Tips for Choosing a quality Power Amplifier

Here are some tips you need to note:

1. Pick of the power that suits your needs. For personal use such as exercise, etc., is sufficient to choose an amplifier with a power of 15-20 watts. In most small power amplifiers are already available facilities such as Head Phone jack (eg Guitar Amplifier Laser 20) which is very useful especially for young people who have a habit of playing music until midnight. By leveraging these channels to Head Phone, then secured another household or neighbors will not be disturbed our music sound. Sound good hasilnya.Apabila amplifier system we will use to train together in a full band with drums, etc., then you should choose a larger power amplifier that is 70 watts or above. Thus the sound produced from the amplifier and sound system will not be drowned by the sound of pounding and pounding beat Drum.Untuk use on stage, you will need a higher power that is at least 125 watts or more, because this amplifier will be able to once we use as a monitor of musical instruments were playing.

2. Choose the facilities we need. Do not buy amplifiers which have facilities that we do not really need when it is increasing the price we pay. Unless the same price we can get better facilities, there is no harm in our selection.

3. Choose a good quality amplifier. If we need an amplifier to your keyboard, then it is advisable to select an amplifier that does not change the color of the original sound generated by the keyboard musical instrument they will be (flat). There are many amplifiers that produce different sounds from the original sound, if this happens there will be other voices that would reduce the original character of the actual sound produced by the keyboard because of the addition or subtraction of a particular frequency. Usually this happens at a very low frequency (low bass) or very high frequency (high treble). (Try the sound system rental, sound rental service) For amplifiers Electric Guitar and Electric Bass this (flat characteristic) does not apply because it specifically for these two types of instruments are required specificity of character frequency. Basically for Electric Guitar amplifier output is not needed for low frequency and high. For Electric Bass needed a low frequency, but not required a high frequency. We can learn from the rental place and the sound system rental-quality musical instrument.

4. Model and performance amplifier can be considered final. The desired model will depend on individual taste. A good model according to a person, not necessarily a good thing according to those who lainnya.Pada most professional musicians model will be the last option or not too overlooked. They will be more concerned with the quality and facilities of the amplifier. Maybe we can find also in the rental services professional sound and musical instrument rental place bagus.Demikian brief tips on choosing an amplifier, hopefully this can help to determine the right choice before you buy an amplifier and produce sound quality music is also of course .

Tips for Choosing Quality Amplifier

1. Pick of the power to suit your sound system. For personal use such as exercise is sufficient to choose an amplifier with 1-20watt power. In most electronic devices / small power amplifiers are already available facilities such as head phone jack (eg laser20 guitar amplifier) ​​is very useful especially for young people who have a habit of playing music until midnight. By leveraging the channel for these headphones, then secured another household or neighbors will not be disturbed "attraction" we. If the amplifier sound system we will use to train together in a group full band * with drum and band instrument, then you should choose a power amplifier 70watt or above. Thus the sound produced from the amplifier will not be drowned by the sound of pounding and pounding drum beats. For use on stage, you will require more resources than most, namely at least 125watt or more, because this amplifier will be at the same we use as a monitor of musical instruments were playing.

2. Select the facilities we need. Do not buy a multimedia system / amplifier that has the facilities that we do not really need, if it is increasing the price we pay. Unless the same price we can get better facilities, there is no harm in our selection.

3. Choose a good quality amplifier. If we need an amplifier to your keyboard, then it is advisable to select an amplifier that does not change the original color generated by the keyboard (flat). There are many Indonesian musical instrument amplifier that produces a different sound from the original sound, if this happens there will be other voices that would reduce the original character of the actual sound produced by the keyboard because of the addition or subtraction of a certain frequency speaker system. Usually this happens at a very low frequency. (Low bass) or very high frequency (high treble). To Lighting System, Electric Amplifier Electric Bass Guitar and this (flat characteristic) does not apply because it specifically for these two types of instruments required specificity of character frequency. Basically for Electric Guitar not dipelukan amplifier output for low frequencies and high. For Electric Bass needed a low frequency, but not required a high frequency.

4. Models and appearance can be thought being given to the last amplifier. The desired model will depend on individual taste. A good model according to a person not necessarily a good thing by other people.

In most professional musicians, models will be the last option or not too overlooked. They will be more concerned with the quality and features of the amplifiers for musical instruments. But if you are confused, you could just rent equipment or hire sound system rental equipment.

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A Low Cost Hearing Aid Circuit

Small and portable unit, Useful for old men and old women

This low-cost, general-purpose electronic hearing aid works off 3V DC (2x1.5V battery). The circuit can be easily assembled on a veroboard. For easy assembling and maintenance, use an 8-pin DIP IC socket for TDA2822M.

