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Measuring audio power ...
Ok, so who knows a bit about measuring audio power ? Setting aside any
furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? Arfa |
Measuring audio power ...
"Arfa Daily" Ok, so who knows a bit about measuring audio power ? ** Well, obviously not you. Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. ** The phrase " audio power meter " is not defined. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? ** AC voltage meters are usually full wave. True RMS types certainly are. Or are you really asking about programme level meters like VUs and PPMs ? ....... Phil |
Measuring audio power ...
On Sun, 25 Jun 2006 10:17:29 GMT, "Arfa Daily"
wrote: Ok, so who knows a bit about measuring audio power ? Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? Arfa The type of rectifier doesn't make a great deal of difference, although full wave probably has the edge on accuracy. Don't put a capacitor after it, just let the meter do the averaging, then do the sums: power = v squared / R. There are audio power meters that approximate true RMS for greater accuracy, but they are from the prehistoric era before we could do all that stuff digitally. If you really want to measure power accurately, use a resistor as the load, and measure its temperature. d -- Pearce Consulting http://www.pearce.uk.com |
Measuring audio power ...
"Don Pearce RF ******" "Arfa Daily Con Man " Ok, so who knows a bit about measuring audio power ? Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? Arfa The type of rectifier doesn't make a great deal of difference, ** Makes one hell of a difference on programme or any asymmetrical wave. although full wave probably has the edge on accuracy. ** Asinine ********. Don't put a capacitor after it, just let the meter do the averaging, then do the sums: power = v squared / R. ** Sure - average rectified sine wave value is *just fine*. On the DARK SIDE of planetoid Pluto !!!!! There are audio power meters that approximate true RMS for greater accuracy, but they are from the prehistoric era before we could do all that stuff digitally. ** More of this cretin's arrogant bull**** trotted out as fact. If you really want to measure power accurately, use a resistor as the load, and measure its temperature. ** Asinine advice, beyond stupidity. WARNING: Have nothing whatever to do with this ****wit's fake business: " Pearce Consulting http://www.pearce.uk.com " The manager is a rabid nut case. ....... Phil |
Measuring audio power ...
"Phil Allison" wrote in message ... "Don Pearce RF ******" "Arfa Daily Con Man " Ok, so who knows a bit about measuring audio power ? Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? Arfa The type of rectifier doesn't make a great deal of difference, ** Makes one hell of a difference on programme or any asymmetrical wave. although full wave probably has the edge on accuracy. ** Asinine ********. OK, that'll do me.... rest snipped/ignored...... |
Measuring audio power ...
On Sun, 25 Jun 2006 12:21:38 +0100, "Keith G"
wrote: "Phil Allison" wrote in message ... "Don Pearce RF ******" "Arfa Daily Con Man " Ok, so who knows a bit about measuring audio power ? Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? Arfa The type of rectifier doesn't make a great deal of difference, ** Makes one hell of a difference on programme or any asymmetrical wave. although full wave probably has the edge on accuracy. ** Asinine ********. OK, that'll do me.... rest snipped/ignored...... Ah! The estimable Phil replied, did he? He occupies the unique position of not making the journey from my ISP to my computer as I refuse to pollute my hard drive with his vile spewings. d -- Pearce Consulting http://www.pearce.uk.com |
Measuring audio power ...
"Keith G" ( snip gratututious plonk insult ) ** What a pathetic pommy, audiophool jerk off. ....... Phil |
Measuring audio power ...
"Don Pearce Autistic Pig " WARNING: Have nothing whatever to do with this ****wit's fake business: " Pearce Consulting http://www.pearce.uk.com " The manager is a rabid nut case. ....... Phil |
Measuring audio power ...
"Don Pearce" wrote in message ... On Sun, 25 Jun 2006 12:21:38 +0100, "Keith G" wrote: "Phil Allison" wrote in message ... "Don Pearce RF ******" "Arfa Daily Con Man " Ok, so who knows a bit about measuring audio power ? Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? Arfa The type of rectifier doesn't make a great deal of difference, ** Makes one hell of a difference on programme or any asymmetrical wave. although full wave probably has the edge on accuracy. ** Asinine ********. OK, that'll do me.... rest snipped/ignored...... Ah! The estimable Phil replied, did he? He occupies the unique position of not making the journey from my ISP to my computer as I refuse to pollute my hard drive with his vile spewings. The guy needs help..... |
Gutless Pommy Wonders
"Keith Gutless Wonder " ** Not up to having a technical debate - are you Keith ? So you post BRAIN DEAD insults while hiding your identity. How pathetic. Typical, useless pommy waste of space and usenet cretin. ....... Phil |
Measuring audio power ...
