DENON PMA-950

Commentary

A pre-main amplifier that pursues high efficiency and high output while taking advantage of the quality of class A operation.

Although it is equipped with a class A power amplifier, it is equipped with a real bias circuit to achieve almost the same body size as an equivalent amplifier of class B operation.
Using the same principle as the POA 3000 and PMA 970, the real bias circuit uses a method in which the bias current rises before the signal current. This reduces power consumption by approximately 1/10 compared to the conventional method in which a large amount of bias current is supplied when there is no signal.

The power amplifier circuit consists of a low-noise FET parallel differential amplifier + direct DC servo in the first stage, and a pre-driver stage of differential amplifier 3-stage current mirror cascode bootstrap output with powerful drive capability in the second stage.

It is equipped with a real drive circuit to improve the phase difference between voltage and current when the speaker is actually loaded.
In this circuit, attention is paid to the operation of the amplifier when the speaker is mounted. In addition to parallel use of power transistors, a real drive line with electronic elements is installed in the protection circuit to eliminate signal loss at the time of a large signal. When a general speaker system is connected, distortion near the high-output fo is reduced by approximately 1/50.

The equalizer circuit consists of an NF-type DC amplifier with newly developed low-noise dual FET and a CR-type equalizing filter. The first stage is a 4-parallel differential amplifier circuit with direct DC servo dual FET to achieve low noise and high SN.
The first stage of the equalizer employs a cascode bootstrap circuit that is not affected by input impedance to reduce distortion.

Equipped with a highly stable original direct DC servo circuit, capacitors are removed from all signal paths from the MC input to the SP output.

The tone control section consists of only the passive elements necessary for tone control. By incorporating these passive elements into the power amplifier, a high-capacity capacitor, which is harmful to sound quality, is eliminated from the signal path, making the configuration simple.
In addition, the configuration of the main circuit is not affected even at the time of tone defeat.

The power supply section is equipped with a large toroidal transformer and a 44,000 μ F block capacitor.
In addition, in order to supply current to the left and right channels of the power stage under the same condition, the layout of the power current pure radiation construction method is adopted to shorten the wiring.
In addition, the power transformer is well shielded to minimize the influence on signal circuits and external devices.

Equipped with a high-speed protection circuit that doubles as a muting operation when the power switch is ON.

It is equipped with a headphone jack with a high / low impedance switching function.

It is equipped with functions such as a subsonic filter, loudness control, muting function and direct couple switch.

Brazilian Rosewood-style side wood is attached to the side.

Model Rating

Type	Pre-main amplifier
Power Amplifier Unit
Circuit system	Direct DC Servo System Denon Class A
Rated Output (Both Channels Driven, Sine Wave Continuous Output)	80W + 80W (8 Ω, 20 Hz to 20 kHz) 100W + 100W (4 Ω, 1 kHz)
Input Sensitivity / Impedance	150mV/40k Ω
Total harmonic distortion rate (60 Hz : 7 kHz = 4 : 1 at rated output)	Not more than 0.004%
Output Bandwidth (IHF, both channel drives)	5 Hz ~ 100 kHz (THD 0.03%)
Frequency response (at 1W output)	1 Hz ~ 250 kHz + 0 -3dB
Signal-to-noise ratio (IHF-A)	110dB
Output impedance	0.1 Ω or less
Slew rate	250 V / μ s
Preamplifier Section (Equalizer Amplifier)
Input Sensitivity / Impedance	Phono1, 2 mm : 2.5mV/47k Ω Phono1, 2 mc : 125 μ V/100 Ω Tuner, AUX, Tape1, 2 : 150mV/40k Ω
Maximum Output / Rated Output	10V/150mV
RIAA deviation	20 Hz ~ 100 kHz ± 0.2 dB (Both MM and MC)
Total harmonic distortion factor	0.001% (at 1 kHz, output 8 V)
<General>
SN ratio (IHF-A, input short circuit)	Phono1, 2 MM : 90 dB Phono1, 2 mc : 75 dB at 250 μ V input Tuner, AUX, Tape1, 2 : 110 dB
Tone control	Bass : + / - 8 dB (100 Hz) Treble : ± 8 dB (10 kHz)
Subsonic filter	18 Hz, 6dB/oct.
Loudness control	100 Hz : + 7 dB, 10 kHz : + 6 dB
Muting	-20dB
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption (Electrical Appliance and Material Control Law)	265W
External dimensions	Width 470x Height 140x Depth 410 mm
Weight	15kg