Audio Clipping Peak Indicator using IC TL062

This Simple Audio Clipping Peak Indicator circuit was expected to distinguish clipping in preamp stages, mixers, equalizer, amplifiers and so on. It can be utilized as a different, convenient unit, to signal by using some LEDs when the output wave form a specific sound stage is "cutting" i.e. is coming to the onset of its maximum permitted peak voltage value before an over-load is happening. This will help the operator in avoiding extreme twisting or distortion in the audio to be created through the sound hardware chain, as if it were shielding your amplifier equipments and speakers from over-loading.



This unit is particularly useful in signaling overload of the input stages in mixers, PA or musical instruments amplification chains, but is also suited to power amplifiers. A careful setting of Trimmer R5 will allow triggering of the LED with a wide range of peak-to-peak input voltages, in order to suit different requirements.

Unfortunately, an oscilloscope and a sine wave frequency generator are required to accurately setup this circuit. Obviously, the unit can be embedded into an existing mixer, preamp or power amplifier, and powered by the internal supply rails in the 9 – 30V range. The power supply can also be obtained from higher voltage rails provided suitable R/C cells are inserted. SW1 and B1 must obviously be omitted.

Circuit Operation
The heart of the audio clipping circuit is a window comparator formed by two op-amps packaged into IC1. This technique allows to detect precisely and symmetrically either the positive or negative peak value reached by the monitored signal. The op-amps outputs are mixed by D1 and D2, smoothed by C4, R7 and R8, and feed the LED driver Q1 with a positive pulse. C5 adds a small output delay in order to allow detection of very short peaks.

Notes:

• With the values shown, the circuit can be easily set up to detect sine wave clipping from less than 1V to 30V peak-to-peak (i.e. 15W into 8 Ohms). If you need to detect higher output peak-to-peak voltages, R1 value must be raised. On the contrary, if the circuit will be used to detect only very low peak-to-peak voltages, it is convenient to lower R1 value to, say, 220K omitting C2. In this way, the adjustment of R5 will be made easier.
• Using a TL062 chip at 9V supply, stand-by current drawing is about 1.5mA and less than 10mA when the LED illuminates. With TL072 or TL082 chips, current drawing is about 4.5mA and 13mA respectively.
• When using power supplies higher than 12V, the value of R10 must be raised accordingly.
• When using power supplies higher than 25V, the working voltage value of C5 must be raised to 35 or 50V.

Parts
R1 – 1M 1/4W Resistor (See Notes)
R2,R3,R8 – 100K 1/4W Resistors
R4,R6 – 10K 1/4W Resistors
R5 – 5K 1/2W Trimmer Cermet or Carbon
R7 – 2K2 1/4W Resistor
R9 – 22K 1/4W Resistor
R10 – 1K 1/4W Resistor (See Notes)
C1,C4 – 220nF 63V Polyester Capacitors
C2 – 4p7 63V Ceramic Capacitor (See Notes)
C3 – 220µF 25V Electrolytic Capacitor
C5 – 10µF 25V Electrolytic Capacitor (See Notes)
D1,D2 – N4148 75V 150mA Diodes
D3 – LED (Any dimension, shape and color)
Q1 – BC547 45V 100mA NPN Transistor
IC1 – TL062 Dual Low current BIFET Op-Amp (or TL072, TL082)
SW1 – SPST Toggle or Slide Switch or Any other switch
B1 – 9V PP3 Battery or a 9V DC power source. Should read at least 1 Ampere.

Read More

How to make a 2 Watt audio amplifier from discrete components

A 2 Watt audio amplifier made from discrete components.


A simple 2 Watt RMS Audio Amplifier which can be made from limited components.

 

Notes
This was one of the earliest circuits that I ever designed and built, in Spring 1982. At that time I had only an analogue meter and a calculator to work with. Although not perfect, this amplifier does have a wide frequency response, low harmonic distortion about 3%, and is capable of driving an 8 ohm speaker to output levels of around 5 watts with slightly higher distortion. Any power supply in the range 12 to 18 Volts DC may be used.

