Hi fi audio amplifiers

1

Hi-Fi Amplifier Circuits

2

Circuits Designed by Edward Reagan Roy.J.T 2.1 Channel Systems-Dual Power Amplifier TDA7240 and TDA1517

The main problem with the design of stereo amplifier with a total bass driver is that the signals of left and right channels, sooner or later, are summarized. As a result of merely adding up, the separation between channels is reduced to a minimum and violated the very idea stereophonic. The most efficient method of summation, known today – signal active smesitelyami – filters with high input impedance, which is often used by field-effect transistors. Subsequent cascades enhance increase the amplitude of the signal.

I tried to make some other way – most to weaken the signals of channels and to make their addition, as late as possible, before entering signal with high sensitivity (TDA 7240 – 46dB). The second chip-TDA 1517, serves as a mid-frequency driver.

I must say that the problem is not solved completely, the separation between channels is desirable to do more, and subjective listening showed a contraction of panoramas, lack of air, which is inherent in amplifiers with independent channels. Listen to music using the device somewhat tiresome, but it very effectively transmits audio material of films and computer games. In any case, the amplifier has shown significant superiority over the multimedia system Logitech Z – 340, which is one of my friends recently

3

bought for $ 60. Another nice time – managed to realize the possibility of simultaneous volume in all channels,

Version 1

Which will agree, very convenient? Thus, the scheme was recommended for the recurrence of 2.1 channel Systems, with the prospect of it improving. Notes __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ____________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __

4

Version 2

Notes __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ____

5

2x30/40W Audio Amplifier with STK465 Simple circuit with higher power output, this amplifier circuit is very easy to build. Just look at the PCB layout of this circuit. The active component required is just the main power amplifier chip STK465.

Component Part list:

R1 = 1K C1 = 1uF/35V R2 = 3,3K C2 = 470pF R3 = 100 C3 = 100uF/60V R4 = 330 C4 = 100uF/60V R5 = 3,3K C5 = 10uF/60V R6 = 1K C6 = 47uF/60V

R7 = 0,33 C7 = 8,2pF R8 = 33k C8 = 0,1uF R9 = 4,7 C9 = 1uF/35V R10 = 1k C10 = 470pF R11 = 3,3k C11 = 100uF/60V R12 = 100 C12 = 100uF/60V

R13 = 330 C13 = 10uF/60V R14 = 3,3k C14 = 47uF/60V R15 = 1k C15 = 8,2pF R16 = 0,33 C16 = 0,1uF R17 = 33k R18 = 4,7 IC1 = STK465 Speaker 40W

6 PCB Layout:

Component placement:

Vcc Max ± 14V P/O =2*30Watts at 8 Ohms

Vcc Typ ± 28V ± 25V &

2*40 Watts at Ohms

Notes __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________

7

5.3W Amplifier With Surround System The AN7147 Dual 5.3-watt Audio Power Amplifier from Panasonic is listed as a ‘replacement type’ so hopefully will be around for some time to come. Together with some extra components, it can represent a simple surround-sound system requiring no opamps or a negative voltage supply. As shown by the circuit diagram the basic stereo amplifier is changed into a surround-sound system by a trick called ‘adding feedback from the opposite channel’. When surround sound is required, the negative feedback signals supplied by C13-R3 and C12-R4 are fed to the inputs of the ‘other’ amplifier. The resulting phase difference causes the surround effect. If surround sound is not required, the effect can be disabled by pressing push-button S1. This causes the bistable built around IC2.A and IC2.B to toggle and drive transistors T1 and T2 such that the above mentioned negative feedback signals are effectively shunted to ground. A high-efficiency LED and a 3.3-kΩ series resistor (R14) should be used to make sure the maximum output current of the CMOS 4001 device is not exceeded. The amplifier should not be loaded with impedance's smaller than 3Ω. The AN7147 will typically supply up to 4.3 watts into 4 Ω. The SIL-12 case needs to be cooled wit a small heatsink of about 6 K/W or better. The quiescent current is modest at just 19 mA.

Notes __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ____ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ________________________________

8

9

6-10W Audio Amplifier with IC TDA2002 This is a class AB audio power amplifier circuit which built using a TDA2002 or TDA2003 power amplifier IC module. These are replacements for the original LM383 which is no longer available. It is easy to build and has a minimum of external components. The module has both short circuit protection and thermal protection. It can drive loads as low as 1.6 ohm and is capable of delivering over 10 watts from a 16 V supply.

Component parts: R1_ potentiometer 10 k ohm R2_ 220 ohm R3_ 2R2 ohm R4_ 1 ohm IC1_ TDA2002/3 amplifier module 1 Heat sink

C1-10uF/50V electrolytic capacitor C2-470uF/16V electrolytic capacitor C3-2200uF 25V electrolytic capacitor 1 C4-100 nF mylar 1 C5-100 nF monoblock 1 C6-100uF 25V ecap 1

Maximum output power will only be obtained with a power supply of greater than 1A at 16V DC, and using 2 ohm

10

speakers (or 2 by 4 ohm speakers in parallel). However approximately 4W RMS can be obtained with a 12V DC, 1A supply into a 4 ohm load. The power supply should be well filtered to reduce mains hum, the on board capacitors alone are not adequate for this purpose but are necessary to ensure stability. Extra filtering is unnecessary if operating from a battery. If two boards are used for stereo, you will need to double the size of the power supply.

Specifications: D.C. Input: 8 – 18V, 10 – 20 VA min. Power output: > 10 W RMS, 2 ohm load, 16V DC supply. > 6W RMS, 4 ohm load, 16V DC supply. > 4W RMS, 4 ohm load, 12V DC supply. THD: < 0.2% (1W, 4 ohm load) Gain: 40 dB maximum. S/N ratio : > 80 dBA. (G = 20 dB) > 60 dBA (G = 40 dB) Frequency response: < 20 Hz to > 40 kHz (-3dB, 4 ohm load) Input level: < 100 mV for full output (G = 40 dB) < 1V for full output(G = 20 dB)

11

7 Watt Audio Power Amplifier Circuit Schematic Small but powerful multipurpose amplifier This small amplifier is constructed around the TDA2003 IC, capable of delivering 4Watts at 4ohms. The TDA 2003 has improved performance with the same pin configuration as the TDA 2002. The additional features of TDA 2002, very low number of external components, ease of assembly, space and cost saving, are maintained. The device provides a high output current capability (up to 3.5A) very low harmonic and cross-over distortion. Completely safe operation is guaranteed due to protection against DC and AC short circuit between all pins and ground, thermal overrange, load dump voltage surge up to 40V and fortuitous open ground. A conventional direct current can be connected as supply.

