Marantz 1180

A stereo pre-main amplifier from Marantz built for low transient intermodulation distortion and wide-band performance.

Overview

The Marantz Model 1180 is a stereo pre-main amplifier designed to keep transient intermodulation distortion (TIM) low and hold stable, high-fidelity performance across a wide frequency range. Marantz paid close attention to DC stability and protection here. The power amplifier section is fully DC-coupled, and the circuitry is aimed at reducing phase distortion. The unit has a tone defeat switch, a loudness contour with Fletcher-Munson curve adjustment, and an independent Tape Copy circuit for dual-deck monitoring and duplication.

Specifications

Rated output (20 Hz to 20 kHz, both channel drive)	90W + 90W (8 Ω) 115W + 115W (4 Ω)
Frequency Response (20 Hz to 20 kHz)	+ 0, -0.2 dB
Total harmonic distortion factor	0.03%
Cross modulation distortion factor	0.03%
Damping factor	60
Input Sensitivity / Impedance Main amplifier input	1.5V/30k Ω
Input Sensitivity / Impedance Phono MM	1.8mV/47k Ω
Input Sensitivity / Impedance Microphone	1.8mV/47k Ω
Input Sensitivity / Impedance High level	180mV/25k Ω
Rated Output / Impedance Pre Out	1.5V/200 Ω
RIAA deviation (20 Hz to 20 kHz)	+ / - 0.2 dB
Tone control characteristics Bass (100 Hz)	+ / - 10 dB
Tone control characteristics Mid (700 Hz)	± 6 dB
Tone control characteristics Treble (10 kHz)	± 10 dB
Filter Low	15 Hz, 18dB/oct.
Filter High	9 kHz, 18dB/oct.
Power consumption	240W (Electrical Appliance and Material Control Law)
Power	100 V, 50Hz/60Hz
External dimensions	Width 416x Height 146x Depth 316 mm
Weight	15kg
Standard Walnut Cabinet	WC-110 (¥ 7,000)
Standard Mahogany Cabinet	WC-110N (¥ 12,000)

Design

The power section is a pure complementary OCL parallel push-pull 3-stage Darlington circuit in a DC configuration, built with low-noise components custom-made by Marantz. The first stage of the power amplifier is a differential amplification cascode bootstrap circuit with low-noise FETs, which keeps temperature and time drift down. The equalizer amplifier uses a 5-transistor configuration with a first-stage differential 3-stage direct-coupled circuit and specially designed low-noise elements. A Bessel filter gives a sharp 18dB/oct. roll-off at 9 kHz and 15 Hz with minimal phase distortion. The ESP circuit is inherited from the P510M. It protects against overcurrent, overvoltage and DC output by limiting the driver signals, so playback isn't interrupted. A 4-second relay delay prevents turn-on shock, and speaker protection disconnects the output if a transistor fails. A peak indicator helps with level setting to avoid clipping, and there is a DC/AC amplifier selection switch.

Context

The Marantz Model 1180 shares its ESP protection circuit with the P510M, which points to a direct design lineage within Marantz's high-end amplifier family of the late 1970s.