Circuit Diagrams:

 A Low Cost hearing Aid Circuit

Parts:
P1 = 10K
R1 = 2.2K
R2 = 330K
R3 = 680R
R4 = 33R
R5 = 100R
R6 = 4.7R
R7 = 4.7R
R8 = 220R
C1 = 0.01uF-10V
C2 = 100nF-63V
C3 = 47uF-10V
C4 = 10uF-10V
C5 = 0.01uF-10V
C6 = 100uF-10V
C7 = 100nF-63V
C8 = 100nF-63V
D1 = Red LED
Q1 = BC547
IC1 = TDA2822M
EP1 = Mono Earphone 32R
SW1 = On-Off Switch

Circuit Operation:

In this circuit, transistor Q1 and associated components form the audio signal preamplifier for the acoustic signals picked up by the condenser microphone and converted into corresponding electrical signals. Resistor R5 and capacitor C3 decouple the power supply of the preamplifier stage. Resistor R1 biases the internal circuit of the low-voltage condenser microphone for proper working. The audio output from the preamplifier stage is fed to the input of the medium-power amplifier circuit via capacitor C2 and volume control P1.

The medium-power amplifier section is wired around popular audio amplifier IC TDA2822M (not TDA2822). This IC, specially designed for portable low-power applications, is readily available in 8-pin mini DIP package. Here the IC is wired in bridge configuration to drive the 32-ohm general-purpose monophonic earphone. Red LED (D1) indicates the power status. Resistor R8 limits the operating current of D1. The audio output of this circuit is 10 to 15mW and the quiescent current drain is below 1 mA.

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20W CLASS A POWER AMPLIFIER ELECTRONIC DIAGRAM

20W CLASS-A POWER AMPLIFIER ELECTRONIC DIAGRAM

The 0.25 Ohm resistor should cause little grief (4 x 1 Ohm 1W resistors in parallel), but some experimentation may be needed here, since the base-emitter voltage of the BC549 determines the current. This circuit works by using the BC549 to steal any excess base current from the compound pair. As soon as the voltage across the 0.25 Ohm resistor exceeds 0.65V, the transistor turns on and achieves balance virtually instantly.

The 1k trimpot in the collector of the first LTP transistor allows the DC offset to be adjusted. The nominal value is around 400 ohms, but making it variable allows you to set the output DC offset to within a few mV of zero. Read More

Creating a Line Follower Robot with AVR

The article "Creating a Line Follower Robot with AVR [Censorship]" is a continuation of Line Follower Robot article with a new AVR ATMega8535 samapai phase Line Follower Robot block diagram. In the article "Creating a Line Follower Robot with AVR Part 1 [Sensor]" This is a review of the sensor used on Line Follower Robot, and the components used. Sensors, can be analogous to the eye of a robot that serves to read the black line of the track robot or vice versa. So that the robot is able to know when he will turn right, when he turned left and when he stopped. Sensors used are usually photo reflector, LDR (Light Dependent Resistor), Photo Diodes and Photo Transistor - mounted on the front two or more below the line follower robot.There also are using the camera as a sensor (or image sensor) to a higher-resolution readout line, making more accurate robot motion.

Line Follower Robot Sensor circuit with AVR ATMega

Robot Sensor circuit with AVR ATMega  Circuit

The working principle of the sensor is simple, when the transmitter (infrared) emitting light onto a white field, the light will be reflected back to the receiver by the white areas and vice versa. This gives the change in the voltage level at the receiver output, but it usually changes the voltage can not be accepted as a TTL logic level. To be able to read by the microcontroller, the sensor voltage should be adjusted to TTL voltage level that is 0-1 volts for logic 0 and 3-5 volts for logic 1. This can be done by installing the operational amplifier is used as a comparator as shown in the picture above.

Op Amp is used as a comparator LM324 IC, because IC is able to work at VCC 5 volt range and there are 4 in 1 Op Amp IC corresponding to the number of sensors are used. The sensitivity of this sensor can be set through R9 which controls the comparator reference point.

Maximizing Sensor Line Follower Robot

Line follower robot sensors can be made with a combination between LED and photo diode. Line follower robot sensor configuration is good to be able to read the track with a hard and fast. To make the robot sensor is firm and fast can not merely rely on the ability of photo diodes and LED configurations only. As an alternative to maximize the performance of line follower robot sensors can be added to the voltage comparator with Op-Amp. Sensor circuit line follower robot equipped with a voltage comparator that is ready to be connected to a microcontroller or PIC can use the following series of robot sensor.