In article , Arfa Daily
wrote: Ok, so who knows a bit about measuring audio power ? Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I suspect this depends on the actual 'power meter' in question. :-) May have a precision rectifier and take an average from that , or may use something else. e.g. the old avos tend to give a decent result if calibrated, you know the load, and are using a sinewave. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? If it uses a rectifier then takes a time-average I'd expect a good one to use a full wave precision rectifier - i.e. one that suppresses the forward voltage drops in the diodes. Cheap enough to do at audio frequencies. These days a meter might simply sample rapidly and work out the rms voltage and report that. Years ago, it might have used an analog multiplier to obtain the square-law for audio. I guess people like Burr-Brown still make these. (?) As Don has pointed out, a thermal meter might be used in some applications. These (and single diodes) still get used for RF power measurements. However unless you are using a sinewave, the reported value may be misleading. Ditto if the load isn't resistive. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Measuring audio power ...
In article , Don Pearce
wrote: The type of rectifier doesn't make a great deal of difference, although full wave probably has the edge on accuracy. Don't put a capacitor after it, just let the meter do the averaging, then do the sums: power = v squared / R. I'd be wary of this unless I knew the details of the meter. I've seen some that can give odd results when asked to give a dc level in the presence of much ac. e.g. One I recall seemed to only sample the input at a low rate, so became confused as the level flutuations 'beat' with its sampling rate. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Measuring audio power ...
In article , Arfa Daily
writes Ok, so who knows a bit about measuring audio power ? Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? Arfa Is this the arfa daily who's a service tech?.. FWIW if its just the output of an audio amp I just use two bloody great 8 ohm resistors on a large heatsink with stout cables to reduce ohmic losses, and connect that to the amp and use me trusty Fluke bench DMM to measure the AC power developed when running a sine wave with the Hewlett Packard distortion analyser keeping note of the distortion level to see when its going into clip. Measure that at a few different frequencies and square the AC measured volts and divide by the 8 'ommes and thats the RMS power. Sufficient and accurate and IMHO a good indication of what the amp will develop..... -- Tony Sayer |
Gutless Pommy Wonders
"Phil Allison" wrote in message ... "Keith Gutless Wonder " ** Not up to having a technical debate - are you Keith ? So you post BRAIN DEAD insults while hiding your identity. How pathetic. Typical, useless pommy waste of space and usenet cretin. Like I've got the time and/or inclination to play *hard case* typing games with you, little boy.... |
Gutless Pommy Wonders
"Keith Gutless Wonder " ** Not up to having a technical debate - ARE you Keith ? So you post BRAIN DEAD insults while hiding your identity. How PATHETIC. Typical, useless pommy waste of space and usenet cretin. ....... Phil |
Measuring audio power ...
"Peter Weis" ** What a pathetic pommy, audiophool jerk off. The whole UK is crawling with them...... ........ Phil |
Gutless Pommy Wonders
"Phil Allison" wrote in message ... "Keith Gutless Wonder " ** Not up to having a technical debate - ARE you Keith ? So you post BRAIN DEAD insults while hiding your identity. How PATHETIC. Typical, useless pommy waste of space and usenet cretin. Hey, dope - did you miss this bit: "Like I've got the time and/or inclination to play *hard case* typing games with you, little boy...." ??? |
Gutless Pommy Wonders
"Keith Gutless Wonder " ** Not up to having a technical debate with ANYONE - ARE you Keith ? So you continue to pots BRAIN DEAD insults while hiding your identity. How bloody PATHETIC !!! Typical, of countless, useless pommy wastes of space and usenet cretins. ....... Phil |
Gutless Pommy Wonders
"Phil Allison" wrote in message ... "Keith Gutless Wonder " ** Not up to having a technical debate with ANYONE - ARE you Keith ? So you continue to pots BRAIN DEAD insults while hiding your identity. How bloody PATHETIC !!! Typical, of countless, useless pommy wastes of space and usenet cretins. The temptation to jerk you around for a couple more hours ('til I go out) just to deprive you of sleep and give you a raggedy-arsed start to the week is strong (what is it now in Horse Trailier - 2:00 am?), but I simply cannot deal with the *boredom/crassness* of it all... (Take yourself off to bed with a nice hot mug of Milo - the world'll seem a better place tomorrow! ;-) |
Measuring audio power ...
