50 Watt Amplifier

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.

Parts

R1(1)200 Ohm 1/4 W Resistor

R2(1)200K 1/4 W Resistor

R3(1)30K 1/4 W Resistor

R5(1)1K 1/4 W Resistor

R6(1)5K 1/4 W Resistor

R7,R10(2)1 Meg (5%) 1/2 W Resistor

R8,R9(2)0.4 Ohm 5 W Resistor

R11(1)10K Pot

R12,R13(2)51K 1/4 W Resistor

R14(1)47K 1/4 W Resistor

C1(1)100uF 35V Electrolytic Capacitor

C2(1)0.011uF Capacitor

C3(1)3750pF Capacitor

C4,C6(2)1000pF Capacitor

C5,C7,C8(3)0.001uF Capacitor

C9(1)50pF Capacitor

C10(1)0.3uF Capacitor

C11,C12(2)10,000uF 50V Electrolytic Capacitor

U1,U2(2)741 Op Amp

U3(1)ICL8063 Audio Amp Transister Driver thingy

Q1(1)2N3055 NPN Power Transistor

Q2(1)2N3791 PNP Power Transistor

BR1(1)250 V 6 Amp Bridge Rectifier

T1(1)50V Center Tapped 5 Amp Transformer

S1(1)SPST 3 Amp Switch

S2(1)DPDT Switch

F1(1)2 Amp Fuse

SPKR1(1)8 Ohm 50W Speaker

MISC(1)Case, 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

source