Line Follower Robot Sensor circuit with voltage comparator

Voltage comparator Circuit

Function of the voltage comparator circuit line follower robot sensor above is:

1. Reinforce the logic level sensor output
2. Amplifies the sensor output signal
3. Control and determine the reference point sensor
4. Reinforce the logic level sensor output is intended to avoid the floating logic conditions, with the goal of getting the process of transition logic (high) to a logic low (low) or vice versa in a fast sensors. So as to enhance the response to the sensor readings track work.

Sensor output voltage levels should be read as well by the TTL logic processor. If the robot sensors rely on photo diodes and LED configurations, then during the reading process is fast track, then the resulting signal has a logic low loevel differences and can not be read as a TTL logic. Therefore, robot sensor voltage levels are still weak need to be corroborated by a voltage comparator, so the TTL logic level differences firm with a strong signal.

The purpose of controlling and determining the sensor reference point is, we can determine the position of the robot sensor readings can be considered as a logic high or logic low.  Choosing process reference value line follower robot sensor readings can be done by adjusting VR1 10kOhm the series "Line Follower Robot Sensor Voltage Comparator With" above.

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Make A Virtual Phone Battery

Virtual cell phone battery is a replacement cell phone batteries for those of you who use the phone as a modem. Including myself, who use the phone as a modem HAIER d1200p internet.  Why must use this virtual battery. For those who surf hobby "full time" with a phone modem, would know the problem, the battery gets hot and fast reply wasteful even worn out.

This tool is a good solution to keep and care for our cell phones from the possibility of damage from over-charging its battery. I created a virtual battery works as follows: We take the source of its power supply from the USB port because the port is very easy and simple to use and simply provide a standard current source when the phone is online (500-750mA).

The workings of the circuit is as follows: Diodes or diode 2Amper in 5239 this standard to provide a useful addition to the polarity of the voltage which is also a component of protection against misuse. You can just use a 1 Amp diode (IN4002-4007). I use the IN 5239 is due to be durable, more resistant to heat. 4v3 zener diode IN4007 and configured to create a portal voltage of 5V (4.3 + 0.7 volt zener Vin4007) and is useful as a protection system against possible voltage spikes in the event of damage to the CPU. 220nF capacitor as a stabilizer and a substitute for the original battery cells.

The following also 100pF capacitor to smooth and filter the dc current through the diode 5239 which came out of the induction logging. Configuration between zener4v3, IN4007 diode and C 220n form a cell replacement from the actual battery cells, because the battery was actually a capacitor which had a large capacity. You can just remove the three components mentioned above. although it can work fine .

But results are not as good as that use virtual cell (replacement), which certainly was the security which we have to think to avoid the things which are not in want. Making way is to use an old cell phone batteries which have been wasting his cell, a raft of this circuit and the solder terminals on the batteries with the polarity distinguished. Make two holes for the cable to the jack / USB jack.

 Determine the length of cable required to taste and use stranded cable with a diameter of at least 1mm. If some type of cell phone batteries are very thin, use a small box for this circuit and connect the two wires to the output voltage again for hp battery casing. Or also if you do not have a former battery casing, use alligator clips to the battery terminal on the phone .. Pin the middle of the virtual pin replacement battery is BSI (Battery Size Insdicator) is useful for HP Nokia.

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Tips for Choosing a quality Power Amplifier

Here are some tips you need to note:

1. Pick of the power that suits your needs. For personal use such as exercise, etc., is sufficient to choose an amplifier with a power of 15-20 watts. In most small power amplifiers are already available facilities such as Head Phone jack (eg Guitar Amplifier Laser 20) which is very useful especially for young people who have a habit of playing music until midnight. By leveraging these channels to Head Phone, then secured another household or neighbors will not be disturbed our music sound. Sound good hasilnya.Apabila amplifier system we will use to train together in a full band with drums, etc., then you should choose a larger power amplifier that is 70 watts or above. Thus the sound produced from the amplifier and sound system will not be drowned by the sound of pounding and pounding beat Drum.Untuk use on stage, you will need a higher power that is at least 125 watts or more, because this amplifier will be able to once we use as a monitor of musical instruments were playing.

2. Choose the facilities we need. Do not buy amplifiers which have facilities that we do not really need when it is increasing the price we pay. Unless the same price we can get better facilities, there is no harm in our selection.

