Schematic & Wiring Diagram

This is a simple and low-cost audio booster circuit design. The circuit is based on general purpose amplifier and switches, 2N3392 transistor packed in TO-92. This circuit should be installed before power amplifier module.

To get the maximum audio performance, use metalfilm resistors, MKM and tantalum capacitors which have small tolerance of its value. Also, use stabilized and regulated 9V power supply for better result. You can simply use LM7809 IC regulator on 12V power supply to get stabilized 9V output. The 100K variable resistor is used to adjust the volume, you may remove this component and use main volume in your audio system.

Here is one of the circuit diagram of a power amplifier with the STK1050 single power chip which is supported by several components that make a better sound output. This amplifier is a single output amplifier, so if you want a stereo amplifier, then you must make a similar circuit.
STK-1050 Features:
STK1050 has some features that make it superior and good for your audio amplifier.

1. Does not require externally connected emitter resistors.
2. Values of emitter resistors have carefully been reviewed to provide superior characteristics.

• Better supply voltage utilization permits designing power supply voltage that are about 0.7V (for RL=4ohms) lower than those required for previous DPP models.
• Maximum allowable power consumption for each resistor is 5W or higher, permitting accomodation for all loads.
• Peak allowable current is 18A or more, providing an ample margin even for peak currents under when short circuited or similar emergencies.
• In particular, maximum output 4 ohms have been enormously improved.

3. Use of emitter resistors facilitates meeting different safety standards and designing PCBs
4. Mutual interferences in the high-frequency range caused by layout of externally connected emitter resistors no longer exist. This facilitates lower distortion factors.
5. Pins are used for emitter resistor output terminals that were not conected in previous DPPs. All other terminals remain uncharged; there is no need for major circuit board changes.

Download STK-1050 datasheet

This is an easy built portable headphone amplifier circuit. You can use this headphone amplifier to amplify your radio receiver, mp3/mp4 player, computer or dvd/cd player. You may connected the input channel directly to those devices.

R1 _______________ 10K
R2 _______________ 100K
R3 _______________ 68K  (see notes)
R4 _______________ 1K5
R5 _______________ 3K3
R6 _______________ 330R
R7 _______________ 4K7
R8 _______________ 2R2
C1 _______________ 1uF 63V
C2 _______________ 100uF 25V
C3 _______________ 470uF 25V
Q1 _______________ BC239C 25V 100mA NPN High-gain Low-noise Transistor
Q2 _______________ BC337 45V 800mA NPN Transistor
Q3 _______________ BC327 45V 800mA PNP Transistor
J1 _______________ Stereo 3mm. Jack socket
SW1 _______________ SPST Switch
B1 _______________ 3V Battery (2xAAA)

R3 value was calculated for headphone impedance up to 300 Ohms. Using 600 Ohms loads or higher, change R3 value to 100K.
Take a note that above circuit only show single channel.

Here the hi-fi power amplifier circuit which will deliver 20W power output. This amplifier circuit use single power IC TDA2040 and a few external components.

Detailed explanation about this 20W Power Amplifier

This is the circuit diagram of dynamic mic amplifier. This simple and easy built circuit can be used as a subtitute of an electret microphone. It will turn an ordinary mini speaker to become a pretty sensitive microphone.

Any NPN transistors can be applied for this circuit, for example: BC547. The circuit will operated from 3v to 9v DC supply. The amplifier configuration used in this dynamic mic amplifier is a common-base amplifier, it accepts the low impedance of the speaker to deliver a gain of more than 100 times.

Above circuit is a inexpensive completely transistorised inverter circuit ideal for driving medium loads of the order of 40 to 60 watts working with battery of 12V, 15 Ah or bigger power capacity.

Transistors T1 and T2 (BC548) make a 50Hz multivibrator. For having proper frequency, the values of resistors R3 and R4 may have to be modified after testing. The complementary outputs from Collectors of transistors T1 and T2 are provided to PNP darlington driver stages formed by transistor pairs T3-T4 and T6-T7 (utilising transistors BD140 and 2N6107). The outputs from the drivers are given to transistors T5 and T8 (2N3055) connected for push-pull operation.

Considerably bigger wattage could be achieved by growing the drive to 2N3055 transistors (by lowering the value of resistors R7 and R8 while increasing their wattage). Appropriate heatsinks may be applied for that output stage transistors to prevent the transistor from overheating. Transformer X1 is really a 230V primary to 9V-0-9V, 10A secondary used in reverse.

Download the document about this 12VDC to 230VAC 60W Inverter Circuit Here