Heathkit AA-111 (1950s–early 1960s)

Name: Heathkit AA-111
Brand: Heathkit

That warm, chimey EL84 glow—hand-built by you, one tube at a time.

Overview

If you ever flipped through an old Heathkit catalog in the late 1950s or early 1960s, you weren’t just looking at electronics—you were staring at a future sound system you could build yourself. The **Heathkit AA-111 Stereo Power Amplifier** was one of those landmark kits, designed for the growing wave of stereo enthusiasts who wanted real performance without the boutique price tag. This wasn’t some glorified radio amp; it was a serious, tube-driven power amplifier built around the sweet-sounding EL84 output tubes, ready to drive real speakers and deliver real dynamics. And it came in a box—wires, tubes, resistors, and all—waiting for your soldering iron.

The AA-111 wasn’t an integrated amp with a phono stage or tone controls. It was a pure, dual-mono power amplifier, meant to be paired with a matching preamp like the AA-11 or AA-141. It carried forward the performance legacy of the earlier AA-30 and was itself an update of the AA-100, refined with Heathkit’s patented **ULTRA-LINEAR® circuit** for improved linearity and lower distortion. For its time, that was a big deal—this wasn’t just another push-pull design cobbled together from textbook schematics. It was engineered, optimized, and laid out for ease of assembly, with a printed circuit board for each channel to keep things clean and consistent, even in amateur hands.

And assemble it you did. The AA-111 arrived as a kit, like nearly all Heath products of the era. No factory-built shortcuts. You got the chassis, the transformers, the tubes, the sockets, the pots, and a thick instruction manual that walked you through every step—from tube socket wiring to bias adjustments. It was as much an education as it was an amplifier. But once completed, it looked like something you’d buy off the shelf: a black chassis, ivory lower front panel, and that distinctive **rugged ventilated dust-cover in metallic bronze-colored steel** that gave it a no-nonsense, industrial elegance.

Specifications

Manufacturer	Heath Company (Heathkit)
Model	AA-111
Type	Stereo Power Amplifier
Channels	2
Power output	14 watts per channel
Power output (IHFM Music Power Output)	32 watts (16 w. per channel) at 0.7% THD, 1kc
Power response	± 1 db from 30 cps to 15 kc at 14 watts output per channel
Harmonic distortion	2% or less at 14 watts, 30 cps to 15 kc
Intermodulation distortion	2% or less 60 and 6,000 cps signals mixed 4:1 at 14 watts output per channel
Hum and noise	76 db below 14 watts output
Channel separation	65 db
Input sensitivity	0.74 v for 14 watts output per channel
Input impedance	500k ohm pot
Outputs	4, 8 and 16 ohm
Damping factor	5.25:1, 4 ohm tap; 10.2:1, 8 ohm tap; 11.5:1, 16 ohm tap
Controls	Left and right channel gain; AC switch; phase switch
Tube complement	2-7199; 4-EL84/6BQ5; 1 GZ34/5AR4
Power requirements	117 volts, 50/60 cycles. 115 watts
Power outlets	2 octal sockets for pre-amp power; supply 300 v at 10 ma. 6.3 volts at 1.1 amps at each socket
Shipping Weight	21 lbs
Overall dimensions	13" W x 8½" D x 6" H

Key Features

ULTRA-LINEAR® Circuit Design

The AA-111 wasn’t just another tube amp with a kit badge. It used Heathkit’s patented **ULTRA-LINEAR® circuit**, a clever feedback technique applied to the output stage that improved linearity and reduced distortion compared to standard pentode or triode configurations. This wasn’t theoretical—owners reported cleaner highs, tighter bass, and a more coherent midrange, especially at higher volumes. It gave the AA-111 a performance edge over simpler designs, making it a favorite among those who wanted Hi-Fi credibility without commercial branding.

Printed Circuit Boards & Clean Layout

For a kit built in the 1950s and early 60s, the AA-111 was surprisingly modern under the hood. Instead of point-to-point wiring, it used **a printed circuit board for each channel**, which helped ensure consistency and reduce assembly errors. Combined with the **neat circuit layout for easy assembly**, this made the build process far more approachable for hobbyists without formal training. The components were mounted on a black chassis, and the layout was designed so you could follow the signal path visually—something Heathkit emphasized in their manuals as both practical and educational.

Built to Last (and Power Other Gear)

The AA-111 wasn’t just an amplifier—it was a power hub. It included **two octal sockets on the back that supplied 300 volts at 10 mA and 6.3 volts at 1.1 amps each**, meant to power a matching preamplifier like the AA-20. That meant you could run your entire front end off one chassis, reducing clutter and ensuring matched power supplies. The transformer-operated power supply was also **fused for safety**, a small but important detail when you’re dealing with high voltages in a home-built unit.

EL84 Power with Real Presence

At the heart of the AA-111 are **four EL84/6BQ5 tubes** in push-pull configuration—two per channel. These small power pentodes are famous for their chimey highs, lively midrange, and a slight softness in the bass that many describe as “musical.” They’re not the brute-force KT88s or 6L6s, but they deliver a character that’s still sought after today. Paired with the ULTRA-LINEAR® design, they gave the AA-111 a sound that was both detailed and forgiving—ideal for the vinyl and FM radio sources of the era.

Historical Context

The AA-111 arrived at a pivotal moment: when stereo was transitioning from a novelty to a living room standard. Alongside the **AA-20 preamp**, it was marketed as a complete kit-based stereo system that brought high-fidelity sound into homes for the first time. You didn’t need to be an engineer to build it, but you felt like one when you turned it on. It was styled to match the AA-11 and AA-141 preamplifiers, creating a cohesive look on the equipment rack—a detail that mattered to audiophiles who cared about both performance and presentation.

It also stood on the shoulders of its predecessor, the AA-30, inheriting its core performance traits while refining the design. The AA-111 was, in essence, an **updated AA-100**, bringing improved circuitry and layout to a proven platform. For Heathkit, this was business as usual: iterate, improve, and empower the hobbyist. No fanfare, no celebrity endorsements—just solid engineering in a box.

Collectibility & Value

Today, the AA-111 is a sought-after piece for vintage audio collectors and tube DIYers, though it doesn’t command the sky-high prices of some boutique brands. Most units need a full **tune-up** before they’re safe to power on—common issues include aging tubes, degraded capacitors, and oxidized switches. Typical restoration work involves replacing faulty resistors and capacitors, cleaning pots and tube sockets, and sometimes replacing original wiring that’s become brittle over time.

Restoration kits have been available, including one listed for **$167 on August 18, 2022**, specifically for filter capacitor repair. Given the high voltages involved, a proper rebuild isn’t a beginner project, but it’s well within reach for anyone with basic tube amp experience. Once restored, owners report **good, clean, strong output from both channels**, and many praise the **"sweet sounding EL84 output tubes"** that give the amp its characteristic warmth and clarity.

There’s no verified current market price from completed sales, but given the cost of restoration and the niche appeal, completed, working units likely trade privately or on forums rather than at auction. Its value lies less in resale and more in the experience: the pride of owning a hand-built piece of audio history that still performs with soul and authority.