Low-Ripple Power Supply

This circuit can be used where a high current is required with a low-ripple voltage (such as in a high-powered class AB amplifier when high-quality reproduction is necessary). Q1, Q1 and R2 can be regarded as a power Darlington transistor. ZD1 and R1 provide a reference voltage at the base of Q1. ZD1 should be chosen thus: ZD1=Vout-1.2 . C2 can be chosen for the degree of smoothness as its value is effectively multiplied by the combined gains of Q1/Q2, if 100uF is chosen for C2, assuming minimum hfe for Q1 and Q2, C=100x15(Q1)x25(Q2)=37,000uF.

DC to DC Converter Multi Output

This circuit will convert DC volt input +9 to +16 DC Volt.
Output will be:
+28V DC
+15V DC
-5V DC
-12V DC

Simple Touch Switch

With touch switch, you can turn on and turn on a electronic device. Touch switch don't need mechanical part, so they will not worn out due to mechanical contact. Touch switches can be used in places where regular switches would not last, such as wet or very dusty areas.

Here the schematic diagram:

Component part list:

Part      Total Qty.    Description

C1         1          10uF 16V     Electrolytic Capacitor
R1, R2     2          100K 1/4 Watt Resistor
R3         1          10 Meg 1/4 Watt Resistor
U1         1          4011 CMOS NAND Gate IC
MISC       1          Board, Wire, Socket For U1

Notes:

1. The contacts an be made with just two loops of wire close together, or two squares etched close together on a PC board.

2. When activated, the output of the circuit goes high for about one second. This pulse can be used to drive a relay, transistor, other logic, etc.

3. You can vary the length of the output pulse by using a smaller or larger capacitor for C1.

Sine Wave Generator (1KHz Frequency)

This is iKHz sine wave generator circuit built based on configuration of inverted Wien bridge (see C1-R3 & C2-R4). R5 and R7 used for output amplutide setting. 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.

Component list:

R1____________5K6  1/4W Resistor
R2____________1K8  1/4W Resistor
R3,R4________15K   1/4W Resistors
R5__________500R   1/2W Trimmer Cermet
R6__________330R   1/4W Resistor
R7__________470R   Linear Potentiometer

C1,C2________10nF  63V Polyester Capacitors
C3__________100µF  25V Electrolytic Capacitor
C4__________470nF  63V Polyester Capacitor

Q1,Q2_______BC238  25V 100mA NPN Transistors
LP1___________12V  40mA Filament Lamp Bulb (See Notes)
J1__________Phono chassis Socket
SW1__________SPST  Slider Switch
B1_____________9V  PP3
Clip for 9V PP3 Battery

Notes:

• The bulb must be a low current type (12V 40-50mA or 6V 50mA) in order to obtain good 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.
• With C1, C2 = 100nF the frequency generated is 100Hz and with C1, C2 = 1nF frequency is 10KHz but R5 requires adjustment.
• High gain transistors are preferred for better performance.

Audio Power Indicator

This is audio level indicator which can be used to measure the audio level output of your amplifier. Simply connect the output of your amplifier to the input of this circuit, then you will know the average value of your amplifier's power.

R1_____________220R  1/2W Resistor
R2,R5,R6,R8____100R  1/4W Resistors
R10,R12,R14____100R  1/4W Resistors
R3_____________220R  1/4W Resistor
R4,R7__________330R  1/2W Resistors
R9_____________560R  1/2W Resistor
R11____________820R  1/2W Resistor
R13______________1K2 1/2W Resistor

D1___________1N4004  400V 1A Diode
D2,D4,D6__BZX79C2V7  2.7V 500mW Zener Diodes
D3,D5,D7,D8,D9,D10   Red LEDs (Any dimension and shape) (See Notes)

Notes:

• The output power indicated by each LED must be doubled when 4 Ohms loads are driven.
• The circuit can be adapted to suit less powerful amplifiers by reducing the number of LEDs and related voltage dividers.
• LEDs of any dimension can be used, but rectangular shaped devices will be more suitable to be compacted in bars or columns.
• For a stereo amplifier, two identical circuits are required.

70 Watt MOSFET Audio Amplifier

This amplifier circuit will give you about 70W output power at 60v supply.
Please visit this page for detail information and characterization

20W Bridge Audio Amplifier based on TDA2005

This is 20W Bridge Audio Amplifier circuit based on the TDA2005 IC, a class B dual audio amplifier, specifically designed for car radio applications etc.
This circuit require Voltage input 18 VDC and will give you Output power - 20 W, 4 Ω

This is the amplifier kit:

This is the schematic:

To get the schematic diagram, component list and component layout, please download this file

8 LED Audio Level Meter

This is 8 LED audio level meter circuit diagram. Build based on 2 pieces of op-amp IC LM324. You should use 4 ICs for stereo audio level meter.
Here the schematic: