Audio Database

The

DENON PMA-790
178,000yen(1982 release)

Description
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The Integrated Amplifier which aimed at correspondence to digital sauce by the powerful construction centering on the power amplifier unreturned [ of 0dB ].

The power amplifier which eliminated the negative return loop unreturned [ of 0dB ] is carried.
This system is a thing adapting the technology developed by POA-8000 in which it does not return, and has structure using a direct distortion servo circuit. A direct distortion servo circuit compares the signal (main signal + distorted ingredient) and incoming signal which are acquired from the output side, detects only a distorted ingredient, then carries out phase inversion of this distorted ingredient, and is adding it to the input side.
Static distortion is driven into the domain of zero by this operation. Moreover, the noise which appears in the output side of amplifier was also regarded as a difference with an incoming signal, and is removed. [ as well as a distorted ingredient ]
Since there is no feedback of a signal and time delay does not arise by this, dynamic distortion which affects the Hearing impression quality is suppressed. Moreover, in order that there may be no NFB circuit, it is not influenced by the back electromotive force from a speaker, but the distorted increase and generating at the time of speaker connection are suppressed.

In PMA-790, in order to aim at correspondence to digital sauce, the direct distortion servo circuit used as the core of a non-feedback system was polished up thoroughly, and the slew rate of the circuit itself is improved. Furthermore, the transmission speed of a signal is sharply raised by attaining high purity-ization of a signal system, such as removing all coupling capacitors and having perfect direct-current composition, from all the signal courses of resulting in a speaker terminal from the input terminal for MC cartridges.

The circuit composition of the voltage magnification stage of a power amplifier part uses the first rank as the 3 steps of differential current mirror by low noise FET, it is attaining low impedance-ization by the complimentary emitter-follower, and the influence of an electric power magnification stage is considering it as the composition which is less than a voltage magnification stage.
Moreover, the last output stage has parallel push pull composition by the power transistor of Pc130W, and also was made into the direct Class-A by the zero crossing linear bias circuit of DENON original, and has canceled generating of switching distortion.

The 600VA class large-sized toroidal transformer, the 66,000-micro F mass condenser, and the fast recovery diode are adopted as a power-source part.

While an equalizer amplifier part gains the high signal to noise ratio because the first rank considers it as 2 parallel differential amplification which uses four low noise FET,The cascode bootstrap was constituted, the distorted increase produced by the impedance rise of the crown compass in the case of MM cartridge was pressed down, and broadband-ization is realized.
Moreover, MC input prepares two positions of High and Low, and is aiming at correspondence to various cartridges.

The dual listening mechanism which switches two cartridges freely and can try listening them is carried.

The broadband real-time tone control which suppressed quality degradation is carried.

The high-speed protection circuit is carried.

Internal

Rating of a mode
Form Integrated Amplifier
<Power amplifier part>
Circuit system Unreturned [ of 0dB ] power amplifier system
Output power (both channel drive)
A sine wave continuation output, 20Hz - 20kHz
240W+240W (4ohms)
200W+200W (6ohms)
150W+150W (8ohms)
Input sensitivity/impedance 150mV/47kohm
THD 0.002% or less (20Hz - 20kHz, Output-power-3dB o'clock)
Cross modulation distortion (60Hz:7kHz=4:1) 0.0015% or less (at the time of an Output-power equivalent amplitude output)
TIM distortion Below a measurement limit
Slew rate }350v/microsecond or more
Output bandwidth (IHF, both channel drive) 5Hz - 80kHz (THD 0.015%)
Frequency response (at the time of 1W output) 1Hz-300kHz+0 -3 dB
Output load impedance (1kHz) 0.1ohm
Output terminal Speaker AorB: 4ohms - 16ohms
Speaker A+B: 8ohm-16ohm
Headphone: 590mW/eight ohms
<Preamplifier part>
Circuit system Broadband equalizer system
Input sensitivity/impedance Phono MM: 2.5mV/47kohm
Phono MC high: 0.25mV/100 ohms
Phono MC low: 0.125mV/100 ohms
Tuner, DAD/Aux, Tape:150mV/47kohm
The maximum except take-off/Output power 12V/150mV
RIAA deflection (MC/MM) 20Hz-100kHz}0.2dB
THD (at the time of 1kHz and 8V output) 0.001% or less
<Synthesis>
Signal to noise ratio (IHF-A, input short circuit) Phono MM: 90dB (at the time of a 2.5mV input)
Phono MC: 75dB (at the time of a 0.25mV input)
Tuner, DAD/Aux, Tape: 110dB (at the time of a 150mV input)
Tone control Bass: }8dB (50Hz/100Hz)
Treble: }8dB (10kHz/20kHz)
Subsonic Filter 18Hz, 6 dB/oct
Muting -20dB
Loudness characteristic Low-pass: +7dB (100Hz)
High region: +6dB (10kHz)
Power source AC100V, 50Hz/60Hz
Power consumption
(Electrical Appliance and Material Control Law)
380W
Dimensions (a base, a knob, a terminal included) Width 506x height 168x depth of 451mm
Weight 20kg