3. Choose a good quality amplifier. If we need an amplifier to your keyboard, then it is advisable to select an amplifier that does not change the color of the original sound generated by the keyboard musical instrument they will be (flat). There are many amplifiers that produce different sounds from the original sound, if this happens there will be other voices that would reduce the original character of the actual sound produced by the keyboard because of the addition or subtraction of a particular frequency. Usually this happens at a very low frequency (low bass) or very high frequency (high treble). (Try the sound system rental, sound rental service) For amplifiers Electric Guitar and Electric Bass this (flat characteristic) does not apply because it specifically for these two types of instruments are required specificity of character frequency. Basically for Electric Guitar amplifier output is not needed for low frequency and high. For Electric Bass needed a low frequency, but not required a high frequency. We can learn from the rental place and the sound system rental-quality musical instrument.

4. Model and performance amplifier can be considered final. The desired model will depend on individual taste. A good model according to a person, not necessarily a good thing according to those who lainnya.Pada most professional musicians model will be the last option or not too overlooked. They will be more concerned with the quality and facilities of the amplifier. Maybe we can find also in the rental services professional sound and musical instrument rental place bagus.Demikian brief tips on choosing an amplifier, hopefully this can help to determine the right choice before you buy an amplifier and produce sound quality music is also of course .

Tips for Choosing Quality Amplifier

1. Pick of the power to suit your sound system. For personal use such as exercise is sufficient to choose an amplifier with 1-20watt power. In most electronic devices / small power amplifiers are already available facilities such as head phone jack (eg laser20 guitar amplifier) ​​is very useful especially for young people who have a habit of playing music until midnight. By leveraging the channel for these headphones, then secured another household or neighbors will not be disturbed "attraction" we. If the amplifier sound system we will use to train together in a group full band * with drum and band instrument, then you should choose a power amplifier 70watt or above. Thus the sound produced from the amplifier will not be drowned by the sound of pounding and pounding drum beats. For use on stage, you will require more resources than most, namely at least 125watt or more, because this amplifier will be at the same we use as a monitor of musical instruments were playing.

2. Select the facilities we need. Do not buy a multimedia system / amplifier that has the facilities that we do not really need, if it is increasing the price we pay. Unless the same price we can get better facilities, there is no harm in our selection.

3. Choose a good quality amplifier. If we need an amplifier to your keyboard, then it is advisable to select an amplifier that does not change the original color generated by the keyboard (flat). There are many Indonesian musical instrument amplifier that produces a different sound from the original sound, if this happens there will be other voices that would reduce the original character of the actual sound produced by the keyboard because of the addition or subtraction of a certain frequency speaker system. Usually this happens at a very low frequency. (Low bass) or very high frequency (high treble). To Lighting System, Electric Amplifier Electric Bass Guitar and this (flat characteristic) does not apply because it specifically for these two types of instruments required specificity of character frequency. Basically for Electric Guitar not dipelukan amplifier output for low frequencies and high. For Electric Bass needed a low frequency, but not required a high frequency.

4. Models and appearance can be thought being given to the last amplifier. The desired model will depend on individual taste. A good model according to a person not necessarily a good thing by other people.

In most professional musicians, models will be the last option or not too overlooked. They will be more concerned with the quality and features of the amplifiers for musical instruments. But if you are confused, you could just rent equipment or hire sound system rental equipment.

Read More

Pure Class A Headphone Amplifier Schematic

400mW RMS into 32 Ohm load, Single-rail Supply - Optional Tilt Control

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This design is derived from the Portable Headphone Amplifierfeaturing an NPN/PNP compound pair emitter follower output stage. An improved output driving capability is gained by making this a push-pull Class-A arrangement. Output power can reach 427mW RMS into a 32 Ohm load at a fixed standing current of 100mA. The single voltage gain stage allows the easy implementation of a shunt-feedback circuitry giving excellent frequency stability.

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Tilt control:

The mentioned shunt-feedback configuration also allows the easy addition of frequency dependent networks in order to obtain an useful, unobtrusive, switchable Tilt control (optional). When SW1 is set in the first position a gentle, shelving bass lift and treble cut is obtained. The central position of SW1 allows a flat frequency response, whereas the third position of this switch enables a shelving treble lift and bass cut.

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Circuit diagram:

Class-A Headphone Amplifier Circuit Diagram

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Parts:

P1 = 22K Dual gang Log Potentiometer (ready for Stereo)

R1 = 15K 1/4W Resistor
R2 = 220K 1/4W Resistor
R3 = 100K 1/2W Trimmer Cermet
R4 = 33K 1/4W Resistor
R5 = 68K 1/4W Resistor
R6 = 50K 1/2W Trimmer Cermet
R7 = 10K 1/4W Resistor
R8 = 47K 1/4W Resistors
R9 = 47K 1/4W Resistors
R10 = 2R2 1/4W Resistors
R11 = 2R2 1/4W Resistors
R12 = 4K7 1/4W Resistor
R13 = 4R7 1/2W Resistor
R14 = 1K2 1/4W Resistor
R15 = 330K 1/4W Resistors (Optional)
R16 = 680K 1/4W Resistor (Optional)
R17 = 220K 1/4W Resistors (Optional)
R18 = 330K 1/4W Resistors (Optional)
R19 = 220K 1/4W Resistors (Optional)
R20 = 22K 1/4W Resistors (Optional)
R21 = 22K 1/4W Resistors (Optional)

