Pioneer A-90D

Commentary

The EX series stereo prestereo pre-main amplifier with built-in D/A converter and improved internal construction to eliminate factors that cause noise and distortion.

Digital input / output is equipped with two optical input systems and one optical output system.
In order to prevent the pulse width from changing when the optical fiber is bent or vibrated, an optical transmission distortion correction circuit is mounted on the input side and output side respectively to reduce noise.

In the DAC section, the phase difference is eliminated by mounting a D/A converter for each L/R, and the separation is improved by separating the L/R.
This D/A converter employs a specially developed glitch less IC that minimizes the occurrence of glitches. This eliminates the analog switch called a digricher, thereby improving performance and sound quality.
Furthermore, by adding an MSB error correction circuit to each IC, the linearity at the 0 cross point is greatly improved.
In addition, in order to prevent degradation of sound quality due to jitter (fluctuation of the clock edge), a PLL with an extremely high jitter suppression effect is adopted for the PLL that generates the clock, and the oscillation circuit is bonded with special resin in order to avoid the effect of vibration.
When the D/A converter operates, only one master clock system is used, and the generation of unnecessary beat components is suppressed by eliminating other asynchronous clocks (such as microcomputer clocks).

The digital filter over-samples by a factor of four to push unwanted high-frequency components into higher bands and eliminate aliasing noise.
The digital filter uses a high-performance IC to achieve an in-band ripple within ± 0.0001 dB and an attenuation error of 100 dB.

The low-pass filter consists of a 5th-order Butterworth low-pass filter with excellent phase characteristics, which is composed of FDNR discrete circuits to reduce phase distortion as well as smooth characteristics.
We are also working to improve sound quality by using high-quality parts and grounding with oxygen-free copper bus bars.

Equipped with a digital recording selector that allows you to record a digital signal on the DAT that is independent of the sound coming from the speakers (this function is only available when watching analog sources).

Digital circuits such as data demodulation, PLL, and digital filter are separated from analog sections such as D/A converter and analog low-pass filter by a separate board, and the digital section is shielded.
In addition, by separating the power supply for the digital circuit and microcomputer from the power supply for the analog system from the transformer, we prevent interference with the analog system, which causes deterioration of sound quality.

It uses direct construction to minimize the signal path and ensure proper positioning.
First, the digital part and analog part are separated, and the signal path after the analog signal becomes the shortest like other analog sources. In addition, each input block is separated and the input / output block is shielded to prevent internal signal degradation and interference.
In the input block, the input and recording selector can be controlled electrically, and the main volume can be controlled mechanically. Thus, the signal path can be minimized. Input sources other than the Adapt/Tape2 jacks can be directly transferred to the main volume by turning ON the Source Direct Switch, so that you can enjoy more pure sound.
The power amplifier block is laid out along the signal flow and guides the output of the power stage directly to the speaker selector. Again, the wiring distance from the power supply is minimized.
In the speaker selector block, the terminals are directly attached to the board on which the relay is attached. In order to minimize the number of terminals, and to give priority to terminal A, the terminal A is placed on the board with terminal A as opposed to the conventional terminal position.

In order to minimize vibration, we have adopted a unique honeycomb shape for the frame chassis.
In order to prevent vibration and resonance of the power transformer, the honeycomb formed by drawing is used for the transformer frame and frame chassis, and the honeycomb formed by punching is used for the bottom plate and bonnet case. In addition, to effectively suppress vibration and resonance of the power transistor, the extruded aluminum honeycomb of the chimney type is used as a heat sink. To suppress external vibration, four large honeycomb insulators made by resin molding are used. In addition, a fifth insulator made of cast iron is used to support the heavy transformer.
In addition, cast iron is used for the transformer case, and pitch material with good thermal conductivity is filled between the cast iron case and the transformer body, and heat radiation fins are provided to prevent the internal resistance of the transformer winding from increasing due to temperature rise.
In addition, it uses a newly developed large-capacity sealed capacitor that is less susceptible to electromagnetic induction.
For the volume, a method of balancing the weight in both directions around the bearing of the rotary knob is adopted. In order to prevent any mechanical stress from being applied to the volume body, and in order to minimize the effect of the vibration of the amplifier, the shield cover supporting the volume substrate is floated from the body part with special paper, and harmful resonance of 2-4kHz is absorbed.

Non-switching circuit TypeIII is adopted, in which switching distortion does not occur in principle.
In addition to stabilizing the idle current, which has been drifting due to changes in the outside air temperature or when a large signal is input or just after the power switch is turned on, the voltage and power stages are clearly separated to improve the speaker drive performance under low load conditions.

It uses a newly developed sealed capacitor in which the cathode of the aluminum electrolytic capacitor and the aluminum case are connected more securely, and the capacitor element is strongly shielded.
This eliminates noise and noise from the capacitor itself, resulting in a high S/N.

The Phono equalizer automatically turns OFF when you do not listen to a record, preventing unwanted noise and improving the sound quality of other sources.
The recording selector also has an ON/OFF function. It operates only when the TONE direct switch is turned ON, and then the clock stops.
A hybrid MC transformer is used for the Phono equalizer circuit.

Copper plating is used for rear panel, bottom plate, transformer frame, speaker terminal and block shield case in order to eliminate electro-striction and reduce vibration.

Uses an extra-thick power cord with OFC polarity display.
In addition, high-quality parts such as audio fuses, rotary knobs made of pure aluminum, gold-plated input / output terminals, and large-size vise terminals are introduced.

Model Rating

Type	Pre-main amplifier with built-in D/A converter
Amplifier Unit
Rated Output (Double-channel Drive, 20 Hz to 20 kHz)	180W + 180W (4 Ω, 0.005%) 150W + 150W (6 ohm, 0.003%) 120W + 120W (8 Ω, 0.003%)
Dynamic Power	400W + 400W (2 Ω) 280W + 280W (4 Ω) 160W + 160W (8 Ω)
Harmonic distortion factor (20 Hz to 20 kHz)	0.003% (8 Ω)
Input Sensitivity / Impedance	Phono MM : 2.5mV/50k Ω Phono MC : 0.25mV/40 Ω CD, Tuner, Line, Tape : 150mV/50k Ω
Maximum Allowable Input (1 kHz, 0.008%)	Phono MM:200mV Phono MC:20mV
Output Level / Impedance	Tape Rec, Rec Out : 150mV/0.8k Ω
Frequency characteristic	Phono MM : 20 Hz to 20 kHz ± 0.2 dB Phono MC : 20 Hz to 20 kHz ± 0.3 dB CD, Tuner : 1 hz to 200 khz + 0 to 3 db
Tone Control (Volume -40dB)	Bass : 100 Hz, ± 8 dB Treble : 10 kHz, ± 8 dB
Subsonic filter	7 Hz, 6dB/oct.
Loudness contour (Volume -40dB)	100 Hz : 5 dB, 10 kHz : 3 dB
S/N ratio (IHF, A-Network, short circuit)	Phono MM : 95 dB at 5 mV Phono MC : 83 dB at 0.5 mV CD, Tuner, Line, DAT/Tape1, 2 : 110 dB
<General>
Power supply voltage	100 VAC, 50Hz/60Hz
AC outlet	Power switch interlock : 2 systems (200W) Power switch not linked : 1 system (100W)
Power consumption (Electrical Appliance and Material Control Law)	365W
External dimensions	Width 457x Height 173x Depth 475 mm
Weight	29.3kg