Circuit
The amplifier operates in Class AB mode; the single 470R preset resistor, PR1 controls the quiescent current flowing through the BD139/140 complimentary output transistors. Adjustment here, is a trade-off between low distortion and low quiescent current. Typically, under quiescent conditions, current is about 15 mA rising to 150 mA with a 50 mV input signal. The frequency response is shown below and is flat from 20Hz to 100kHz:

Bode Plot

 

 The circuit is DC biased so that the emitters of the BD139 and BD140 are at approximately half supply voltage, to allow for a maximum output voltage swing. R9 and R10 provide a degree of temperature stabilization which works as follows. If the output transistors are warm, the emitter currents will increase. This causes a greater voltage drop across R9 and R10 reducing the available bias current. All four transistors are direct coupled which ensures:-

(i) A good low frequency response
(ii) Temperature and bias change stability.

DC Voltages of Prototype
The following voltage checks were made on my prototype. All voltage are made with respect to (wrt) 0 Volt and shown in the table below.

The BC109C and 2N3906 operate in common emitter. This alone will provide a very high open loop gain. The output BD139/140 pair operate in emitter follower, allowing the amplifier to drive low impedance speakers. The signal to noise ration is shown below:

Signal to Noise Ratio:

This amplifier has a S/n ratio of 115dB at 1kHz. Overall gain is provided by the ratio of the 22k and 1k resistor. A heat sink on the BD139/140 pair is recommended but not essential, though the transistors will run "hot" to the touch.

Fourier Analysis
A quick measure of the distortion of this amplifier was performed. Operating on a 15V DC power supply with an input sinusoidal waveform of 100mV peak to peak at 1KHz produced the following results in Tina.

Fourier Coefficients

The number of samples was set to 4096 and Fourier coefficients up to the 16^th harmonic were calculated. The sum of the all harmonics up to 16KHz amounted to just under 2.9% total harmonic distortion, the results are plotted below.

Harmonic Distortion

The second and third harmonic are the biggest contribution to overall distortion. Choosing a different amplifier design, a different visaing scheme or more evenly match components can reduce distortion accordingly. At the time this amplifier was made, I only had an analogue multimeter, so all things considered, it was not too bad an effort.

Picture of my Prototype
Finally an image of the original which has stood the test of time. The BD139,140 power transistors can be seen on the left hand side, the preset near top center, the BC109C center right and 2N3906 is buried under a miniature screened audio cable, center bottom.

Cheap 12V Battery for the project above

Read More

How to make your own simple 5pf Capacitor

It is surely possible to make your own capacitors.At least those with small values, like up to 5-100pF

PARTS:

 

– Insulated wire (24-gauge, stranded or unstranded) 

That’s it!  Simply twist the two wires together – six or seven times will do the trick – and voila!, you have entered the dark art of making your own capacitors!

 

All you need is an inchworm of wire.

Two examples of 5pf capacitors. They kind of look like the Einsturzede Neubauten dude…

 
 Wanna check to see if you’re little twisting shenanigans have capacitance?  Bring on the multimeter, an essential tool on your work bench.  Adjust your multimeter to read ohms, making sure that it also displays your output in farads.

Essentially, a capacitor only consists of two metal plates separated by an insulator.  The insulation of our 24-gauge wire acts as a buffer between two pieces of copper from making a completely closed connection from the shortest path.

Read More

Simple 150 Watt amplifier circuit using transistors

This is the cheapest 150 Watt amplifier circuit you can make,I think.Based on two Darlington power transistors TIP 142 and TIP 147 ,this circuit can deliver a blasting 150 W Rms to a 4 Ohm speaker.Enough for you to get rocked?;then try out this.

TIP 147 and 142 are complementary Darlington pair transistors which can handle 5 A current and 100V ,famous for their ruggedness. Here two BC 558 transistors Q5 and Q4 are wired as pre amplifier and TIP 142 ,TIP 147 together with TIP41  (Q1,Q2,Q3) is used for driving the speaker.This circuit is designed so rugged that this can be assembled even on a perf board or even by pin to pin soldering.The circuit can be powered from a +/-45V, 5A  dual power supply.You must try this circuit.Its working great!

The preamplifier section of this circuit is based around Q4 and Q5 which forms a differential amplifier. The use of a differential amplifier in the input stage reduces noise and also provides a means for applying negative feedback. Thus overall performance of the amplifier is improved. Input signal is applied to the base of Q5 through the DC decoupling capacitor C2. Feedback voltage is applied to the base of Q4 from the junction of 0.33 ohm resistors through the 22K resistor.

A complementary Class AB push-pull stage is built around the transistors Q1 and Q2 for driving the loud speaker. Diodes D1 and D2 biases the complementary pair and ensures Class AB operation. Transistor Q3 drives the push-pull pair and its base is directly coupled to the collector of Q5.

