Altec Lansing 770A (1970)

Name: Altec Lansing 770A
Brand: Altec Lansing

A dual-channel electronic crossover bi-amplifier released in 1970, designed to power Altec's active speaker systems with precision frequency control and low distortion.

Overview

The Altec Lansing 770A is a self-contained electronic crossover bi-amplifier made for active speaker setups, combining both signal splitting and amplification in one unit. Built by Altec and released in 1970, it was specifically engineered to drive Altec speakers with optimized damping and minimal distortion. It features separate amplifiers for low and high frequencies, with front-panel gain controls to fine-tune balance between bands. The unit integrates a switchable crossover at 500 Hz or 800 Hz, aligning with Altec’s specified active speaker requirements.

Specifications

Output (Low Band)	60 Wrms (8 Ω)
Output (High Pass)	30 Wrms (8 Ω)
Harmonic distortion factor	0.3% or Less (20 Hz to 20 kHz)
Frequency characteristic	20 Hz to 20 kHz ± 0.5 dB
Damping factor	25
Hum, noise level	-80dB or less
Input sensitivity	0.5Vrms
Crossover frequency	500 Hz, 800 Hz (switchable)
Damping property	12dB/oct
Control range	26dB
External dimensions	Width 230x Height 165x Depth 230 mm

Design

The 770A integrates an electronic crossover and dual power amplifiers for low and high frequencies in a single chassis. It eliminates DC crossover distortion and reduces IM distortion below detectable levels using the conventional IHF method. The damping factor is optimized for Altec speakers, and the crossover frequency switches between 500 Hz and 800 Hz as specified by Altec. Front-panel gain controls allow adjustment of bass and treble amplifier balance. A built-in fail-safe protection circuit guards the output transistors from damage due to unexpected faults.

Context

The 770A was used in Altec active speaker systems such as the 2873A Barcelona and 2875A Granada, serving as the dedicated amplifier-crossover unit for these professional and high-end installations.