Pioneer A-D5a

Commentary

A pre-main amplifier developed as a successor to A-D5.

Direct Energy MOS-FET is used for the output stage.
Since the on-resistance of this element is very small, it realizes excellent power linearity and has high low-load drive capability.

Wide range linear circuit is used for the circuit structure.
This circuit employs a simple structure in which the required gain is obtained by one stage amplification using a current feedback circuit. It has excellent current linearity, flat output impedance, and stable driving from low to high frequencies is possible.

By combining a direct energy MOS-FET with a wide-range linear circuit, the A-D5a eliminates the choke coil at the source resistance and the speaker output terminal, and realizes a simple design, low heat generation, and compact size.

Super-ring toroidal transformer is used for the power supply.
Although this transformer has low loss, the leakage flux that is a source of noise in the amplifier is small, making it possible to supply clean power.

The smoothing capacitor uses an complimentary service capacitance pair.
In this condenser, the magnetic field generated on the positive side and the magnetic field generated on the negative side cancel each other.

The internal layout is symmetrical and symmetrical to minimize the signal path.
In addition, direct-energy MOS-FETs uses an independent heat sink made of thick aluminum extruding material to eliminate insulation between the power elements and the heat sink, which could not be eliminated by conventional amplifiers. Mutual interference between the direct-energy MOS-FETs at the output stage is eliminated. The volume knob also uses a stabilizer to eliminate resonance.

The chassis and rear panel features a copper-plated ハイコンダクション chassis structure that increases electrical conductivity and reduces high-frequency impedance. The potential difference inside the chassis is reduced, improving electrical stability and creating a more realistic sound field.

Equipped with a direct button that passes through the balance circuit and tone circuit.

Uses a large capacity 3P extra-thick type OFC power cord.

A banana plug-compatible speaker terminal is used for the output terminal.
Each terminal has a gold-plated input / output terminal.

Wireless remote control is included.

Model Rating

Type	Pre-main amplifier
Maximum practical power	150W + 150W (EIAJ, 4 ω)
Rated Output (Both channel drive)	110W + 110W (4 ω, 20 Hz to 20 kHz, 0.2%) 60W + 60W (8 Ω, 20 Hz to 20 kHz, 0.05%)
Input Sensitivity / Impedance	Phono MM : 2.8mV/50k Ω CD, Tuner, Line, Tape1/MD, Tape2/monitor : 200mV/50k Ω
Phono maximum allowable input	Phono MM : 150 mV (1 kHz, 0.02%)
Output Level / Impedance	Tape1/MD, Tape2/Monitor : 200mV/1k Ω Tape rec : 200mV/1k Ω
Frequency characteristic	Phono MM : 20 Hz to 20 kHz ± 0.3 dB CD, Tuner, Line, Tape1/MD, Tape2/Monitor : 5 Hz to 100 kHz + 0 -2dB
Tone control	Bass : ± 8 dB (100 Hz) Treble : ± 8 dB (10 kHz)
Loudness contour (Vol -30dB)	+ 5 dB (100 Hz), + 3 dB (10 kHz)
Signal-to-noise ratio (IHF, A-network, short circuit)	Phono MM:88dB(at 5mV) CD, Tuner, Line, Tape1/MD, Tape2/Monitor : 108 dB
Speaker load impedance	A, B : 4 Ω ~ 16 Ω A + B : 8 Ω ~ 32 Ω
AC outlet	Power switch interlock : 1 system (100W) Power switch not linked : 1 system (100W)
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	160W (Electrical Appliance and Material Control Law)
External dimensions	Width 420x Height 128x Depth 335 mm
Weight	6.2kg
Attachment	Wireless Remote Control