Sound Level Meter

Description

This is a one chip sound level meter that can be use for displaying sound level of an amplifier or simply the sound level from a microphone.The heart of the circuit is IC LM 3915 Audio level IC.Even though it is a stand alone IC , a peak detector based on Transistor BC 558 and diode 1N4001 is also included for better performance.

Tips

Supply voltage can be from 3V to 20V.The input is set for audio line voltage (1V peak to peak) and has a max input voltage of 1.3V. To make the circuit use a moving dot display instead of bar graph display,Pin 9 can be should be disconnected from +V.

Parts List.
C1 2.2uF 25V Electrolytic Capacitor
C2, C3 0.1uF Ceramic Disc Capacitor
R1, R3 1K 1/4W Resistor
R2 10K 1/4W Resistor
R4 100K 1/4W Resistor
R5 1M 1/4W Resistor
D1 1N4001 Silicon Diode
Q1 BC 558 PNP Transistor
LED1-LED10 Standard LED or LED Array
U1 LM3915 Audio Level IC
MISC Board, Wire, Socket For U1

19 Watt Amplifier using LA 4440

Description

This is the circuit diagram of a simple 19 watt amplifier using IC LA4440 from Sanyo.It uses very less components other than the IC LA4440.A very high quality circuit with respect to its cost and ideal for beginners.

Here IC LA 4440 is wired as a bridge amplifier to deliver a 19 W Rms on a 4 Ohm speaker. The IC has built in thermal, over voltage and short circuit protection.The IC also incorporates a audio muting function,but that is not used here.

Notes .

• Use a 12 V DC power supply able to deliver at least 3A current . IC can with stand up to 25 volt , but I prefer it should not be nothing more than 16V.
• Don’t forget to fit a proper heat sink with IC.
• Assemble the board on a good quality PCB.Carefully understand the specifications of LA 4440 given below before proceeding
• Use a 4 Ohm speaker as load. 8 Ohm speaker can also be used but the power output will drop to half (9.5 W) .
• For stereo assemble two copies of the amplifier given here.
• 

18 W MOSFET Amplifier Circuit

Description

This circuit is an audio amplifier capable of delivering a decent output power with a minimum no: of parts , with considerable sound quality.

The amplifier employs only two transistors one MOSFET and few resistors and capacitors in a shunt feedback scheme.This tiny circuit can can deliver a whopping 18Watts into 8 Ohm speaker or 30W into a 4 Ohm speaker.

To get such a good performance and stability out of this this much few components a high quality well regulated DC power supply is necessary. This is very essential for reducing noise and getting a constant output power on varying loads. A good DC voltage regulator able of providing more than 2 Amps @ 40V can be used.You can expect such a power supply design very soon here in the power supply section.

Tips.

Assemble the board on a good quality PCB.Use a preamplifier board with tone control prior to this amplifier to get better performance. If you don’t want no problem because this amplifier circuit has enough punch with in it.

Components.

R1………………2K2 1/4W Resistance
R2………………27K 1/4W Resistance
R3R4………….2K2 1/2W Trimmers
R5………………100R 1/4W Resistance
R6………………1K 1/4W Resistance
R7,R8……….. .330R 1/4W Resistance

C1 ………………22µF 25V Electrolytic Capacitance
C2 ………………47pF 63V Polyester or Ceramic Capacitance
C3,C4 …………100µF 50V Electrolytic Capacitance
C5 ………………2200µF 50V Electrolytic Capacitance

Q1 ………………BC550C
Q2 ………………IRF530 or MTP12N10
Q3……………… IRF9530 or MTP12P10

25 Watt Power Amplifier using TDA2009

Description

Here is the circuit diagram of a 25 W power amplifier made of TDA 2009 IC.TDA 2009 has two channels each rating 12.5 watts on 4 Ohm load.Here the two channels are bridged to get a single out put channel weighting 25 W.

TDA 2009 IC has also built in features such as short circuit protection,thermal protection, overload protection etc using very low external components.The most interesting factor I see about this IC is that it require no dual supply.

Circuit Diagram of Amplifier and Power Supply

Notes

• Do not connect more than 24 V to TDA 2009.
• If 5 ampere bridge is not available make one using four 5 A diodes.
• Fit a proper size heat sink to TDA 2009
• Do not operate the circuit without heat sink.
• For volume control connect a 10K pot
• All capacitors in this circuit must be rated above 25 V.

• Capacitors with + mark are electrolytic and that lead will be positive.Other capacitors will be normally ceramic.If there is exception that will be given there in the circuit or parts list.This law applies to all circuits in this site.

Tweeter Crossover circuit

Description

A single coil speaker is not good in handling high and low frequency at the same time. If we could filter out the low frequency and play it through a tweeter ,it will produce more sound quality than using a single speaker.This is what is realized here.Here the high frequencies are filtered out using a low pass filter made of C1,C2 and R1 and send to the tweeter.The low frequency is only fed to the woofer.

Circuit Diagram with Parts List

Notes

• The tweeter can be a 2 to 3 inch, 4 to 8 Ohm one .
• R1 is used to adjust match the the tweeters output level to that of woofer.
• C1 and C2 are electrolytic capacitors.
• R1 should be rated more than 2 Watts.