12

Parts: R1 = 470R R2 = 47R R3 = 100R R4 = 1R C1 = 1822pF C2 = 100nF-63V C3 = 100nF-63v C4 = 10uF-25V C5 = 470uF-25V C6 = 1000uF-35v C7 = 1000uF-35V IC1 = TDA2003 Specifications: • • • • • • • •

Music power output: 7W / 4ohm RMS output: 3.5W / 4ohm or 2W / 8ohm Total harmonic distortion: 0.05% (1W / 1kHz) Frequency response: 20Hz to 20kHz (-3dB) Signal/noise ratio: 86dB (A weighted) Input sensitivity: 40mV / 150Kohm Overload and short-circuit protected Supply voltage: 15V DC (8 to 18V DC possible) / 0.5A

13

18W + 18W Stereo Hi-Fi Audio Amplifier (TDA2030) 2 x 18W Hi-Fi Stereo Power Amplifier based around two TDA2030 ICs. It has good input sensitivity, low distortion, good operating stability and full protection against overloads and output short-circuits. It can be used as a booster amplifier for existing small systems or to drive a second pair of speakers besides the ones already connected to the system. The board needs a symmetrical power supply of ±18Vdc/3A and can be connected to loads of 8 or 4 Ohm. Large heat sink is required for this circuit. Diagram shown below indicates only left channel. Make two circuits for stereo version. Picture of the project:

18+18 Watt Hi-Fi Stereo Audio Amplifier Circuit Diagram

14

Circuit Diagram:

Parts: R1 = 22K R2 = 680R R3 = 22K R4 = 1R-1w D1 = 1N4001 D2 = 1N4001 C1 = 1uf-25V C2 = 22uF-25V C3 = 100nF-63V C4 = 100nF-63V C5 = 100uF-25V C6 = 100uF-25V C7 = 220nF-63V IC = TDA2030 If it does not work: 1. Check your work for possible dry joints, bridges across adjacent tracks or soldering flux residues that usually cause problems. 2. Check again all the external connections to and from the circuit to see if there is a mistake there.

15

3. See that there are no components missing or inserted in the wrong places. 4. Make sure that all the polarized components have been soldered the right way round. 5. Make sure the supply has the correct voltage and is connected the right way round to your circuit. 6. Check your project for faulty or damaged components.

Technical Specifications: • Supply voltage = ±18Vdc/3A symmetrical (see text) • Current consumption = 3A maximum • Input impedance = 500K Ohms • Input sensitivity = 250 mV • Signal to noise ratio = 80 dB • Frequency response = 20 - 20,000 Hz ± 1 dB • Distortion = 0.5 % maximum • Load impedance = 4 - 8 ohm Notes __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ________________________________________________________________

16

20 Watts Car Stereo Amplifier TDA2004 It is a powerful amplifier. It works with IC TDA 2004. TDA2004 has low noise, low distortion, and robust. The robustness is supported by its operation safety protection features: very inductive loads, load dump voltage surge, overheating, and output AC-ground short, fortuitous open ground. Other important things is space and cost saving : very low external components counts, and very simple mounting system with no need for electrical isolation between the package and the heat sink because the heat contact metal of the package is already connected to ground

17

20W Bridge Amplifier using TDA7240A This is a simple bridge amplifier based on TDA7240A. This circuit is designed for car audio system, but you may use this circuit for your small home audio application…The TDA7240A is a 20W bridge audio amplifier IC designed especially for car radio applications. The low external component count and compact Heptawatt 7-pin power package the TDA7240A occupies little space on the printed circuit board. Reliable operation is guaranteed by a comprehensive array of on-chip protection features. These include protection against AC and DC output short circuits (to ground and across the load), load dump transients, and junction over temperature. Additionally, the TDA7240A protects the loudspeaker when one output is shortcircuited to ground.

PCB Layout:

18

24W amplifier using TDA1516 Here is the circuit diagram of a simple 24W mono amplifier using IC TDA1516.The TDA1516 is an integrated class B power amplifier in a 13 pin SIL package. The IC has many useful features such as short circuit protection, load dump protection, thermal protection, reverse polarity protection etc. Here the IC is wired in BTL mode to deliver 24W of power into a 4 ohm speaker. This amplifier can be operated from a 12V DC supply and this makes it suitable for car audio applications.

__________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________

19

32W Hi-Fi Audio Amplifier with TDA2050 Here is a Hi-Fi power amplifier circuit, built with a power IC TDA2050. This circuit will produce a power output up to 32watt. With good sound quality, high power and very low distortion feature, this circuit will be very suitable for simple and cheap audio systems.

TDA2050 Amplifier PCB Design:

About TDA2050: The TDA 2050 is a monolithic integrated circuit in Pentawatt package, intended for use as an audio class AB audio amplifier. Thanks to its high power capability the

20

TDA2050 is able to provide up to 35W true rms power into 4 ohm load @ THD =10%, VS = ±18V, f = 1KHz and up to 32W into 8ohm load @ THD = 10%, VS = ±22V, f = 1KHz. Moreover, the TDA 2050 delivers typically 50W music power into 4 ohm load over 1 sec at VS=22.5V, f = 1 KHz. The high power and very low harmonic and crossover distortion (THD = 0.05% typ, @ VS = ±22V, PO = 0.1 to 15W, RL=8ohm, f = 100Hz to 15 KHz) make the device most suitable for both HiFi and high class TV sets. TDA2050 Features: • • • • • •

High output power High operating supply voltage Single or split supply operations Very low distortion Short circuit protection (out to GND) Thermal shutdown

Notes: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ______________________________________________

21

35W Hi-Fi AUDIO POWER AMPLIFIER by TDA2050 If you want to build hi-fi power amplifier the size about 30watt to 50Watt at good sound and build easy. I advise the circuit that builds with the integrated circuit. You ware IC TDA2050 then like very the circuit model class AB audio amplifier.

Thanks to its high power capability the TDA2050 is able to provide up to 35W true rms power into speaker 4 ohm load at THD =10%, VS =ï€ ï€ ï‚±18V, f = 1KHz and up to 32W into 8ohm load @THD = 10%, VS = 22V, f = 1KHz.Moreover, the TDA 2050 delivers typically 50W music power into 4 ohm load over 1 sec at VS=22.5V, f = 1KHz May take an interest want to try build already, try out this circuit use voltage Vcc +/- 25V. Part C1-0, 47-22mF C2-22mF C3C4-100nF C5-100(150) nF

22

R1R3-47kO R2-1-3,3kO R4-1-4, 7oM/0,25W Rt-4oM

PCB: 35W Hi-Fi AUDIO POWER AMPLIFIER by TDA2050

on PCB : 35W Hi-Fi AUDIO POWER AMPLIFIER by TDA2050

23

36 Watt Audio Power Amplifier Using TDA1562Q

It's based on a Philips class-H audio amplifier IC and can deliver 36W RMS OR 70W music power, all from a 13.8V supply. Our new Mighty Midget Amplifier can really pack a punch - around 36W RMS continuous into a 4-ohm load when using a 13.8V supply. However, it's the 70W of output power that it can deliver during dynamic (music) signal conditions that really make you sit up and take notice. As can be seen from the photos and the circuit diagram, the Mighty Midget uses just a handful of parts. It's built on a PC board that measures just 104mm x 39mm but while its size may be modest, these's nothing at all modest about its power output. And the noise and distortion figures are pretty good too.

