Download this circuit in PDFUniversal Preamplifier
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Most audio amplifier systems must have preamplifiers with many different characteristics. These include high-gain linear response for magnetic microphones, low-gain linear response for tuners, and high-gain RIAA equalization for magnetic phone cartridges.
To meet this broad requirement, most amplifier designers include a single universal preamplifier circuit. Basically a high-gain linear amplifier, its characteristics can be altered by switching alternative resistor filter networks into its feedback system.
For example, when the selector switch is set to the Mag phono position, alternative input sources can be selected by S1-a, and appropriate linear-response gain control feedback resistors 220K, 470K, and 1M are now selected by S1-b. Those feedback resistor values are selected between 10 kilo ohms and 10 megohms to suit individual listener tastes. Circuit gain will be proportional, to the feedback resistor value.
| Description |
Most audio amplifier systems must have preamplifiers with many different characteristics. These include high-gain linear response for magnetic microphones, low-gain linear response for tuners, and high-gain RIAA equalization for magnetic phone cartridges.
To meet this broad requirement, most amplifier designers include a single universal preamplifier circuit. Basically a high-gain linear amplifier, its characteristics can be altered by switching alternative resistor filter networks into its feedback system.
For example, when the selector switch is set to the Mag phono position, alternative input sources can be selected by S1-a, and appropriate linear-response gain control feedback resistors 220K, 470K, and 1M are now selected by S1-b. Those feedback resistor values are selected between 10 kilo ohms and 10 megohms to suit individual listener tastes. Circuit gain will be proportional, to the feedback resistor value.
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Portable Audio Amplifiers
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Stereo per channel
VCC=9V;RL=4?/3W
VCC=9V;RL=8?/2W
Bridge Application
VCC=9V;RL=8?/5W
VCC=9V;RL=4?/8W
Supply Voltage min = DC3v @ 500mA
Supply Voltage max = DC12v @ 500mA
Supply Voltage recommended = DC9v @500mA
DESCRIPTION
Above circuits are based on TEA2025 is a monolithic integrated audio amplifier in a 16-pin plastic dual in line package manufactured by UTC .Circuit has an Internal Thermal Protector. It is designed for portable cassette players and radios. You can also use it as your PC Audio Amplifier. A few external components required to build this circuit. Use 9v transformer to play the circuit. But not more than DC12v. Because it can damage the amplifier IC. So build n Enjoy.
Description |
Stereo per channel
VCC=9V;RL=4?/3W
VCC=9V;RL=8?/2W
Bridge Application
VCC=9V;RL=8?/5W
VCC=9V;RL=4?/8W
Supply Voltage min = DC3v @ 500mA
Supply Voltage max = DC12v @ 500mA
Supply Voltage recommended = DC9v @500mA
DESCRIPTION
Above circuits are based on TEA2025 is a monolithic integrated audio amplifier in a 16-pin plastic dual in line package manufactured by UTC .Circuit has an Internal Thermal Protector. It is designed for portable cassette players and radios. You can also use it as your PC Audio Amplifier. A few external components required to build this circuit. Use 9v transformer to play the circuit. But not more than DC12v. Because it can damage the amplifier IC. So build n Enjoy.
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600W Audio Amplifier
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POWER :
Maximum Output power @ 8ohms : 300watt
Absolute max power supply voltage :±38V to ±40V
Recommended power supply voltage :±30V to ±35V
GENERAL DISCRIPTION :
The circuit is based around {LM4702}manufactured by NATIONAL semiconductors&{MJ11029-MJ11028} by ON semiconductors It is a high fidelity audio power amplifier. Designed for demanding consumer and pro-audio applications. You can also use this circuit with AV receivers, Audiophile power amps, Pro Audio High voltage industrial applications etc Amplifier output power maybe scaled by changing the supply voltage and number of output devices. The circuit includes thermal shutdown circuitry that activates when the die temperature exceeds 150°c. CIRCUIT�s mute function, when activated, mutes the input drive signal and forces the amplifier output to a quiescent state.
Description |
POWER :
Maximum Output power @ 8ohms : 300watt
Absolute max power supply voltage :±38V to ±40V
Recommended power supply voltage :±30V to ±35V
GENERAL DISCRIPTION :
The circuit is based around {LM4702}manufactured by NATIONAL semiconductors&{MJ11029-MJ11028} by ON semiconductors It is a high fidelity audio power amplifier. Designed for demanding consumer and pro-audio applications. You can also use this circuit with AV receivers, Audiophile power amps, Pro Audio High voltage industrial applications etc Amplifier output power maybe scaled by changing the supply voltage and number of output devices. The circuit includes thermal shutdown circuitry that activates when the die temperature exceeds 150°c. CIRCUIT�s mute function, when activated, mutes the input drive signal and forces the amplifier output to a quiescent state.
