Sumo Andromeda II Power Amp

Description

The Sumo Andromeda II Power Amplifier is a high-power solid-state stereo amplifier that became a respected component in the world of late-1980s and early-1990s high-end audio. Produced by Sumo in Chatsworth, California, the Andromeda II was designed to deliver exceptional output power, wide bandwidth, and precise control over demanding loudspeakers. With its robust construction and advanced circuitry, the amplifier was intended for serious audiophiles seeking both dynamic authority and refined musical detail.

The Andromeda II evolved from the original Andromeda design created by legendary audio engineer James Bongiorno, whose earlier work included classic amplifiers for companies such as Marantz, SAE, and GAS. His designs were known for combining high current capability with wide bandwidth and minimal distortion, and the Andromeda series continued that engineering philosophy.

At its core, the Andromeda II is a Class-AB stereo power amplifier capable of producing substantial output power—240 watts per channel into 8 ohms and up to 400 watts per channel into 4 ohms. This level of power allows the amplifier to drive difficult speaker loads while maintaining stability and control.

One of the defining characteristics of the amplifier is its very wide bandwidth and fast transient response. With a frequency response extending from deep subsonic frequencies up to well beyond the audible range, the amplifier can reproduce musical signals with exceptional accuracy and speed. The design features a slew rate of approximately 115 V/µs and rise time under 2 microseconds, ensuring rapid response to sudden musical transients such as percussion or dynamic orchestral passages.

The Andromeda II was also engineered with a very high damping factor—greater than 500—which allows it to maintain tight control over speaker drivers, particularly in the bass region. This helps produce powerful, well-defined low frequencies and reduces unwanted speaker resonance.

Internally, the amplifier features a substantial power supply and large heat-dissipating chassis. The design includes more than 1,000 square inches of heat-dissipating surface area, allowing the amplifier to manage the heat generated by its high output stage and maintain stable operation during demanding listening sessions.

The front panel design is understated but purposeful, with a brushed black aluminum faceplate and rack-mount capable chassis. Despite its simple appearance, the Andromeda II is a physically substantial component, weighing roughly 55 pounds, reflecting the heavy transformer and power supply required to support its output capability.

Today, the Sumo Andromeda II is considered a classic vintage high-power amplifier. Audiophiles and collectors still appreciate it for its combination of power, reliability, and dynamic sound character. Many enthusiasts pair it with vintage or modern high-end speakers, where its strong current delivery and fast response continue to provide impressive performance decades after its introduction.

Review Quotes

“A powerful amplifier with impressive bandwidth and speed.”

“Delivers massive headroom and excellent speaker control.”

“The Andromeda’s wide bandwidth and high output give it tremendous dynamic authority.”

These comments highlight the amplifier’s reputation for high power, fast response, and strong control over difficult loudspeakers.

Product Specifications

• Type: Solid-state stereo power amplifier

• Amplifier Class: Class-AB

• Manufacturer: Sumo (Chatsworth, California, USA)

• Year Introduced: Around 1989

Power Output

• 240 watts per channel into 8 Ω

• 400 watts per channel into 4 Ω

Performance

• Frequency response: ±0.1 dB (20 Hz – 20 kHz)

• Extended bandwidth: 0.1 Hz – 170 kHz (-3 dB)

• Total harmonic distortion: ≤0.05%

• Intermodulation distortion: 0.05%

• Signal-to-noise ratio: ~110 dB

• Slew rate: 115 V/µs

• Rise time: < 2 µs

• Damping factor: > 500

Inputs / Connectivity

• Input impedance: 47 kΩ

• Input sensitivity: 1.8 V RMS

• Stereo RCA inputs

• Dual speaker outputs

Physical Specifications

• Dimensions: 19 in W × 7 in H × 16.75 in D

• Weight: ~55 lb (25 kg)

• Power consumption: up to 900 W

• Construction: large heat-sink chassis with extensive cooling area