The cheap 100 watt transistor power amplifier project

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  Posted by momename - September 12, 2012 at 12:09 am

This Power Amp OCL 100 watt circuit by transistors.They has been an old circuits, but very well amplifier schematic.
We use only all transistor MJ15003 and MJ15004 is the main in circuits, and the power supply +38V 0 -38V 3A. follow stye of OCL amp and They has Specification are
power output : 105watt at 4 ohm load, 88watt at 8 ohms load
input sensitivity : 0.5V
Frequency response : 10-10kHZ +/- 1dB
THD: 0.07% at 50 watt , 0.1% at 100 watt.

This power amp OCL 100w is a very excellent sound quality. Since we provide the circuit in look All direct coupling form is connection join together direct all, to cut-off frequency low-loss problems, the super bass really do not tell who.
The signal Input of the tone controls enter via C1 to the base pin of transistor Q1, which together with the Q2 is differential amplifier, the signal from the collection pin of Q1 supplied to the bas pin of the Q5, which it acts as the pre-driver circuit.
- The transistor Q4 is setting level bias or act as to control Idle current in this circuit. Which we can adjust level idle current by By adjusting the VR1.

circuit-of-the-cheap-100-watt-transistor-power-amplifier-project-mj15003mj15004
Circuit of The cheap 100 watt transistor power amplifier project

- The transistor Q3 acts as a boost trapping.
- The output signal from the Q5 will enter to base pin of Q8,Q9.which acts as the driver circuit. For the signal output to drive the output transistors Q10, Q11.
- Both output transistors Q10, Q11, we used the number on the circuit are MJ15003, MJ15004. This couple can use up to 200W, so not problem in durability.
If you want to save. May be represented by a pair of output are 2N3055, MJ2955 each of the two parallel each other instead.

Creation
-Check the assembly of all equipment to correct the circuit, without the output transistors, Using a voltmeter measure the voltage at the speaker. By also does not have a speaker. At the end of this process was completed and ready to operate immediately.
-Put the power supply to the circuit, then to measure the voltage is 0V or not higher than 0.25V, if not in this means that the circuit failure, need to check first.

pcb-of-the-cheap-100-watt-transistor-power-amplifier-project-mj15003mj15004
PCB of The cheap 100 watt transistor power amplifier project
-The later, on output transistors, and then use an ammeter to measure the current is supplied with short input circuit. Measuring that positive or negative wire. Then, adjust VR1 until reading about the current 20-40 mA.
- For transistor Q4, when the device successfully. Should be installed on the cooling pad. Which installation of the output transistor. To help control the the bias current output relative to the temperature change of the output transistor.
- The power supply circuit is got by power of transformer T1, which provides voltage to the coil in the secondary coil is 27-0-27 volt, 5 amp.
- The Diodes Bridge rectifier should be not lower than 5 Amp 100V, The filter capacitor C7, C8 we used a 1,000uF 50V, the voltage at the capacitor afer through the filter will can about 38V.


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