24

Circuit diagram:

At the heart of the circuit is the TDA1562Q IC, described by Philips as a "monolithic integrated Bridge-Tied Load (BTL) class-H high-efficiency power amplifier". It comes in a 17-pin "DIL-bent-SIL" plastic package and is not only designed for use in car audio and portable PA work but for mains applications as well; eg, mini/midi audio components and TV sound. Parts layout:

25

PCB layout:

Performance: Output power:----------------------36W RMS into 4R Music power:-----------------------70W into 4R Frequency response:---------------1dB down at 28Hz and 55kHz Input sensitivity:-------------------130mV RMS (for 36W into 4?) Harmonic distortion: ----------------typically 0.2% (see graphs) Signal-to-noise ratio:----------------95dB unweighted (22Hz to 22kHz)

26

50W Power Amplifier with IC TDA7294 This is a great audio amplifier circuit based on single power IC TDA7294. TDA7294 is intended for use as a high quality audio class AB amplifier in hi-fi applications. It has very low noise and distortion, wide bandwidth and good output current capability, enabling it to supply high power into both 4Ω and 8Ω loads. It has both short circuit and thermal protection, so is quite robust.

Component part list: R1 R2, R3, R5 R4 R6 IC1 Heat sink

150R 10K 680R 22K TDA 7294

C1 C2 C3, C6 C4, C5 C7, C9 C8, C10

1u5F or 1u 2n7F 22uF 63V 10uF 63V 2200uF 50V 100nF

27

With the addition of a handful of parts and a suitable power supply, this module will deliver over 50W RMS into 4 or 8 ohms with < 0.1% Total Harmonic Distortion (THD) and < 0.1% Intermodulation Distortion (IMD). A similar circuit was published in Elektor magazine, 11/96. It is also suitable as a replacement power amp stage, or upgrade for many existing amplifiers of between 30W50W, provided they have a suitable dual supply, and most do. Notes: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ______________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________

28

60 Watt Audio Power Amplifier Circuit Diagram

High Quality, powerful unit: 90W into 4 Ohm load, Also suited as guitar or bass amplifier

To celebrate the hundredth design posted to this website, and to fulfil the requests of many correspondents wanting an amplifier more powerful than the 25W MosFet, a 60 90W High Quality power amplifier design is presented here. Circuit topology is about the same of the above mentioned amplifier, but the extremely rugged IRFP240 and IRFP9240 MosFet devices are used as the output pair, and well renowned high voltage Motorola's transistors are employed in the preceding stages. The supply rails voltage was kept prudentially at the rather low value of + and - 40V. For those wishing to experiment, the supply rails voltage could be raised to + and - 50V maximum, allowing the amplifier to approach the 100W into 8 Ohm target: enjoy! A matching, discrete components, Modular Preamplifier design is available here: Modular Audio Preamplifier.

29

Amplifier section:

60 Watt MosFet Audio Power Amplifier Circuit Diagram Parts: R1______________47K R2_______________4K7 R3______________22K R4_______________1K R5,R12,R13_____330R R6_______________1K5 R7______________15K R8______________33K R9_____________150K R10____________500R R11_____________39R R14,R15_________R33 R16_____________10R

1/4W Resistor 1/4W Resistor 1/4W Resistor 1/4W Resistor 1/4W Resistors 1/4W Resistor 1/4W Resistor 1/4W Resistor 1/4W Resistor 1/2W Trimmer Cermet 1/4W Resistor 2.5W Resistors 2.5W Resistor

30

R17_____________R22 5W Resistor (wirewound) C1_____________470nF 63V Polyester Capacitor C2_____________470pF 63V Polystyrene or ceramic Capacitor C3______________47µF 63V Electrolytic Capacitor C4,C8,C9,C11___100nF 63V Polyester Capacitors C5______________10pF 63V Polystyrene or ceramic Capacitor C6_______________1µF 63V Polyester Capacitor C7,C10_________100µF 63V Electrolytic Capacitors D1___________1N4002 100V 1A Diode D2_____________5mm. Red LED Q1,Q2,Q4_____MPSA43 200V 500mA NPN Transistors Q3,Q5________BC546 65V 100mA NPN Transistors Q6___________MJE340 200V 500mA NPN Transistor Q7___________MJE350 200V 500mA PNP Transistor Q8___________IRFP240 200V 20A N-Channel Hexfet Transistor Q9___________IRFP9240 200V 12A P-Channel Hexfet Transistor Power supply :

60 Watt MosFet Audio Amplifier Power Supply Circuit Diagram Parts: R1_______________3K9

1W

Resistor

31

C1,C2_________4700µF 63V Electrolytic Capacitors (See Notes) C3,C4__________100nF 63V Polyester Capacitors D1_____________400V 8A Diode bridge D2_____________5mm. Red LED F1,F2__________4A Fuses with sockets T1_____________230V or 115V Primary, 30+30V Secondary 160VA Mains transformer PL1____________Male Mains plug SW1____________SPST Mains switch Notes: 1. In the original circuit, a three-diode string was wired in series to R10. Two of these diodes are now replaced by a red LED in order to achieve improved quiescent current stability over a larger temperature range. Thanks to David Edwards of LedeAudio for this suggestion. 2. A small, U-shaped heatsink must be fitted to Q6 & Q7. 3. Q8 & Q9 must be mounted on large heatsinks. 4. Quiescent current can be measured by means of an Avo-meter wired in series to the positive supply rail and no input signal. 5. Set the Trimmer R10 to its minimum resistance. 6. Power-on the amplifier and adjust R10 to read a current drawing of about 120 - 130mA. 7. Wait about 15 minutes, watch if the current is varying and readjust if necessary. 8. The value suggested for C1 and C2 in the Power Supply Parts List is the minimum required for a mono amplifier. For optimum performance and in stereo configurations, this value should be increased: 10000µF is a good compromise. 9. A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of R1, R3, C2, C3 and C4 and the

32

ground input wire. Connect R7 and C7 to C11 to output ground. Then connect separately the input and output grounds to the power supply ground. Technical data: • Output power: • 60 Watt RMS @ 8 Ohm (1KHz sinewave) - 90W RMS @ 4 Ohm • Sensitivity: • 1V RMS input for 58W output • Frequency response: • 30Hz to 20KHz -1dB • Total harmonic distortion @ 1KHz: • 1W 0.003% 10W 0.006% 20W 0.01% 40W 0.013% 60W 0.018% • Total harmonic distortion @10KHz: • 1W 0.005% 10W 0.02% 20W 0.03% 40W 0.06% 60W 0.09% • Unconditionally stable on capacitive loads

Notes: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________

68W Power Amplifier with LM3886

33

The LM3886 is a high-performance audio power amplifier capable of delivering 68W of continuous average power to a 4 load and 38W into 8 with 0.1% THD+N from 20Hz20kHz.

Features: Maximum Output Power : 68W RMS - 108W Peak THD : %0.03 at 60W SNR : 110dB at 60 W - 92.5dB at 1W PSRR : 120dB Protection Circuitries: DC /AC Short circuit protection and thermal protection

34

Output Class

: Conjugate AB-A

The performance of the LM3886, utilizing its Self Peak Instantaneous Temperature (°Ke) (SPiKe™) protection circuitry, puts it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area (SOA). SPiKe protection means that these parts are completely safeguarded at the output against overvoltage, under voltage, overloads, including shorts to the supplies, thermal runaway and instantaneous temperature peaks. The LM3886 maintains an excellent signal-to-noise ratio of greater than 92dB with a typical low noise floor of 2.0µV. It exhibits extremely low THD+N values of 0.03% at the rated output into the rated load over the audio spectrum, and provides excellent linearity with an IMD (SMPTE) typical rating of 0.004%.