C1 = 10µF 25V Electrolytic Capacitors
C2 = 10µF 25V Electrolytic Capacitors
C3 = 10µF 25V Electrolytic Capacitors
C4 = 10µF 25V Electrolytic Capacitors
C5 = 220µF 25V Electrolytic Capacitors
C6 = 100nF 63V Polyester Capacitors
C7 = 220µF 25V Electrolytic Capacitors
C8 = 2200µF 25V Electrolytic Capacitor
C9 = 1nF 63V Polyester Capacitors (Optional)
C10 = 470pF 63V Polystyrene or Ceramic Capacitor (Optional)
C13 = 15nF 63V Polyester Capacitor (Optional)
C11 = 1nF 63V Polyester Capacitors (Optional)
C12 = 1nF 63V Polyester Capacitors (Optional)

D1 = 5mm. or 3mm. LED
D2 = 1N4002 100V 1A Diodes
D3 = 1N4002 100V 1A Diodes

Q1 = BC550C 45V 100mA Low noise High gain NPN Transistors
Q2 = BC550C 45V 100mA Low noise High gain NPN Transistors
Q3 = BC560C 45V 100mA Low noise High gain PNP Transistor
Q4 = BD136 45V 1.5A PNP Transistor
Q5 = BD135 45V 1.5A NPN Transistor

IC1 = 7815 15V 1A Positive voltage regulator IC
T1 = 220V Primary, 15+15V Secondary-5VA Mains transformer

SW1 = 4 poles 3 ways rotary Switch (ready for Stereo)
SW2 = SPST slide or toggle Switch

J1 = RCA audio input socket
J2 = 6mm. or 3mm. Stereo Jack socket
PL1 = Male Mains plug

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Notes:

• Q4, Q5 and IC1 must be fitted with a small U-shaped heatsink.
• For a Stereo version of this circuit, all parts must be doubled except P1, IC1, R14, D1, D2, D3, C8, T1, SW1, SW2, J2 and PL1.
• If the Tilt Control is not needed, omit SW1, all resistors from R15 onwards and all capacitors from C9 onwards. Connect the rightmost terminal of R1 to the Base of Q1.
• Before setting quiescent current rotate the volume control P1 to the minimum, Trimmer R6 to zero resistance and Trimmer R3 to about the middle of its travel.
• Connect a suitable headphone set or, better, a 33 Ohm 1/2W resistor to the amplifier output.
• Connect a Multimeter, set to measure about 10Vdc fsd, across the positive end of C5 and the negative ground.
• Switch on the supply and rotate R3 in order to read about 7.7-7.8V on the Multimeter display.
• Switch off the supply, disconnect the Multimeter and reconnect it, set to measure at least 200mA fsd, in series to the positive supply of the amplifier.
• Switch on the supply and rotate R6 slowly until a reading of about 100mA is displayed.
• Check again the voltage at the positive end of C5 and readjust R3 if necessary.
• Wait about 15 minutes, watch if the current is varying and readjust if necessary.
• Those lucky enough to reach an oscilloscope and a 1KHz sine wave generator, can drive the amplifier to the maximum output power and adjust R3 in order to obtain a symmetrical clipping of the sine wave displayed.

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Technical data:

• Output power (1KHz sinewave):
• 32 Ohm: 427mW RMS
• 64 Ohm: 262mW RMS
• 100 Ohm: 176mW RMS
• 300 Ohm: 64mW RMS
• 600 Ohm: 35mW RMS
• 2000 Ohm: 10mW RMS

Sensitivity:

• 140mV input for 1V RMS output into 32 Ohm load (31mW)
• 500mV input for 3.5V RMS output into 32 Ohm load (380mW)
• Total harmonic distortion into 32 Ohm load @ 1KHz:
• 1V RMS 0.005% 3V RMS 0.015% 3.65V RMS (onset of clipping) 0.018%
• Total harmonic distortion into 32 Ohm load @ 10KHz:
• 1V RMS 0.02% 3V RMS 0.055% 3.65V RMS (onset of clipping) 0.1%
• Unconditionally stable on capacitive loads

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Build a 25W Class A Power Audio Amplifier Circuit Diagram

This is the 25W Class-A power audio amplifier circuit. The output devices are MJL4281A (NPN) and MJL4302A (PNP), and have high bandwidth, fantastic SOA (safe operating area), high linearity and high gain. Driver transistors are MJE15034 (NPN) and MJE15035 (PNP). All devices are rated at 350V, using the power transistors having a 230W dissipation and the drivers are 50W.

