18W Audio Amplifier

source: RED Free Circuit Designs

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-- High Quality very simple unit

-- No need for a preamplifier

Circuit diagram:

Amplifier parts:

P1 = 22K	Log.Potentiometer (Dual-gang for stereo)
R1 = 1K	1/4W Resistor
R2 = 4K7	1/4W Resistor
R3 = 100R	1/4W Resistor
R4 = 4K7	1/4W Resistor
R5 = 82K	1/4W Resistor
R6 = 10R	1/2W Resistor
R7 = R22	4W Resistor (wirewound)
R8 = 1K	1/2W Trimmer Cermet (optional)
C1 = 470nF	63V Polyester Capacitor
C2,C5 = 100΅F	3V Tantalum bead Capacitors
C3,C4 = 470΅F	25V Electrolytic Capacitors
C6 = 100nF	63V Polyester Capacitor
D1 = 1N4148	75V 150mA Diode
IC1 = TLE2141C	Low noise,high voltage,high slew-rate Op-amp
Q1 = BC182	50V 100mA NPN Transistor
Q2 = BC212	50V 100mA PNP Transistor
Q3 = TIP42A	60V 6A PNP Transistor
Q4 = TIP41A	60V 6A NPN Transistor
J1	RCA audio input socket

Power supply parts:

R9 = 2K2	1/4W Resistor
C7,C8 = 4700΅F	25V Electrolytic Capacitors
D2	100V 4A Diode bridge
D3	5mm. Red LED
T1	220V Primary, 15 + 15V Secondary 50VA Mains transformer
PL1	Male Mains plug
SW1	SPST Mains switch

Notes:

• Can be directly connected to CD players, tuners and tape recorders.

• Don't exceed 23 + 23V supply.

  Q3 and Q4 must be mounted on heatsink.

  D1 must be in thermal contact with Q1.

  Quiescent current (best measured with an Avo-meter in series with Q3 Emitter) is not critical.

  Adjust R3 to read a current between 20 to 30 mA with no input signal.

  To facilitate current setting add R8 (optional).

  A correct grounding is very important to eliminate hum and ground loops. Connect in the same point the ground sides of J1, P1, C2, C3 &C4. Connect C6 at the output ground.

  Then connect separately the input and output grounds at the power supply ground.

Technical data:

Output power: 18 Watt RMS @ 8 Ohm (1KHz sinewave)

Sensitivity: 150mV input for 18W output

Frequency response: 30Hz to 20KHz -1dB

Total harmonic distortion @ 1KHz: 0.1W 0.02% 1W 0.01% 5W 0.01% 10W 0.03%
Total harmonic distortion @10KHz: 0.1W 0.04% 1W 0.05% 5W 0.06% 10W 0.15%

Unconditionally stable on capacitive loads

from:: http://www.electronics-lab.com/projects/audio/012/index.html

22 Watt Audio Amplifier

source: unknown

The 22 watt amp is easy to build, and very inexpensive. The circuit can be used as a booster in a car audio system, an amp for satellite speakers in a surround sound or home theater system, or as an amp for computer speakers. The circuit is quite compact and uses only about 60 watts. The circuit is not mine, it came from Popular Electronics.


Schematic

Parts

Part	Total Qty.	Description
R1	1	39K 1/4 Watt Resistor
C1,C2	2	10uf 25V Electrolytic Capacitor
C3	1	100uf 25V Electrolytic Capacitor
C4	1	47uf 25V Electrolytic Capacitor
C5	1	0.1uf 25V Ceramic Capacitor
C6	1	2200uf 25V Electrolytic Capacitor
U1	1	TDA1554 Two Channel Audio Amp Chip
MISC	1	Heatsink For U1, Binding Posts (For Output), RCA Jacks (For Input), Wire, Board

Notes

1. The circuit works best with 4 ohm speakers, but 8 ohm units will do.

2. The circuit dissipates roughly 28 watts of heat, so a good heatsink is necessary. The chip should run cool enough to touch with the proper heatsink installed.

3. The circuit operates at 12 Volts at about 5 Amps at full volume. Lower volumes use less current, and therefore produce less heat.

4. Printed circuit board is preferred, but universal solder or perf board will do. Keep lead length short.

from :: http://www.electronics-lab.com/projects/audio/006/index.html

25W Mosfet audio amplifier

25W Mosfet audio amplifier

source: RED Free Circuit Designs

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-- High Quality simple unit

-- No need for a preamplifier

Circuit diagram:

Parts:

R1,R4 = 47K	1/4W Resistors
R2 = 4K7	1/4W Resistors
R3 = 1K5	1/4W Resistors
R5 = 390R	1/4W Resistors
R6 = 470R	1/4W Resistors
R7 = 33K	1/4W Resistors
R8 = 150K	1/4W Resistors
R9 = 15K	1/4W Resistors
R10 = 27R	1/4W Resistors
R11 = 500R	1/2W Trimmer Cermet
R12,R13,R16 = 10R	1/4W Resistors
R14,R15 = 220R	1/4W Resistors
R17 = 8R2	2W Resistor
R18 = R22	4W Resistor (wirewound)
C1 = 470nF	63V Polyester Capacitor
C2 = 330pF	63V Polystyrene Capacitor
C3,C5 = 470΅F	63V Electrolytic Capacitors
C4,C6,C8,C11 = 100nF	63V Polyester Capacitors
C7 = 100΅F	25V Electrolytic Capacitor
C9 = 10pF	63V Polystyrene Capacitor
C10 = 1΅F	63V Polyester Capacitor
Q1-Q5 = BC560C	45V100mA Low noise High gain PNP Transistors
Q6 = BD140	80V 1.5A PNP Transistor
Q7 = BD139	80V 1.5A NPN Transistor
Q8 = IRF532	100V 12A N-Channel Hexfet Transistor
Q9 = IRF9532	100V 10A P-Channel Hexfet Transistor

Power supply circuit diagram:

Parts:

R1 = 3K3	1/2W Resistor
C1 = 10nF	1000V Polyester Capacitor
C2,C3 = 4700΅F	50V Electrolytic Capacitors
C4,C5 = 100nF	63V Polyester Capacitors
D1	200V 8A Diode bridge
D2	5mm. Red LED
F1,F2	3.15A Fuses with sockets
T1	220V Primary, 25 + 25V Secondary 120VA Mains transformer
PL1	Male Mains plug
SW1	SPST Mains switch

Notes:

• Can be directly connected to CD players, tuners and tape recorders. Simply add a 10K Log potentiometer (dual gang for stereo) and a switch to cope with the various sources you need.

• Q6 & Q7 must have a small U-shaped heatsink.

• Q8 & Q9 must be mounted on heatsink.

• Adjust R11 to set quiescent current at 100mA (best measured with an Avo-meter in series with Q8 Drain) with no input signal.

• A correct grounding is very important to eliminate hum and ground loops. Connect in the same point the ground sides of R1, R4, R9, C3 to C8. Connect C11 at output ground. Then connect separately the input and output grounds at power supply ground.

Technical data:

Output power: well in excess of 25Watt RMS @ 8 Ohm (1KHz sinewave)

Sensitivity: 200mV input for 25W output

Frequency response: 30Hz to 20KHz -1dB

Total harmonic distortion @ 1KHz: 0.1W 0.014% 1W 0.006% 10W 0.006% 20W 0.007% 25W 0.01%
Total harmonic distortion @10KHz: 0.1W 0.024% 1W 0.016% 10W 0.02% 20W 0.045% 25W 0.07%

Unconditionally stable on capacitive loads

form :: http://www.electronics-lab.com/projects/audio/001/index.html