__________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________

80W Audio Amplifier Based on TDA7295

35

Below is a 80W amplifier circuit is constructed by using a power IC TDA7295. With a very simple design, makes this circuit very easy to build. TDA7295 has many features to support your audio system, the most important is that the IC has very low distortion and very low noise feature. Schematic diagram:

Notes: • • •

Power supply voltage should not exceed 40V. Use stable and regulated power supply. The power supply should be has minimum current output 2A. Use heatsink to prevent overheating on the power IC.

PCB Layout:

36

About TDA7295: The TDA7295 is a monolithic integrated circuit in Multiwatt15 package, intended for use as audio class AB amplifier in Hi-Fi field applications such as home theatre and topclass TV. The wide voltage range and to the high out current capability make the TDA7295 able to supply the highest power into both 4W and 8W loads even in presence of poor supply regulation, with high Supply Voltage Rejection. The built in muting function with turn on delay simplifies the remote operation avoiding switching on-off noises.

100Watt MONO Amplifier Circuit with TDA7294

37

Using the integrated circuit TDA7294 is best suited to operate in Hi-Fi audio applications, amplifier class AB. Sovereignty is capable of delivering both 4 ohm and 8 ohm loads, since the IC output current and a wide range of voltage. In addition, 8 ohm load with 0.1% harmonic distortion (THD) can be supplied with 50 W RMS, with the addition of sufficient power and the minimum number of components. Eliminates the presence of heat sink water temperature at a rate of 1, 4 ° C / W. In standby mode, is treated with PIN-9, while the MUTE input from the pin 10 is treated. In standby mode is always a priority for the MUTE input. The amplifier will be activated immediately, while inclusion. This is certainly connected through lessons without constantly on the supply rail. The conversion of clicks is by increasing the time constants of C5 C6 and & R4 & R3 can be eliminated. Due to internal thermal protection of the IC, the temperature at 145 ° C can cause MUTE condition and at 150 ° C, the amplifier is in standby mode. The Circuit amplifier must not be made without the presence of a radiator that internally to generate a negative supply rail is connected to be operated. In IC, the radiator of the amplifier in a grounded metal enclosure to be mounted in isolation. The maximum voltage for 8 ohm load 40V to 30V for 4 ohm loads, a transformer with 80 VA and 150 VA for two modules in a stereo amplifier rated.

38

39

150Watt Power Amplifier circuit with IC TDA7294

150W power amplifier circuit Circuit review-diagram B above. It is almost identical, except for connections SIM have been removed and some signs of components have been displaced. 220UF 100nF Although I have shown how C1 3.3UF Electro bipolar, you can use the CAP polyester, if you want. If power will be used for serednochastotnyh or tweeter in the system biamped or triamped, C1 may be reduced by the cost 100nF (-3dB at 72Hz). For general use, you can use a 1uF polyester, giving-3dB frequency of 7.2Hz, but bass extension is better with a higher value, as shown. New circuit boards can work as Dual Mono Power – PCB track can be divided, and each amplifier is powered by its own proposal. Although IMO not much sense, it also enables the PCB, halved and each half has its own power connector. The output connections can be made for

40

printed circuit pin, or you can use to pay “shovel (AKA speed connection) LUG – Council provides regulations on this subject. More details can be construction, purchase of PCBs, and all options are described in detail. As you can see, there are provisions to use TDA7294 well. This circuit is almost identical, but a specification higher. There are links on the board to connect contacts 1 and 5 (it should not be connected to the TDA727). Use TDA7294, fees can run bridged (BTL or bridge tied load) to about 150 W at 8 ohms. I think P87B be used to provide phase signal is necessary for BTL operation. Although it is common to see AMP as a reversal, there is a very low resistance at first, and may lead to unacceptable pressures and possible distortion. P87B be managed separately by each amplifier, and the best way to control the amplifiers.While parallel operation is often recommended, I strongly recommend that you run the amps in parallel. There are very strict requirements for greater tolerance for parallel operation – usually amplifiers must correspond to 0.1% or more for all audio traffic and beyond. A very low output resistance of members, even inconsistencies 100mV (instantly, any voltage and frequency) can cause large amounts of current flowing through the circuits. Although 0.1Ω resistors are usually offered, inconsistencies 100mV voltage (0.15% at the peak voltage 60V) 0.5A cause a circulating current. This leads to overheating and protection of anger involved.

41

200 Watts STK4050 Amplifier suitable for Sub-Woofer

Description: Output Power Load Resistance Input Impedance Maximum Supply Recommended

: 200 Watts : 8 Ohms : 55K : (+95v)-0-(-95v) : (+66v)-0-(-66v)

42

200watts amplifier using TDA 2030

43

600 Watts Stereo Amplifier (300Watts/Channel) Power Supply:

44

• •

Speakers Must be 300 Watts or more power. Use 8Ohms Impedance Speakers.

45

A Balanced Output Board for the Stereo DAC Circuit diagram:

46

This add-on board is designed to provide a pair of balanced audio outputs for the High-Quality Stereo DAC (Digital to Analog Converter). Two 3-pin male XLR connectors are used for the new outputs and they can either replace or augment the existing unbalanced outputs without affecting their performance. Balanced audio is used in recording studios and on stage because of its improved noise immunity. This is due to the fact that the signal is sent differentially (i.e., as two signals 180° out of phase) and then converted to a single-ended voltage signal at the far end. If any noise is picked up in the cable, it affects the two out-of-phase signals equally so that when the signals are subsequently subtracted, most of the noise is eliminated.

47

Parts layout:

48

In addition, the DAC’s performance at the balanced outputs generally exceeds that of the unbalanced outputs, although only by a small margin. The signal-to-noise ratio, frequency response and channel separation are all better, although we measured a tiny bit more distortion from the balanced outputs. However, both levels are so low as to be almost negligible.

Audio Power Amplifier 60W with TDA7294 Description The TDA7294 amplifier module is a monolithic integrated circuit. It is intended for use as an audio class AB amplifier in hi-fi applications. It has a wide voltage range and output current capability, enabling it to supply the highest power into both 4 ohm and 8n ohm loads. With the addition of a handful of parts and a suitable power supply, this module will deliver 50W RMS into 8-ohm with 0.1% THD. you the user must supply a heavy duty heatsink rated at 1.4°C/W. Pin 10 is the MUTE input and

49

pin 9 provides a STANDBY mode. Muting should always take place before standby mode is selected. Connecting these pins permanently to the supply rail (insert links) ensures that the amplifier comes on immediately on power up. Increasing the time constants R3-C6 and R4C5 may eliminate any switch-on clicks. The IC has internal thermal protection that causes the mute to cut in at 145°C and switches the amplifier into standby at 150°C. Do not operate the module without a heatsink. The heatsink tab on the TDA7294 IC is internally connected to the negative supply rail. If the module is mounted inside an earthed metal enclosure then the IC must be insulated from the heatsink. If not, the negative supply rail will be shorted to ground. Specifications • • •

Input sensitivity 1.3V (50W into 8W) Input impedance 10K Frequency response 15Hz - 100kHz