5-Band Graphic Equalizer
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This complete high quality, low noise 5-BAND GRAPHIC EQUALIZER circuit is based around Monolithic Linear integrated circuit LA3600 manufactured by SANYO. This circuit is very easy to build and has good Quality. You can use it with Portable component stereos, tape-recorders, radio-cassette recorders, car stereos etc...
It is On-chip one operational amplifier. 5-band graphic equalizer for one channel can be formed easily by externally connecting capacitors and variable resistors which fix fo (resonance frequency). Series connection of two LA3600�s makes multiband (6 to 10 bands) available. It is Highly stable to capacitive load. Maximum supply voltage VCC max 20V must not be exceeded. The operating voltage is in the range of 5 to 15V. Application of power with the pin-to-pin spaces shorted causes breakdown or deterioration of the IC to occur. When mounting the IC on the board or applying power, make sure that the pin-to-pin spaces are not shorted with solder, etc.
Description |
This complete high quality, low noise 5-BAND GRAPHIC EQUALIZER circuit is based around Monolithic Linear integrated circuit LA3600 manufactured by SANYO. This circuit is very easy to build and has good Quality. You can use it with Portable component stereos, tape-recorders, radio-cassette recorders, car stereos etc...
It is On-chip one operational amplifier. 5-band graphic equalizer for one channel can be formed easily by externally connecting capacitors and variable resistors which fix fo (resonance frequency). Series connection of two LA3600�s makes multiband (6 to 10 bands) available. It is Highly stable to capacitive load. Maximum supply voltage VCC max 20V must not be exceeded. The operating voltage is in the range of 5 to 15V. Application of power with the pin-to-pin spaces shorted causes breakdown or deterioration of the IC to occur. When mounting the IC on the board or applying power, make sure that the pin-to-pin spaces are not shorted with solder, etc.
200W Audio Amplifier
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Output Power : 200Watts
Load Resistance : 8ohms
Input impedance : 55K
Maximum supply voltage : (+95v)-0-(-95v)
Recommended supply voltage : (+66v)-0-(-66v)
This complete high quality, low noise mono audio power amplifier is based around the Hybrid Integrated Circuit STK4050 manufactured by Sanyo. The circuit incorporates volume and has a maximum music output power of 200W.The circuit incorporates an on board power supply; therefore, only centre tapped transformer is required to power the circuit. I t has very good quality sound. U can use it with your Home Theatre your PC & etc... You can also use it as Subwoofer Amplifier. It is a compact package for THIN-TYPE Audio sets. Easy Heatsink design to disperse heat generated in THIN-TYPE audio sets. Constant-Current circuit to Reduce supply switch-ON and switch-OFF shock noise. External supply switch-On and switch-OFF shock noise muting, Load short-circuit protection, thermal shutdown and other circuits can be tailored-designed.
Description |
Output Power : 200Watts
Load Resistance : 8ohms
Input impedance : 55K
Maximum supply voltage : (+95v)-0-(-95v)
Recommended supply voltage : (+66v)-0-(-66v)
This complete high quality, low noise mono audio power amplifier is based around the Hybrid Integrated Circuit STK4050 manufactured by Sanyo. The circuit incorporates volume and has a maximum music output power of 200W.The circuit incorporates an on board power supply; therefore, only centre tapped transformer is required to power the circuit. I t has very good quality sound. U can use it with your Home Theatre your PC & etc... You can also use it as Subwoofer Amplifier. It is a compact package for THIN-TYPE Audio sets. Easy Heatsink design to disperse heat generated in THIN-TYPE audio sets. Constant-Current circuit to Reduce supply switch-ON and switch-OFF shock noise. External supply switch-On and switch-OFF shock noise muting, Load short-circuit protection, thermal shutdown and other circuits can be tailored-designed.
