Marantz MODEL 1120 (circa 1972–1976)

A 60-watt integrated amplifier out of Sun Valley with a relay that watches the speakers, and a service manual that tells you how to keep it alive.

Overview

The Model 1120 weighs 12.2kg and measures 390 × 133 × 349mm. That is heavy for its footprint, and shallow enough for a shelf that would never hold one of the big receivers from the same era. It's a console stereo amplifier, meaning a pre-main integrated: phono stage, tone controls, and power amp in one chassis. Marantz built it in the U.S.A. It belongs to the company's solid-state generation, the one that followed the tube gear and preceded the receiver wars.

The headline number is 60W + 60W into 8Ω, both channels driven across 20Hz - 20kHz. That is double the power of the Model 1060, its smaller sibling in the line. The 1060 was a 30W-per-channel amp, and the 1120 was the step up for someone who wanted headroom without buying a receiver. Distortion is held to 0.2% or less at rated output for both total harmonic and SMPTE cross-modulation. Frequency response is flat to ±0.5dB from 20Hz to 20kHz at 1W. Power bandwidth runs from 10Hz to 40kHz, wider than the rated band, which suggests the output stage has room above and below the published figures.

Where the 1120 gets interesting is the electrical architecture. All stages of the power amplifier are directly connected — no output coupling capacitor in the signal path — built around a differential input stage whose two transistors are matched and thermally bonded into one unit so they track each other's temperature. Diode-based compensation handles drift, and a special air-core coil in the high-frequency path keeps the distortion factor from degrading up top. The output transistors were a special type developed jointly by Marantz and Motorola, which is the kind of detail that shows up in a service manual and nowhere else.

On paper the amp is quiet. Phono equivalent input noise is rated at 1.8μV or less, and the equivalent noise from the magnetic phono input all the way to the speaker terminals is specified as better than 140dB below 60W into an 8Ω load. Damping factor is 30 or more into 8Ω. That's not the highest figure of the era, but enough to keep most speakers of the period under control. Input sensitivity is 1.1mV on the low-level inputs and 110mV high-level, with 47kΩ impedance on phono and mic and 25kΩ on the high-level jacks. Gain is 60dB from phono to pre-out, 40dB from phono to record out, and 20dB from high level to pre-out. It runs on 100VAC at 50/60Hz and draws 200W.

Key Features

Relay Protection Borrowed from the Model 500

The protection circuit is the same type used in the Model 500. A relay monitors for leakage current to the speakers and opens if it finds any. The same relay timing delays speaker connection at power-on, which mutes the usual turn-on thump. Marantz used a special contact relay made in Austria to keep dust contamination and contact wear out of the equation. That's an unusual sourcing choice, and it shows up in the service documentation. The output devices are a current-sensor type that controls the current of the complementary stage, and a thermostat on the heatsink triggers if things get too hot. The service manual is blunt about it: never parallel the loudspeaker terminals of one channel with another, or the output devices will be damaged.

Direct-Coupled Differential Power Stage

Every stage of the power amp is directly connected, with a differential amplifier circuit at the top. Marantz matched the two transistors of that differential pair into a single thermally-bonded unit, a "perfect pair" in the company's phrasing, so both halves stay in the same thermal state. A diode on each part provides temperature compensation, and the air-core coil handles the high-frequency end. The design avoids the coupling capacitors that would otherwise sit in the signal path and roll off the low end.

Two-Stage Phono Equalizer and Constant-Voltage Preamp Supply

The pre-section equalizer is a two-stage design: a differential amplifier up front and a SEPP pure complementary stage at the output. A 1.0μF capacitor at the top of the differential circuit cuts unnecessary high-frequency content. A 22MΩ resistor is inserted specifically to eliminate the click when switching equalizer settings. The tone circuit is also a two-stage direct-coupled type, with CR-type low and high filters. The preamp runs off a constant-voltage supply that doubles as a full ripple filter on both the positive and negative rails.

Six Boards, Copper Foil, and a Scope Out Jack

Almost all the parts sit on six printed circuit boards. Marantz used a wire clamp rather than wire wrapping to secure lead wires, coated the board foils to prevent corrosion and breakage, and shielded the back of the input terminal board with copper foil to keep induced noise out. The front panel has a scope out terminal for monitoring cartridge phase characteristics.

Historical Context

The production record for the 1120 is tangled. Sources variously place it in 1973-75, tag a first year of 1973, or list it as 1974-1976. At least one unit in circulation was built in July 1975. A service bulletin in the manual carries an engineering approval date of 5-23-73, which pushes the design earlier than most listings suggest. Original price is just as unsettled. A Japanese-market record lists ¥175,000 with a "around 1972?" note, a Marantz dealer list dated October 1st 1974 shows $449.95, and at least one secondary-market listing claims an original price of $895. Treat any single figure with suspicion.

The family relationship is clear. The 1120 has double the power of the Model 1060, and the 1060 is the little brother in both power and dimensions. Marantz built the 1060 in Japan and the 1120 in the U.S.A., which is worth knowing when you're hunting parts. The walnut cabinet WC-1 (¥7,900) and the rack-mount adapters RA-1 (¥17,500) and RA-2 (¥6,500) were sold separately as options, so a bare chassis on the used market isn't necessarily incomplete. No substantive period reviews or detailed production history have surfaced. The service manual is freely downloadable, and original paper copies turn up from parts dealers with the fold-out schematics intact. One unconfirmed claim circulating on a manual page holds that the FM section is identical to the ST-7001 tuner. That's a strange remark for an integrated amplifier, and not something to repeat as fact.

Collectibility & Value

Market data is thin and scattered. A wood-cased 1120 in excellent condition has been listed on eBay at $1,147. A Reverb listing that had been completely rebuilt in the prior 60 days, mostly new transistors and capacitors, showed a $100 price drop to $795 from an original $895 ask. HifiShark tracks pricing and global availability, but the excerpt gives no specific figure.

Repair notes from owners point to a few recurring issues. One video documents an 1120 making a loud squealing sound through the speakers. Another covers a protection relay that won't fire alongside a burnt transistor in the preamp. Neither is universal, but both are the kind of fault a unit sitting unused for years is likely to develop. The service manual warns against discharging the filter capacitors with a dead short. The 8000mfd, 50V caps hold enough charge to vaporize a screwdriver blade, and the manual recommends a 10-ohm, 1-watt resistor instead. Idling power should land between 15 and 35 watts at 120VAC, and anything above 35 watts means stop and find the fault. DC balance at the outputs should sit at 0V ±50mV per channel, and the relay should click in between 2 and 10 seconds after power-on. Spare speaker terminals and screws do surface on the secondary market, and the service manual is easy to find.