25W Class-A Power Audio Amplifier Circuit Diagram

•  The supply voltage must be a maximum of ±25V. This supply is simply obtained from a 20-0-20V transformer, recommended current is 1A.
•  All resistors ought to be 1/4W or 1/2W 1% metal film for lowest noise, with the exception of R9, R10 and R15 which ought to be 1/2W varieties, and R13, R14 have to be 5W wirewound.
•  Using the suggested and advised 25V supplies, Q4 will typically not need a heatsink. The output drivers (Q5 and Q6) recommended to use a heatsink, even though it doesn’t have to be big.

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How to Make a 40 watt Single Chip Amplifier Circuit

Philips have developed the Type TDA1514 AF amplifier chip, which is remarkable for its l excellent specifications, ruggedness and output power.

The circuit diagram shows that very few components are . needed to make this high- performance amplifier.

The device is housed in a 9-pin SIL POWER enclosure which has a thermal resistance of less than 1.5 K/W so that the heatsink required must have a thermal resistance of no more than 3.8 K/Wif the chip is operated at its maximum dissipation of l9 W (Ub= i-27.5 L Ta=5O °C).

The power supply to feed the chip must be capable of delivering a current of at least 3 A; the quiescent current demand of the amplifier as shown is about 60 mA.


Make sure, however, that the tracks and connections to the Sl i supply and output terminals are as short as possible, and use H double tracks where this is I necessary. In this context, it is advisable to fit decoupling 5 capacitors C3 and Ca as close as 3 possible to the chip supply  pins. Resistors R2 and R3. 

The supply voltage 1 should not exceed +/-27.5v. Although this project is not supported by a ready—made printed circuit board, you should not C experience too much difficulty  in constructing the amplifier if it F $ is built on a piece of Veroboard.

Courtesy: Elektor Electronics

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Class A Power Amp mosfet

A power MOSFET is biased using a pot (needed to correct for different device characteristics) so that the voltage at the drain is about 1/2 the supply voltage. Current is limited using a constant current source, and this needs to be set to provide a current that is higher than the maximum peak current to the speaker. Since the amp is not DC coupled, an output capacitor is needed to keep the DC out of the loudspeakers. An input cap is also needed to stop the source (the preamp, or for my tests, an audio oscillator) from stealing the bias voltage.

Read More original Source:
http://www.sound.westhost.com/project36.htm

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A Headphone Monitoring Switch

In any recording situation, monitoring is critical to make sure youre getting what you want on tape. This is just as true in field recording, but in most cases, ones monitoring options are severely limited--stereo headphone is the only choice.

Headphone Monitoring Switch  :

Since I often use dual-mono mics, hearing a stereo feed of the two is not always convenient. I wanted the option to hear JUST the left mic in BOTH ears, or just the right mic in both ears, as well as a normal stereo signal. This is simple enough to do with a big rotary switch. When completed, you can create a little box that your headphones plug into, which in turn is plugged into the stereo phone output of your deck. Then, by turning the knob on the switch box, you can hear normal stereo, left-only mono, right-only mono, left+right mono and even left-right reversed stereo (or normal stereo again). 

Note the use of summing resistors in the left+right mono section. This was an attempt to prevent the two outputs from "fighting" each other if there were very different voltages in left and right outputs. I used 8 ohm resistors here, but a higher value might be better. Maybe ~20 ohms? Also, I initially decided to put normal stereo on both ends of the switchs travel so Id always be able to find it without looking. However, I sometimes wish to have left-right reversed. If youd like to try this, simply swap the leads on one of the "normal stereo" connections. 

One final caveat: The left only/right-only mono positions are -6dB down, since only one half of the decks headphone amp is driving your phones when the switch is in those positions. 

Source by : Ediagramlab

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Relay Toggle Circuit Using a 555 Timer

This 555 timer circuit below toggles a relay when a button is pressed. Pins 2 and 6, the threshold and trigger inputs, are held at 1/2 the supply voltage by the two 10K resistors. When the output is high, the capacitor charges through the 100K resistor, and discharges when the output is low. When the button is pressed, the capacitor voltage is applied to pins 2 and 6 which causes the output to change to the opposite state. When the button is released, the capacitor will charge or discharge to the new level at the output (pin 3). The parts are not critical, the resistors can be somewhat higher or lower, but the 2 resistors at pins 2 and 6 should be equal values, and the resistor connected to the cap should be 10 times greater or more.

