TRIO KA-800
¥ 64,800 (around 1980)
Commentary
Pre-main amplifier with Σ drive.
In the Σ drive system, the conventional concept of NFB, which was completed in the case of the amplifier, is extended to the input terminal of the speaker. The speaker cable is also considered as one of the internal wiring of the amplifier, and the performance at the input terminal of the speaker is guaranteed.
First of all, we have installed a unique Σ cable that connects the + side of the speaker and the feedback point of the power amplifier to control various types of distortion at the input terminal of the speaker, including reverse distortion caused by the magnetic circuit of the speaker.
In addition, by separating the ground point and the power loop on the - side cable, the potential difference between the input terminal of the speaker and the ground point is completely eliminated from the concept of one point grounding.
The MM/MC switching system is used in the equalizer amplifier section. The gain can be switched between MM35.6 dB and MC57.6 dB so that various cartridges can be used easily without replacing the input pin plug.
Low-noise IC is used for the circuit.
The power amplifier uses a new high-speed method that applies NFB uniformly over the entire audible band, and a straight DC amplifier that does not have a low-pass capacitor for all signal systems, including the NF loop, from the Tuner (AUX) terminal to the SP terminal.
The tone control section uses a main tone system using a power amplifier.
Audio quality is improved even when using tone controls because the signal path can be simplified.
It uses a fader system that allows you to preset the volume position. If you set the volume level you normally use with the preset level knob, you can smoothly fade in and out simply by lightly touching the fader.
First, when you turn on the power switch, the volume goes up to the set volume and the fader lights up blue. When you touch the fader again, the volume goes down to 0 and the illumination turns white.
It takes about one second to touch and fade. If you want to change the volume while the sound is being emitted, you can adjust it with the preset knob.
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Model Rating
| Type | Σ drive amplifier | ||
| Rated Output (20 Hz to 20 kHz, Both Channel Operation) | 55W + 55W (8 Ω, Phono → sp out) | ||
| Total Harmonic Distortion Factor (20 Hz to 20 kHz, 8 Ω) |
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| Intermodulation distortion factor (60 hz : 7 khz = 4 : 1) | Tuner, AUX, Tape → sp out : 0.009% (8 Ω at rated output) | ||
| Frequency characteristic | DC ~ 350 khz -3dB (Tuner, AUX, Tape → sp out) | ||
| Damping factor (100 Hz) | 100 | ||
| Input Sensitivity / Impedance | Phono MM → sp out : 2.5mV/47k Ω Phono MC → sp out : 0.2mV/100 Ω Tuner, AUX, Tape → sp out : 150mV/47k Ω |
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| Signal-to-noise ratio (IHF-A) | Phono MM → sp out : 84 dB Phono MC → sp out : 64 dB Tuner, AUX, Tape → sp out : 105 dB |
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| Tone control | Bass 400 Hz : ± 7.5 dB (100 Hz) Treble 3 kHz : ± 7.5 dB (10 kHz) |
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| Loudness control (Volume -30dB) | +10dB(100Hz) | ||
| Subsonic filter (-3dB) | 18 Hz, 6dB/oct. | ||
| Rise time | 1 μ s (Tuner, AUX, Tape → sp out) | ||
| Slew rate | ± 100 V / μ s (Tuner, AUX, Tape → sp out) | ||
| Phono maximum allowable input (Phono → Tape rec, 1 kHz, distortion rate 0.005%) |
MM:200mV MC:10mV |
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| PhonoRIAA deviation | 30 Hz to 20 kHz ± 0.3 dB | ||
| Output Level / Impedance | Tape rec (PIN) : 150mV/220 Ω | ||
| Power supply voltage | 100 VAC, 50Hz/60Hz | ||
| Rated power consumption (Electrical Appliance and Material Control Law) | 160W | ||
| Power outlet | Power switch interlock : 2 systems Power switch not linked : 1 system |
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| External dimensions | Width 440x Height 123x Depth 375 mm | ||
| Weight | 8.5kg |