Pioneer A-04

Commentary

This pre-main amplifier was developed based on the concept of wide range technology that expresses the nuance of music by focusing on sound quality outside the audible band.

It is equipped with a newly developed wide-range circuit for stable amplification of input signals from digital devices.
This is a simple circuit that uses a single-stage amplifier circuit to obtain the required gain. It has excellent current linearity and flat output impedance from low to high range.
This allows for accurate reproduction and a spacious speaker drive over a wide bandwidth.

In order to enhance the power supply capability, we have adopted a large power transformer in the power supply section to suppress the deterioration of sound quality caused by the leakage flux generated by the transformer.

In order to prevent the generation of sound nigori due to the mutual interference of each circuit, the power supply section and power amplifier section are shielded, and the adjacent power amplifier section and voltage amplifier section are shielded and separated by a newly developed Aero heat sink. This 3 box chamber structure is adopted.

The newly developed Aero heat sink has been adopted as the heat sink, and since there is no parallel face facing the structure itself, standing waves are hardly generated.
In addition, resonance, which is the nigori of sound quality, is suppressed, and high heat transfer effect is obtained by extending two sheets at a time from the back surface of the mounting part of the fin and power transistor. In addition, heat inside the amplifier, which generates a large amount of heat, is radiated effectively, and uniform temperature is realized.

The volume uses a 40 mm square large unit to eliminate gang errors.
In addition, a copper volume stabilizer is used through a copper volume stabilizer to prevent vibration from being transmitted to the volume.

A computer simulation is also performed on one of the screw stops to select a position that is less susceptible to vibration, and copper plating is used for the screw, which is effective in absorbing vibration.

A high-rigidity honeycomb structure has been adopted for the insulator to increase the vibration absorption rate, and an insulator is also attached directly under the heavy transformer to balance the dead weight.
By attaching a cushion to the contact part and housing side of the insulator, the transmission of vibration is suppressed.

The Phono equalizer uses a single-chip dual-FET input configuration.

It features thick oxygen-free copper power cords with polarity indication, gold-plated I/O pin jacks, a vise speaker terminal, and well-designed resistors and capacitors.

Model Rating

Type	Stereo pre-main amplifier
Rated Output (Double-channel Drive, 20 Hz to 20 kHz)	90W + 90W (4 ohm, 0.2%) 45W + 45W (8 Ω, 0.02%)
Damping factor	160 (20 Hz ~ 20 kHz, 8 Ω)
Input Sensitivity / Impedance	Phono MM : 2.8mV/50k Ω Phono MC : 0.25mV/100 Ω CD, Tuner, Line, DAT/Tape1, Tape2 : 200mV/30k Ω
Phono maximum allowable input	MM : 200 mV (1 kHz, 0.1%) MC : 16 mv (1 khz, 0.1%)
Output Level / Impedance	DAT/Tape1, Tape2, Line, Rec, Adapter Out : 200mV/1k Ω
Frequency characteristic	Phono MM : 20 Hz to 20 kHz ± 0.2 dB Phono MC : 20 Hz to 20 kHz ± 0.3 dB CD, Tuner, Line, DAT/Tape1, Tape2 : 1 Hz to 150 kHz + 0 -3dB
S/N (IHF, A-network Short circuit)	Phono MM:87dB(2.8mV) Phono MC:67dB(0.25mV) CD, Tuner, Line, DAT/Tape1, Tape2 : 108 dB
Tone Control (Volume-30dB)	Bass : 100 Hz, ± 8 dB Treble : 10 kHz, ± 8 dB
Loudness contour (Volume-30dB)	100Hz:5dB 10kHz:3dB
Speaker load impedance	A, B : 4 Ω ~ 16 Ω A + B : 8 Ω ~ 32 Ω
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption (Electrical Appliance and Material Control Law)	145W
AC outlet	Power switch interlock : 2 systems, 100W Power switch not linked : 1 system, 100W
External dimensions	Width 440x Height 161x Depth 435 mm
Weight	15.2kg