Marantz PM-25
The Marantz PM-25 is a 1980s integrated stereo amplifier designed for simple system setups and casual listening. It delivers clean, high-fidelity sound in a minimalist package, featuring a single pair of speaker terminals.
It includes Bass and Treble tone controls with a Tone Defeat option for a cleaner signal path, but does not feature a Loudness function. The output stage is built around 2SC4267 and 2SA1631 transistors, with relay-based speaker protection.
Manufacturer: Marantz
Status: Active company
Official website: marantz.com
General Specifications
Maximum power (8Ω): 30WFrequency response (±1dB): 10Hz-50kHz
THD (30W): <0.1%
IMD (30W): <0.03%
Signal to noise ratio (Line): 86dB
Signal to noise ratio (MM): 83dB
Input sensitivity (Line): 150mV
Input sensitivity (MM): 2.5mV
Damping factor: 200
Speaker load impedance: 8Ω-16Ω
Dimensions (WHD): 420×118×292mm
Weight: 5.3kg
Produced: 1982-1990
Initial price: 450DM
Measured Values
Maximum power (8Ω): 37WFrequency response (20Hz-20kHz): <1.0dB
Channel imbalance: <0.5dB
THD (1kHz, 1W): 0.0042%
THD+N (1kHz, 1W): 0.026%
THD (1kHz, 20W): 0.019%
THD+N (1kHz, 20W): 0.031%
IMD (70Hz, 5kHz, 1W): 0.026%
Noise: -70.7dB
Amplification: 106.3
DC offset L: -13.6mV
DC offset R: -14.2mV
Factory Specification Sheet
Factory specification images are sourced directly from the device's original service manual or user manual. These documents are produced by the manufacturer and provide authoritative information on the product's specifications.
Maximum Power
Maximum power is measured using 8Ω resistors on both channels. A 1kHz sine wave input signal is applied and gradually increased until higher harmonics rise significantly. Typically, this is the point at which output clipping occurs.
Frequency Response
Frequency response is measured using several equilizer settings. 'Flat' indicates the tone controls are either turned off or set to their neutral position. 'Max' and 'Min' refer to the maximum and minimum tone control positions, respectively. In the phono section, the expected response follows the RIAA equalization curve.
Residual Noise
These graphs display the noise levels at various volume positions. To eliminate any interference from the input signal, the input lines are shorted during the measurement. Generally, the noise is highest at the mid-point of the volume range (50%)
Distorsion
Total harmonic distortion (THD) is measured using a 1kHz sine wave input, with the output level adjusted to meet different conditions. Intermodulation distortion (IMD) is measured using 'two sine' input signal. THD versus voltage is measured with a 1kHz sine wave input, while THD versus frequency is measured at various output levels.