•

Output power 50W into 8W (0.1% THD), 82W into 4W (0.1% THD)

•

THD (40W into 8W) 0.002% (1kHz), < 0.04% (20Hz 20kHz) Power Supply +/-30Vdc

•

Circuit diagram

50

POWER SUPPLY The maximum supply voltage of the IC is +/-40V. However the maximum dissipation of the IC would be exceeded when using a 4-ohm load at that voltage. Therefore the supply voltage used should be kept down to a safe +/-30V. The mains transformer used to power the module should be rated at a minimum of 80VA. If you want to run two modules in a stereo amplifier you can use a common power supply. In this case the transformer should be rated at 150VA. Parts List for Power Amplifier • • • • • • • • • • • •

R1=180ohm R2-3-5=10Kohm R4=22Kohm R6=680ohm C1=1.5uF 63V MKT Polyester C2=2.7nF 63V MKT Polyester C3-4=100nF 100V MKT Polyester C5-6=10uF 63V Electrolytic C7=22uF 63V Electrolytic C8=33uF 25V Electrolytic C9-10=1000uF 63V Electrolytic IC1=TDA7294 on Heatsink

51 • • • •

J1=2pin connector with 2.54mm step JP1-2=2pin Jumper with 2.54mm step J2=3pin connector J3=2pin connector All Resistors is 1/4W 1% All Electrolytic Capacitors is Axial

Power Supply

Parts List for Power supply • • • • • • • •

TR1=230Vac//2X22Vac, 80VA for single Amplifier, 150VA for dual Amplifier BR1=Diode Bridge >15A C1=22nF 630V Polyester MKT C2....5=22nF 100V Polyester MKT C6-7=10.000uF 63V For single Amplifier C8-9=10.000uF 63V For dual Amplifier* C10-11=1uF 63V Polyester MKT F1=Fuse 0.5A slow

52

Audio Splitter This circuit is suitable to amplify and distribute the audio signals. The input audio signal is applied to the J1 and after passing through the P1, It is buffered and amplified by the IC1 prepared to redistribute. It has 3 outputs to drive 3 audio lines with 300 ohms impedance. Parts: • J1 = RCA Socket (See Notes) • P1 = 100K-Potentiometre • R* = 10K-100K • R1 = 560K • R2 = 1K • R3 = 2.2K • R4 = 2.7K • R5 = 2.7K • R6 = 330R • R7 = 330R • R8 = 330R • C1 = 100uF-25V • C2 = 100uF-25V • C3 = 100uF-25V • D1 = BZX79C18 • D2 = BZX79C18 • Q1 = BC337 • Q2 = BC327 • IC1 = NE5532-34

53

Notes: • J1 will be RCA Audio input female socket. • R* is on your choice it can be choose between 10K to 100K resistor. • Output capacitor’s value is between 100uf to 470uf and power handling is 25V to 50V. • You can power up this circuit via +12V/-12V regulated supply but you have to remove following parts Q1-Q2-C2-C3-D1-D2. • Maximum power ratings +35V/-35V

Compact High-Performance 20W+20W Stereo Amplifier Amplifiers which run from 12V DC generally don’t put out much power and they are usually not hi-fi as well.

54

But this little stereo amplifier ticks the power and low distortion boxes. With a 14.4V supply, it will deliver 20 watts per channel into 4-ohm loads at clipping while harmonic distortion at lower power levels is typically less than 0.03%. This is an ideal project for anyone wanting a compact stereo amplifier that can run from a 12V battery. It could be just the ticket for buskers who want a small but gutsy amplifier which will run from an SLA battery or it could used anywhere that 12V DC is available – in cars, recreational vehicles, remote houses with 12V DC power or where ever.

However, by using the TDA7377 power amplifier IC and making some other improvements, the THD (total harmonic distortion) of the new design are about 50 times better than the older unit. The bottom line is that the THD under typical conditions is around just 0.03% or less. It is also able to deliver more output power due to the improved output transistors in the new power amplifier IC. In addition, its idle power consumption is low – not much more than 1W. As a result, if you don’t push it too

55

hard it will run cool and won’t drain the battery too quickly. And because the IC has self-protection circuitry, it’s just about indestructible. It will self-limit or shut down if it overheats and the outputs are deactivated if they are shorted. With a 12V supply, the largest voltage swing a conventional solid-state power amplifier can generate is ±6V. This results in a meagre 4.5W RMS into 4O and 2.25W RMS into 8O, without considering losses in the output transistors. Even if the DC supply is around 14.4V (the maximum that can normally be expected from a 12V car battery), that only brings the power figures up to 6.48W and 3.24W for 4Ohms and 8Ohms loads respectively – still not really enough. There are three common solutions to this problem. The first is to boost the supply voltage using a switch mode DC converter. This greatly increases the cost and complexity of the amplifier but it is one way of getting a lot of power from a 12V supply. However, we wanted to keep this project simple and that rules out this technique.

56

57

There are variations on the boosting method, such as the class H architecture used in the TDA1562Q IC featured in the Portapal PA Amplifier (SILICON CHIP, February 2003). It is able to achieve 40W/channel but with >0.1% THD. In that case, the amplifier output itself provides the switching for a charge pump. The second method is to lower the speaker impedance. Some car speakers have impedance as low as 2O, which allows twice as much power to be delivered at the same supply voltage. However, we don’t want to restrict this amplifier to 2O loudspeakers.

58

Car Audio Power Amp TDA 2616 HiFi Circuit Here is the circuit diagram of a 2X12 watt HiFi amplifier circuit using IC TDA 2616 from Phillips. A quiet simple and robust circuit using very less components. This makes the circuit ideal for a portable power amplifier. The circuit delivers 12 W power on 8 Ohm speaker for each channel at +/- 12 V dual supply. The TDA2616 is a stereo power amplifier IC comes in a 9lead single-in-line SIL9 plastic power package SOT131. This IC is specially designed for mains fed amplifier circuits, such as stereo radio, tape and television .The IC has good gain balance of both channels and Hi-fi in accordance with IEC 268 and DIN 45500 standards. Also the IC TDA 2616 has special inbuilt circuit for the suppression of noise signals at the inputs, during switchon and switch-off.This prevents click sounds during power on and power off. All capacitors except C10 & C9 are ceramic.

All capacitors must be rated 50V.

59

Dual Power Amplifier Using TDA7293 MOSFET As readers will know, there are already several power amplifier projects, two using IC power amps (aka power opamps). Both have been popular, and this project is not designed to replace either of them. However, it is significantly smaller than the others, so it makes building a multiple amp unit somewhat easier because the space demand is much lower. It's quite simple to include 4 amps (two boards) into a small space, but be aware that good heatsinking is essential if you expect to run these amps at significant power levels.

