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Cheap 100 to 150 Watt Audio Amplifier

Now, this is an interesting one. A cheap and quick way to build an audio amplifier with between 100-150 Watts output.

Screenshot: Cheap 100 to 150 Watt Audio Amplifier

Jon Tirone (Also known as John Fisher) shares a circuit diagram and picture of the printed circuit board he used for a cheap and easy-to-build audio amplifier with an impressive 100 - 150 watts output power. It also shows the circuit diagram for a split power supply, which is used to power it up!

It uses the following components:

  • 2 x 22k Resistors
  • 2 x 3.3K Resistors (1 Watt)
  • 2 x 0.33 Ohm Resistors (5+ Watts Heat Dissipation)
  • 1 x 33 Ohm Resistor
  • 1 x 220 Ohm Resistor
  • 1 x 27K Resistor
  • 1 x 1K5 Resistor
  • 1 x 10uF Capacitor
  • 1 x 10 uF Capacitor @ 63v
  • 1 x 100uF Capacitor @ 50v
  • 2 x 1N4007 Diodes
  • 2 x 2N258, BC558 or equivalent
  • 1 x TIP142 Darlington Pair Transistor
  • 1 x TIP41 Epitaxial Silicon Transistor
  • 1 x TIP147 Power Darlington

According to the notes, it works extremely well, but it doesn't give an exact measure of distortion levels. Please come back and submit a comment if you build it so that we can all know how good it really is :)

Alternate References:
admsh says: (January 3 2008, 6:35am)

This is the usefull site for hobbies in electronics.

ElectroKits says: (January 30 2008, 2:15pm)

Just to let you all know... there have been some comments posted on forums across the internet stating that this audio amplifier is not good, and potentially even dangerous. Other comments state that it works fine.

Please be careful if you choose to build this circuit - and post your results here so that others will know how the amplifier works.

robby007 says: (March 3 2008, 10:51am)

i built the curcit exactly as you have it byt i get no sound from it. the only difference is that i use a1015 transistors instead of the ones on the drawing. what can i do to correct this problem?

jenel says: (March 4 2008, 3:04am)

is these realy a good amp circuit? i wonder why others cannot do these circuit. maybe they dont know how to build this one.
is it tested? i dont know how it works and i dont know how to test it.

ElectroKits says: (March 4 2008, 3:15am)

Robby007 - I'm not familiar with that transistor - is it identical to the ones that are listed above?!

Jenel - There are confirmed cases of this audio amplifier working correctly, but there are also cases of the circuit not working well. Like all electronic circuit, it depends on how it's constructed. If there are solder bridges or dry joints, then it won't work as well as if the soldering and construction was perfect.

robby007 says: (March 6 2008, 8:02am)

i trashed the curcit and rebuild it now the tip42 gets hot whenever i attached the speaker. how can i solve this

dejan47 says: (March 11 2008, 3:16am)

this amplifier really works.. i built it using a breadboard and changed some values of the resistors since i can't find them and my power supply output is only 17 volts.. and it works.. it sounds good.. and i think it will sound better if i increase my power supply output..

jacko says: (March 17 2008, 6:41am)

whenevei i connect out-put speaker the tip 42 darlington gets verry hot in no time. what can i do to resolve this problem?

azmis says: (March 20 2008, 8:46pm)

TIP42 become hot its because wrong connection on it, double check it, ive build this amp and it works fine, use minimum power supply at +-20vdc

spark9 says: (March 27 2008, 3:10am)

Maybe you should use a heat sink for tip 42 and perhaps
the rest of the power transistors. If you look close at the picture, you can clearly see that the transistors are mounted to a piece of aluminum which is commonly used in amplifiers!

furball99 says: (March 28 2008, 2:52pm)

I built this amp and it works great with an normal 8 ohm speaker, but im wanting to hook it up to a high impedance acustic underwater speaker and I need a matching tranformer. Anyone have any suggestions on how to go about this?

Jeo0 says: (April 7 2008, 9:49am)

Well the Amplifier really sounds good but i must say the circuit is a not too good, I always have trouble assembling a stereo of this circuit but it always work well with Mono, what i did was to assemble a double power supply for stereo which cost me alot,Robby if you still have problems with the tip 42 then try to use separate dc power supply.

joe_neng says: (April 15 2008, 5:55pm)

your site is excellent

mkaurt says: (April 23 2008, 12:59pm)

iam sorry to say that this is a very poor design of a BJT amplifier and it does not work. The design is not satisfactory. I tried it with all the indicated values...not working! what a waste of time.

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