Pioneer A-004

Commentary

A pre-main amplifier with an emphasis on tape operation function and a 2 dc amplifier configuration for improved sound quality.

Equipped with a recording selector, it is possible to air check FM while listening to a record, or conversely record while listening to FM.
In addition, the Tape2 terminal is provided on the front, so you can easily connect another deck.

It uses class AB operation mode and operates in class A with beautiful sound during normal music playback. It has power margin close to class B amplifier, so high quality playback is possible even during peak hours.

The power amplifier and the flat amplifier have a DC configuration without the condenser in the NFB circuit, so that the phase shift in the low-frequency range caused by the condenser, the degradation of damping, and the generation of the transient intermodulation distortion are suppressed.
We also intend to improve the characteristics by using the group transistor RET with excellent switching characteristics even in the ultra-high frequency range.

The power supply section is equipped with a large transformer and an electrolytic capacitor of 10,000 μ Fx4. In addition, regenerative capacity is improved by reducing the impedance of the point distribution.

The equalizer amplifier section uses a differential amplifier with a low-noise transistor at the first stage.

It uses a 32-step attenuator type volume of decibel display.
It also has a -20dB muting switch.

Equipped with a subsonic filter and tone ON-OFF switch.

The pre-part and power part can be used separately.

Model Rating

Type	Stereo pre-main amplifier
Power Amplifier Unit
Effective output (both channel drive, 8 Ω)	60W + 60W (5 hz ~ 30 khz, THD 0.02%) 60W + 60W (5 Hz ~ 60 kHz, THD 0.05%)
Harmonic distortion factor	0.02% (Effective Output, 5 Hz to 30 kHz, 8 Ω)
Intermodulation distortion factor (50 hz : 7 khz = 4 : 1)	0.01% (8 Ω at effective output)
Output Bandwidth (IHF, double-channel drive, 8 ω)	5 Hz ~ 50 kHz (THD 0.02%) 5 Hz ~ 100 kHz (THD 0.05%)
Frequency response (at 1W output)	5 Hz ~ 200 kHz + 0 -1dB
Damping factor	40 (5 Hz ~ 30 kHz, 8 Ω)
Signal-to-noise ratio	115 dB (IHF, A-network, short circuit)
Preamplifier Section
Input Sensitivity / Impedance	Phono1, 2 (MM) : 2.5mV/50k Ω Tuner, Aux, Tape play1, 2 : 150mV/50k Ω
Phono maximum allowable input	MM : 250 mV (1 kHz, 0.02% THD)
Harmonic distortion factor (5 Hz to 30 kHz)	0.005% (1 V Output)
Frequency characteristic	Phono : 20 Hz to 20 kHz ± 0.2 dB Tuner, Aux, and Tape play : 5 hz to 100 khz + 0 to 1 db
Signal-to-noise ratio (IHF, A-network Short circuit)	Phono MM:87dB Tuner, Aux, Tape play : 97 dB
Subsonic filter	15 Hz, 6dB/oct.
<General>
AC outlet	Power switch interlock : 2 systems Power switch not linked : 2 systems
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	180W (Electrical Appliance and Material Control Law) 450W maximum
External dimensions	Width 420x Height 155x Depth 378 mm
Weight	13.1kg