Circuit diagram :

Relay Toggle Circuit Diagram

Advantages of this circuit are the large hystersis range at the input which avoids false triggering, and only a few parts are needed for construction. One disadvantage is the relay may be engaged when power is first applied. To solve this problem, you could tie the reset line (pin 4) to another resistor/capacitor combination with the capacitor at ground and the resistor at the +V point. This will cause pin 4 to be held near ground for a short period which will reset the output when power is applied.

The 100 ohm resistor and 100uF capacitor serve to filter noise on the supply line if the circuit is used in a automotive application. They may not be necessary. The circuit may work well without those parts.

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Build a Tesla Coil Wiring diagram Schematic

Build a Tesla Coil Circuit Diagram. The Tesla coil described here can.generate 25,000 V. So, even though the output current is low, be very careful! The main component is a flyback transformer from a discarded TV. A new primary windin_g is needed. Begin by winding 5 turns of #18 wire on the core. Then, twist a loop in the wire, and finish by winding five more turns. 

Wrap with electrical tape, but leave the loop exposed. A four-tum winding must be wound over the ten-turn winding that you`ve just finished.That is done the same way. First wind two turns of# 18 wire, then make a loop, and finish by winding two more turns. Again, wrap the new winding with electrical tape, leaving the loop exposed. When the windings are finished, the two loops shouldn`t be more than 1/.-inch apart, but take care that they do not touch. Connect a 240-U resistor between the two loops. 

The modified transformer now should look like the one shown. Connect the transformer as shown. The 27 -U resistor and two transistors should be mounted on a heatsink and must be insulated from it. The output of the high-voltage winding should begin to oscillate as soon as the schema is connected to a 12-V de power supply. Ifit does not, reverse the connections to the base leads of the transistors. In normal operation, you should be able to araw l-inch sparks from the high-voltage lead using an insulated screwdriver.

Tesla Coil Circuit Diagram

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Build a Differential Instrumentation Amplifier Wiring diagram Schematic

Build a Differential Instrumentation Amplifier Circuit Diagram. An instrumentation amplifier is a type of differential amplifier that has been outfitted with input buffer amplifiers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment.This schema relies on extremely high input impedance for effective operation. The HA-5180 with its JFET input stage, performs well as a preamplifier. 

 Differential Instrumentation Amplifier Circuit Diagram

The standard three amplifier configuration is used with very close matching of the resistor ratios R5/R4 and (R7 + R8)/R6, to insure high common-mode rejection (CMR). The gain is controlled through R3 and is equal to 2RI/R3. Additional gain can be had by increasing the ratios R5!R4 and (R7 + R8)!R6. The capacitors C1 and C2 improve the ac response by limiting the effects of transients and noise. 

Two suggested values are given for maximum transient suppression at frequencies of interest. Some of the faster DVM`s are operating at peak sampling frequency of 3-kHz, hence the 4-kHz, low-pass time constant. The 40kHz, low-pass time constant for ac voltage ranges is an arbitrary choice, but should be chosen to match the bandwidth of the other components in the system. C1 and C2 might however, reduce CMR for ac signals if not closely matched. Input impedances have also been added to provide adequate de bias currents for the HA-5180 when open-schemaed.

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Build a High Voltage Inverter Wiring diagram Schematic

The High Voltage Inverter Circuit Diagram converts a de voltage (V +) to a high-amplitude square wave in the audio-frequency range. The dual timer, IC2, provides an inexpensive alternative to the traditional transformer for providing complementary base drive to the power transistors, Ql and Q2. You can convert a 6 to 12 V battery output, for example, to an ac amplitude, which is limited primarily by the power rating of transformer Tl. 

Connect timer IC1 as an oscillator to provide a symmetrical square-wave drive to both inputs of IC2. The timing components, R2 and Cl, produce a 2.2-kHz output frequency. By connecting half of IC2 in the inverting mode and the other half in noninverting mode, the timer`s outputs alternately drive the two transistors. 

 Build a High Voltage Inverter Circuit Diagram

You can operate the audio-output transformer, Tl, as a step-up transformer by connecting it backwards using the output winding as an input. The transformer delivers an output voltage across RL of 4 x N x V+V pk-pk, where Nis the transformer turns ratio. For the schema shown, the output swing is 100 x V+V pk-pk.

