Pioneer A-07

Commentary

Stereo pre-main amplifier with symmetrical twin monaural structure.

In order to obtain realistic and rich stereo images, the A-07 has a symmetrical structure that includes CFCs, rear panels and volume in addition to the symmetrical layout of the internal circuit as represented by the twin transformer. This makes the environment such as current, magnetic field, temperature distribution, and mechanical stress distribution uniform, and minimizes left and right characteristic errors caused by parts.

The A-07 is equipped with a wide-range linear circuit that obtains the required gain by one stage amplification using a current feedback circuit. This circuit flattens the damping factor over a wide range and realizes a reliable speaker drive. In addition, the stability of the circuit itself is enhanced by the adoption of a cross-array power stage, a newly developed output stage with excellent power linearity and temperature stability.
As a result, superior high-frequency characteristics have been obtained, phase characteristics have been dramatically improved, and characteristics that are resistant to high-frequency noise have been realized.

Uses carefully selected high-reliability parts.
In addition to the custom-made polypropylene film condenser with thorough tuning of sound quality, we have adopted winding resistance, mold resistance and sealed relays that ensure stability regardless of the operating environment to achieve high accuracy and reliability.
In addition, we have adopted a high-precision attenuator volume that is not easily affected by minute vibrations, enabling accurate and stable control by reducing left-right interlocking errors.

Each block is separated by a frame in which each block is separated by a frame. Mutual interference between blocks is eliminated by shielding the amplifier, power supply and control.
The rear panel has pin jacks arranged radially around the ground, which is the operation standard of the amplifier, to improve electrical stability. In addition, an aero-wing heat sink with excellent heat dissipation and vibration damping characteristics is adopted. The high heat transfer effect equalizes the temperature of the power transistor, while eliminating parallel planes in the structure itself to suppress standing waves and resonances that cause noise turbidity.

Advanced Direct Construction is used to keep the signal path as simple as possible.
In this method, the signal selected by the signal switching relay immediately after the input terminal is input to a single board connected to the volume and the amplifier circuit by the shortest length, thereby further shortening the signal path and improving electrical stability.

It is equipped with a gain selector.
This is a function to switch the gain of the amplifier to make the most of the output of the connected source device. When listening at a low volume or using a high-efficiency speaker, the S/N ratio can be improved by setting it to the 26 dB position, enabling fine volume control.

An insulated circuit is adopted in which the electric circuit, control circuit and power supply section of both left and right channels are electrically independent. This circuit uses a photocoupler to eliminate interference caused by current loops between circuits.

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

Uses highly reliable gold-plated input terminal.

The power cable is drawn from directly under the power transformer to reduce the influence of external noise, and large-capacity extra-thick OFC cable is used for wire material.

A large vise type speaker terminal is adopted.

Model Rating

Type	Stereo pre-main amplifier
Rated Output (Double-channel Drive, 20 Hz to 20 kHz)	100W + 100W (4 Ω, 0.03%) 50W + 50W (8 Ω, 0.01%)
Damping factor	300 (20 Hz ~ 20 kHz, 8 Ω) 350 (1 kHz, 8 Ω)
Input Sensitivity / Impedance	Phono MM : 2.8mV/50k Ω CD, Tuner, Line, Tape : 200mV/50k Ω
Phono maximum allowable input	MM : 150 mV (1 kHz, 0.2%)
Output Level / Impedance	Tape rec : 200mV/1k Ω
Frequency characteristic	Phono MM : 20 Hz to 20 kHz ± 0.3 dB CD, Tuner, Line, Tape : 1.5 hz to 400 khz + 0 -3dB
S/N (IHF, A-network Short circuit)	Phono MM:84dB CD, Tuner, Line, Tape : 105 dB
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption (Electrical Appliance and Material Control Law)	200W
External dimensions	Width 440x Height 164x Depth 479 mm
Weight	23.3kg