Marantz Model 240

Commentary

This is a power amplifier that has been completed with careful adjustment, gathering all the attention paid to everything from transistor selection to resistors and switches.

Differential amplification, pure complimentary service a differential-amplification, pure, and all-stage direct connection OCL circuit.
In both the differential amplifier stage and the push-pull output stage, transistors of a perfect pair selected for selection are adopted, and the basic circuit itself is adjusted so that it is perfectly balanced in DC.

In a high power amplifier, the operation close to class B is performed when the level is small, so notching distortion peculiar to transistor occurred.
In order to cope with this problem, sufficient idling current is supplied for class AB operation to realize bare characteristics that can be used without feedback.

Separate boards are used for each block to avoid interference between the first and last stages, and a sufficiently thick ground line is used.

Two smoothing capacitors of 60V20000 μ F are used for the power supply.

Model Rating

Type	Stereo power amplifier
Output (at rated output, both channels, 20 Hz to 20 kHz)	4 Ω : 300W (150W + 150W), Typically 340W 8 Ω : 250W (125W + 125W), Typically 280W 16 Ω : 128W (64W + 64W), Typically 150W
Total harmonic distortion factor	0.1% or Less (20 Hz to 20000 Hz, Rated Output) Typically 0.05%
Cross modulation distortion factor	0.1% or less (at rated output, any two frequencies from 20 Hz to 20 kHz) Typically 0.05%
Frequency characteristic	2 Hz ~ 100 kHz + 0 -1.5 dB 20 Hz ~ 20 kHz + 0 -0.5 dB
Power Band With (IHF)	5 Hz to 45000 Hz
Input Sensitivity / Impedance	1.5V/100k Ω
Damping factor	100 or More (8 Ω)
<General>
Total Noise	Better than 106 dB below rated power into 8 Ω
Pwer	100 VAC, 50Hz/60Hz 220Volts optional on special order
Power consumption	480W
External dimensions	Width 362x Height 156x Depth 241 mm
Weight	11.8kg