The TDA7293 IC uses a MOSFET power stage, where the others featured use bipolar transistors. The main benefit of the MOSFET stage is that it doesn't need such radical protection circuitry as a bipolar stage, so unpleasant protection circuit artifacts are eliminated. There are no apparent downsides to the TDA7293, although it was found that one batch required a much higher voltage on the Standby and Mute pins than specified, or the amps would not work. This is not a limitation, since both are tied to the positive supply rail and are therefore disabled. This particular project has been planned for a long time, but for some reason I never got around to completing the board or the project description. This is now rectified, and it's ready to "rock and roll". The board is very small - only 77 x 31mm, so getting it into tight spaces is easy ... provided adequate heat sinking is available of course. Description the TDA7293 has a bewildering number of options, even allowing you to add a second power stage (in another IC) in parallel with

60

the main one. This improves power into low impedance loads, but is a rather expensive way to get a relatively small power increase. It also features muting and standby functions, although I've elected not to use these. The schematic is shown in Figure 1, and is based on the PCB version. All unnecessary functions have been disabled, so it functions as a perfectly normal power amplifier. While the board is designed to take two TDA7293 ICs, it can naturally be operated with only one, and the PCB is small enough so that this is not an inconvenience. A LED is included to indicate that power is available, and because of the low current this will typically be a high brightness type.

The IC has been shown in the same format that's shown in the data sheet, but has been cleaned up for publication here. Since there are two amps on the board, there are two of most of the things shown, other than the power supply bypass caps and LED "Power good" indicator. These ICs are extremely reliable (as are most power amp ICs), and to reduce the PCB size as much as possible, fuse clips and fuses have not been included. Instead, there are fusible tracks on the board that will fail if there is a catastrophic fault. While this is not an extremely reliable fuse, the purpose is to prevent power transformer failure, not to protect the amplifiers or PCB. I normally use a gain of 23 (27dB) for all amplifiers, and the TDA7293 is specified for a minimum gain of 26dB, below which it may oscillate. Although this is only a small margin, tests so far indicate that the amp is completely stable. If you wish, you may increase the gain to 28 (29dB) to give a bit more safety margin. To do this, just change the input and feedback resistors (R3A/B and R4A/B) from 22k to 27k. The circuit is conventional, and is very simple because all additional internal functions are unused. The LED is optional, and if you don't think you'll need it, it may be omitted, along with series

61

resistor R3. All connections can be made with plugs and sockets, or hard wired. In most cases, I expect that hard wiring will be the most common, as the connectors is a pain to wire, and add unnecessary cost as well as reduce reliability. The TDA7293 specifications might lead you to believe that it can use supply voltages of up to ±50V. With zero input signal (and therefore no output) it might, but I don't recommend anything greater than ±35V if 4 ohm loads are expected, although ±42V will be fine if you can provide good heat sinking. In general, the lower supply voltage is more than acceptable for 99% of all applications, and higher voltages should not be used unless there is no choice. Naturally, if you can afford to lose a few ICs to experiments, then go for the 42V supplies (obtained from a 30+30V transformer).

Construction Because of the pin spacing, these ICs are extremely awkward to use without a PCB. Consequently, I recommend that you use the ESP board because it makes building the amplifier very simple. The PCBs are double sided with plated-through holes, so are very unforgiving of mistakes unless you have a good solder sucker. The best way to remove parts from a double sided board is to cut the pins off the component, then remove each pin fragment individually. This is obviously not something you'd wish to do if a power amp IC were installed incorrectly, since it will be unusable afterwards.

Figure

2

-

TDA7293V

Pinots The diagram above shows the pinouts for the TDA7293V (the "V" means vertical mounting). Soldering the ICs must be left until last.

62

Mount the ICs on your heatsink temporarily, and slide the PCB over the pins. Make sure that all pins go through their holes, and that there is no strain on the ICs that may try to left the edge off the heatsink. When ICs and PCB are straight and aligned, carefully solder at least 4 pins on each IC to hold them in place. The remaining pins can then be soldered. Remember, if you mess up the alignment at this point in construction, it can be extremely difficult to fix, so take your time to ensure there are no mistakes. This amplifier must not be connected to a preamp that does not have an output coupling capacitor. Even though there is a cap in the feedback circuit, it can still pass DC because there is no input cap on the PCB. I normally include an input cap, but the goal of this board was to allow it to fit into the smallest space possible, and the available board space is not enough to include another capacitor. A volume control (typically 10k log/ audio taper) may be connected in the input circuit if desired. Note that the metal tab of the TDA7293 is connected to the -Ve supply, so must be insulated from the heatsink. The more care you take with the mounting arrangement, the better. While you can use a screw through an insulating bush and a piece of mica to insulate the tab, a better alternative is to use a clamping bar of some kind. How you go about this depends a lot on your home workshop tools and abilities, but one arrangement I've found highly satisfactory is a suitable length of 6.25mm square solid steel bar. This is very strong, and allows good pressure on the mica (or Kapton) for maximum heat transfer. Naturally, heatsink compound is absolutely essential. Do not be tempted to use silicone insulation washers unless you are using the amp at very low supply voltages (no more than ±25V). Its thermal transfer characteristics are not good enough to allow the amp to produce more than about 10 - 20W of music, and even that can be taxing for silicone washers. The amp will shut down if it overheats, but that curtails one's listening enjoyment until it cools down again. Power Supply A suitable power supply is shown below, and is completely unremarkable in all respects. The transformer may be a conventional (E-I) laminated type or a toroid. The latter has the

63

advantage of lower leakage flux, so will tend to inject less noise into the chassis and wiring. Conventional transformers are usually perfectly alright though, provided you take care with the mounting location. The bridge rectifier should be a 35A 400V type, as they are cheap, readily available and extremely rugged. Electrolytic capacitors should be rated at 50V. The cap connected across the transformer secondary (C4) should be rated at 275V AC (X Class), although a 630V DC cap will also work. This capacitor reduces "conducted emissions", namely the switching transients created by the diodes that are coupled through the transformer onto the mains supply. The power supply will work without this cap, and will most likely pass CE and C-Tick tests as well, but for the small added cost you have a bit of extra peace of mind as regards mains noise.

The supply shown includes a "loop breaker", which is intended to prevent earth/ ground loops to prevent hum when systems are interconnected. Please be aware that it may not be legal to install this circuit in some countries. The diodes must be high current types preferably rated at no less than 3A (1N5401 or similar). The loop breaker works by allowing you to have the chassis earthed as required in most countries, but lets the internal electronics "float", isolated from the mains earth by the 10 ohm resistor. RF noise is bypassed by the 100nF cap, and if a primary to secondary fault develops in the transformer, the fault current will be bypassed to earth via the diodes. If the fault persists and the internal fuse (or main power circuit breaker) hasn't opened, one or both diodes will fail. Semiconductor devices fail short-circuit, so fault current is connected directly to safety earth. Be very careful when first applying mains power to the supply. Check all wiring thoroughly; verify that all mains connections are protected from accidental contact. If available, use a Variac, otherwise use a standard 100W incandescent lamp in series with the mains. This will limit the current to a safe value if there is a major fault.