"tony sayer" wrote in message ... In article , Arfa Daily writes Ok, so who knows a bit about measuring audio power ? Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? Arfa Is this the arfa daily who's a service tech?.. FWIW if its just the output of an audio amp I just use two bloody great 8 ohm resistors on a large heatsink with stout cables to reduce ohmic losses, and connect that to the amp and use me trusty Fluke bench DMM to measure the AC power developed when running a sine wave with the Hewlett Packard distortion analyser keeping note of the distortion level to see when its going into clip. Measure that at a few different frequencies and square the AC measured volts and divide by the 8 'ommes and thats the RMS power. Sufficient and accurate and IMHO a good indication of what the amp will develop..... -- Tony Sayer Hi Tony That's me. Useful input. Thanks. Arfa |
Gutless Pommy Wonder
"Phil Allison" wrote in message ... "Keith the Gutless ****ing Pommy Wonder " ** Not up to having a technical debate with ANYONE - ARE you Keith ? So you continue to post your BRAIN DEAD insults while hiding your identity. How bloody PATHETIC !!! Typical, of countless, useless pommy wastes of space and all usenet cretins. **** OFF ...... Phool You said it! Still can't sleep, eh? Clue: Just try *counting* the sheep, don't try shagging them all..... (Gotta be 01:30 now....??) |
Gutless Pommy Wonder
"Keith the Gutless ****ing Pommy Wonder " ** Not up to having a technical debate with ANYONE - ARE you Keith ? So you STILL continue to post your BRAIN DEAD insults while hiding your identity. How bloody PATHETIC !!! Typical, of countless, useless pommy wastes of space and all usenet cretins. **** THE HELL OFF ....... Phil |
Measuring audio power ...
In article , Arfa Daily
writes "tony sayer" wrote in message ... In article , Arfa Daily writes Ok, so who knows a bit about measuring audio power ? Setting aside any furious arguments about peak power, rms power, average power, backpeddling average peak music power on any given friday in March etc, does an audio power meter sum the power in both half cycles to arrive at a reading, or just one. I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? Arfa Is this the arfa daily who's a service tech?.. FWIW if its just the output of an audio amp I just use two bloody great 8 ohm resistors on a large heatsink with stout cables to reduce ohmic losses, and connect that to the amp and use me trusty Fluke bench DMM to measure the AC power developed when running a sine wave with the Hewlett Packard distortion analyser keeping note of the distortion level to see when its going into clip. Measure that at a few different frequencies and square the AC measured volts and divide by the 8 'ommes and thats the RMS power. Sufficient and accurate and IMHO a good indication of what the amp will develop..... -- Tony Sayer Hi Tony That's me. Useful input. Thanks. Arfa Thought it was. The above power test was much the same whilst at Neve, Audix, Audiolab, and SCPD.. AKA the BBC...;-)) -- Tony Sayer |
Measuring audio power ...
On Sun, 25 Jun 2006 13:40:03 +0100, Jim Lesurf
wrote: In article , Don Pearce wrote: The type of rectifier doesn't make a great deal of difference, although full wave probably has the edge on accuracy. Don't put a capacitor after it, just let the meter do the averaging, then do the sums: power = v squared / R. I'd be wary of this unless I knew the details of the meter. I've seen some that can give odd results when asked to give a dc level in the presence of much ac. e.g. One I recall seemed to only sample the input at a low rate, so became confused as the level flutuations 'beat' with its sampling rate. Slainte, Jim I reckoned that the chosen method (and prologue) indicated no great ambition for accuracy, more a wish to get some sort of idea. Now damping the meter movement with a big cap is fine and it will take the ballistics out of the equation, but it will now certainly be a peak reading meter that doesn't correspond to apparent loudness in any but the vaguest way. Also, I assumed that this is a real meter with a needle, not a sampling DMM - otherwise why the question about rectifiers? It could simply have been used on a AC range. Mine will read Watts or dBWatts by setting an appropriate impedance in a menu. d -- Pearce Consulting http://www.pearce.uk.com |
Measuring audio power ...
"Jim Lesurf" Arfa Daily I guess what I'm asking is half wave reccy ahead of the meter, or full wave bridge ? If it uses a rectifier then takes a time-average I'd expect a good one to use a full wave precision rectifier - i.e. one that suppresses the forward voltage drops in the diodes. Cheap enough to do at audio frequencies. ** OPs needs real info - Jim. Not dumb guesses from someone with no idea how a DMM actually works. These days a meter might simply sample rapidly and work out the rms voltage and report that. ** Pigs might fly as well. Years ago, it might have used an analog multiplier to obtain the square-law for audio. ** Got no idea at all how a " true rms" DMM actually operates - Jim ? Never come across any " rms to DC " converters made by Analog Devices? Only been around for over 20 years. I guess people like Burr-Brown still make these. (?) As Don has pointed out, a thermal meter might be used in some applications. ** The ASS said no such thing. Why cover up for the demented fool ? These (and single diodes) still get used for RF power measurements. ** Damn shame then how OP is asking about **audio** !! However unless you are using a sinewave, the reported value may be misleading. Ditto if the load isn't resistive. ** Better have a look at the AD636. http://www.farnell.com/datasheets/57885.pdf Covers audio band measurements very comfortably. ........ Phil |
Gutless Ozzie Poof
"Poof Allison" wrote in message ... "Keith the Gutless ****ing Pommy Wonder " ** Not up to having a technical debate with ANYONE - ARE you Keith ? So you STILL continue to post your BRAIN DEAD insults while hiding your identity. How bloody PATHETIC !!! Typical, of countless, useless pommy wastes of space and all usenet cretins. **** THE HELL OFF :-) I've got it now!! You're a poof, aren't you? (What's it got to be now - 2:30 am? You won't look your best tomorrow.....) Ciao! |
Measuring audio power ...
