Altec Lansing 1224A Electronic Crossover Biamplifier

At 35 lbs and 19 inches wide, it’s a heavy, no-nonsense box built to split signals and drive drivers—hard.

Overview

The Altec Lansing 1224A Electronic Crossover Biamplifier isn’t the kind of gear you show off on a shelf. It’s a workhorse, designed to live inside speaker cabinets used in permanent installations, portable PA rigs, and professional sound reinforcement setups. This isn’t a stereo amp for your living room—it’s a single chassis that combines an electronic crossover and dual amplifiers, one for low frequencies and one for high, all in one rugged package. The idea was simple: feed it a line-level signal, let it split that signal at 500 Hz, 800 Hz, or 1500 Hz, then amplify each band separately before sending them to dedicated drivers. That kind of integration was smart engineering for the time—reducing signal loss, minimizing interference, and simplifying system design for installers who needed reliability above all.

Owners report it was built like a tank, and the construction backs that up: an all-steel chassis, internal heatsinks, and a toroidal transformer tucked inside a compact 19-inch rackable form. It runs on 120V AC and can reportedly be converted in the field for 240V operation, which suggests it saw use beyond North America. The crossover is fully electronic and adjustable via switch settings, letting users match it to different speaker systems without swapping components. While it lacks the polish of consumer-grade gear, its purpose is clear—durability, function, and clean power where it counts.

Specifications

Key Features

Electronic Crossover with Selectable Frequencies

The heart of the 1224A is its onboard electronic crossover, which splits the incoming signal before amplification—a true biamplified design. This avoids the power loss and phase issues common in passive crossovers. Users can select crossover points at 500 Hz, 800 Hz, or 1500 Hz via internal switches, making it adaptable to various two-way speaker systems. According to available documentation, the crossover operates at line level, sending the low-pass signal to the LF amp and the high-pass to the HF amp. One noted quirk: some units are missing the external frequency switch, but the setting can still be changed manually with a key or tool—hardly elegant, but functional.

Dual-Mono, Fully Discrete Amplifier Design

Inside the steel case, the 1224A uses a dual-mono, fully discrete amplifier topology. There’s no shared circuitry between the low and high-frequency channels, which improves isolation and reduces crosstalk. Each channel runs on its own set of Sanken output transistors and is powered by a shared but robust toroidal transformer. The use of discrete components (no ICs in the signal path) was standard for pro gear of its class and era, offering reliability and repairability. The 4 x 15,000µF filter capacitors suggest a strong power reservoir, helping maintain headroom during dynamic peaks.

Rugged, Install-Friendly Chassis

Built for the road and permanent installs, the 1224A’s all-steel chassis and internal heatsinks reflect a no-frills, industrial design. It fits standard 19-inch racks and weighs in at 35 lbs—substantial, but manageable for a unit packing this much circuitry. The RCA inputs and 5-way binding posts are straightforward, with no exotic connectors or shielding. While not glamorous, the layout prioritizes serviceability and durability. According to owner reports, the RCA jacks are prone to loosening over time and may require re-soldering—a known weak point in an otherwise solid build.

Collectibility & Value

The Altec 1224A trades today between $300 and $500, depending on condition and whether it’s been serviced. Its value hinges on functionality—collectors and users alike expect it to work, not just sit as a display piece. The most common failure point is aging electrolytic capacitors, particularly the four 15,000µF filter caps. Replacing them is considered routine maintenance, and sources suggest it’s a wise step if the unit still has its original capacitors. The RCA input jacks are another known issue, often needing re-soldering due to mechanical stress. A manual was available from Telex as recently as 2001, suggesting parts and documentation weren’t entirely lost to time, though sourcing them now may require digging.

eBay Listings

As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.

Related Models

• Altec 1592A
• Altec 26420 (1975)
• Altec 288D (1975)
• Altec 288L (1975)
• Altec 290C (1975)
• Luxman L-530 (1975)
• Luxman R-404 (1975)
• Luxman RV-371 (1975)
• Luxman SQ-38U (1975)
• Luxman T-14 (1972)