Sorry, I hit the + sign for the = sign. It should be P=IE and P(rms)=I(rms)E(rms)! I sometimes have fat fingers and because it is 4:24 AM and somewhat dark I am more prone to fat finger error. ----- Original Message ----- From: "Richard Graziano" To: Sent: Friday, June 18, 2004 4:14 AM Subject: Re: [EE:] What makes a powerful amplifier... powerful? > If you mean why are some amplifiers capable of delivering a greater sound to > large speakers than others it is because the amplifier output stages can > develop more current at a specified voltage across a load (i.e., speakers). > Power, simply put, is a product of current and voltage for DC circuits. In > AC circuits (like audio) the power is the rms product of the current and > voltage. Power is typically measured in watts denoted sometimes by W but > usually by P: P(ac) I(rms)E(rms) or P(dc) = IE. Because the root mean > square of all of the infinitesimal segments under the sine curve (the AC > expression) is .707 we sometimes use that value to compute power. Actually, > however, it is not quite that simple because factors such as phase and other > things need to be considered, depending on the actual circumstances of the > design and application. In a simple balanced three phase circuit, for > example, the power would be P + IE times the square root of three. You know > what will happen if you replace your 100 watt light bulb with a flashlight > bulb. You will not have the same light output. And you know what will > happen if you try to put 120vac into it. The load must also be capable of > dissipating the power that is input. The question about the impedance is > simplified by thinking of impedance as a form of AC resistance. The lower > the load impedance the more current is needed to drive it. Does that make > sense? > > So what makes some amplifiers more powerful? They can deliver more rms > volt-amp product to a given load that is capable of dissipating it. The > question about clipping is one of driving the output components into > saturation. For example, if you have a gain of 10 and the amplifier > operates at a maximum of 20 volts you can input a signal of up to 2 volts > because 2 volts times the gain of 10 will be 20 volts. Suppose you input a > sine curve of 2 volts. You will get a sine curve of 20 volts at the output. > But if you input a sine curve of 4 volts you will still only get 20 volts at > the output and the sine curve will look more like a square wave because > everything above 20 volts will be maxed out at 20 volts and stay flat until > the input level falls below the maximum allowable input of 2 volts. > Sometimes analog comparators such as the LM 339 or the LM311 are used to > convert a sine to a square by this principle. The analog comparator is a > special type of high gain amplifier that has what is called a high slewing > rate. That is another way of expressing the rate of change of voltage with > respect to time. I hope this helps get you started. > > > > ----- Original Message ----- > From: "Thomas" > To: > Sent: Friday, June 18, 2004 12:40 AM > Subject: [EE:] What makes a powerful amplifier... powerful? > > > > Hi Everyone, > > > > I have been using many different kinds of low powered > > Audio Amplifiers (below 2W) before. Some can deliver > > 200mW. Some can deliver 2W. > > > > What makes a powerful amplifier... powerful? Is it > > because its output impedance is low? > > > > If you try to force it to deliver more that what it is > > designed to do, the output signal clips or distorts. > > Why is that? (Please try not to give me answer like > > "because you force it to deliver more that what it is > > designed to do..." > > Please help! > > > > > > > > > > __________________________________ > > Do you Yahoo!? > > New and Improved Yahoo! Mail - 100MB free storage! > > http://promotions.yahoo.com/new_mail > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body