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AA-181 Mono Combination Amplifier


  • Full 25 watt output—hi-fi rated
  • Separate bass and treble tone controls
  • Four switched inputs
  • Modern styling—matches AJ-21 and AJ-31

The Heathkit AA-181 Preamp-Amplifier combination replaces the famous A-9C Amplifier, a long-time favorite with hi-fi fans the world over. With increased power, true hi-fi rated performance and completely new styling, it is designed to complement and match perfectly with the new AJ-31 and AJ-21 Tuners on the opposite page to provide a coordinated monophonic system. Housed in a beautiful charcoal grey steel cabinet with ivory-colored bezel and lower front panel, this beautiful amplifier is a striking component in any music system setting.

In addition to these visual advances, the AA-181 gives you a preamplifier, power amplifier and power supply, all in one compact unit to provide more than enough hi-fi power to drive any acoustic suspension speaker system such as the AS-2 or AS-10. It has excellent gain characteristics and employs fixed-bias push-pull 7591 tubes to provide 25 watts of dependable hi-fi rated power with minimum distortion.

AA-181 Internal View The inside of the Heathkit AA-181 Amplifier shows the roomy arrangement for easy assembly and the sturdy components that guarantee long life.

The preamplifier section features four separate inputs (microphone, magnetic phono cartridge, crystal or ceramic phono cartridge and auxiliary), each properly compensated and selected by the panel-mounted selector switch. The separate bass and treble tone controls each offer 15 db boost and cut. Twin-triode miniature tubes in the preamplifier, tone control and phase splitter stages assure low hum and noise levels. The output transformer is tapped at 4, 8 and 16 ohms to match practically any speaker system. A shielded, heavy-duty power transformer assures long, trouble-free life. The neon pilot light serves as a convenient operating reminder.

SPECIFICATIONS—Power output: 25 watts Heath Hi-Fi Rating; 30 watts IHFM Music Power Output (0.7% THD @ 1 KC) Power response: ± 1 db, 30 cps to 15 kc at 25 watts output. Harmonic distortion: Less than 2% at 30 cps-15KC and less than 0.7% at 1 KC at 25 watts output. Intermodulation Distortion: Less than 2% at 25 watts using 60 cps and 6,000 cps signals 4:1. Hum and noise: Microphone—60db or better; Mag. Phono—55db or better; Xtal Phono—60 db or better; Auxiliary—60 db or better. Input sensitivity: For 25 watts output with tone controls Flat: Microphone—9mv; Mag phono—5 mv (at 1 KC); Xtal Phono—120 mv; Auxiliary—200 mv. Outputs: 4, 8 and 16 ohms. Damping factor: 9. Controls: 4-position selector switch; volume control, bass control and treble control with ON/OFF switch. Tube complement: 2-6EU7, 1-12AU7, 2-7591, 1-5AR4; 1 selenium bias rectifier. Power requirements: 117 v. 50-60 cycles, 120-135 watts. Power outlets: 1 AC receptacle unswitched. Indicator: Neon pilot light. Color and finish: Charcoal grey with ivory bezel and lower front panel. Dimensions: 13½" W. x 4-15/16" H. x 9½" D. Shipping Weight: 21 lbs.

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