Marantz 2245
The Marantz 2245 is a classic stereo receiver from the early 1970s and one of the first-generation models in the famous 22xx series.
The power amplifier is fully discrete and uses Motorola SJ2513 and SJ2514 TO-3 output transistors in a collector-output push-pull configuration. The power supply is filtered by two 9000µF capacitors. Speaker outputs are protected with a relay, and two pairs of speakers are supported.
The tuner section uses a 4-gang tuning capacitor and a discrete FM discriminator, except for the TA7060 IC. The stereo decoder is fully discrete.
The internal construction is robust and well organized. Components are accessible, but the boards do not have connectors, so not all sections are easily serviceable. The soundstage is warm and lush with non-fatiguing highs, a typical Marantz sound signature from the 1970s.
Manufacturer: Marantz
Status: Active company
Official website: marantz.com
General Specifications
Maximum power (8Ω): 45WFrequency response (-3dB): 7Hz-70kHz
THD: 0.3%
IMD: 0.3%
Signal to noise ratio (Line): 80dB
Input sensitivity (Line): 180mV
Input sensitivity (Phono): 1.8mV
Damping factor: 45
Speaker load impedance: 4Ω-16Ω
Dimensions (WHD): 440×137×356mm
Weight: 15.6kg
Produced: 1971-1976
Initial price: $450
Measured Values
Maximum power (8Ω): 53WFrequency response (20Hz-20kHz): <1.0dB
Channel imbalance: <1.0dB
THD (1kHz, 1W): 0.0054%
THD+N (1kHz, 1W): 0.023%
THD (1kHz, 20W): 0.0058%
THD+N (1kHz, 20W): 0.013%
IMD (70Hz, 5kHz, 1W): 0.018%
Noise: -62.1dB
Amplification: 110.9
DC offset L: -0.6mV
DC offset R: 1.5mV
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.
FM Tuner
Measurements of the tuner section were performed using an FM signal generator, with its output fed directly into the antenna input. AM measurements were not conducted.