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Infrared cordless Headphone Amplifier
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Using this low cost Project one can reproduce AUDIO from TV without disturbing anyone. It does not use any wire between TV and HEADPHONE. In place of pair of wires it uses invisible Infrared light to transmit audio signals from TV to Headphone. Without using any lens a range of up to 6 meters is possible. Range can be extended by using Lenses and Reflectors with IR sensors comprising transmitters and receivers. IR transmitter uses two-stage transistor amplifier to drive two IR leds connected in series. An audio output transformer is used (in reverse) to couple Audio output from TV to the IR transmitter. Transistors (BC547) & (BD140) amplify the audio signals received from TV through audio transformer low impedance output windings (lower gauge or thicker wire) are used for connection to TV side while high impedance are connected to the IR transmitter. This IR transmitter can be powered by 9v mains Adaptor or 9v Battery. Led in transmitter circuit functions as power-on indicator. IR receiver uses 3-stage transistors amplifier. The first two transistors (BC549c)from audio signal amplifier. While the third transistor(BD139)is used to drive a headphone. Adjust potmetre for max clarity. Direct photo transistor towards the IR Leds of transmitter for max range. A 9v Battery can be used to receiver circuit for portable operation
Three Channel Audio Mixer
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| Description |
Above schematic is for a three channel audio mixer. That will provide an overall gain of one between the output and each input channel. Each input channel includes a single 0.1uf capacitor and 100-Kilohms resistor to provide an output impedance of 100K. The number of input channels to this audio mixer can be increased by adding more capacitors and resistors with same value as capacitor(0.1uf) and resistor(100K). The mixer should be located between the output of tone control circuitry and the input to the power amplifier. One input should be taken from the output of the tone control circuit, and the other inputs should either be grounded or taken from desired source.
ACTIVE BASS TONE CONTROLLER
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ACTIVE BASS TONE CONTROLLER circuit diagram
It is very useful (and has Best Quality) for 1 -100watt AUDIO AMPLIFIERS
20W Audio Amplifier using LM1875
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| Specifications |
| 20W Audio Amplifier kit is based on LM1875 IC.
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| Parts List |
| PCB |
| Download |
20W Bridge Audio Amplifier
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Circuit provided by
| Specifications |
| 20W Bridge Audio Amplifier kit, based on the TDA2005 IC, a class B dual audio amplifier, specifically designed for car radio applications etc.
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| Schematic |
| Parts List |
| PCB |
| Download |
Stereo tape head preamplifier using LA3161
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| Specifications |
| The Stereo Tape Head Preamplifier kit is based on LA3161 IC from SANYO.
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| Schematic |
| Parts List |
| PCB |
| Download |
Tiny audio amplifier using LM386
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| Specifications |
| Schematic |
| Parts List |
| Inputs - Outputs configuration |
| PCB |
| Download |
5,000W ultra-light, high-power amplifier, without switching-mode power supply
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This circuit is of an 2x 2,500W RMS stereo amplifier, super-light and without switching-mode power supply. The circuit just shows a channel, and the power supply that it assists to the two channels. The audio circuit should be duplicated, but the power supply assists to the two channels without problems.
A special care should be destined to the insulating transformer of the audio line, that should be of audio-high-quality, of the type used in microphone pre amps input line. The whole group (2 channels) of 5,000W RMS it should not weigh more than 32 lbs, already inside of an appropriate metallic box.
WARNING:
This circuit is exclusively for amateur use. It contains not-isolated parts of the electric AC net and it can be very dangerous. The connections for the speakers are not isolated of the domestic AC net and it requests extra care. This procedure seeks to substitute a conventional power supply with great weight and cost reduction, without necessarily to use a switching-mode power supply.
This procedure cannot be allowed in some countries for commercial-use. The author doesn't have any responsibility for the form as that circuit it will be applied.
2N3055 Power Amplifier
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Some comments:
- capacitor C1 regulates the low frequencies (bass), as the capacitance grows, the low frequncies are getting louder.
- capacitor C2 regulates the higher frequencies (treble), as the capacitance grows, the higher frequencies are getting quiter.
- this is a class B amplifier, this means, that a current must flow through the end transistors, even if there is no signal on the input. This current can be regulated with the 500Ω trimmer resistor. As this current incrases, the sound of the amplifier gets better, but the end transistors are more heating. But if this current decrases, the transistors are not heating so much, but the sound gets worse...
Amplifier schematic:< sub> 
Simple and low cost. The optimal supply voltage is around 50V, but this amp work from 30 to 60V. The maximal input voltage is around 0.8 - 1V. As you can see, in this design the components have a big tolerance, so you can build it almost of the components, which you find at home. The and transistors can be any NPN type power transistor, but do not use Darlington types... The output power is around 60W.
Some comments:
- capacitor C1 regulates the low frequencies (bass), as the capacitance grows, the low frequncies are getting louder.
- capacitor C2 regulates the higher frequencies (treble), as the capacitance grows, the higher frequencies are getting quiter.
- this is a class B amplifier, this means, that a current must flow through the end transistors, even if there is no signal on the input. This current can be regulated with the 500Ω trimmer resistor. As this current incrases, the sound of the amplifier gets better, but the end transistors are more heating. But if this current decrases, the transistors are not heating so much, but the sound gets worse...
