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File name: | symamp.rar [preview ] |
Size: | 64 kB |
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Descr: | usilvatel za manqcy-400W |
Group: | Electronics > Documentation |
Uploaded: | 18-09-2005 |
User: | bai_tishan |
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Extracted files: | 1 | |
File name symamp.pdf Construction notes for the symmetrical 400 watt amplifier Introduction The symmetrical amplifier is an update of one of my designs, which appeared in the Australian electronics magazine Silicon Chip in June 1994. The main changes made in this design was, the addition of a clipping detector circuit and bias circuit modifications for the use of International Rectifier HEXFET MOSFET's. Later modifications where made to the error amp and VAS stages which improved the overall sound of the amplifier. Tools you will need to complete the construction of this module A good temperature controlled soldering Iron Resin core 40/60 solder A mini drill or a drill press, which can handle drill, bit sizes down to 0.6mm A small flat blade screwdriver and 1 point Philip's screwdriver. An electric hand drill Pre-cut and drilled Aluminium right angle bracket, 196mm long, 3mm to 5mm thick. To mount the Mosfets onto. The Error Amp Stage The first stage is what I call an asymmetrical input error amplifier. It has the ability to accept an unbalanced I/P source only. Now I will explain how each device in this stage works together. Q2, Q3, R35- R36, form the main differential error amplifier, which then has its collectors connected to a cascode load. Q4, Q5, R4 and ZD2 form the cascode stage, which provides a constant 14.4 volts on the collectors of Q4, Q5. Q1, R8, R7, ZD1 and C1 form a constant current source, which supplies 1.5milliamps to the first differential stage. These modules form the first stage of the amplifier and basically set up how the whole amplifier is biased from front to back. The Voltage Amplification Stage This next stage provides most of the voltage amplification that the next stage needs to drive the o/p stage to full power. Q6, Q7, Q8, Q9, R15, R14, R12, R13, C3, C7, C8 form the second differential voltage amplification stage. Q7 and Q9 form what is known as a current mirror load for the second differential stage and basically force this stage to share the current supplied from R15, which is about 8milliamps. The remaining components, namely the caps provide local frequency compensation for this stage. The Bias Stage As the name suggests Q10, R34, 37, 38, C12form the Bias stage. Its main purpose is to provide the MOSFET Gates with a stable and compensated supply voltage. The Output Stage or Current Amplification Stage Once again as the name suggests this stage converts the voltage developed in the VAS and provides all the amperes needed to drive 8 or 4 Ohm loads. 2-Ohm loads are not possible unless more o/p devices are added. Power supply requirements for the 400 Amplifier The power supply components for this amplifier are as follows and are expressed for Two Channels. 1 x Toroidal Transformer with a Core rating of 625VA. Primary windings are made to suit your local mains supply. Eg: for Australia One single primary winding with a 240VAC rating. For USA, 110VAC, 115VAC and I believe there is a 220-Volt AC mains supply in some areas of the United St |
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