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Build a 4 18Mhz Converter Wiring diagram Schematic

Build a 4-18Mhz Converter Circuit Diagram. The unit consists of RF amplifier Q1, local oscillatorQ2, and mixer Q3. The two bands are covered without a band switch by using an i-f or 3.5 MHz. The oscillator range is 7.5 to 14.5 MHz. Incoming signals from 4 to 11 MHz are mixed with the oscillator to produce the 3.5-MHz i-f.

Signals from 11 to 18 MHz are mixed with the oscillator to also produce an i-f of 3.5 MHz. At any one oscillator frequency, the two incoming signals are 7 MHz apart. Rf amplifier input Cl/L1 comprises a high-Q, lightly loaded, tuned schema; this is essential for good band separation.

Build a 4-18Mhz Converter Circuit Diagram

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Build a Uhf TV Preamplifier Wiring diagram Schematic

Build a UHF TV Preamplifier Circuit Diagram. An inexpensive. antenna-mounted, UHF TV preamplifier can add more than 25 dB of gain. The first stage of the preamp is biased for optimum noise, the second stage for optimum gain. Ll, L2 strip line `` J../8 part of PC board.

UHF TV Preamplifier Circuit Diagram

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Build a Hv Power Supply With 9 To 15Vdc Input Wiring diagram Schematic

Build a Hv Power Supply With 9 To 15Vdc Input Circuit Diagram. This Hv Power Supply is The combination Hartley oscillator/step-up transformer shown in A can generate significant negative high voltage, especially if the voltage output of the transformer is multiplied by the schema in B. 

Simple Hv Power Supply With 9 To 15Vdc Input Circuit Diagram

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Class A Headphone Amplifier

     This circuit is derived from the Portable Headphone Amplifier featuring an NPN/PNP compound pair emitter follower output stage. An improved output driving capability is gained by making this a push-pull Class-A arrangement. Output power can reach 427mW RMS into a 32 Ohm load at a fixed standing current of 100mA. The single voltage gain stage allows the easy implementation of a shunt-feedback circuitry giving excellent frequency stability.

     The above mentioned shunt-feedback configuration also allows the easy addition of frequency dependent networks in order to obtain an useful, unobtrusive, switchable Tilt control (optional). When SW1 is set in the first position a gentle, shelving bass lift and treble cut is obtained. The central position of SW1 allows a flat frequency response, whereas the third position of this switch enables a shelving treble lift and bass cut.

     Before setting quiescent current rotate the volume control P1 to the minimum, Trimmer R6 to zero resistance and Trimmer R3 to about the middle of its travel. 

Connect a suitable headphone set or, better, a 33 Ohm 1/2W resistor to the amplifier output. 

Connect a Multimeter, set to measure about 10Vdc fsd, across the positive end of C5 and the negative ground.  Switch on the supply and rotate R3 in order to read about 7.7-7.8V on the Multimeter display. 

Switch off the supply, disconnect the Multimeter and reconnect it, set to measure at least 200mA fsd, in series to the positive supply of the amplifier.  Switch on the supply and rotate R6 slowly until a reading of about 100mA is displayed.  Check again the voltage at the positive end of C5 and readjust R3 if necessary.  Wait about 15 minutes, watch if the current is varying and readjust if necessary.

P1 : 22K Dual gang Log Potentiometer 
R1 : 15K 
R2 : 220K
R3 : 100K
R4 : 33K 
R5 : 68K 
R6 : 50K 
R7 : 10K 
R8,R9 : 47K 
R10,R11 : 2R2 
R12 : 4K7
R13 : 4R7
R14 : 1K2
R15,R18 : 330K
R16 : 680K
R17,R19 : 220K
R20,R21 : 22K
C1,C2,C3,C4 : 10µF/25V 
C5,C7 : 220µF/25V
C6,C11 : 100nF
C8 : 2200µF/25V
C9,C12 : 1nF
C10 : 470pF
C13 : 15nF
D1 : LED
D2,D3 : 1N4002 
Q1,Q2 : BC550C 
Q3 : BC560C 
Q4 : BD136 
Q5 : BD135 
IC1 : 7815
T1 : 15CT/5VA Mains transformer
SW1 : 4 poles 3 ways rotary Switch 
SW2 : SPST slide or toggle Switch

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Accu charger use a diac and triac

This circuit can be used to charge Accu and cells battery , the circuit can has a very stable output that would make the battery last longer  and maximize the added battery capacity. When charge was also quite fast , so it can optimize the time.

A diac is used in the gate circuit to provide a threshold level for firing the triac . C3 and R4 provide a transient suppression network. R1 , R2 , R3 , C1 , and C2 provide a hase - shift network for the signal being applied to the gate. R1 is selected to limit the maximum charging current at full rotation of R2.

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