DENON PMA-540

Commentary

Pre-main amplifier with super equalizer and real drive circuit.

When using MC cartridges as well as MM cartridges, capacitors are removed from all stages of the signal path from the phono input terminal to the speaker output terminal.
The fully capacitorless configuration is realized by adopting the direct DC servo circuit that is also included in the PMA 970. It effectively shuts out DC drift and ensures stability in the ultra-low frequency range.

The EQ amplifier section is equipped with a super-equalizer that combines the advantages of the NF (feedback type) and CR (non-feedback type) types, thereby achieving excellent RIAA deviation.
The super equalizer consists of an NF-type DC amplifier with low-noise dual FET and a CR-type equalizing filter. The first stage consists of parallel differential amplification with dual FET of direct DC servo system. This eliminates DC temperature drift while improving S/N and distortion factor.

A real drive circuit is mounted to reduce distortion factor.
This circuit focuses on the operation of the amplifier at the time of mounting the speaker and reduces the distortion of the amplifier at the time of reactive load. It realizes good characteristics even at high power and low distortion.

The power amplifier consists of a first stage low-noise FET differential-direct-DC servo system + two stage transistor differential-3-stage pre-driver + Darlington connection complimentary service push-pull.
In addition, it is equipped with a 0 cross linear bias circuit and a built-in high-speed thermal feedback circuit to further enhance the merits of the non-switching system. It stabilizes the bias quickly from power-on and realizes high stability against external factors such as temperature such as temperature change and time lapse. It not only eliminates switching distortion but also reduces crossover distortion.

The tone circuit has a real-time tone control circuit.
This circuit consists of only the passive elements necessary for tone control, and by incorporating them into the power amplifier, large capacitors harmful to sound quality are removed from the signal path.

The power supply consists of a multi-shielded power transformer and a 30,000 μ F block capacitor.

In order to reduce magnetic materials as much as possible, an L-angle and an aluminum radiator are combined, and the inside of the amplifier is organized neatly.
In addition, the advantage of a simple circuit is improved by remote control of the input switching section to greatly shorten the signal path.

It is equipped with a direct couple switch.

In addition to the Rec out off function that eliminates the effect on sound quality, it is equipped with a subsonic filter and loudness control.

Model Rating

Type	Pre-main amplifier
<Power Amplifier Unit (Tuner in → SP out)>
Rated Output (Double-channel Drive, Sine Wave Continuous Output, 20 Hz to 20 kHz)	100W + 100W (4 Ω) 80W + 80W (8 Ω)
Input Sensitivity / Impedance	150mV/40k Ω
Total Harmonic Distortion Factor (20 Hz to 20 kHz, Rated Output -3dB)	Not more than 0.007%
Intermodulation distortion factor (60 Hz : 7 kHz = 4 : 1, equivalent to rated output)	Not more than 0.005%
Output Bandwidth (IHF, both channel drives)	4 Hz ~ 100 kHz (THD0.1%)
Frequency response (at 1W output)	1.5 Hz ~ 250 kHz + 0 -3dB
Output Impedance (1 kHz)	0.08 Ω
Speaker output	AORb : 4 Ω ~ 16 Ω A + B : 8 Ω ~ 16 Ω
Preamplifier Section (Phono In → Rec Out Excluding Input Sensitivity / Impedance)
Input Sensitivity / Impedance	Phono MM : 2.5mV/50k Ω Phono MC : 0.25mV/100 Ω Tuner, AUX, Tape : 150mV/40k Ω
Maximum Output / Rated Output	10V/150mV
RIAA deviation (MM, MC)	20 Hz to 100 kHz ± 0.2 dB
Total Harmonic Distortion Factor (1 kHz at 6 V output)	Not more than 0.002%
<General>
SN ratio (IHF-A, input short circuit)	Phono MM : 88 dB at 2.5 mV input Phono MC : 72 dB (at 0.25 mV input) Tuner, AUX, Tape : 106 dB
Tone control	Bass : ± 8 dB (100 Hz) Treble : ± 8 dB (10 kHz)
Subsonic filter	18 Hz, 6dB/oct.
Loudness control	100 Hz : + 7.5 dB, 10 kHz : + 5.5 dB
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption (Electrical Appliance and Material Control Law)	210W
External dimensions	Width 434x Height 112x Depth 390 mm
Weight	9.7kg