TRIO KA-8004

Commentary

Solid state pre-main amplifier announced as the highest model of the HI-ATC series.

All stages are connected directly to the power amplifier, and the interstage coupling capacitor is removed from the first stage to the last stage.
In addition, a ± 2 power supply system using a first stage differential system is adopted. By setting the potential at the output terminal of the amplifier to 0 and applying deep NFB, various characteristics are extended to the ultra-low frequency range.
In addition, a pure complimentary service circuit using the Darlington method of PNP-NPN is adopted for the output stage to reduce distortion of the amplifier.

The equalizer amplifier is equipped with a 3-stage PNP-PNP-NPN direct-coupled equalizer circuit with a differential amplifier using a low-noise PNP transistor at the first stage, thereby improving dynamic range and stability.

Immediately after the EQ, a buffer amplifier consisting of a complimentary service using a metal can-shield transistor is mounted.

A constant current drive system is adopted for the pure complimentary service circuit to improve various characteristics and realize a stable power supply.

The tone control employs an NFB switching type tone control that eliminates the undulation of the characteristics around the turnover frequency, which had been unavoidable in the past.
It also has a tone control and defeat position.

Equipped with 18dB/oct low-cut filter, it can cut rumble components, etc.
In addition, a high-cut filter is installed to cut out hiss and scratch noise of the record.

A protection circuit consisting of an ASO (excess current) detection circuit and a DC drift detection circuit is mounted so that the output terminals of the speaker and amplifier can be separated when full power is output in the ultra low frequency range or when an error occurs in the amplifier.
If either one of the detection circuits operates, the discharge circuit is turned ON, the Schmidt circuit is activated, and the relay circuit is driven to disconnect the output terminal of the amplifier from the speaker.

Metal cancel transistors are used for all transistors.

A block plate is directly connected to various switches such as tone control and filter to eliminate excess lead wires and improve the inductive hum and SN ratio.

We have developed a shield wire by wire wrapping up to the ground part by improving the conventional shield wire, eliminating the sound quality degradation caused by soldering the excess part.

Model Rating

Type	Solid-state stereo premain amplifier
Power Amplifier Unit
Effective power	20 Hz to 20 kHz, both channel operation : 55W + 55W (8 Ω) 1 kHz Single channel operation : 100W/100W (4 Ω) 80W/80W (8 Ω) Both channel operation : 85W + 85W (4 Ω) 60W + 60W (8 Ω)
Music Power (IHF)	300W (4 Ω) 180W (8 Ω)
Total harmonic distortion factor (8 Ω)	0.2% (at rated output) 0.05% (Rated Output -3dB)
Cross modulation distortion factor	0.2% (at rated output) 0.05% (Rated Output -3dB)
Output Bandwidth (IHF)	6 Hz to 45 kHz
SN ratio (closed circuit)	110dB
Residual noise (8 Ω)	0.3 mV (0.012 μ W)
Input Sensitivity / Impedance	1.0V/50k Ω
Optimum load impedance	4 Ω ~ 16 Ω
Damping factor	50 or more
Output terminal	Speakers and headphones : 4 Ω ~ 16 Ω
Preamplifier Section
Input Sensitivity / Impedance	Phono1 : 2.5mV/30k Ω, 50k Ω Phono2 : 2.5mV/50k Ω Tuner, AUX, Tape PlayA, B : 150mV/100k Ω MIC : 2.5mV/50k Ω
Signal-to-noise ratio	Phono1, 2 : 70 dB Tuner, AUX, Tape PlayA, B : 80 dB MIC:70dB
Maximum Allowable Input (1 kHz)	560mV(P-P)
Output Level / Impedance	Tape Play A, B Pin : 150mV/100 Ω Din : 40mV/50 Ω Pre Out: 1V/100 Ω
Frequency characteristic	Tuner, AUX, Tape Play : 20 Hz to 50 kHz + 0 -2dB MIC : 50 Hz ~ 10 kHz + 0 -1dB
Tone control	bass: 100 Hz ± 6 dB (turnover : 200 Hz) 100 Hz ± 6 dB (turnover : 400 Hz) Treble: 10 kHz ± 10 dB (Turnover : 3 kHz) 10 kHz ± 6 dB (Turnover : 6 kHz)
Filter	Low : 20 Hz, 40 Hz, 18dB/oct. High : 7 kHz, 6dB/oct.
Loudness control (rated output -30dB)	100Hz:+8dB 10kHz:+3dB
<General>
Power supply voltage	100 VAC / 117 V, 50Hz/60Hz
AC outlet	Power switch interlock : Route 3, 300W Power switch not linked : 1 system, 100W
Rated power consumption (Electrical Appliance and Material Control Law)	135W
External dimensions	Width 435x Height 153x Depth 300 mm
Weight	12.9kg