Audio Database

The

DENON PRA-2000
200,000yen(1979 release)

Description
 
Control amplifier which challenged the limit of the disc play and carries real-time equalizer amplifier.

The no returning type real-time equalizer amplifier into which CR type was developed further is adopted as an equalizer part.
Composition consisted of two steps of direct-current linear amplifier and CR type equalizing filter of interstage by newly developed low-noise FET, FET of the first rank considered it as parallel differential, and the cascode bootstrap circuit which prevents degradation of the characteristic in a high region is adopted, improving S/N sharply.
Removed the input coupling capacitor and not only [ furthermore, ] lost coloring of the sound by a capacitor.The 150V high-voltage-power-supply operation and the interval with high output and a high-speed transistor which are called Pc800 mW-fT120MHz have realized the high output and the extensive dynamic range of a clipping level 47V.
Moreover, low impedance-ization of CR type equalizing filter has attained high S/N.
A polypropylene form capacitor and ±1% class metal tunic vapor deposition resistance are adopted as CR element.

Phono3 terminal has structure linking directly to MC head amplifier of transistor 22 stone composition.
This head amplifier part has circuit composition equivalent to highest-class head amplifier HA-1000 of DENON, such as carrying out multistage type parallel connection of the PNP type low noise transistor advantageous to the reduction in noise to the first rank.
Furthermore, in order to secure the engine performance as exclusive MC head amplifier, it has a regulated power supply of ±15V equipped with the booster which increases a supply power source in a head amplifier board, power-source impedance is held down to the minimum, and high S/N and high speed-ization are attained.

The low impedance volume circuit of 10kohm is adopted as a flat amplifier part.
This is involved with degradation of S/N by high resistance thermal noise, and a Miller effect with a transistor,The demerit considered in high impedance volumes, such as formation of the high cut filter by the stray capacitance of distorted increase, high manual training, and wiring etc. and aggravation of a slew-rate rise time, is canceled.
Moreover, the direct direct-current servo system is adopted, and by the servo return circuit replaced with the parallel composition of first rank FET differential amplifier, and the amplifier only for a servo, while attaining low distortion and high S/N-ization, the output coupling capacitor is removed.

Each selector switch serves as a soft push type of the electronic adoption which changes by light touch in consideration of operativity.
It arranges in the position which does not receive the influence of leading about of reed relay with few secular changes of audio signal wiring, and consideration of a sound quality side is aimed at.
Moreover, a one shot trigger circuit works at the time of a change, and compound functions, such as a one shot muting mechanism in which the power by the side of an output will be in an OFF state temporarily, are carried.

The large-sized toroidal transformer of 5-fold shield which took leakage flux into consideration to the rate of power source variation more than enough strongly is carried in the power-source part. This toroidal transformer serves as 1.2mm of diameter of winding wire phi capacity 50VA.

In order to send a high sound of the quality which eliminated unnecessary coloring to power amplifier, the signal from a disc has adopted the system direct sent to flat amplifier from equalizer amplifier, without passing along buffer amplifier. As for Phono each system, AUX, Tuner, and Tape are automatically connected to buffer amplifier by function change as it is to flat amplifier.
Furthermore, the object for the impedance matching of Tuner and Tape and the buffer amplifier for Subsonic 単数形 prevented generating of secondary higher-harmonic-wave distortion which has newly developed symmetrical type complimentary FET-direct current composition, and poses a problem, and have obtained quantity S/N. Moreover, while preventing distorted generating by the input return capacity of first rank FET, the cascode bootstrap circuit adopted also with equalizer amplifier is adopted for high-pressure operation of 150V.

The mutual intervention is prevented by arranging the right-and-left channel of each part on equal terms, and also separating a signal unit and a power-source part.
Moreover, MC head amplifier and equalizer amplifier including the shield between an amplifier part top board and a lower board are made into the two-step structure of aluminum board use for prevention of maintenance of high S/N, and magnetostriction.

The emergency protector circuit which protects the element of power amplifier at the time of abnormalities is carried.

The high-class part selected carefully in audios including lambda capacitor is adopted.

Functions, such as a Subsonic Filter and two-step muting, are carried.

Rear
Internal

Rating of a mode
Form Control amplifier
<MC head amplifier part (Phono3 ->rec out)>
Input sensitivity/impedance 0.125mV/100 ohms
Maximum permissible input 19mV(1kHz)
THD 0.003% or less (20Hz - 20kHz)
Frequency response 20Hz-100kHz±0.2dB
Signal to noise ratio (IHF-A) 79dB
Input conversion noise level -157dBV
Separation 70dB or more (20Hz - 20kHz)
Gain (only head amplifier part) 26dB
<Equalizer amplifier part (Phono1, 2 ->rec out)>
Input sensitivity/impedance 2.5mV/50kohm
The change to 100 ohms is possible for Phono2.
Maximum permissible input 380mV(1kHz)
The maximum except take-off/Output power 23V/150mV
THD 0.002% or less (20Hz - 20kHz, 4V output)
RIAA deflection 20Hz-100kHz±0.2dB
Signal to noise ratio (IHF-A) 86dB
Separation 100dB or more (20Hz - 1kHz)
90dB or more (20kHz)
Gain 35.6dB(1kHz)
<Preamplifier part (AUX->pre out)>
Input sensitivity/impedance Tuner, AUX, Tape1, 2:150mV/50kohm
Maximum permissible input 23V
The maximum except take-off/Output power 25V/1.5V
THD 0.002% or less (20Hz - 20kHz, 3V output)
Frequency response 10Hz-100kHz+0 -0.1 dB
10Hz-500kHz+0 -1 dB
Signal to noise ratio (IHF-A) 105dB or more
Separation (20Hz - 20kHz) 100dB or more (Volume MAX)
80dB or more (Volume-20dB)
Gain 20dB
Muting - 20dB&-infinity
Subsonic Filter 16Hz, 12 dB/oct
TIM distortion 0.003% or less
IM distortion 0.002% or less
<Synthesis>
The semiconductor used Transistor: 149 pieces
FET: 14 pieces
IC: One piece
Diode: 68 pieces
Rectification stack: Three pieces
Reed relay: Seven pieces
Relay: Two pieces
LED: Six pieces
AC outlet Power-switch linkage: Two lines
Power-switch un-interlocking.: One line
Power supply voltage AC100V, 50Hz/60Hz
Power consumption 38W
Dimensions Width 455x height 132x depth of 357mm
Weight 10.5kg
Attachment Low capacity connecting cord x1