Audio Amplifier Fine Tuning


Most ham CW and SSB communication is between 300Hz to 3000Hz. The following is a chart reprinted from the SGS data sheet intended to aid the designer for fine tuning the audio amplifier.

Part Value Purpose Larger Value Smaller Value
C21 2.2 mfd Input DC decoupling Noise at switch-on, switch-off
C22 470 mfd Ripple rejection Degradation of SVR
C25 0.1 mfd Supply bypassing Danger of oscillation
C24 1000 mfd Output coupling to load Higher low frequency cutoff
C26 0.1 mfd Frequency stability Danger of oscillation at high frequencies with inductive loads
C23 39 pf Upper frequency cutoff Lower bandwidth Larger bandwidth
R7 220 ohm Setting of gain Increase of drain current
R8 2.2 ohm Setting of gain and SVR Degradation of SVR
R9 1 ohm Frequency stability Danger of oscillation at high frequencies with inductive loads
R6 39 ohm Upper frequency cutoff Poor high frequency attenuation Danger of oscillation

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Last Update: 01/14/2000
Web Author: David White, WN5Y