Pioneer A-05

Commentary

This is a pre-main amplifier that inherits the technology of high-end machines.

The chassis layout has a symmetrical twin monaural structure.
In addition to the symmetrical layout of the internal circuit and structure represented by the twin transformer, the A-05 has a fully symmetrical structure including the front panel, rear panel, and volume, so that the environment such as current, magnetic field, temperature distribution, and mechanical stress distribution can be made uniform. This minimizes the characteristic error of L/R caused by parts.
In addition, all compromises have been made to simplify the circuit, and the signal path has been straightened to achieve higher quality playback.

Wide-range linear circuit ver. 5 is adopted to improve the time axis characteristics of the transmission system.
Conventional amplifier circuits are equipped with choke coils for the speaker output terminals, capacitors for each input terminal, and phase compensation capacitors to ensure stability against high frequencies. However, these parts prevent the simplification of the circuit and the amplification of pure sound. The choke coil adversely affects the output impedance in the high frequency range, and the phase compensation capacitor adversely affects the sound quality.
In order to solve this problem, the wide-range linear circuit is designed to obtain the necessary gain by one stage amplification using a current feedback circuit, and the damping factor is made flat over a wide range to obtain excellent speaker drive power.

Dedicated tuning parts such as custom-designed volume and original organic semiconductor condenser are adopted.

The power transformer uses a toroidal transformer with an oriented core.
The core section without corners suppresses the generation of beat and improves the S/N feeling.

It is equipped with a gain selector to cut off the excess gain and increase the purity of the sound when playing at a small volume.
There are two selector positions, 40 dB and 26 dB. The 40 dB position gives you more power, and the 26 dB position gives you more natural music playback.

The phono equalizer uses a single-chip dual FET as its input circuit.

An OFC power cord is used for the power cable, and external noise is eliminated by drawing the power cord from directly under the power transformer.

Uses gold-plated input / output terminals.

A large vise type speaker terminal with low transmission loss is adopted.

Model Rating

Type	Pre-main amplifier
Rated Output (Both channel drive)	90W + 90W (4 ω, 20 Hz to 20 kHz, 0.05%) 45W + 45W (8 ω, 20 Hz-20 kHz, 0.03%)
Damping factor	300 (20 Hz ~ 20 kHz, 8 Ω)
Input Sensitivity / Impedance	Phono MM : 2.8mV/50k Ω CD, Tuner, Line, DAT/Tape1, Tape2/CDR : 200mV/30k Ω
Phono maximum allowable input	Phono MM : 150 mV (1 kHz, 0.02%)
Output Level / Impedance	DAT/Tape1, Tape2/CDR : 200mV/1k Ω
Frequency characteristic	Phono MM : 20 Hz to 20 kHz ± 0.3 dB CD, Tuner, Line, DAT/Tape1, Tape2/CDR : 5 hz to 300 khz + 0 to 3 db
Signal-to-noise ratio (IHF-A network Short circuit)	Phono MM:84dB(2.8mV) CD, Tuner, Line, DAT/Tape1, Tape2/CDR : 105 dB
Speaker load impedance	4 Ω ~ 16 Ω
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	170W (Electrical Appliance and Material Control Law)
External dimensions	Width 440x Height 163x Depth 476 mm
Weight	15.1kg