 Circuit Diagram & Parts List .

 

Notes.

• Remember TIP 142 and 147 are Darlington pairs  .They are shown as conventional transistors in figure for ease.So don’t get confused.Even though each of them have 2 transistors ,2 resistors and 1 diode inside ,only three pins ,base emitter and collector are coming out.Rest are connected internally.So its quite OK to assume each of them as transistor for ease.
• Use a well regulated and filtered power supply.
• Connect a 10K POT in series with the input as volume control if you need.Not shown in circuit diagram.
• All electrolytic capacitors must be rated at least 50volts.

Power supply for this circuit.

A  +40/-40 unregulated dual supply for powering this amplifier project is shown below.  This power supply is only enough for powering one channel and for stereo applications double the current ratings of  the transformer, diodes and fuses.

 

TIP 142 & 147 Internal diagram and pin out.

 TIP 142-TIP 147 Pin Out Diagram with Schematics

Read More

A Simple Day Light Sensor Circuit using cheap components like LDR and UM66 IC

This circuit will help you to make a Light Sensitive Morning Alarm circuit using limited components.

The morning light or other light is sensed by an LDR (Light Dependent Resistor) or Photoresistor and it triggers the alarming section. The circuit generates a melodious alarming tone when light falls on it. 

Wire-up the circuit as shown in schematic diagram and place the LDR next to the window pane closer to your bed. Since the LDR is more sensitive to light, so make sure it will not be false triggered. 

The electronic components used in this circuit is cheap, so you can make this at your own home at very low cost and it consumes very less power, hence it ensures long working life.

The entire circuit can be classified into two sections

a. Light Sensing Section

b. Alarming Section

The light sensing part consists of a Light Dependent Resistor (LDR) or a photoresistor, which is a two terminal device having the capability to detect light (Photons).

The LDR decreases its resistance when suitable amount of light falls on it. The working principle of this circuit is based on the switching action of an npn transitor (SL 100). As i mentioned above, the LDR conducts current (Lowers its resistivity), when light falls on it and make the transistor switched ON.

The alarming section of the circuit consists of a Melody Generator IC (UM66), an NPN transistor (BC 548) and a Speaker. The output voltage from the Light Sensor Section is used to drive the alarm. The tone generated by UM66 is fed to the base of an NPN transistor, inorder to amplify the signal enough to drive the Loud-Speaker.

The whole circuit is powered by a Single 6V battery.

Read More

Cheapest High power LED driver circuit schematic

There are many other articles on internet with simpler circuits but none of them are cost effective or as cheap as this one.
Using some easy to get cheap components you can make a much better LED driver than you would have thought of.




In market, we can get 1Watt and  3Watt LED easily. And the ratings of those 1Watt LEds are  Forward Voltage 3.2V – 3.6V, Forward Current 300mA and for the 3Watt ones,m the ratings are Forward Voltage: VF3.4V , Forward Current :700mA .

So we consider 3.4volts as optimal voltage, and thus the 1watt LED is giving 3.4×0.3=1.02Watt and for 3watt it is, 2.38Watts.

So here’s the simplest circuit that can be used.

Here, for a fixed reference supply, LM7805 regulator I.C which can deliver upto 1Amps of current, and in our cases the max required current is 700ma or 0.7Amps, so no problem there. And since the resistor “R” will be eating the extra 1.6 volts(5.0-3.4). So what would be the value of R?

For 1 watt model, there’s current of 300mA, so the value of the resistor should be 5.3 Ohms(appx) and wattage should be 0.48. So a 5.6ohms 1/2watt general purpose resistor will do the job perfectly. And similarly, for the 3Watt model, the value of R would be 2.2Ohm 1.25Watt(or 2Watt).

We can feed any voltage greater than 5.5 volts, so we can run this circuit in 6Volts supply or in 12 volts supply.

Read More

Simple and Cheap 100W Inverter Circuit

Inverter is a small circuit which will convert the direct current (DC) to alternating current (AC). The power of a battery is converted in to’ main voltages’ or AC power. This power can be used for electronic appliances like television, mobile phones, computer etc. the main function of the inverter is to convert DC to AC and step-up transformer is used to create main voltages from resulting AC.

In the block diagram battery supply is given to the MOSFET driver where it will convert DC to AC and the resulting AC is given to the step up transformer from the step up transformer we will the get the original voltage.

