50 Watt Amplifier

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This is a handy, easy to build general purpose 50 watt amp. The amp has an input for a radio, TV, stereo or other line level device. It also has a phono input for a record player, guitar, microphone or other un-amplified source. With the addition of a low pass filter at the input, it makes a great amp for a small subwoofer.


This is the schematic of the 50 Watt Amp


Total Qty.
R11200 Ohm 1/4 W Resistor
R21200K 1/4 W Resistor
R3130K 1/4 W Resistor
R511K 1/4 W Resistor
R615K 1/4 W Resistor
R7,R1021 Meg (5%) 1/2 W Resistor
R8,R920.4 Ohm 5 W Resistor
R11110K Pot
R12,R13251K 1/4 W Resistor
R14147K 1/4 W Resistor
C11100uF 35V Electrolytic Capacitor
C210.011uF Capacitor
C313750pF Capacitor
C4,C621000pF Capacitor
C5,C7,C830.001uF Capacitor
C9150pF Capacitor
C1010.3uF Capacitor
C11,C12210,000uF 50V Electrolytic Capacitor
U1,U22741 Op Amp
U31ICL8063 Audio Amp Transister Driver thingy
Q112N3055 NPN Power Transistor
Q212N3791 PNP Power Transistor
BR11250 V 6 Amp Bridge Rectifier
T1150V Center Tapped 5 Amp Transformer
S11SPST 3 Amp Switch
S21DPDT Switch
F112 Amp Fuse
SPKR118 Ohm 50W Speaker
MISC1Case, Knobs, Line Cord, Binding Posts Or Phono Plugs (For Input And Output), Heatsinks For Q1 And Q2


  1. I know I skipped R4. That is not a problem :-)
  2. Distortion is less than 0.1% up to 100HZ and increases to about 1% at 20kHz.
  3. I haven't been able to find anyone who sells a suitable T1. You can always use two 24V 5A units in series. If you are building two amps (for stereo), then I would suggest using an old microwave transformer and rewinding it. Follow the instructions in the 12V To 120V Inverter, execpt wind 26 turns, twist a loop (center tap) and wind 26 more turns. That should work out to around 50 volts. You may need to add or remove turns depending on your transformer.
  4. Q1 and Q2 will require heatsinks.
  5. You may have trouble finding U3 because it is discontinued. Please don't email me about sources...I can't find it either. See if any of the sources in Where To Get Parts has it. A possible source was sent in by JBWilliams:
    Zigma Electronics
    8803 Shirless Ave.
    Northbridge, CA 91324
    United States
    Phone: 818-772-7590

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Add A Comment

50 Watt Amplifier
Wednesday, May 27, 2015 6:34:37 AM
cant you show the picture how its looks in life ?
50 Watt Amplifier
Sunday, April 15, 2012 11:30:27 PM
Can someone please tell me where to connect all the earth GNDs...
50 Watt Amplifier
Tuesday, March 02, 2010 7:48:48 AM
ICL8063(U3),which other IC can I use to replace it for better result.Kindly reply through my e-mail.Thanks.from Nigeria
50 Watt Amplifier
Tuesday, December 22, 2009 9:31:07 PM
what value low pass filter do you recommend for use as with a bass guiter? Should I build it separate, or utilize a second input with the filter? That way I can use the amp for other things if needed.
50 Watt Amplifier
Monday, October 26, 2009 3:30:56 AM
I'd use replacements where the 741 opamps are. They have crappy frequency response, crappy noise ratings, and crappy slew rate.
50 Watt Amplifier
Monday, October 26, 2009 3:27:57 AM
p=v^2/r p power in watts v rms voltage, volts r load resistance
50 Watt Amplifier
Sunday, June 21, 2009 10:10:59 AM
U3 also known as ECG8063
computations of output power of an amplifier
Monday, January 26, 2009 2:55:41 AM
does anybody can tell me about the computations of output power of an amplifier?just reply on my e-mail.
50 Watt Amplifier
Tuesday, December 02, 2008 9:58:57 AM
where ic can i use for U3
joevilou mallen
50 Watt Amplifier
Tuesday, November 25, 2008 3:18:28 AM
i have 8 ohms speaker,,, could you send me a diagram that fit on it???? what is the wattage of th amplifier???? hope any body can send ma a diagram on it. thank you guys and good luck!!
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