Pioneer - A-91D Solid state integrated amplifier

Pioneer A-91D Urushi series in as good as new condition, part of my personal collection, with no reserve price.

Reference non-switching digital integrated amplifier

Here is an extraordinary amplifier ready for digital playback: the A-91D. It is even equipped with a digital circuit for Compact Disc.

With the A-91D, program signals follow the shortest direct path from one circuit to another, minimizing noise and preserving musical purity. We made this possible by ensuring that switching and actual control occur near the circuits or input terminals. A 'LINE DIRECT' switch further optimizes the signal path by connecting the input selector directly to the power amplifier, bypassing all intermediate circuits (except for volume control) both physically and electrically. This allows for exceptionally clear and pure reproduction from any source.

Lighter vibrations can cause slight sound degradation due to microscopic moving parts and devices. For this reason, we eliminated them by using a non-resonant frame, insulators, and a heat sink, all with a honeycomb structure. These elements also contribute to the rigidity of the entire frame. Using separate circuit blocks helps improve sound clarity by minimizing interference.

Our new type III non-volatile circuit offers excellent low-impedance driving capability combined with low distortion. Our exclusive power amplifier design provides additional benefits: first, it eliminates switching distortion to add clarity to the sound. Second, it fully stabilizes the idle current, so that distortion caused by thermal fluctuations is reduced to zero. Third, the distortion created by power transistors is reduced to 1/50 of the original value. Fourth, load variations are suppressed, and dynamic response is improved when absorbing large currents at low impedances, thanks to the separation of voltage and current amplification stages.

The A-91D is designed to drive low impedances of 6 or even 4 ohms with low distortion across a wide range of frequencies. Supporting it are two high-capacity power transformers. They are housed in cast iron, finned enclosures filled with damping agents that dissipate heat to prevent the increase in resistance and impedance that high temperatures can cause. They are also solid and non-resonant, and magnetically shielded to prevent magnetic radiation from affecting delicate signals.

In the A-91D, we have extended the digital advantages by including independent digital conversion circuits. There are two D/A converters (digital-to-analog) without glitches (one for each channel), a digital filter that uses a sampling frequency four times higher than normal (176.4 kHz), and an analog low-pass filter made with high-quality discrete components. Use the A-91D with a CD player with digital output, such as the Pioneer PD-M90X, and you will get digital sound in its purest form. It features six digital inputs and three digital outputs, of which two inputs and one output are equipped with optical interfaces to allow electrical isolation. An optical transfer distortion canceller has been added to eliminate jitter and ensure accurate optical transmission.

The A-91D delivers a continuous average output power of 120 watts per channel, minimum, at 8 ohms, from 20 Hz to 20,000 Hz, with total harmonic distortion not exceeding 0.003%.

General Data:
Producer: Pioneer
Model: A-91 D
Range of models: Urushi series
Type: Integrated amplifier
Years of manufacture: 1987 - 1991
Made in: Japan
Color: Black, sides in wood.
Energy consumption: 1,000 W
Dimensions: 457 x 173 x 457 mm (L x H x D)
Weight: 29.2 kg
Original price approximately: 2,500 German Marks.

Connections

Number of entries
1x Phono (Cinch): 2.5 mV / 50 kOhm (MM), 0.2 mV / 100 Ohm (MC).
CD, Tuner, Line 1, Line 2, 2x Tape In (Cinch): 150 mV / 50 kOhm
DAT1, ADTP/DAT2, Digital 1, 2, 3

Digital inputs: coaxial and optical
Number of releases:
Tape output 3x (Cinch): 150 mV / 2.2 kOhm
Digital outputs: coaxial and optical
Headphones (6.3 mm jack)
Two pairs of speakers.

Technical data

Continuous power (total harmonic distortion factor)
8 Ohm: 120 W (0.003%)
6 Ohm: 140 W (0.003%)
4 Ohm: 150 W (0.008%)
Dynamic power
8 Ohm: 150 W
4 Ohms: 170 W
Total harmonic distortion: 0.003%
Attenuation factor: 200 / 70 (8 Ohm, 1 kHz / 20 Hz - 20 kHz)
Frequency response: 5 - 80,000 Hz (0.05%, 8 Ohm)
Signal to Noise Ratio:
Stereo channel separation
Tone control
Bassi: yes, ±8db (100 Hz).
Alti: yes, ±8dB (10 kHz)

Sound intensity: yes, + 5 dB (100 Hz) / + 3 dB (10 kHz)
High filter: yes
Low filter (subsonic): yes, 17 Hz (12 dB/octave)
Yes
Straight/Line-Direct: yes

Special features:

Part of the D/A converter
Device from the Urushi series
Professional and insured shipping
Please make sure the photos are part of the description.
The shipping costs are higher given the weight of the object.