Audiophiles believe that the simpler the amplifier is, the fewer unnecessary parts it contains, the better it sounds. They may be wrong in this matter, but one cannot but agree that an amplifier containing few parts can be built faster.
Instructions
Step 1
Many modern sound cards develop enough voltage to drive an amplifier with just one stage, but their output power is too low to drive a speaker (unlike sound cards from the nineties with built-in two-watt amplifiers). Therefore, assemble a single-stage additional amplifier for a modern sound card. For it, you need only one transistor of the P213, P214 or P215 type installed on a very large heat sink.
Step 2
Any of these transistors have a p-n-p structure. This means that the positive terminal of the power supply must be connected to the common wire in the amplifier. On the other hand, apply a negative voltage to the supply bus. It should be several volts.
Step 3
Connect a speaker with an impedance of at least 8 ohms between the supply bus and the collector of the transistor. Connect its emitter to the common wire.
Step 4
Use a variable resistor with a resistance of about 100 kilo-ohms as a volume control. Ground its left terminal, apply an input signal to its right with respect to the common wire. Connect the middle output through a non-polar capacitor with a capacity of about one microfarad to the base of the transistor.
Step 5
Turn on the power to the amplifier and signal source. Adjust the volume. The sound will be very hoarse. This is due to the fact that the bias has not yet been applied to the base of the transistor.
Step 6
Try connecting resistors of various values from 300 to 10 kilo-ohms between the collector and the base of the transistor. Choose one of them, when using which the wheezing is almost inaudible, but the sound volume does not decrease, and the transistor itself practically does not heat up.
Step 7
Turn off the power to the power supply, solder the resistor you chose, then turn on the power to both devices again.
Step 8
To make the amplifier stereo, collect one more stage of the same and feed it with a signal from another stereo channel. Place the device in a convenient housing.