Amplifier schematic:
Motorola Hi-Fi power amplifier
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I am very contented with this amplifier. It gives a very good sound quality.
Have fun with it!
This is a very simple, low cost, Hi-Fi quality power amplifier. You can build it 5 ways, like it�s shown in the table (from 20 W to 80 W RMS).
Some comments:
- The first thing that you must do, is to measure the end transistors (T3 and T4) amplifying coefficient, the hfe or β. If their disagreement is bigger than 30 %, the amplifier would not give a clear sound. I used MJ3001 and MJ2501 transistors, and this disagreement was around 5%.
- Before the first �turning on� you must short circuit the inputs of the amp, and put a mA-meter on the output, than turn the amplifier on, and tune the R13 pot, to decrease the DC current on the output, to some uA-s, or in a lucky situation to zero. I was able to decrease it to 10 uA.
< sub> - The first thing that you must do, is to measure the end transistors (T3 and T4) amplifying coefficient, the hfe or β. If their disagreement is bigger than 30 %, the amplifier would not give a clear sound. I used MJ3001 and MJ2501 transistors, and this disagreement was around 5%.
- Before the first �turning on� you must short circuit the inputs of the amp, and put a mA-meter on the output, than turn the amplifier on, and tune the R13 pot, to decrease the DC current on the output, to some uA-s, or in a lucky situation to zero. I was able to decrease it to 10 uA.
Have fun with it!
Amplifier of acoustic frequencies with preamplifier
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TECHNICAL CHARACTERISTICS:
Tendency of catering: 15V
Force of expense: 4,2Wrms in the 4W
Minimal signal of entry: 94mVp-p with preamplifier, 0,65Vp-p without the preamplifier.
Materially:
| R1 | 2,2KW |
| R2 | 330KW |
| R3 | 4,7KW logarithmic potentiometer |
| R4 | 330W |
| R5 | 1KW |
| R6 | 1,5W |
| C1, C6 | 100nF polyester |
| C2 | 100mF/25V ilektrolytjko's |
| C3, C7 | 1mF/25V electrolytic |
| C4 | 1000uF/25V electrolytic |
| C5 | 10uF/25V electrolytic |
| Q1 | BC547 |
| U1 | TDA2002 |
| LS1 | Loudspeaker. |
Notes:
Proportionally the resistance of loudspeaker changes the force that it can give the amplifier:
| LS1 | Force of expense |
| 2W | 6,5Wrms |
| 4W | 4,2Wrms |
| 6W | 3Wrms |
| 8W | 2,25Wrms |
FET Audio Mixer
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This simple circuit mixes two or more channels into one channel (eg. stereo into mono). The circuit can mix as many or as few channels as you like and consumes very little power. The mixer is shown with two inputs, but you can add as many as you want by just duplicating the "sections" which are clearly visible on the schematic.
Schematic
Parts
| Part | Total Qty. | Description |
| R1, R3 | 2 | 10K Pot |
| R2, R4 | 2 | 100K 1/4 W Resistor |
| R5 | 1 | 6.8K 1/4 W Resistor |
| C1, C2, C3 | 3 | 0.1uF Capacitor |
| Q1 | 1 | 2N3819 Junction FET |
| MISC | 1 | Wire, Shielded (Metal) Case, Phono Or Other Plug For Output |
Notes
1. As many or as few channels as are required can be added to the mixer. Do this by just duplicating the input "sections" which are clearly shown on the schematic. One version of this mixer I saw had 25 inputs!
2. A shielded case is probably needed to reduce hum and help stop oscillations.
3. The circuit can be powered by a single 9 volt battery.
Sound Level Meter
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This nifty sound level meter is a perfect one chip replacement for the standard analog meters. It is completely solid state and will never wear out. The whole circuit is based on the LM3915 audio level IC and uses only a few external components.
Schematic
Corrected schematic by "Eplanet"
Original Schematic
Parts
| Part | Total Qty. | Description |
| C1 | 1 | 2.2uF 25V Electrolytic Capacitor |
| R1 | 1 | 1K 1/4W Resistor |
| D1 | 1 | 1N4002 Silicon Diode |
| LED1-LED10 | 10 | Standard LED or LED Array |
| U1 | 1 | LM3915 Audio Level IC |
| MISC | 1 | Board, Wire, Socket For U1 |
Notes
1. V+ can be anywhere from 3V to 20V.
2. The input is designed for standard audio line voltage (1V P-P) and has a maximum input voltage of 1.3V.
3. Pin 9 can be disconnected from ground to make the circuit use a moving dot display instead of a bar graph display.
