Note
Allied Radio catalog 1966 (copyright 1965), p. 73.
CQ, Dec 1965, p. 47.
Allied Radio catalog 1967 (copyright 1966), p. 74.
Allied Radio catalog 1968 (copyright 1967), p. 497.
The Knight-Kit Model C-577 is a compact, transistorized audio compressor and preamplifier manufactured by Allied Radio of Chicago. Designed as an easy-to-build kit , it inserts between a microphone and a transmitter's audio input to increase average modulation levels without causing overmodulation or severe distortion.
The unit is housed in a sea blue and silver metal enclosure measuring 2.5 x 6.25 x 3 inches. The front panel features a central edgewise meter that provides a visual indication of audio level and compression. The control layout includes:
– COMP LEVEL: A rotary control located on the left side to adjust the degree of audio compression.
– OUTPUT LEVEL: A rotary control on the right side to match the output signal level to the transmitter's microphone input.
– COMPRESSOR (IN / OUT): A slide switch located directly below the meter to switch the compression circuit in or out.
The C-577 uses a solid-state design built around three silicon transistors mounted on a printed circuit board. It is powered internally by a standard 9-volt battery, which helps keep hum and noise more than 50 dB down from maximum output. Interfacing is handled via double-shielded cables provided with the kit, supporting push-to-talk switching.
Specifications
– Gain & Preamplification: Provides up to 26 dB of gain at 1 kHz, making it suitable for boosting low-output microphones.
– Compression Threshold: Compression begins with input signals as low as 2 mV, limiting full compression output to around 50 mV.
– Frequency Response: Tailored for communications speech, staying within 2 dB from 300 Hz to 5,000 Hz.
– Impedance: Input and output impedances are rated at greater than 50,000 ohms.
References
Review. 73, Jan 1966, p. 80.