64

When the loop breaker is used, all input and output connectors must be insulated from the chassis, or the loop breaker is bypassed and will do nothing useful. The body of a level pot (if used) can be connected to chassis, because the pot internals are insulated from the body, mounting thread and shaft. Note that the DC ground for the amplifiers must come from the physical centre tap between the two filter caps. This should be a very solid connection (heavy gauge wire or a copper plate), with the transformer centre tap connected to one side, and the amplifier earth connections from the other. DC must be taken from the capacitors - never from the bridge rectifier. The order of the fuse and power switch is arbitrary - they can be in any order, and in many cases the order is determined by the physical wiring of the IEC connector if a fused type is used. With a fused IEC connector, the fuse is before the switch and it cannot be removed while the mains lead is inserted. I have shown a 2A slow-blow fuse, but this depends on the size and type of transformer and your mains supply voltage. Some manufacturers give a recommended fuse rating, others don't. The fuse shown is suitable for a 150VA transformer at 230V AC, and is deliberately oversized to ensure that it will not be subject to nuisance blowing due to transformer inrush current. A 2A fuse will fail almost instantly if there is a major fault. Make sure that the mains earth (ground) is securely connected to guarantee a low resistance connection that cannot loosen or come free under any circumstances. The accepted method varies from one country to the next, and the earth connection must be made to the standards that apply in your country. WARNING: This power supply circuit requires experience with mains wiring. Do not attempt construction unless experienced, capable and suitably qualified if this is a requirement where you live. Death or serious injury may result from incorrect wiring. Testing

65

never attempt to operate the amplifier without the TDA7293 ICs attached to a heatsink! Connect to a suitable power supply - remember that the supply earth (ground) must be connected! When powering up for the first time, use 100 ohm 5W "safety" resistors in series with each supply to limit the current if you have made a mistake in the wiring. If available, use a variable bench supply - you don't need much current to test operation, and around 500mA is more than enough. If using a current limited bench supply, the safety resistors can be omitted. Do not connect a speaker to the amplifier at this stage! If using a normal power supply for the amp tests, apply power (±35V via the safety resistors) and verify that the current is no more than 60mA or so - about 6V across each 100 ohm resistor. No load current can vary, so don't panic if you measure a little more or less. Verify that the DC voltage at both outputs is less than 100mV. Using another 100 ohm resistor in series with a small speaker, or an oscilloscope, apply a sinewave signal at about 400Hz to the input and watch (or listen) for signal. The signal level needs to be adjusted to ensure the amp isn't clipping, and the waveform should be clean, with no evidence of parasitic oscillation or audible distortion. If everything tests out as described, wire the amplifier directly to the power supply and finish off any internal wiring in the amp. Once complete, it's ready to use.

66

67

LA4460 IC AMPLIFIER

68

25 watts Hi-Fi Amplifier using IC LM1875

25 watts Amplifier using IC LM1875

69

Paraphase Tone Controller As opposed to the widespread Baxandall circuit (dating back to 1952!) a ‘paraphrase’ tone control supplies a straight frequency response as long as the bass and treble controls are in the same position. This unique property makes the ‘Paraphase’ configuration of interest if only treble or bass needs to be adjusted - it is not possible to adjust both at the same time! Essentially, it’s the difference in setting of the tone controls that determines the slope of the frequency response, and the degree of bass/treble correction. The circuit is simplicity itself, based on two networks C1-C2-C3/R9-R10-R11 and C5-C6C7/R12-R13-R14. Picture of the project:

Paraphase Tone Controller Circuit The first is for the high frequencies (treble) response, the second, for the low frequencies (bass). The roll-off points have been selected, in combination with C4 and C8, for the sum of the two output signals to re-appear with a ‘straight’ frequency response again at the output. Roughly equal output levels from the networks are ensured by R6

70

= 7.15 k and R8 = 6.80 k. However, the operating principle requires the input signals to the two networks to be in antiphase. For best operation the networks are driven by two buffers providing some extra gain. Circuit diagram:

Paraphase Tone Controller Circuit Diagram The gain of IC1.D is slightly higher than that of IC1.C to ensure the overall response curve remains as flat as possible at equal settings of the tone controls. Because each network introduces a loss of about 1.72 (times), IC1.D and IC1.C first amplify the signal. The gain is set at about 8 (times) allowing input signal levels up to 1 V to pass the circuit at maximum gain and distortion-free. The gain also compensates the attenuation if you prefer to keep the tone controls at the mid positions for a straight response.

Parts and PCB layout:

71

Parts and PCB Layout To audio fans, the circuit is rewarding to experiment with, especially in respect of the crossover point of the two networks. R3 and R4 determine the control range, which may be increased (within limits) by using lower resistor values here. The values shown ensure a tone control range of about 20 dB. IC1.B buffers the summed signal across R15. C9 removes any DC-offset voltage and R16 protects the output buffer from the effects of too high capacitive loads. R17, finally, keeps the output at 0 V. The choice of the quad opamp is relatively uncritical. Here the unassuming TL074 is used but you may even apply rail to rail opamps as long as they are stable at unity gain. Also, watch the supply voltage range. A simple circuit board was designed for the project. Linear-law potentiometers may be fitted directly onto the board. Two boards are required for a stereo application. The relevant connections on the boards are then wired to a stereo control potentiometer.

72

Specification: • Current consumption (no signal) 8 mA • Max. input signal 1 Veff (at max. gain) • Gain at 20 Hz +13.1 dB max. –6.9 dB min. • at 20 kHz +12.2 dB max. –7.6 dB min • Gain (controls at mid position) 2.38 x • Distortion (1 Veff, 1 kHz) 0.002% (B = 22kHz) 0.005% (B = 80 kHz) COMPONENTS LIST Resistors R1-R4 = 10k R5, R7 = 1k R6 = 7k15 R8 = 6k80 R9, R10, R11 = 8k2 R12, R13, R14 = 2k2 R15 = 1M R16 = 100R R17 = 100k P1, P2 = 100k preset or chassismount control potentiometer, linear law Capacitors C1,C2,C3 = 47nF MKT, lead pitch 5mm C4 = 68nF MKT, lead pitch 5mm C5,C6,C7 = 10nF MKT, lead pitch 5mm C8,C10,C11 = 100nF MKT, lead pitch 5mm C9 = 2µF2 MKT, lead pitch 5mm or 7.5mm Semiconductors IC1 = TL074 Miscellaneous K1, K2 = line socket, PCB mount, e.g. T-709G (Monacor/Monarch)

73

Simple Hybrid Audio Amplifier The debate still goes on as to which are better, valves or transistors. We don’t intend to get involved in that argument here. But if you can’t make your mind up, you should try out this simple amplifier. This amplifier uses a valve as a pre-amplifier and a MOSFET in the output stage. The strong negative feedback makes the frequency response as flat as a pancake. In the prototype of the amplifier we’ve also tried a few alternative components.

For example, the BUZ11 can be replaced by an IRFZ34N and an ECC83 can be used instead of the ECC88. In that case the anode voltage should be reduced slightly to 155 V. The ECC83 (or its US equivalent the 12AX7) requires 2 x 6.3 V for the filament supply and there is no screen between the two triodes, normally connected to pin 9. This pin is now connected to the common of the two filaments. The filaments are connected to ground via R5. If you’re keeping an eye on the quality, you should at least use MKT types for coupling capacitors C1, C4 and C7. Better still are MKP capacitors. For C8 you should have a look at Panasonic’s range of audio grade electrolytics. P1 is used to set the amount of negative feedback. The larger the negative feedback is, the flatter the frequency response will be, but the smaller the overall gain becomes.

