Parts List:
R1 = 5K6 - 1/4W
R2 = 1K8 - 1/4W
R3,R4 = 15K - 1/4W
R5 = 500R - 1/2W Trimmer Cermet
R6 = 330R - 1/4W
R7 = 470R - Linear Potentiometer
C1,C2 = 10nF
C3 = 100µF/25V
C4 = 470nF
Q1,Q2 = BC238
LP1 = 12V 40mA Filament Lamp Bulb (See Notes)
J1 = Phono chassis Socket
SW1 = SPST Slider Switch
B1 = 9V PP3
Circuit Notes:
- High gain transistors are preferred for better performance.
- The bulb must be a low current type (12V 40-50mA or 6V 50mA) in order to obtain excellent long term stability and low distortion.
- Using a bulb differing from specifications may require a change of R6 value to 220 or 150 Ohms to ensure proper circuit's oscillation.
- Distortion @ 1V RMS output is 0.15% using a 12V 40mA bulb, raising to 0.5% with a 12V 100mA one.
- Set R5 to read 1V RMS on an Audio Millivoltmeter connected to the output with R7 rotated fully clockwise, or to view a sinewave of 2.828V Peak-to-Peak amplitude on the oscilloscope.
- With C1, C2 = 100nF the frequency generated is 100Hz and with C1, C2 = 1nF frequency is 10KHz but R5 requires adjustment.
About Audio Amplifier
An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.
The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels.
While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts. More explanation about power audio amplifier can be found at wikipedia.org
An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.
The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels.
While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts. More explanation about power audio amplifier can be found at wikipedia.org
This is a video tutorial about how to a very simple audio amplifier based on the LM386 amplifier chip. It can be built for less than $20 (or might be less than $8 in some countries) and used to amplify any low level audio signal including a guitar, bass or mp3 player.
Watch the video:
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