Circuit description of 70/40 watts hi-fi amplifier

The 40/70 watts amplifier circuit is built around transistor, configured in various modes. The single to be amplified is given to base of transistor T1 configured as differential amplifier with T2. Transistor T3 is used to maintain the current of differential amplifier.

Transistor  T4 with T5 forms a cascaded pair derived by Transistor  T1. For better result Transistor  T6 and T7 again configured as cascaded pair and provide constant current source  to cascade pair T4 and T5 in this amplifier circuit.

Temperature coefficient of Transistor s T10 and t11 is compensated by Transistor  T8 and T9 which act like diodes. Transistor T10 with T12 & T14 and Transistor  T11 with T13 & T15 form a triple Darligton pairs.

The current through T4 and T5 is kept at a value of this output of this circuit consists of triple Darlington pair. The small change in the Vbe of T10 & T11 changes output current of hi-fi amplifier greatly.

In order to prevent distortion in the 40/70 watts hi-fi amplifier when capacitive loads are connected to the output, coil L1 is used to prevent DC voltage across the speaker and is connected in series to speaker. The total gain amplifier circuit is approximate 32 and is value is calculated by (R7 + R8)/R8.

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Resistors (all ¼-watt, ± 5% Carbon)

R_1, R7 = 100 KΩ

R₂, R₃, R₉ = 1.2 KΩ

R₄, R₅, R₆ = 2.7 KΩ/2W

R₈ = 4.7 KΩ

R₁₀, R₁₃, R₁₆, R₁₈, R₁₉ = 100 Ω

R₁₁ = 3.3 KΩ

R₁₂, R₁₇ = 680 Ω

R₁₄, R₁₅, R₂₂, R₂₃, R₂₄, R₂₅ = 1 Ω/2W

R₂₀ = 10 Ω/2W

R₂₁ = 1o Ω/1W

VR₁ = 100 Ω

Capacitors

C₁ = 1 µF/polyester

C₂, C₃ = 25 µF/25V electrolytic

C₄, C₈, C₉ = o.1 µF polyester

C₅ = 10 µF/60V electrolytic

C₆ = 4.7 µF/10V electrolytic

C₇ = 56 pF ceramic disc

Semiconductors

T₁, T₂, T₃ = BC546B

T₄ = BC558B

T₅, T₁₁ = 2N4033

T₆, T₁₀ = 2N3019

T₇ = BC548B

T₈, T₉ = BC147B

T₁₂ = BD140

T₁₃ = BD139

T₁₄ = 2N3055

T₁₅ = MJ2955

ZD₁ = 3.3V 400mW zener diode

ZD₂ = 3.9V, 400mW zener diode

Miscellaneous

L₁ = Coil having 20 turns of 20 SWG over thin pencil

F₁ = 3.5 Ampere fuse

Easy 9 way clap ckt diagram

The clap switch circuit is build around two IC's -

1. NE555 Timer IC which is configured in monostable mode.

2. 7490 IC which is a decade and binary counter. It contains four master slave flop and also contain divide by two and divide by five counter. It can be used as divide by 9 counter by connecting Q0 with clock input pin1 (CP1) and providing clock pulse to CP0 that is on pin14. It can also be used as divide by 6 counter by connecting Q0 with CP0 and giving input pulse at CP1.

7490 IC will provide you the 9 different combination to "on" and "off" the four different application in 9 claps. Similarly 7492 IC is also available which will provide you 11 different combination of  output for controlling the four appliances. And another is 7493 which provide 15 different ways to control the four appliances.

When you clap in front of the Mic, clapping sound is converted into electrical energy by the microphone. These weak signals are then amplified by the transistor which acts as preamplifier. Sensitivity of the signals can be improved with the help of VR1. Now the transistor T1’s output is feed to monostable circuit which is wired NE555 . Whenever you clap in front of microphone, output pin 3 of IC1 goes high and this is fed to clock input of IC2 pin 14. The output of IC2 is now provided to transistor T2-T4 through 100 ohm resistor to derive the corresponding relay connected to it. We have also connected different colour  to indicate the state of the different appliances. If LED glows means that device is "on". If LED does not glows means device is "off".