To regulate the positive and negative rails for the output stage, this PSU uses 16 transistors and a good number of further parts a further six transistors are used to regulate the supplies to the small-signal stages. For example, consider the circuit put forward by John Linsley-Hood. The much higher component count must reduce overall reliability, and getting it working in the first place will take longer and be more difficult. The overall amplifier system is at least twice as complicated. Complex and therefore potentially less reliable.However, this adds significant circuitry, and there is no guarantee that a failed output device will not cause a collateral failure in the regulators that leaves the speakers still in jeopardy. The possibility exists of electronic shutdown in the event of an amplifier DC fault, so that an output relay can be dispensed with.This means four for a stereo amplifier, making the overall system very expensive.

If not, there will be interchannel crosstalk unless there is a separate regulator for each channel.

However, you can only afford to be careless with the PSRR of the power amp if the regulators can maintain completely clean supply rails in the face of sudden current demands. Can be designed so that virtually no ripple is present on the DC output (in other words the ripple is below the white noise the regulator generates) allowing relaxation of amplifier supply-rail rejection requirements.Having said that, if your amplifier is clipping regularly you might consider turning it down a bit. Clipping behavior will be cleaner, as the clipped peaks of the output waveform are not modulated by the ripple on the supply rails.A regulated supply-rail voltage to a power amplifier gives absolutely consistent audio power output in the face of mains voltage variation.There are, however, still load-dependent losses in the output stage to consider. This is considered to have marketing advantages in some circles, though it is not clear why you would want to operate an amplifier on the verge of clipping. A regulated supply-rail voltage means that the amplifier can be made to approximate more closely to a perfect voltage source, which would give twice the power into 4 О© than it gives into 8 О©.This worsens with increasing current drawn. The bridge rectifier will generate bursts of RF at a 100 Hz repetition rate as the diodes turn off. The absence of switch-mode technology does not mean total silence as regards RF emissions.Transformer primary tappings must be changed for different countries and mains voltages.The mains transformer will be relatively heavy and bulky.Significant ripple is present on the DC output and so the PSRR of the amplifier will need careful attention the problem is, however, not hard (if you read the second part of this chapter) and output hum levels below -100 dBu are easily attainable.On the other hand, the amplifier will always deliver the maximum possible power it can. The power into 4 О© will not be twice that into 8 О©, because the supply voltage will fall with increased current demand.The amplifier can deliver higher power on transient peaks, which is just what is required.No possibility of instability or HF interference from switch-mode frequencies.Simple, reliable, and cheap (relatively speaking вЂ“ the traditional copper and iron mains transformer will probably be the most expensive component in the amplifier).The International Energy Agency is urging a 1 W standby power limit for all energy-using products. The design of this is straightforward вЂ“ or at least it was until the introduction of new initiatives to limit the amount of standby power that a piece of equipment is allowed to consume. Many amplifiers now have some form of microcontroller to handle on/off switching by mains relays and other housekeeping functions this is usually powered by a separate small standby transformer, which remains powered when the amplifier supply is switched off. I am here dealing only with the main supply for the actual power amplifier rails. It is therefore worthwhile to examine the pros and cons of each technology in a little more detail. It is immediately obvious that the first and simplest option will be the most cost-effective, but at first glance it seems likely to compromise noise and ripple performance, and possibly interchannel crosstalk. a simple unregulated power supply consisting of transformer, rectifiers, and reservoir capacitors There are three principal ways to power an amplifier:ДЎ.

Audio transformer design