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.

Schematic

This is the schematic of the 50 Watt Amp

Parts
Part
Total Qty.
Description
Substitutions
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

Notes

  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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Comments

jake
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.
george
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!!
anonymous
50 Watt Amplifier
Tuesday, August 05, 2008 3:38:45 AM
how about posting pcb layout for ease..

(Editor's notes: Make one, send it to me, and I'll post it.)
manjula
50 Watt Amplifier
Friday, June 27, 2008 4:45:33 AM
i could not buy ICL8063 Audio Amp Transister Driver thingy
TOLUWASE
50 Watt Amplifier
Monday, February 18, 2008 1:02:40 PM
Thanks to you my Brothers in this great field (electronics), the AF circuit I downloaded from this (your) site really worked for the project I proposed (higher wattage), only a little components was added. Thanks, Toluwase 4m Nigeria
aneesh
50 Watt Amplifier
Monday, January 28, 2008 5:01:09 AM
Very good but quite expensive
rononymous
50 Watt Amplifier
Saturday, January 26, 2008 4:51:02 AM
not as good as bipolar amplifier.difficult circuit to build
jhun
50 Watt Amplifier
Saturday, January 12, 2008 2:07:43 AM
sir can you give me a circuit diagram of 50 watts and 8 ohms output?
anonymous
50 Watt Amplifier
Wednesday, January 09, 2008 11:01:53 PM
can u forward me a low cost 100 watt guitar amp. in my email plzzzzzz????where its circuit is simple???
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