Powerful Mono Amplifier (HIGH BASS) by JLCPCB.COM


Introduction: Powerful Mono Amplifier (HIGH BASS) by JLCPCB.COM

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This is the cheapest 150 Watt amplifier circuit you can make,I think.
Based on two Darlington power transistors TIP 142 and TIP 147 ,this circuit can deliver a blasting 150 W Rms to a 4 Ohm speaker. You can get more than 250Watts Rms if you use 2SC5200 and 2SA1943 in the replacement of TIP142 and TIP 147 respectively.

TIP 147 and 142 are complementary Darlington pair transistors which can handle 5 A current and 100V ,famous for their ruggedness. Here two BC 558 transistors Q5 and Q4 are wired as pre amplifier and TIP 142 ,TIP 147 together with TIP41 (Q1,Q2,Q3) is used for driving the speaker.This circuit is designed so rugged that this can be assembled even on a perf board or even by pin to pin soldering.The circuit can be powered from a +/-45V, 5A dual power supply.You must try this circuit.Its working great!

The PCB board used in this project is provided by jlcpcb.com and it is the 2 layer board in which you do not have to put any of the jumpers on the board and the board's quality is great due to which the amplifier's sound quality is great and totally noise proof. If you want to make your own custom based board the you must visit www.jlcpcb.com and order your first 10PCB boards only for 2$ and without any shipping costs.

Technical Specifications:

The preamplifier section of this circuit is based around Q4 and Q5 which
forms a differential amplifier. The use of a differential amplifier in the input stage reduces noise and also provides a means for applying negative feedback. Thus overall performance of the amplifier is improved. Input signal is applied to the base of Q5 through the DC decoupling capacitor C2. Feedback voltage is applied to the base of Q4 from the junction of 0.33 ohm resistors through the 22K resistor. A complementary Class AB push-pull stage is built around the transistors Q1 and Q2 for driving the loud speaker. Diodes D1 and D2 biases the complementary pair and ensures Class AB operation. Transistor Q3 drives the push-pull pair and its base is directly coupled to the collector of Q5.

BOM's (Build On Materials)

TIP142 X 1
TIP147 X 1
TIP41 X 1
BC558 X 2
1N4007 X 2


27K X 1
22K X 2
1.5K X 1
220Ohm X 1
33Ohm X 1
3.3K 1Watt X 2
0.33Ohm 5Watt X 2


10UF / 50V X 1
100UF / 50V X 1
0.1UF / 50V X 1

Step 1: Solder All the Resistors

As this circuit is so small and requires very less components so you must start from resistors.Firstly. Add the first resistor at the input stage which is of 27K, then add the 1.5K resistor which is along with the 27K resistor, after that add the two 3.3K 1Watts resistors and then add 22K resistors and then solder the 33Ohms resistor, after soldering the 1/4Watts resistors, Now add two 0.33OHM 5Watt wire wound resistors as you can see in the image. Connect all the resistors just like that.

Step 2: Solder All the Three Capacitors Including 10UF, 0.1UF and 100UF

Now, After soldering all the resistors, Add all the capacitors which are total three only in the amplifier stage of this circuit. Firstly, Add 0.1UF / 50V Capacitor at the input stage of the amplifier, Secondly, add the 10UF/50 V capacitor and finally add the 100UF/50 V Capacitor and solder them all.
Make sure that all the capacitors used in this circuit are must of 50Volts or higher and nor less than 50Volts.

Step 3: Solder the 1N4007 Diodes

Now add and solder the two 1N4007 Diodes.
There are only two diodes used in this circuit in the amplifier section and you can use either 1N4007 or 1N4001 or any other same size and same rating diodes of the same size, There is no restriction of using the same number diodes.

Step 4: Solder the Small Transistors BC558 and TIP41

Now Add the input Pre Stage Transistors and for that, firstly add the two BC558 Transistors and the add the TIP41 Transistor which is the only one in this circuit. You can use any same rating transistor (must be PNP) in place of TIP41 such as D313 which is the perfect alternate of this transistor. Add these three components and gently solder them.

Step 5: Solder the Power Transistors TIP142 & TIP147

Now add the two Power Transistors TIP142 and TIP147 and solder them. This is the power and the output stage of the amplifier which is considered as the backbone of the amplifier. TIP142 is the PNP where as TIP147 in the NPN transistors and they both are darlington pairs, You can also add alternates and replace these output transistors to have more powerful output such as you can replace your TIP142 with 2SC5200 (NPN) and TIP147 with 2SA1943 (PNP) Transistors without altering any other component in the circuit. And you can have more than the double power at the output by using these great alternates.

