PREAMP_WITH_TEST_TONE

Published:2009/6/28 23:35:00 Author:May | From:SeekIC

Built around Signetics N5558V dual opamp or equivalent Motorola MC1458CP2, National LM1458, or Texas Instruments SN72558P. First half of opamp is used either as gain stage for increasing voltage level of carbon microphone or as AF Wienbridge tone oscillator, depending on position of S1. Frequency is determined byvaluesof C1, C2, R4 and R5. Silicon signal diodes form nonlinear control element. Adjust R6 until oscillator out-put at TPt is 10 V P-P. FET provides constant current through variable resistance of carbon microphone, to give audio input voltage. Sec-ond opamp is active low-pass filter with 3.3-kHz cutoff, rolloff of 12 dB per octave, and voltage gain of 10.-H. Olson, An IC Mike Preamp That Doubles as a Tone Generator, 73 Magazine, March 1974, p 45 and 47-48.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Amplifier_Circuit/PREAMP_WITH_TEST_TONE.html

Print this Page | Comments | Reading(3)