Audio Database

The

Pioneer A-717
79,800yen(1987 release)

Description
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The Integrated Amplifier which aimed at the review from fundamental viewpoints, such as a circuitry, a construction, physical properties, etc. which are the origins of amplifier, and was developed as the compilation in order to correspond to the digital source.

The design concept of this amplifier is roughly divided and is collected by three points.
First, in order to make a signal path into the shortest distance, consideration is carried out to the placement of each signal block. Next, thorough measure against vibration proof and measures against absent-resonance-ized are taken. And the improvement in the speaker drive capacity at the time of a low load intensity is achieved.

First, in order to make a signal path into the shortest distance, the structure called a direct construction is adopted.
This is making each circuitry block separate and shielding-izing an I/O block, and has prevented ill effects, such as a failure of the signal in the interior, and an interference between signals.
In input block, it was considered as the structure which can operate mechanically an input & recording selector and a main volume by remote control, and shortest-ization of leading about of a signal path is attained. Furthermore, since a signal will not flow into the front panel side if the input signal chosen with the input selector turns ON a Source-Direct switchpoint, a purer sound can be enjoyed.
A power amplifier block is arranged along with the fluence of a signal, and leads the output of the power stage to a speaker selector straight. Here, distance from a power-source part is made into the shortest.
The speaker selector block is also attaining direct attachment shortest-ization for the speaker termination to the substrate which attached the relay. As a result, priority is given to the shortest-ized speaker termination A, and A termination is arranged at the bottom.

Since no vibrating and absent-resonance-ization are put into practice, the absent-resonance-ized construction has been adopted, four kinds of honeycomb form is adopted, a transformer part and a volume system are also united, and the oscillation and the vibration are lessened in total.
It is in a bottom plate or a bonnet case about the honeycomb by punching. In order to suppress an oscillation and vibration of a power transistor effectively, it is an extrusion honeycomb heat sink of aluminum. In order to stop an extraneous vibration, the honeycomb by resin shaping is adopted as a large-sized honeycomb insulator, respectively.
Moreover, in the transformer case, the shielding effect was high, the internal loss was high at the high rigidity, it excelled in the periodic-damping property, and cast iron with almost no resonance frequency is adopted. While being filled up with a thermally conductive good pitch material between this cast iron case and the main unit of a transformer, the heat-dissipation fan was prepared and the incrementation in the internal resistance of the transformer coil by a temperature rise is prevented.
Furthermore, it was hard to cause electromagnetic induction and the mass newly developed seal dead capacitor which is hard to receive is adopted.

Since it has an ill effect on a tone quality, the way of maintaining a weight balance in bothways focusing on the bearing of the rotary knob of a volume is adopted, and a mechanical stress is kept from starting a volume main unit with the structure where a loading is applied to the axis of a volume or an oscillation is caused. Moreover, in order to suppress the influence of an oscillation of amplifier to a min, the floating of the shielding cover supporting a volume platform is carried out from a body section with a special paper, and a 2-4kHz vibration harmful to a tone quality is absorbed.

Non switching circuit type dBASE III is adopted.
The switching skewness made type IBM PCN II which is not generated theoretically upgrade further, this circuitry stabilized the idle current which carries out a drift by transition of outside temperature etc. in an instant immediately after power-switch ON and at the time of the Taishin number input, and it has succeeded in suppressing an occurrence of thermal distortion.
Moreover, a detection and correction of the difference of the input/output signals of the power stage are raised, and nonlinear distortion is reduced, and also the voltage amplification stage and the power amplification stage are separated clearly, and the power amplification stage does not have influence in the voltage amplification stage by concentrating on a speaker drive at the time of the Oide power, and is improving the speaker drive capacity at the time of a low load intensity.

The newly developed seal dead capacitor that connected the aluminum case with the cathode of the aluminum electrolytic capacitor more certainly is adopted. By shielding a capacitor element powerfully, running out of the noise from the capacitor itself was lost, and high S/N is realized.

The Phono equalizer could be turned OFF when not hearing a record, and it has prevented the unnecessary noise occurrence.
Moreover, the OFF functionality is also given to the recording selector and the purity of sound is raised by using simple circuitry.
An equalizer part has improved S/N by adoption of low-noise Hi-gm FET etc. while stabilizing an operation in inside and a quantity region by adopting an original NF-CR type circuitry.

The component partses of a copper plating are adopted as a rear-panel fraction, a bottom plate fraction, etc. for the distorted measure against an electromagnetic, and an oscillating measure.

The polar attached-indicator oxygen-free-high-conductivity-copper very-thick power cord is adopted as a power cord. This code is adopting a material with a low dielectric constant as an insulating material, and making the capacitance of a power cord small, and is suppressing the influence of external noise.
Moreover, the polarity of the coil of a transformer is managed and the noise which enters through a code is also held down to the min.

The part which thought as important tone qualities, such as a fuse for audios, is adopted.

An aluminum Naked began to delete to a rotary knob, and elegance is adopted.

Internal
Electrolytic
Seal
Insulator
The Input
Honeycomb
Power
Honeycomb
Oxygen-free-high-conductivity-copper The

Rating of a mode
Form Stereo Integrated Amplifier
Effective output
(Both channel drive, 20Hz - 20kHz)
100W+100W (0.003%, 8ohm)
120W+120W (0.003%, 6ohm)
150W+150W (0.005%, 4ohm)
Dumping factor (1kHz, 8ohm) 200
Input sensitivity/impedance Phono MC: 0.2mV/100 ohm
Phono man month: 2.5mV / 50kohm
compact disk, Tuner, Line, Tape:150mV /, 50kohm
Phono maximum permissible input
(THD 0.008%, 1kHz)
Phono MC:19mV
Phono MM:200mV
An Output voltage/impedance Tape Rec, ADPT Out:150mV /, 2.2kohm
Frequency characteristic Phono MC: 20Hz-20kHz}0.3dB
Phono man month: 20Hz-20kHz}0.2dB
compact disk, Tuner, Line, and Tape:1Hz-150kHz+0 -3 dB
Tone control (-40dB) Bass: }8dB (100Hz)
Treble: }8dB (10kHz)
Subsonic Filter 5Hz(12dB/oct)
Loudness contour (-40dB) 100Hz/10kHz(5dB/3dB
S/N
(An IHFA network, a short circuit)
Phono MC:71dB(0.25mV)
Phono MM:89dB(2.5mV
compact disk, Tuner, Line, DAT/Tape1, Tape2:108dB
Speaker load impedance 4ohm-16ohm
Supply voltage AC100V, 50Hz/60Hz
AC outlet Power-switch interlock: Two lines (200W)
Power-switch un-interlocking.: One line (100W)
Power consumption (Electrical Appliance and Material Control Law) 270W
Dimensions Width 420x height 162x depth of 435mm
Weight 19.6kg