Source : http://www.mitedu.freeserve.co.uk/Circuits/Audio/t-ctrl.htm
This is a very simple, low cost, Hi-Fi quality power amplifier. You can build it 5 ways, like it�s shown in the table (from 20 W to 80 W RMS).
Some comments:
- The first thing that you must do, is to measure the end transistors (T3 and T4) amplifying coefficient, the hfe or β. If their disagreement is bigger than 30 %, the amplifier would not give a clear sound. I used MJ3001 and MJ2501 transistors, and this disagreement was around 5%.
- Before the first �turning on� you must short circuit the inputs of the amp, and put a mA-meter on the output, than turn the amplifier on, and tune the R13 pot, to decrease the DC current on the output, to some uA-s, or in a lucky situation to zero. I was able to decrease it to 10 uA.
Simple and low cost. The optimal supply voltage is around 50V, but this amp work from 30 to 60V. The maximal input voltage is around 0.8 - 1V. As you can see, in this design the components have a big tolerance, so you can build it almost of the components, which you find at home. The and transistors can be any NPN type power transistor, but do not use Darlington types... The output power is around 60W.
Some comments:
- capacitor C1 regulates the low frequencies (bass), as the capacitance grows, the low frequncies are getting louder.
- capacitor C2 regulates the higher frequencies (treble), as the capacitance grows, the higher frequencies are getting quiter.
- this is a class B amplifier, this means, that a current must flow through the end transistors, even if there is no signal on the input. This current can be regulated with the 500Ω trimmer resistor. As this current incrases, the sound of the amplifier gets better, but the end transistors are more heating. But if this current decrases, the transistors are not heating so much, but the sound gets worse...
copy from : http://www.electronics-lab.com/projects/audio/042/index.html
thank you.
| -- 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.
| 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 |
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.
25W Mosfet audio amplifier
source: RED Free Circuit Designs
| -- 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