DENON PRA-1003
¥ 93,000 (around 1977)
Commentary
This is a control amplifier that thoroughly reexamines the equalizer amplifier, which is important for record playback.
All stages of the ICL are connected directly to the equalizer amplifier section. Coupling capacitors are installed only at the output terminals. No coupling capacitors are used between the input terminals and stages. This allows for more faithful waveform transmission. The RIAA-NFB (negative feedback) element uses ± 1% metal film resistance and polypropylene capacitor to ensure highly accurate characteristics.
In the first stage, ultra-low-noise FET transistors are used in parallel to sufficiently suppress noise generation, and four transistors are used for differential amplification, which is received by emitter-follower transistors. This realizes an input-equivalent noise level of -138dB (V) and high S/N ratio.
The emitter-follower complimentary service is amplified by a class A push-pull current-mirror differential-circuit, and drives a pure push-pull output-stage. The power supply for this output-stage is ± 38 V high voltage. A 0.8W-class collector loss (Pc) output-transistor and a current mirror configuration that cancels out distortion combine to achieve a high saturation level of up to 20 Vrms.
The Phono2 has an impedance switching function, which can be switched according to the performance of the cartridge.
Each input terminal is grounded when the cord is not connected to it to prevent unpleasant noise.
In addition, in order to prevent contact noise that is likely to occur due to deterioration of plating, the contact surfaces of all input / output terminals are plated with gold. This plating is 0.5 microns thick, about two times thicker than normal plating, which reduces deterioration due to wear.
It can be connected to a Route 3 tape deck. The input / output terminals of Tape3 are provided on the front for easy connection.
You can record three decks simultaneously while listening to the Phono/Tuner/Aux source through the speakers, record Phono1 while listening to the Aux/Tuner, and record Tuner while listening to the Aux/Phono.
Tape-to-tape copying can be done in three ways : 1 → 2/3 simultaneous, 2 → 1, and 3 → 1.
The flat amplifier section has a gain of 16.5 dB and is normally a flat amplifier with a pure NFB of 90 dB. However, when tone control is required, the NFB resistor is switched to the tone control reactance.
The circuit consists of seven single-channel channels. The first stage is PNP-type differential-amplification, the second stage is NPN-type current-mirror-type differential-amplification, and the last stage is class A pure complimentary service push-pull.
The attenuator uses a 2-dB step type with a 21-click stopper.
This attenuator has a special design that does not degrade the high-frequency response when the volume is reduced. It also has a special structure that is shielded with a large gap between the left and right elements to eliminate channel interference.
The equalizer amplifier units are completely separated from each other on the left and right sides. At the same time, electrostatic interference between the channels is eliminated by a shield plate. In addition, the following switches are connected to ground by two circuits in the center of the six circuit type. This improves crosstalk.
A new common-emitter two stage amplifier circuit is used for the muting amplifier and holding circuit that senses power ON / OFF and activates the output relay. This circuit uses DC positive feedback to increase the initial operating current and eliminate relay operation delay caused by variations in the exciting voltage of the relay. This prevents pop noise caused by charge / discharge of the entire amplifier circuit.
The muting time is about 8 seconds.
It is equipped with a real headphone amplifier for monitor.
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Model Rating
| Type | Control amplifier | ||
| <MC/MM Equalizer Amplifier Section (Phono in-Rec out)> | |||
| Input Sensitivity / Impedance | Phono1 : 2.5mV/50k Ω Phono2 : 2.5mV/30k Ω, 50k Ω, 100k Ω |
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| Maximum allowable input | 320mV(1kHz) | ||
| Maximum power output | 20V | ||
| Rated output | 150mV | ||
| Total harmonic distortion factor |
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| RIAA deviation | 20 Hz to 20 kHz ± 0.2 dB | ||
| Signal-to-noise ratio (IHF-A network) | 86dB | ||
| Crosstalk | -100dB or less (20 Hz, 1 kHz) -90dB or less (20 kHz) |
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| Gain | 35.6dB(1kHz) | ||
| Flat Amplifier Section (CDin to Preout) | |||
| Input Sensitivity / Impedance | Tuner, Aux : 150mV/50k Ω Tape PB : 150mV/50k Ω |
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| Maximum power output | 10V | ||
| Rated output | 1V | ||
| Total harmonic distortion factor |
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| Transmission frequency characteristic | 10 Hz to 100 kHz + 0 -1dB 20 Hz to 20 kHz ± 0.5 dB (Tone Flat) |
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| Signal-to-noise ratio (IHF-A network) | 100 dB or more | ||
| Crosstalk | -100dB or less (20 Hz, 1 kHz) -85dB or less (20 kHz) |
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| Gain control | 0, -10, -20dB (0 dB = 16.5 dB) | ||
| Tape monitor | Route 3 | ||
| Tape copy | 1 → 3, 2 2 → 1 3 → 1 |
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| Tone control | Bass : ± 10 dB (50 Hz) Treble : ± 10 dB (20 kHz) |
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| Filter amplifier | Low : 20 Hz, 18dB/oct. High : 9 kHz, 6dB/oct. |
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| <General> | |||
| Crosstalk | -100dB (20 Hz, 1 kHz) -80dB(20kHz) |
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| Semiconductor used | 2SC1775x15 Pieces 2SA726x9 Pieces 2SA872x11 Pieces 2SC1313x5 Pieces 2SC1735x2 Pieces 2SA850x2 Pieces 2SC1626x1 pc 2SA816x1 pc 2SK68Ax8 ICx1 Piece Diode x30 pcs |
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| Power supply voltage | 100 VAC, 50Hz/60Hz | ||
| Power consumption | 9W (Electrical Appliance and Material Control Law) | ||
| External dimensions | Width 410x Height 170x Depth 270 mm (Including Knobs and Feet) | ||
| Weight | 7kg | ||
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