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Amperite Instruction Sheets
Dated January 2, 1937

This is a delightful little eight-page booklet that was published on January 2, 1937. This was an era in which we built circuits around vacuum tubes and did the wiring ourselves. The resolution of the download is high in order to preserve details of the schematics, some of which are quite small.

Page 1 discusses and describes the Amperite Model HI-71 High-Impedance HIV Velocity Microphone, connecting it to an amplifier, appropriate cable length, using the mic with Amateur Radio transmitters, eliminating hum and audio oscillation, and dealing with low output and feedback.
Page 2 provides information on the Model RB-HB micro­phone, mixing the outputs of multiple high-impedance mics, and the wiring of plugs and switch connections.
Page 3 presents technical specifications of the Amperite 7-Point Velocity Microphones, tips for modifying frequency response, and microphone techniques for announcers.
Page 4 gives cable length, transformers, preamplifiers for low-impedance velocity microphones, impedance matching, hum, induced RF, and excessive amplification and distortion.
Page 5 defines pickup angle, 360-degree pickup, feed­back, connecting low-impedance velocity microphones in parallel, and the function of constant-impedance pads in the circuit.
Page 6 offers both battery and AC-powered preamplifier schematics, a 15-watt audio amplifier for public address work, and the Amperite guarantee policy.
Page 7 furnishes us with designs for equipping multiple low-impedance microphones with switches, and the circuitry of the dual-impedance Model RBDI.
Page 8 is devoted to the complete schematic of “a most economical amplifier for any wattage output.” Even the power supply is included in the circuit diagram, and all component values are given. Now where did I leave my soldering iron?

Amperite Instruction Sheets
Download the Amperite Instruction Sheet booklet.
(7.2-megabyte high-resolution eight-page PDF)