LED Audio Level Meter Circuit

This circuit uses two quad op-amps to form an eight LED audio level meter. The op-amp used in this particular circuit is the LM324. It is a popular IC and should be available from many parts stores.

LED audio level meter
LED audio level meter schematic
The 1K resistors in the circuit are essential so that the LED's turn on at different audio levels. There is no reason why you can't change these resistors, although anything above 5K may cause some of the LED's to never switch on. This circuit is easily expandable with more op-amps, and is not limited to use with the LM324. Pretty much any op-amp will work as long as you look up the pinouts and make sure everything is properly connected.

The 33K resistor on the schematic is to keep the signal input to the circuit at a low level. It is unlikely you will find a 33K resistor, so the closest you can get should do. The value of this resistor may need to be changed, so it is best you breadboard this circuit before actually constructing it on PCB. The circuit in it's current form will accept line level inputs from sources such as the aux out on a Hi-Fi, all though could be easily modified to accept speaker inputs.

The audio + is connected to the main positive rail, while the audio - is used for signal input. The 50k pot can be used to vary the sensitivity of the circuit.

Circuit Convert Mono to Stereo Audio Signal

This circuit is used to convert a mono audio signal into a stereo signal that can be panned between the left and right channel by a 0-10V control signal, it is intended for analog synthesizer systems.

Circuit Convert Mono to Stereo Audio Signal
Circuit Convert Mono to Stereo Audio Signal Schematic

Simple Power Amplifier Circuit

Simple Power Amplifier Circuit Diagram
Simple Power Amplifier Circuit Diagram

Tr1 BCY70 (or BC 182L or BC212L or BC214L)
Tr2/3/4 BFY50/51
Tr5 BFX88
Tr6/7 2N3055

Risk of instability if no input connected. When testing, connect R (about 3k3). The Simple Power Amplifier Circuit needs well smoothed power supply of about 20 to 30 volts. Peak power is well over 10 Watts.

100W Power Amplifier Circuit [PCB]

Power Amplifier 100W
High Power Amplifier
Technical Specifications - Characteristics 100W Power Amplifier :
Output power (f=1 KHz, d=0.5 %): 100 W in 8 ohm
Supply voltage: ................ с 40 V
Quiescent current: ............. 50 mA
Maximum current: ............... 2.6 A
Sensitivity: . 600 mV
Frequency response: ............ 10-35000 Hz (-1 dB)
Distortion HD: ................. 0.01 %
Intermodulation dist.: ......... 0.02 %
Signal/noise: 83 dBConstruction

100W Power Amplifier Circuit Diagram :

Part list

L1 : 10 turns with wire 0,5mm turned on a restistor of 1W
If  you use a 4Ohm speaker you will place R3,4,17,23 at the board
If you use a 8Ohm speaker you will place D7 D8 and R28.
For R2 and R16 if you don't find a 0,47Ohm place two of 1 Ohm parallel.
R16 must be 0,47Ohm...the 1Ohm must be a typographical error, take care of this, i haven't tested it.

Printed Circuit Board 100W Power Amplifier PCB:

PCB design Circuit 100W amplifier

component placement

If it does not work :
Check your work for possible dry joints, bridges across adjacent tracks or soldering flux residues that usually cause problems.  Check again all the external connections to and from the circuit to see if there is a mistake there.
- See that there are no components missing or inserted in the wrong places. 
- Make sure that all the polarised components have been soldered the right way round. - Make sure the supply has the correct voltage and is connected the right way round to your circuit. 
- Check your project for faulty or damaged components. If everything checks and your project still fails to work, please contact your retailer and the Smart Kit Service will repair it for you.

10 W Audio Amplifier Circuit Diagram

This circuit is a general-purpose 10-W audio amplifier for moderate-power PA or modulator use in an AM transmitter. With higher voltages and a change in bias resistors, up to 30 W can be obtained. The Output Stage Amplifier using transistor 2N3055 and MJE2055.

10 W Audio Amplifier Circuit Diagram
10 W Audio Amplifier Circuit Diagram

3-Way Crossover Speaker Circuit

Design simply what best fit the drivers' capabilities while focusing on keeping the woofer in doing its job handling the bass, the mids handling the full midrange and so on. 500Hz and 4000Hz were chosen as the crossover frequencies. An L-pad circuit I felt was essential in keeping the response of the speaker perfect as possible. I didn't want anything to stick out. A schematic of the Hi-Vi 3 way crossover design is shown below.

3 Way Crossover Circuit Diagram
3 Way Crossover Speaker Circuit Diagram

Two Colour LED Light Bar Circuit

This circuit is a circuit run on alternating two insignia.It uses the 2-color LED with a built-participating in 3-pin single.This preference look for away the glow of every LED until the base.It turns alternating to one more color.In in the least way to the moon on the moon essential end, afterward the LED end of the first LED.Circuit consists of, nand gate ic.Two 10 Counter circuits IC, and IC JK flip washout.

Two Colour LED Light Bar Circuit Diagram

company of the circuit is not speaking into 3 sets.It is a solid of gesture generators, a set of parade and control.Set the signal generator is IC1a,and IC1b quantity 4011 is a signal generator.The R2, R3, C2 determine the frequency generated.The hint is fed to a set of impressions is the figure 4011 IC2 and IC3.The 10 counter circuits to output to the LED, and Is the same, but the effort should ensue performed individual by the side of region. Therefore, the show from pin 11 of IC 2 and tested pro D2 and D3,To pin 3 of IC4.The integrated circuit IC 4 is a JK flip slump is connected to a T flip flop.The signal input pin 3 and pin 1 is the output hint at.Which sends a signal to the Reset IC either obstruct working.IC4 on the anniversary, it want output the originally moment in time, happening contrast to pin1.IC3 progress to handiwork, IC2 stopped.
IC2 is controlled by signals from pin 1 of IC4, to IC1c.earlier to control IC2.The IC3 is connected to pins 1 through D1 to the control again.