30W to 60W RMS OTL amplifier circuit and tone control with PCB

This is 60W RMS OTL integrated audio amplifier circuit using 2N3055 and normal transistor.

It is so cheap and can build easily. And, It’s durable and very loud sound for mini PA

From the previous project, some people say that Not suitable for a small party. Because of soft and does not durable.

50W RMS OTL integrated audio amplifier circuit with tone control

So I highly recommend this project are The classic OTL integrated amplifier that power output 55 watts.

The its feature is loudly than other circuits and watts are equal. the speaker has durability and be difficulty damage.

And build easier OCL amplifier.

Although some people say that it is not good bass. But if you try, you may like it.

Recommended: 30W OCL amplifier circuit with tone control

50W to 60W OTL amplifier working

Look at a block diagram of this project.

As show Figture fo this circuits.

Figure 1 the complete circuits of circuit diagram.

They consists of two large parts are the main amplifier and tone control circuit Same as the previous circuit.

How does circuit wirks

50W OTL Amplifier usiing 2N3055

The tone control circuit consists of Q1-transistor and IC1( op-amp IC-LM741).

The signal input will enter to C1 and R3 into base of Q1. Which acts as matching between the input circuit and tone control-IC1.

VR1 is used to adjust the bass sound.

VR2 is used to adjust the treble sound.

Which this circuit can adjust the bass/treble to upper or lower up to 18 dB.

The output from the tone control will be entered through C8-capacitor to the level sound controller circuit is VR3-potentiometer and the loudness controller.

The signal from volume will enter through to base of transistor-Q2.

To amplifier the signal higher, that enter to pre driver Q3.

To drive the driver circuit with Q4, Q5 and the both power transistors Q6, Q7 next.

How to builds

Since the circuit is designed as well. So easy to create. However, to the best results. Should perform the following.

Single side PCB layout of 35W to 50W OTL amplifier circuit

The Figure 2 Actual-size, single-sided PCB layout for the circuit.


Figure 3 the Component layout for the PCB

1. Check the correct finished in putting all components.
2. Do not connect the power transistor.
3. Use the voltmeter measures at 2 points C17, C18 compare to ground.
4. connects the positive 56 volts to this circuit and then adjust VR4 until read meter about 28 volts.
5. connects properly the power transistors to the circuit

Also: 100w amplifier circuit with PCB

The power supply circuit

In the figure 4, The voltage 56V for this circuit. We are derived from the bridge rectifier to change from AC40V. to as DCV. then pass the filter capacitors , and then will obtained is the 56VDC.

56V Power supply for 50W amplifier integrated audio amplifier circuit

Figure 4 The power supply circuit

The transformer that use for the mono type, should use size is 2A and size under 3A in the stereo system.

Read next: 4 transistor audio amplifier circuit

The detail of parts list

IC1: LM741, General Purpose Op-Amp
Q1, Q3: BC548, 45V 100mA NPN Transistor
Q2: BC557, 45V 100mA PNP Transistor
Q4: BD139, 80A 1.5A PNP transistor.
Q5: BD140, 80V 1.5 PNP Transistor
Q6, Q7: 2N3055 100V, 15A, 115W, >2,5MHz NPN transistor
ZD1: 18V 0.5W Zener Diode
D1, D2: 1N4148, 75V 150mA Diodes

0.25W Resistors
R1, R10: 56K
R2, R9: 47K
R3, R20: 1K
R4, R11, R15, R16: 2.2K
R5, R6, R7, R8, R23: 10K
R12: 100K
R13: 270K
R14: 150K
R17: 100 ohms
R18, R21: 3.9K
R19: 3K
R20: 1K
R22, R26: 20 ohms
R24: 390 ohms
R25, R27: 120 ohms
R28, R29: 0.5 ohms 1W
R30: 10 ohms 1W

VR1, VR2: 100KB
VR3: 50KA CT

Electrolytic Capacitors
C1, C2, C12: 10uF 16V
C7, C8: 22uF 16V
C9, C13, C15: 47uF 16V
C10: 4.7uF 16V
C11, C16: 220uF 16V
C18: 2,200uF 35V

Polyester Capacitor
C3, C4: 0.033uF
C5, C6: 0.0033uF
C14: 470pF
C17: 0.047uF
C19: 0.001uF
C20: 0.01uF

The detail parts of the power supply
T1: Transformer Secondary for 40 volts 3A-5A. ( for a stereo system)
D1-D4: Bridge diode >5A.200V
C1: 0.01uF 100V, Polyester Capacitor
C2: 10,000uF 63V, Electrolytic Capacitors

What is more?

Is it too high power? You want lower, right?

Try below.

30W OTL amplifier working using 2N3055

Friends may like old power amplifier circuits. Today I will show you the integrated OTL power amplifier circuit with PCB,  35W.  Using 2N3055 is the main component.

How it works

It is an interesting circuit. Because of moderately sound 35 watts at the 8 ohms loudspeakers.

It is the OTL type, so it is easy to build, economize, and durable.

35W OTL Integrated amplifier using 2N3055

Besides it still has the full function to adjust the output sound. Such as  Volume, Bass, Treble, Mid Range, etc.

Then, it is convenient for you, who is a novice want to build a power amplifier circuit.

Keep used by oneself and I have model PCB simply give friends.

PCB layout of Integrated OTL amplifier 35W using 2N3055

The 36V power supply of 35 watts amplifier

PCB layout of 35 watts to 45 watts amplifier using 2N3055 transistor

This is a 36V to 50V Power supply circuit for 35 Watts to 50 watts amplifier circuit.

36V to 48V DC Power supply circuit

Get convenient in building with Have a good time. With the sound of music.

Selecting and substituting components

These circuits are highly flexible. I believe that he has good electronic skills. But I want to review him about the transistor substitution number.

And pinouts of different transistors. Look at below.

The Small transistor. Look at Their Pinout of TO-92:

  • 2SC458, 2SC945, 2SC1815 and more.
  • BC547, BC557

Power transistor 2N3055. Look at the pinout of the TO-3 transistor.

Use TIP3055(TO-3P). We easily install it on the heatsink.

Look at TO-39 and TO-225 transistors.

Sometimes we can use 2N3053 instead of BD139. And, 2N4037 instead of BD140.

Check out these related articles, too:

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I always try to make Electronics Learning Easy.

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Apichet Garaipoom

I love the electronic circuits. I will collect a lot of circuit electronics to teach my son and are useful for everyone.
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