
Dual Rec Selector with Source Selector function and CD Direct Switch are installed.
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Model Rating
| Type | Integrated amplifier |
| Rated Output (20 Hz to 20 kHz, Both Channel Operation) | 130W + 130W (6 Ω, THD 0.006%) 110W + 110W (8 Ω, THD 0.004%) |
| Dynamic Power | 315W (2 Ω) 235W (4 Ω) 125W (8 Ω) |
| Total Harmonic Distortion Factor (CD) | 0.0006% (at rated output, 1 kHz, 8 Ω) 0.004% (Rated Output, 20 Hz to 20 kHz, 8 Ω) 0.003% (20 Hz to 20 kHz at 1/2 Rated Output) |
| Intermodulation distortion factor (60 hz : 7 khz = 4 : 1) | 0.004% (8 Ω at rated output) |
| Frequency Response (Line → Speaker) | 5 Hz ~ 80 kHz + 0 -3dB |
| Damping factor | 1000(50Hz) |
| Input Sensitivity / Impedance | Phono MM : 2.5mV/47k Ω Phono MC : 0.2mV/100 Ω DAT, CD, Tuner, Aux, Tape : 150mV/47k Ω |
| SN ratio (input short / EIAJ) | Phono MM:87dB/78dB Phono MC:70dB/74dB DAT, CD, Tuner, Aux, Tape : 108dB/82dB |
| Tone control | Bass : ± 10 dB (100 Hz) Treble : ± 10 dB (10 kHz) |
| Loudness control (Vol-30dB) | 9dB(100Hz) |
| Subsonic filter | 18 Hz, -6dB/oct. |
| Output bandwidth (0.04% distortion rate, 8 Ω) | 5 Hz to 50 kHz |
| Phono maximum allowable input (Phono → Tape Rec, 1 khz, 0.004%) |
Phono MM:200mV Phono MC:15mV |
| Output Level / Impedance | Tape rec : 150mV/330 Ω |
| Power outlet | Power switch interlock : 1 system, 100W Power switch not linked : 2 systems, 400W |
| Pwer | 100 VAC, 50Hz/60Hz |
| Rated power consumption (Electrical Appliance and Material Control Law) | 270W |
| Maximum external dimensions | Width 440x Height 171x Depth 441 mm |
| Weight | 15.5kg |