Step 6: Solder the 6Ampere Diodes

Now Come tot he Power Supply Section of the amplifier which is situated below the circuit and is having the four 6Ampere Diodes for full bridge rectification and two Capacitors for filtered output after the rectification. Just add these four Diodes and solder them. Use any 6Amperes Diodes.

Step 7: Finally Solder the Bigger Capacitors 4700UF / 50V or Higher in the Power Supply Section

Finally, Now add the two Bigger sized Capacitors of rating 4700UF/50Volts and solder them. You can use the capacitors above that rating but not less than 4700UF and 50Volts.
These capacitors are used to filter the rectified output from the diodes and supply the filtered output to the amplifier.

The PCB Board used in this project is manufactured by JLCPCB which is the leading manufacturer of PCB boards and produce a very good quality PCB boards at very cheap price and you can order your own designed PCB to their website www.jlcpcb.com and you can avail their offer of getting your first 10PCB's order only for 2$ without paying any shipping costs. Order Now to get 10 PCB's for 2$ only by JLCPCB



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    2 Discussions

    I have a few comments and questions:

    There are a few issues with the PCB. The input coupling capacitor is shown as a 0.1uF capacitor on the silkscreen but is a 10uF capacitor on the schematic. The power supply filter capacitors are called out as 6300uF on the PCB silkscreen but the text specifies 4500uF capacitors. The pads for the filter capacitors are enormous. Far larger than any lead I have ever seen. The BOM calls out a 0.1uF capacitor that is not in the schematic. Have these issues been fixed? If someone orders your PCB there will be quite a bit of confusion.

    The schematic shown is almost incomprehensible. I would strongly recommend revising it to make the design easier to understand. I would also recommend showing the power supply design in the schematic and specifying a part number for the rectifier diodes. Simply stating that any 6 amp diodes will work is not accurate. A transformer recommendation is also important. The transformer I used was a Hammond toroidal 60V 10A CT transformer that lists for $70. Folks should probably be aware of that before they commit to building what you described as the cheapest design. I think you haven't gone far enough to describe a complete amplifier.

    There are some issues with the design I have questions about:

    The Darlington output transistors have a base-emitter drop of 1.4V. Two bias diodes are not sufficient to eliminate crossover distortion. In the testing I did using your schematic I needed five 1N4007 diodes to bias both output transistors on and eliminate crossover distortion.

    The unregulated power supply indicated is insufficient to produce 150W into a 4 Ohms. My 60V center tapped transformer (30-0-30) could only achieve +/- 42.3V after rectifier drops and no load. Under load I could only achieve 100W before clipping occurred due to the 3V ripple voltage on the filter capacitors. A very noticable 120Hz hum is heard at high volume. It's really not possible to achieve more than 100W with this design. Not that 100W is bad, but it's not 150W, or higher just by changing transistors.

    I'm very concerned with the PCB layout. There are two 0.33 Ohm 5W resistors landed right over a 1/4 watt 33 Ohm resistor. 100W speaker load will result in a dissipation for these resistors of just over 4W. Right onto a 1/4 W resistor. Your 33 Ohm resistor isn't going to survive for long.

    The datasheet for the the BC558 transistors specifies a CE voltage no greater than 30V. But when I built the circuit, CE voltage was over 40V. Those transistors will probably not last long. A transistor with a higher CE voltage would have been a better choice.

    I'm not sure why the 3.3K Ohm resistors were specified as 1W. The maximum dissipation I measured is 1/4 W for only one of the resistors so 1/2 W would have worked and fit properly on the PCB instead of the odd placement indicated in the photos.

    There is no heat sink specified and that is really important in high power designs.

    Have you tested this design and the PCB for performance and reliability? Just hooking this up and saying, "Wow that's loud" isn't sufficient. There seems to be a lot of errors and omissions in the design and PCB layout, and some really weird component placement during soldering. If your intent was to advertise what JLCPCB can do, this project needed a bit more thought, planning, and a bit more design review.

    My intention is to clarify these issues before someone orders a PCB and components, and is disappointed. I do not in any way intend to unfairly criticize the author. The circuit described does indeed work. But I believe performance is overstated, important details have been omitted, and the overall design presented is unreliable.

    To be honest, it looks like you got in a hurry to promote a PCB manufacturer instead of describe a project that anyone can make.


    1 reply

    Unfortunately i have to agree with you, this instructable would need to be more detailed since its fairly simple design which means it should be more "noob" friendly so one step with short soldering course would be helpful, doesnt even include what alternative transistor someone might get or how to chose one or transformer that would be good to power it, heatsink, case etc.

    To OP dont take this as bad comment, it would be really nice if you could explain it more in details or even add few more pictures, 1/3 of the text is advertisement for pcb manufacturer, at least you could go in details of designing pcb.