Main Components:

CD4047: CD4047 is a multi vibrator with very low power consumption designed by TEXAS INSTRUMENTS.it can operate in monostable multivibrator and also astable multivibrator.in the astable multivibrator mode it can operate in free running or gatable modes and also provides good astable frequency stability. It can generate 50% duty cycle which will create a pulse, which can be applied for inverter circuit. This is mainly used in frequency discriminators, timing circuits frequency divisions etc.

IRF540: IRF540 is a N-channel enhanced mode silicon gate field effect transistor (MOSFET).they are mainly used in switching regulators, switching converters relay drivers etc. the reason for using them in the INVERTER circuit is the because it is a high switching transistor , can work in very low gate drive power and have high input impedance.

IRF540 Symbol:

 

Simple 100W Inverter Circuit Diagram:

 Explanation:

• In the circuit diagram we can observe that 12V battery is connecter to the diode LED and also connected to the pin8 of the IC 4047 which is VCC or power supply pin and also to pin 4 and 5 which are astable and  complement astable of  the IC. Diode in the circuit will help not give any reverse current, LED will work as a indicator to the battery is working or not.
•  IC CD4047 will work in the astable multivibrator mode. To work it in astable multivibrator mode we need an external capacitor which should be connected between the pin1 and pin3. Pin2 is connected by the resistor and a variable resistor to change the change the output frequency of the IC. Remaining pins are grounded .The pins 10 and 11 are connected to the gate of the mosfets IRF540. The pin 10 and 11 are Q and ~Q from these pins the output frequencies is generated with 50% duty cycle.
• The output frequency is connected to the mosfets through resistor which will help to prevent to the loading of the mosfets. The main AC current is generated by the two mosfets which will act as a two electronic switches. The battery current is made to flow upper half or positive half of the primary coil of transformer through Q1 this is done when the pin 10 becomes high and lower half or negative half is done by opposite current flow through the primary coil of transformer, this is done when pin 11 is high. By switching the two mosfets current is generated.
• This AC is given to the step up transformer of the secondary coil from this coil only we will get the increased AC voltage , this AC voltage is so high; from step up transformer we will get the max voltage. Zenor diode will help avoid the reverse current. 

NOTE: The generated AC is not equal to the normal AC mains or house hold current. You cannot use this voltage for pure electric appliances like heater, electric cooker etc. Because of the fast switching of mosfets heat is dissipated which will effect the efficiency, use heat sink to remove this problem. The transformer can be bought through transformer manufacturer in your city or town.

Read More

Lead Acid Battery Charger Circuit

To successfully charge a battery, it should be supplied with DC current and not AC. This circuit shows how you can use DC voltage to regulate and finally charge the battery.
Now if you have AC voltage, you can convert it using a rectifier bridge and pass it through filter to obtain DC voltage which can then be used in this circuit to charge the Lead Acid Battery. Car also consists a lead acid battery.

As seen in the DC voltage is given to the DC voltage regulator here we use LM317 which is a DC voltage regulator. The regulated DC out voltage is given to battery. There is also a trickle charge mode circuitry which will help to reduce the current when the battery is fully charged.

Components of Lead Acid Battery Charger Circuit:

LM317: LM317 is voltage regulator invented by Robert C. Dobkin and Robert J. Widlar in 1970.the main function of this voltage regulator is to regulate the voltage and give the constant voltage without any noise disturbance; for example if we have 42v and we want only 10v so to get this output we will give 42v to a voltage regulator and uninterrupted 10v. For LM317 there is no maximum voltage unless the difference between the input and output voltage should not exceed maximum differential voltage. The maximum differential voltage is around 40V and also it give exceed output current of 1.5A for 1.2v to 37V .it has three pins input, output and adjustable pin. In the adjustable we can adjust the difference between the input and output voltages. Minimum voltage should be 18V which is given as input voltage to the regulator.

Lead Battery: Lead Battery is a rechargeable battery in the 1857 by gaston plante. The main advantages of Lead battery is it will dissipate very little energy (if energy dissipation is less it can work for long time with high efficiency),it has very low energy to weight ratio, it can deliver high current’s and very low cost.