74

Circuit diagram:

Simple Hybrid Audio Amplifier Circuit Diagram With P2 you can set the quiescent current through T2. We have chosen a fairly high current of 1.3 A, making the output stage work in Class A mode. This does generate a relatively large amount of heat, so you should use a large heatsink for T2 with a thermal coefficient of 1 K/W or better. For L1 we connected two secondary windings in series from a 2x18V/225 VA toroidal transformer. The resulting inductance of 150 mH was quite a bit more than the recommended 50 mH. However, with an output power of 1 W the amplifier had difficulty reproducing signals below 160 Hz. The distortion rose to as much as 9% for a signal of 20 Hz at 100 mW. To properly reproduce low-frequency signals the amplifier needs a much larger coil with an iron core and an air gap. This prevents the core from saturating when a large DC current flows through the coil.

75

Parts layout:

Such a core may be found in obsolete equipment, such as old video recorders. A suitable core consists of welded E and I sections. These transformers can be converted to the required inductor as follows: cut through the welding, remove the windings, add 250 to 300 windings of 0.8 mm enamelled copper wire, firmly fix the E and I sections back together with a piece of paper in between as isolation. The concepts used in this circuit lend themselves very well to some experimentation. The number of supply voltages can be a bit of a problem to start with. For this reason we have designed a power supply especially for use with this amplifier (Quad power supply for hybrid amp). This can of course just as easily be used with other amplifiers. The supply uses a cascade stage to output an unstabilised voltage of 170 V for the SRPP (single rail push pull) stage (V1).

76

PCB layout:

During initial measurements we found that the ripple on this supply was responsible for a severe hum at the output of the amplifier. To get round this problem we designed a separate voltage regulator (High-voltage regulator with short circuit protection), which can cope with these high voltages. If you use a separate transformer for the filament supply you can try and see if the circuit works without R5. During the testing we used a DC voltage for the filament supply. Although you may not suspect it from the test measurements (see table), this amplifier doesn’t sound bad. In fact, it is easily better than many consumer amplifiers. The output power is fairly limited, but is still enough to let your neighbours enjoy the music as well. It is possible to make the amplifier more powerful, in which case we recommend that you use more than one MOSFET in the output stage. The inductor also needs to be made beefier. Since this is a Class A amplifier, the supply needs to be able to output the required current, which becomes much greater at higher output powers. The efficiency of the amplifier is a bit over 30%.

77

78

STK4050V 200 watts audio amplifier circuit . This amplifier schematic circuit is based on STK4050V high power audio amplifier IC and is designed does deliver up to 200 watts audio power on a single channel. . STK4050V supports addition of electronic circuits for thermal shutdown and load-short protection circuit as well as pop noise muting which occurs when the power supply switch is turned on and off.

The maximum output power of STK4050V audio amplifier is around 200 watts on 8 ohms load impedance with 66 volts split power supply. If you want to make this STK4050 power amplifier you need to make a separate thermal protection and load short protection circuit because STK4050V don’t offer this kind of protection and you can destroy the chip and the speaker box.

79

Studio Series Stereo Headphone Amplifier A top-class unit for the audio enthusiast! Here's a top-class headphone amplifier that can drive high or low impedance 'phones to full power levels, with very low noise and distortion. For best performance, it can be teamed with the Stereo Preamplifier described last month. Alternatively, it can be used as a standalone unit, requiring only a power supply and a volume control pot for use with any line-level signal source (CD/MP3 player etc). It even includes dual outputs, so you can listen with a friend! Picture of the circuit:

80

Many of our high-power audio amplifier designs already provide an output for headphones. The additional circuitry required for headphone support is simple; just two resistors in series with the loudspeaker outputs to limit the drive current and protect the ’phones in the case of amplifier failure. Considering its simplicity, this resistive limiting scheme works well, although it will cause distortion if the load is non-linear – a likely prospect with most headphones. Apart from eliminating this potential source of distortion, there are a number of other reasons why you might consider building a separate headphone amplifier.

Parts layout:

81

Another reason might be for use with the latest "high-tech" audio electronics gear. The headphone outputs in much of this gear cannot drive low-impedance ’phones – or at least not to decent listening levels. In addition, available output power in portable devices is deliberately limited to conserve battery energy. This means that lots of distortion might be present at higher listening levels, even with sensitive headphones. One way around this is to feed the line-level outputs of this gear into your power amplifier and then plug your low-

82

impedance headphones into that. That works but then you’re tethered to an immovable object. Besides, the power required to drive headphones is around 1/1000th of that required to drive loudspeakers, so a large power amplifier could be considered a tad oversized for the job! Circuit diagram:

Features & Performance Main Features: • High performance – very low noise & distortion • Drives high and low-impedance headphones • High output power (up to 200mW; into 8? and 32?) • Dual headphone sockets – can drive two pairs! • Works with a preamp or any line-level audio source Measured Performance: Frequency response.......................... flat from 10Hz to 20kHz (see graphs) Rated output power........................... 200mW into 8? and 32?, 85mW into 600? Max. output power (current or voltage

83

limited)...............575mW into 8?, 700mW into 32?, 130mW into 600? Harmonic distortion........................ typically .0005% (600? load),.001% (32? load) and .005% (8? load) Signal-to-noise ratio (A-weighted)......................... -130dB (600?), -120dB (32?) and -111dB (8?) with respect to 100mW output power. Channel crosstalk.................. better than -68dB from 20Hz-20kHz at 100m? output power (see graphs) Input impedance.................................... ~47k? || 47pF Output impedance..................... ~5? Note: All tests were performed with the amplifier driven from low source impedance. For crosstalk measurements, the nondriven input was back-terminated into 600?. CAUTION! Continual exposure to very high noise levels (including loud music) will cause hearing loss and can cause tinnitus. Hearing loss is cumulative, gradual and almost symptomless!

TDA7350 power amplifier circuit

84 This schematic circuit is a class AB audio power amplifier based on the TDA7350 IC designed in a Multiwatt package .This TDA7350 power amplifier can be used for car radio applications and many other . The TDA7350 require few external components and can be used in stereo mode or mono (bridge) mode. If you want to make a simple power amplifier with very few external components required you can use this amplifier based on the TDA7350. The TDA7350 amplifier has many features like: high output power, no noise on on/off switch, programmable turn-on delay, ac-dc short circuit protections, overrating temperature protection and more. For this power amplifier we need to use 4 ohms or 2 ohms speakers. If we use stereo configuration the output power is 11W on 2 ohms and 6.5W on 4 ohms with 10% distortion and if we use the bridge mode the output power is 20 W on 4 ohms speaker. For the TDA7350 power amplifier is need a dc power supply with a maximum output voltage of 18 volts ( the typical power supply needed by TDA7350 power amplifier is 14.4 volts ) . As you can see in both circuits (tda7350 bridge and stereo) the schematic is almost the same, the major difference is that the pin 2 and 4 are connected each other in the bridge configuration.

85

86

2X15 Watts Stereo Amplifier Using TDA 4935

87

4 Channel Output Amplifier using Single Chip TDA 7381

88

Voltage Doubler Using IC 555

2Km FM Transmitter

89

12V Voltage Booster

POLICE SIREN using IC555

90

0-30 Volt 3Amps Variable Regulator by using LM 723