Delivering Amplifier Watts and Power (Public)

all right all right um dave rat and this is the first video on a series i'm going to do about power amps and what and how all watts are not created equal or maybe more accurately all watts are not delivered equally you know the concept of power i mean it's very when we're looking at power amplifiers or speakers um you know it's really easy to have the go-to of how many watts does it handle or how much wattage does the amplifier put out and we're comparing we see two amps they both put out 1000 watts per channel or 500 watts per channel and eight ohms and we say okay these amps are going to be uh the same they're going to be relatively similar and um we can you know this one's a little cheaper this one has some more features and we move on from there but in reality that's not the whole picture and not only is it not the whole picture the picture is constantly changing over time so 20 years ago or 30 years ago when you looked at the power amp specs and you looked at how many watts it put out into what impedance that's completely different than the typical amplifier now and how many watts it puts out not the actual number but how the watts are delivered and how it's specified same thing goes with home hi-fi and car stereo amplifiers um for example um to dive a little further into that let's say that um well let's look at a um an analogy of um car velocity it takes let's say you have a car that weighs 2 000 pounds a vehicle that weighs 2 000 pounds certain amount of air resistance wind resistance certain amount of rolling resistance certain air in the tires whatever it is in order to bring that vehicle up to let's say 60 miles an hour you're going to need a certain amount of power a certain amount of energy transferred into motion to get this thing going at 60 miles an hour and battle the resistance or whatever it is now you can achieve this in multiple ways one way to achieve it would be to have a big huge engine and turning very slowly and geared in such a way that it every road couple rotations it moves it really far it's a big powerful engine moving slowly another way you could put a little tiny engine in there and have it moving very quickly spinning very fast and then gear ratio down to get it to where it's going um a good example of that is you know in an older muscle car you might be in third gear to get to 60 miles an hour and on a smaller you know inexpensive car you might be in fifth gear or sixth gear at 60 miles an hour so the gear ratio small engine turning pass the velocity is the same the power is the same the watts are the same but there's other variables how long did it take to get to 60 miles an hour what's the acceleration to get there um how long can it maintain let's say it goes 120 miles an hour how long can it maintain 120 miles an hour can it just get there for a minute and then it runs out of juice does it take a long time to get there well power amps are the same way how quickly an app can deliver the amount of power is something that i think is underdetermined and i haven't done a lot of testing and i hope through this series to um not only do some testing but maybe um find some new and interesting um ways of looking at how power is delivered and see if we can um find ways finding difference between an amp that say maybe delivers power very quickly or one that delivers it slow and for example an example for that let's say that um i wanted to push this car with a stick you know i had a bowling ball or something that rolls and i want to push it with a stick up to ten five miles an hour i'm gonna run and push this thing with a broom a bowling ball with a broom or whatever it is um if that broom handle is like a yardstick and really long and thin when i go to push it that yardstick bends and then it goes and the ball gets up to speed uh but if i push it with a two by four you know the ball gets going right away um this kind of time lag between when the power is created and delivered to its final destination or drawn from its final destination there could be things that slow that down um that kind of bottleneck that energy inside the amplifier or the way the amps are the watts are being generated or that bottleneck could be in the cabling if you have a long skinny you know long low gauge wire you might be able to get 500 watts at the end but all that resistance makes it um unable to deliver a massive amount of power very quickly um let's see what else do we got we've got the ability to oh how long can it deliver the power so let's say some an amplifier puts out a thousand watts per channel how long can it do it uh modern amplifiers rated at a thousand watts of channel typically don't put out a thousand watts of channel for very long if you look at the response on an oscilloscope and you measure it they will come in peak up and they'll hit that thousand watts so you get a sine wave and it'll go up and then after a fairly short period of time half a quarter of a second or a 10 oh 20 milliseconds i don't know some we'll find out if the different