Lead Acid Battery Charger Circuit Diagram:

The circuit diagram can be seen below:

 Circuit Explanation:

• The DC voltage is connected to the Vin of the LM317 in between we have connected the capacitors will be opened but if it had any AC noise it will remove it.
• The Vout of the LM317 is given to the battery which is to be charged, pin1Adjustment pin of the LM317 is connected to the transistor Q1, Resistor R1, R2, R5 which will help to adjust the regulator.
• The output of regulated voltage and current is controlled by the transistor Q1, resistor R1 and R2 and potentiometer R5.potentiometer which is used to set the charging current. Resistor R2 will have more current when the battery is getting charged. This will help to conduct the transistor Q1. The conduction of Q1 will help to adjust the voltage of LM317.
• TRICKLE CHARGE MODE: in this mode if the battery is charged the reverse current will flow. If the LED has glown then we can say that battery is charged. The diode D2 will protect the LM317 from the reverse current. When the battery is fully charged it will reduce the charge current. If the charge current the transistor will get off so the voltage regulator cannot be adjusted.

NOTE:

1. The battery should be charged with 1/10^th it’s charging current.so the voltage regulator must generate 1/10^th of the charging current produced by the battery
2. Heat sink should be attached to the LM317 to the get the better efficiency.

Read More

Bipolar LED Driver Circuit

A Bi color LED is a special type of LED consists of two diodes connected in inverse direction to each other inside a package. A bi color LED generally consists of three terminals- a common pin and two separate pins. 


 
The common pin can be connected to ground if it is a common anode LED or connected to +5V supply, if it is a common cathode. However there is another type of bi color LED with two terminals. The device functions as per the positive signal given to one of the terminals. For instance for a green and red bi color LED, a positive signal at the green terminal and negative signal at red terminal ensures the green LED to be forward biased and red LED to be reverse biased. This causes the green light to flash. Same is the case for the red LED. However if both the terminals are given negative signals, neither of the diodes would conduct and the device would remain off.  If positive signal is applied to both the terminals, a different color, based on the combination of the LED colors, would flash.

Here, we are designing a simple bi color LED driver circuit using a Microcontroller. The LED used here has a forward voltage drop of 2.2V and hence can be biased using a 5V supply. The control is done by the microcontroller program, based on the inputs given from two push buttons.

Principle Behind Bi-Polar LED Driver Circuit:

The circuit uses a microcontroller to drive the bipolar LED. The input command is given from the three push buttons and based on the inputs; the microcontroller is accordingly programmed to send appropriate signals to the two output pins. These output pins are connected to the terminals of the bi-polar LED.

Bipolar LED Driver Circuit Diagram:

 Bipolar LED Driver Circuit Design:

It is a simple circuit and the design mainly involves designing the interfacing of Microcontroller, designing the oscillator and reset circuits for the microcontroller and selection of the LED resistor.

The microcontroller interfacing is accomplished by connecting two push button switches to port P1 and connecting the two terminals of bi color LED to port P2.

The oscillator design is done by selecting two 10pF ceramic capacitors in order to provide stability. The clock signal is generated using an 11MHz Crystal Oscillator. The reset circuit is designed by selecting an electrolyte capacitor of 10uF and a resistor of 10K to achieve a reset pulse width of 100ms. The voltage drop across the resistor is kept around 1.2V.

The first part of design involves writing the code for the microcontroller. This involves the following steps.

1. Create a new project in the Keil window.
2. Select the target device for the project. Here we select AT89C51 from Atmel.
3. Create a new file such that a blank text field appears.
4. Write the code. The code is written, keeping in mind the following algorithm,
5. Assign a variable to the input and output port.
6. Check if one of the inputs is active low.
7. In case one of the inputs is at logic low, assign a logic high signal to one of the LED terminals.
8. In case none are at logic low, make sure the LED is switched off.
9. Save the code with .c extension.
10. Add the code to the source folder under target folder.
11. Create a Hex file by clicking the ‘Configure Flash Tools’ under ‘Flash’ menu.

The second part involves drawing the circuit on simulation software. Here we use Proteus. The circuit is drawn based on the design method described above.

The third part involves simulating the circuit. This is done by first adding the hex file to the microcontroller and then clicking on the run button.

Working of Bipolar LED Driver Circuit

Once the circuit is switched on, the microcontroller continuously scans the input pins at port P1. Suppose the first button is pressed, the microcontroller receives a low logic signal at the corresponding input pin and accordingly the compiler assigns a high logic signal to pin P0.0 and low logic signal to pin P0.1. This causes the red light of the LED to glow.

