DENON PMA-740
¥ 59,800 (released in 1983)
Commentary
Stereo pre-main amplifier with non-feedback 0 db amplifier.
Equipped with a non-feedback 0 db power amplifier that eliminates negative feedback loops.
This system is an application of the non-feedback technology developed in POA-8000, and uses a direct distortion servo circuit. The direct distortion servo circuit compares the input signal with the signal obtained from the output side (main signal + distortion component) to detect only the distortion component, and then applies the inverted phase of this distortion component to the input side.
This action drives the static distortion into the 0 region, and the noise appearing at the output side of the amplifier is treated as a difference from the input signal and is removed in the same way as the distortion component.
As a result, there is no signal feedback and no time delay, so the dynamic distortion which affects the auditory quality is suppressed. In addition, since there is no NFB circuit, it is not affected by the back electromotive force from the speaker, so the increase and generation of the distortion when the speaker is connected are suppressed.
A Pc150W power transistor is used for the power amplifier section.
In order to cope with the high dynamic range of digital sources, we have adopted a large transformer with multiple shields, a large capacitor of 20,000 μ F, and a fast recovery diode for the power supply.
The equalizer section is equipped with a unique super-equalizer to achieve a wide bandwidth.
Built-in high-speed protection circuit.
Model Rating
Type | Pre-main amplifier |
Power Amplifier Unit | |
Circuit system | Non-feedback 0 db power amplifier system |
Rated output (both channel drive Sine wave continuous output, 20 Hz to 20 kHz) |
120W + 120W (6 Ω) 105W + 105W (8 Ω) |
Input Sensitivity / Impedance | 150mV/30k Ω |
Total harmonic distortion rate (20 Hz to 20 kHz) | 0.005% or Less (at Rated Output -3dB) |
Intermodulation distortion factor (60 hz : 7 khz = 4 : 1) | 0.0025% or Less (at Rated Output Equivalent Amplitude Output) |
TIM distortion factor | Below the measurement limit |
Slew rate | ± 200 V / μ s or more |
Output Bandwidth (IHF, both channel drives) | 5 Hz ~ 80 kHz (THD 0.03%) |
Frequency response (at 1W output) | 4 Hz ~ 150 kHz + 0 -3dB |
Output Impedance (1 kHz) | 0.1 Ω |
Output terminal | Speaker AORb : 6 Ω ~ 16 Ω Speaker A + B : 12 Ω ~ 16 Ω Headphone : 410mW/8 Ω |
Preamplifier Section | |
Circuit system | Super equalizer system |
Input Sensitivity / Impedance | Phono MM : 2.5mV/47k Ω Phono MC : 0.2mV/100 Ω Tuner, DAD/Aux, Tape : 150mV/30k Ω |
Maximum Output / Rated Output | 10V/150mV |
RIAA Deviation (MC) | 20 Hz to 100 kHz ± 0.3 dB |
Total Harmonic Distortion Factor (at 1 khz, 8 v output) | Not more than 0.002% |
<General> | |
SN ratio (IHF-A, input short circuit) | Phono MM : 86 dB (at 2.5 mV input) Phono MC : 70 dB (at 0.25 mV input) Tuner, DAD/Aux, Tape : 106 dB at 150 mV input |
Tone control | Bass : ± 8 dB (100 Hz) Treble : ± 8 dB (10 kHz) |
Muting | -20dB |
Loudness property | Low frequency : + 7 dB (100 Hz) High frequency : + 6 dB (10 kHz) |
Pwer | 100 VAC, 50Hz/60Hz |
Power consumption (Electrical Appliance and Material Control Law) | 195W |
External Dimensions (including legs, knobs, terminals) | Width 434x Height 112x Depth 398 mm |
Weight | 10.2kg |