amps are very different um it'll drop down and hit a lower level so if we look at the you know it kind of drops down and that drop might be multi-stage it might be able to deliver a thousand watts for 0.2 seconds and then it then it trickles down and delivers 600 watts for another 0.2 seconds and then it delivers 300 watts continuously um [Music] and that's just its ability to actually spit out that power now if you look at like an old ant you look at an old like class a b or a class h or whatever like crest stamps i've done a lot of testing with you could put it they'll put out 800 watts and it'll just put it out continuously um but then you run into another problem how long can that happen because not only do you have the initial surges but then you've got these thermal time frames if you're putting out 800 watts we'll do it with a sine wave for an hour a day a month things get hot and into what impedance there's a lot more heat generated into two ohms two ohm loads than there is into eight ohm loads and going even further in that fun complexity uh the same amp may have completely different response and uh delivery of the power at different impedances so you might have an amp that at eight ohms it puts out 500 watts per channel i'll use an old like a old crest amp like um as an example it'll put out 800 watts and it'll hold that 800 watts and do or 500 watts into 8 ohms for an extended period of time um but it doesn't go over it might put out 550 watts or 530 watts for a fraction of a second and then drop down to that 500 there's the surge voltage is not that much higher than its actual output voltage at eight ohms but at four ohms it might be rated at let's say a thousand watts um no it's rated at 800 watts not quite double the 500 it might be rated at 800 but it'll put out that thousand for a little while and then drop to 800 um per channel and then if you go to two ohms it might be rated at um i'll say 1200 watts per channel the two ohms but for a fraction of a second it might put out the full 2000 and what i'm saying is because when you cut the impedance half you have an 8 ohm puts out a 500 watts into 8 ohms if you go to 4 ohms if all things were perfect it would put out double the power because you have half the load and if there was no losses involved so the amount of time whether it's a thermal issue over an extended period of time or that up close a momentary surge all of these have impacts and then the question comes what do we really want for the music that we're doing for that we're reproducing do we really need a thousand watts continuous if we take a sine wave and put it into an amplifier and put a full thousand watts yes that's a good test of how its thermal capacity and its long-term output but is that even relevant to what we're doing because music even highly compressed music is five to one or better eight to one ten to one ratio between its average power demand versus its peak power demand so having an amp that puts out burst power is of very high peaks with an average power of one-third that or one-quarter that may be and actually is superior for most applications uh an app that puts out 800 500 watts continuous versus one that puts 200 watts continuous but has a 1500 or a 1200 watt peak instantaneous peak 1200 watt peak 300 watts continuous let's say burst is 500 watts continuous with a 550 peak the one with the higher peak is going to be noticeably or should be we're going to test it out noticeably louder clearer and more dynamic sounding for most music applications and i'll wrap it up here for today i think i've got a test method that will allow us to hear some of this i haven't done it yet it's all theoretical in my head but if it works as i hope it does we should be able to run amps at full power and play it back through small speakers i'll build up a little shunt load a little um load that loads down the output of the amp and takes a small percentage of that power and runs it to a little speaker or home service speaker or to a recordable signal and we can start to compare the way the same amp sounds under various loads and the way different apps sound like an old crest amp i've got a chevron amp which is a very hi-fi channel amp that we had in inventory and then i've got some power soft amps and i'll see what else i got so we'll kind of compare new to old and [Music] everything against itself so i'm not really sure all the videos i'll do but um i'll start diving in and it should be fun let's see and hopefully out of this we'll come up with a way to refine what we're looking for an app and be able to look at the specs when they do spec them out properly um and get a better idea of whether it's going to work for application all right and i'm gonna get working on it now [Music] [Music] hmm

Channel: Dave Rat

Views: 11,109

Rating: 4.9068322 out of 5

Keywords: Dave Rat, Pro Audio, Rat Sound., Mixing Tips, Pro Audio Mixing, Pro Sound, Live Sound, SoundTools, Rat Sound Systems, Audio Engineer, Sound Engineer

Id: wQ4N-gCCl0o

Length: 12min 52sec (772 seconds)

Published: Sun Aug 22 2021