DENON PMA-730
¥ 49,800 (around 1982)
Commentary
A stereo pre-main amplifier equipped with a non-feedback 0 dB power amplifier and super equalizer.
The non-feedback system is realized by a direct distortion servo circuit.
This servo circuit compares the input signal with the signal obtained from the output side (main signal + distortion component) to detect only the distortion component, inverts the phase of this distortion component, and adds it to the input side, reducing the static distortion to the theoretical 0 range.
Unlike the negative feedback (NFB) method, this non-feedback method does not return the output signal to the input side, so there is no dynamic distortion, no influence of the back electromotive force of the speaker, and the circuit can be simplified and high-speed.
In order to support low-impedance speakers, the power supply and power amplifier stages have been strengthened so that full-power playback can be performed safely up to 4 Ω speakers.
The power amplifier circuit consists of a two stage current mirror with a low-noise transistor for the first stage and a low-impedance complimentary service and emitter follower for complete separation from the power amplifier.
The power amplifier stage is a push-pull configuration of a high-speed power transistor for higher power.
The input of this power amplifier has a built-in filter that cuts out harmful ultra-low frequency noise.
A super-equalizer has been developed and installed to respond to wide-range cartridges and power amplifiers, realizing a frequency response of 100 kHz.
The first stage consists of differential amplification using a low-noise dual FET, and the second stage consists of an OP amplifier and a CR-type equalizing filter using a DC servo system.
In order to maximize the performance of the MC cartridge, the input condenser, which greatly influences the sound quality, is removed from the MC input terminal, and the condenser is completely removed from the Rec out. In addition, a higher gain is also provided.
Equipped with tone control, loudness control, and Rec out selector.
Equipped with high-speed protection circuit.
.JPG)
Model Rating
| Type | Pre-main amplifier |
| Power Amplifier Unit | |
| Circuit system | Non-feedback 0 db power amplifier system |
| Rated Output (Both Channels Driven, Sine Wave Continuous Output) | 60W + 60W (4 Ω ~ 8 Ω, 20 Hz ~ 20 kHz) |
| Input Sensitivity / Impedance | Tuner, Tape, Aux : 150mV/47k Ω |
| Total harmonic distortion rate (20 Hz to 20 kHz at rated output of -3dB) | Not more than 0.009% |
| Intermodulation distortion factor (60 hz : 7 khz = 4 : 1) | 0.005% or Less (at Rated Output Equivalent Amplitude Output) |
| TIM distortion factor | Below the measurement limit |
| Slew rate | 150 V / μ sec |
| Output Bandwidth (IHF, double-channel drive, THD 0.1%) | 5 Hz to 80 kHz |
| Frequency response (at 1W output) | 4 Hz ~ 150 kHz + 0 -3dB |
| Output Impedance (1 kHz) | 0.1 Ω |
| Output terminal | Speaker AORb : 4 Ω ~ 16 Ω Speaker A + B : 8 Ω ~ 16 Ω Headphone : 230mW/8 Ω |
| Preamplifier Section | |
| Circuit system | Super equalizer system using DC servo |
| Input Sensitivity / Impedance | Phono MM : 2.5mV/47k Ω Phono MC : 0.2mV/100 Ω |
| Maximum Output / Rated Output | 10V/150mV |
| RIAA deviation (both MC and MM) | 20 Hz to 100 kHz ± 0.3 dB |
| Total harmonic distortion factor | 0.002% or Less (at 1 kHz, 8 V Output) |
| <General> | |
| SN ratio (IHF-A, input short circuit) | Phono MM:86dB Phono MC:70dB Tuner, Aux, Tape : 106 dB |
| Tone control | Bass : ± 8 dB (100 Hz) Treble : ± 8 dB (10 kHz) |
| 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) | 150W |
| External dimensions | Width 434x Height 112x Depth 390 mm |
| Weight | 9kg |