Now when the second button is pressed, the compiler will accordingly assign a low logic signal to the pin P0.0 and a high logic signal to pin P0.1. This causes the green light to glow. On pressing the third button, low logic signals will be assigned to both the output pins and the LED will be switched off. In the meanwhile a low logic signal is always given to the common pin.

Bipolar LED Driver Applications:

1. This circuit can be used for indication purposes.
2. This circuit can be used at applications where flashing of light is required, as in beacon flashing.

Limitations of Bipolar LED Driver Circuit:

1. This is a theoretical circuit and may require changes for practical implementations.
2. Most of the bi color LEDs requires higher supply voltage than 5V because of their higher forward voltage rate and this circuit only provides 5V supply voltage to the LED.
3. The LED resistor provides a voltage drop which decreases the biasing voltage of the LED.

  

Read More

Simple audio amplifier using LM386.

The LM386 is an audio amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.

Parts will be assembled and connected according to the following schematic:

This project uses an integrated circuit with capacity of 10 transistors to amplify much better with much less power drain on the batteries than our simple amplifier.

Following parts are required:

• A LM386 integrated circuit amplifier chip
  This is the main working part of the amplifier.
• A small speaker
  
• Some jumper wires 
• 9 volt DC adapter of 2 Amps or more or  9 volt battery clip and  9 volt battery  

The Three Penny Radio normally has a piezoelectric earphone attached at points J-20 and E-22. We replace the earphone with our amplifier.
Below is a closeup of the amplifier section:
 

 Here you can see that we have connected the Three Penny Radio output at J-20 to the ground rail below the blue line. This rail has all of its holes connected together. We connect the black (negative) wire from the battery to the ground rail. We connect the red (positive) wire from the battery to the power rail, just above the red line at the top of the photo. Having the power and ground connected to these rails makes it easier to connect the other parts, and makes it easier to see where all the connections are.

You can connect your audio source instead of radio.

The other output from the Three Penny Radio us plugged into E-22.
Using the labeled grid as before, the parts are connected this way:

• LM386 amplifier chip at E-24, E-25, E-26, E-27 and F-24, F-25, F-26, and F-27.
• Jumper wire: F-20 to ground rail.
• Jumper wire: C-22 to C-26.
• Jumper wire: A-25 to ground rail.
• Jumper wire: A-27 to ground rail.
• Jumper wire: J-26 to power rail.
• Speaker: red wire to H-27 and black wire to ground rail.
• Negative 9 volt battery wire (black): ground rail.
• Positive 9 volt battery wire (red): power rail.

When all the wires are connected properly, you should be able to hear radio stations coming from the speaker. They will not be particularly loud, but we can increase the volume 10-fold with a simple adjustment.

 

We put a 10 microfarad capacitor connecting pins 1 and 8 of the integrated circuit (put the negative capacitor lead into hole D-24 and the positive capacitor lead into hole G-24).

This bypasses a resistor inside the integrated circuit, boosting the gain from 20 to 200.

One problem with the circuit so far is that the speaker will get warm and the battery will not last long. This is because a certain amount of DC current is going through the speaker. Direct current (DC) does not make sounds, and so this current is a complete waste of battery power, and simply warms up the speaker coil.

 

We fix this problem by putting a 220 microfarad capacitor between the integrated circuit output pin (pin 5, in hole F-27) and the red speaker wire. The positive capacitor lead is put into hole J-27, and the negative capacitor lead is put into hole J-29. The red speaker wire is moved to hole G-29.

To prevent the capacitor from changing the sound, we add two more components to create a "filter" that lets only audio frequencies get to the speaker.

 

Here we have moved the negative lead of the 220 microfarad capacitor to hole J-28, and moved the red wire of the speaker to H-28. We put a 10 ohm resistor into holes G-27 and G-30. A 0.047 microfarad capacitor goes into hole F-30 and the ground rail.

Our amplifier is working pretty well now. But our little speaker has a high tinny voice, because of its size. It would be nice if it had a little more power on the lower frequencies, what we call "bass response".

We can arrange to amplify the lower frequencies more than the high ones. We make another filter from a 0.033 microfarad capacitor and a 10,000 ohm resistor, and connect that between the output pin and pin 1 of the integrated circuit. This will feed some of the low frequencies back into the amplifier to be amplified again.

We put the 10,000 ohm resistor in holes C-24 and F-29. We put the 0.033 microfarad capacitor in holes I-27 and I-29.

 The amplifier is now ready with much better sound.

Read More