DENON PRA-6000
¥ 450,000 (released in 1982)
Commentary
Based on the development and design philosophy of real-time audio technology, this preamplifier incorporates pure non-feedback circuits in all stages from MC head amplifier to equalizer amplifier and final high-level amplifier.
The pure non-feedback circuit cancels the distortion of the output signal by combining the input transistor and the transistor operating in the reverse mode. The basic circuit is a single-stage amplifier circuit in which a constant current source is inserted at the common connection point of the N-channel FET and the PNP transistor and the P-channel FET and the NPN transistor.
Since the output current of the FET has a power transfer characteristic with respect to the input voltage, the distortion generated in the FET is only the second harmonic distortion. The distortion is canceled by combining the N-channel FET and the P-channel FET.
Two sets of pure non-feedback circuits are installed in the equalizer amplifier section to ensure high S/N, low distortion rate, and wide dynamic range. Furthermore, by utilizing the characteristics of current amplification, which is a feature of pure non-feedback circuits, and by combining high-precision C and R elements, ultra-wide band and high precision are realized.
The circuit consists of 16 ultra-low noise Hi gmFET and 30 transistors per channel.
The MC head amplifier uses carefully selected 16 ultra low-noise Hi-channel and 18 transistors (per one gmFET). It is superior to a dedicated head amplifier. It also uses a newly developed high-stability power supply and a floating power supply system that is not affected by power supply ripple to reduce noise.
The high-level amplifier section consists of a pure non-feedback circuit (and pure non-feedback tone control).
The tone control turnover frequency can be switched. In addition, at the defeat position, the tone control element is detached and the transmission characteristic becomes flat.
A 10k Ω low-impedance volume is used to prevent changes in transmission frequency characteristics, distortion, and deterioration of noise due to the position of the volume.
The signal path and each unit amplifier have symmetrical left and right channels and have a structure to shut out interference between the channels to obtain high separation.
In addition, a moisture-resistant glass epoxy board, a oxygen-free copper earth line, and a high-quality film capacitor are used to reduce the impedance of the power supply.
Non-magnetic aluminum plates are used in the main chassis of power transformers, MC head amplifiers and equalizer amplifiers to prevent magnetic distortion.
Each stage of the MC head amplifier, equalizer amplifier and high-level amplifier is equipped with a DC servo amplifier that eliminates unnecessary DC components, enabling direct playback without capacitors in all signal paths from the MC input to the pre-output.
The power transformer uses a large-capacity 100 VA toroidal transformer with very low leakage flux and excellent power supply fluctuation factor. The rectifier uses a 1.2A/200V fast-recovery type diode to speed up the power supply.
The ± 60 v power supply for the equalizer amplifier and high-level amplifier achieves high quality by using a 2,200 μ F/100V electrolytic capacitor, a stabilized power supply circuit with low noise and excellent response, a high-quality film capacitor, and a glass epoxy board.
In addition to the newly developed high-stability power supply using high-performance tracking regulator IC for the reference voltage, the power supply floating system is adopted for the drive power supply ± 30 v of the MC head amplifier to suppress noise generation.
The front panel uses 15 mm thick flat glass processed with high precision using special diamond processing technology, and the upper surface uses 6 mm thick smoked glass with printing on the back.
In addition, the side panel is treated with champagne gold and anodized.
Equipped with two subsonic filters.
It is equipped with a recording selector switch and a Rec off position to disconnect the tape recording terminal.
Equipped with a flashing indicator to display muting, noise is prevented when power is turned on / off or input selector is switched.
The muting circuit also has a manual switch to turn off the pre-output.
All input / output terminals are gold-plated.
Model Rating
Type | Stereo preamplifier | ||||
MC Head Amplifier Section (Phono1, 3 mc in to Rec out) | |||||
Input Sensitivity / Impedance | 0.125mV/100 Ω | ||||
Maximum Allowable Input (1 kHz) | 19mV | ||||
Total harmonic distortion factor | 0.002% or Less (20 Hz to 20 kHz) | ||||
Frequency response (RIAA deviation) | 10 Hz to 100 kHz ± 0.2 dB | ||||
Signal-to-noise ratio | 76 dB (input equivalent noise level -154dBV) | ||||
Equalizer Amplifier Section (Phono1, 2 mm in to Rec out) | |||||
Input Sensitivity / Impedance | 2.5mV/50k Ω * Phono2 can be switched to 100 Ω |
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Maximum Allowable Input (1 kHz) | 380mV | ||||
Maximum power output | 23V | ||||
Rated output | 150mV | ||||
Total harmonic distortion factor | 0.002% or Less (20 Hz ~ 20 kHz, at 2 V Output) | ||||
RIAA deviation | 10 Hz to 100 kHz ± 0.2 dB | ||||
Signal-to-noise ratio (IHF-A weight) | ± 380 V / μ sec | ||||
Separation | 20 Hz to 1 kHz : 80 dB or more 20 kHz : 70 dB or more |
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Gain | 35.6dB(1kHz) | ||||
High-Level Amplifier Section (Aux in to Pre out) | |||||
Input Sensitivity / Impedance | Tuner, Aux, DAD, Tape1, 2 : 150mV/50k Ω | ||||
Rated output | 1.5V | ||||
Total harmonic distortion factor | 0.002% or Less (20 Hz ~ 20 kHz, at 5 V Output) | ||||
Frequency characteristic | 2 Hz ~ 300 kHz + 0 -3dB 10 Hz ~ 100 kHz + 0 -0.3 dB |
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Signal-to-noise ratio (IHF-A weight) | 100dB | ||||
Separation |
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Tone control | Turnover frequency : 125Hz/2kHz, 125Hz/8kHz, 500Hz/2kHz, 500Hz/8kHz Points of increase / decrease : ± 0.5 db, ± 1.0 db, ± 2.0 db, ± 4.0 db, ± 8.0 db (at a frequency of 20 Hz and 20 kHz) |
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Muting | - ∞ (Muting display blinks) | ||||
Subsonic filter | 16 Hz, 12dB/oct. 20 Hz, 6dB/oct. |
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<Others> | |||||
Main Parts Used | Transistor : 171 units FET : 80 IC : 11 Diode : 123 units Rectifier stack : 1 Lead relay : 8 units Relays : 2 |
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Power supply voltage | 100 VAC, 50Hz/60Hz | ||||
AC outlet | Power switch interlock : Route 3, Total 210W Power switch not linked : 2 systems, Total 700W |
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Power consumption | 90W | ||||
External dimensions | Width 455x Height 134x Depth 392 mm (including height of knobs and legs) | ||||
Weight | 14.3kg | ||||
Attachment | Low-volume connection code |