Marantz 170DC Vintage Power Amplifier — 86 WPC | Level 2 Service

Designed in the USA and built in Japan during Marantz’s most celebrated era, the Model 170DC is a genuine Golden Age stereo power amplifier — a serious, beautifully constructed piece of engineering that still commands attention and respect among vintage audio enthusiasts decades after it left the factory.

The 170DC’s name is more than a model designation — “DC” refers to a true direct-current coupled amplification circuit that carries the audio signal through all gain stages without AC coupling capacitors in the signal path. Marantz’s engineering team adopted this approach with a specific goal: the elimination of TIM (transient intermodulation distortion), which they identified as a key degrader of musical transients and dynamic accuracy in conventional amplifier designs of the era. This design philosophy, favoured by audio engineers in the late 1970s and early 1980s, delivers a more pure waveform with minimal phase shift and frequency distortion — resulting in a sonic character many describe as tube-like: warm, full-bodied, and musical despite being solid-state. The circuit is a pure complementary OCL (Output Capacitor-Less) parallel push-pull 3-stage Darlington configuration with a fully independent symmetrical layout identical in architecture to the legendary Model 250 — a topology chosen for its inherent load stability and power linearity. The first stage employs a differential amplification cascode bootstrap circuit using audio-specification low-noise dual FETs, minimizing both temperature and time drift to maintain stable DC operation throughout the amplifier’s working life.

The power supply is muscular and well-considered: a large transformer paired with 18,800µF × 2 filter capacitors provides the headroom and current delivery that 86 watts per channel demands — and that dynamic musical peaks well above rated power require. The result is an amplifier capable of delivering 108 WPC into 4Ω and 170 WPC into 2Ω when programme material calls for it. The protection circuitry is drawn directly from Marantz’s flagship Model 510M: the ESP (Energy Sensor Protection) circuit monitors output current, voltage, and DC generation simultaneously — measuring total energy rather than instantaneous values, allowing it to protect speakers without interrupting programme material during brief transient peaks. A 4-second relay delay on power-up eliminates turn-on thump at the speakers.

A distinctive and immediately recognizable feature of the 170DC is its iconic pair of large blue-illuminated VU meters — logarithmic peak-reading instruments spanning –40 dB to +3 dB with peak hold indicators. These meters serve both functional and aesthetic purposes: they allow you to confirm balanced channel operation at a glance, and they provide that classic, unmistakable Marantz aesthetic that makes Golden Age separates instantly recognizable across a room. A DC/AC coupling switch on the rear panel provides flexibility when pairing with different preamplifiers. The 170DC has no independent power switch — it was designed to be powered from the switched AC outlet of a matching Marantz preamp such as the 3250B or 3300, which makes it a natural and elegant partner in a vintage Marantz separates system, though it pairs equally well with any quality preamplifier using a switched outlet or power bar.

Owners consistently describe the 170DC’s sonic character in warm terms: “Sounds like a tube amp. Bassy, controlled, musical and smooth… definitely on the romantic side of sound. Great for vintage LPs and Jazz.” Another long-time owner adds: “Wow. I own several solid state integrated and standalone power amps and this is by far my favourite one… it can sing!”

This unit presents in very good vintage condition — the classic black faceplate and silver chassis show normal patina consistent with careful use over decades. The blue VU meters illuminate brightly and beautifully, all controls operate smoothly, and the gold-plated RCA inputs are clean. This unit has undergone our comprehensive Level 2 service and testing, which should ensure many more years of reliable performance ahead.

Type: Stereo power amplifier, Designed in USA, Made in Japan (1977–1980)
Circuit topology: True DC-coupled, pure complementary OCL parallel push-pull 3-stage Darlington
Power output: 86 WPC into 8Ω; 108 WPC into 4Ω; 170 WPC into 2Ω
THD: 0.03% (rated output, 20 Hz–20 kHz)
IMD: 0.03%
Frequency response: 20 Hz – 20 kHz (+0/–0.2 dB)
Damping factor: 60 (8Ω)
Input sensitivity/impedance: 1.5V / 30kΩ; gold-plated RCA connectors
Residual noise (IHF-A): 0.046 mV
Metering: Blue-illuminated logarithmic peak-reading VU meters, –40 dB to +3 dB, with peak indicators
DC/AC coupling switch: Yes (rear panel)
Power switch: None — designed to be powered from a preamp switched outlet
Protection: ESP circuit (current/voltage/DC/energy sensing) + 4-second relay turn-on delay
Semiconductors: 53 transistors, 49 diodes, 4 dual FETs

Dimensions: (Width x Height x Depth) 16.4 x 5.75 x 11.9 inches (416 x 146 x 302 mm)
Weight: 31.1 lbs (14.1 kg)

A genuine Golden Age power amplifier from Marantz’s finest era — comprehensively serviced, beautifully presented in vintage condition, and ready to bring its warm, authoritative sound to a new system for years to come. Designed in the USA, built in Japan.

Backed by Radique Audio’s Bumper-to-Bumper Warranty and our Perpetual Trade-Back Program, you can purchase with confidence.