"Don Pearce" wrote in message ... On Sun, 25 Jun 2006 13:40:03 +0100, Jim Lesurf wrote: In article , Don Pearce wrote: The type of rectifier doesn't make a great deal of difference, although full wave probably has the edge on accuracy. Don't put a capacitor after it, just let the meter do the averaging, then do the sums: power = v squared / R. I'd be wary of this unless I knew the details of the meter. I've seen some that can give odd results when asked to give a dc level in the presence of much ac. e.g. One I recall seemed to only sample the input at a low rate, so became confused as the level flutuations 'beat' with its sampling rate. Slainte, Jim I reckoned that the chosen method (and prologue) indicated no great ambition for accuracy, more a wish to get some sort of idea. Now damping the meter movement with a big cap is fine and it will take the ballistics out of the equation, but it will now certainly be a peak reading meter that doesn't correspond to apparent loudness in any but the vaguest way. Also, I assumed that this is a real meter with a needle, not a sampling DMM - otherwise why the question about rectifiers? It could simply have been used on a AC range. Mine will read Watts or dBWatts by setting an appropriate impedance in a menu. d -- Pearce Consulting http://www.pearce.uk.com Hi Don Yeah, you're right. No great need for any accuracy in this application. Because of the large numbers of group amps that I'm repairing at the moment, I've put together a big resistive load, capable of handling a couple of hundred watts. I've put some heavy duty relay switching in it for 16, 8 and 4 ohms, with automatic power-on default to 16. One or two other useful odds and sods like a very heavily attenuated little speaker and volume control, so that you can leave it squeaking away up the corner on a soak test, and a + /- LED bar arrangement to give a rough and ready idea of output symmetry, through socket so that a genuine cab can be substituted for the load, and a BNC socket for my 'scope. I thought it might be useful to put a very basic power meter on there too, just to get an idea of how much smoke an amp was generating. So I had a little play with a couple of spare sets of relay contacts on the load resistor switching relays, and hung a three way switch in there too. Three pots and a half dozen resistors later, I had a meter showing sensible readings for full scales of 10, 50 and 100 watts into 4, 8 and 16 ohm loads, but for straight DC from the bench power supply. It was just for interest then that I asked the question about whether 'real' meters read the power in the whole wave, or just one half. So when an amp says its output is 50w RMS, setting aside all the debate about whether RMS is valid, just taking it to mean what we all know the manufacturers want us understand by that, is it 100 watts of power contained in one half cycle, or one whole cycle. I'm sure you all know what I mean - I'm just not putting it very well ... Arfa |
Measuring audio power ...
tony sayer wrote:
FWIW if its just the output of an audio amp I just use two bloody great 8 ohm resistors on a large heatsink with stout cables to reduce ohmic losses, and connect that to the amp and use me trusty Fluke bench DMM to measure the AC power developed when running a sine wave with the Hewlett Packard distortion analyser keeping note of the distortion level to see when its going into clip. Measure that at a few different frequencies and square the AC measured volts and divide by the 8 'ommes and thats the RMS power. Sufficient and accurate and IMHO a good indication of what the amp will develop..... -- Tony Sayer That's exactly what I do, except I use a Levell millivoltmeter. With two large 8ohm resistors, it's easy to get a 4ohm load when needed. S. |
Measuring audio power ...
On Sun, 25 Jun 2006 20:01:55 GMT, "Arfa Daily"
wrote: It was just for interest then that I asked the question about whether 'real' meters read the power in the whole wave, or just one half. So when an amp says its output is 50w RMS, setting aside all the debate about whether RMS is valid, just taking it to mean what we all know the manufacturers want us understand by that, is it 100 watts of power contained in one half cycle, or one whole cycle. I'm sure you all know what I mean - I'm just not putting it very well ... Yup. "Real" audio power meters have an interesting design where the permanent magnet in the meter is replaced by a coil, which carries the same current as the movement. The result is that whichever way the current flows, it sends the needle upwards, so the meter naturally rectifies without diodes. Also, the deflection varies as the square of the current, so it is automatically linear on a power scale. d -- Pearce Consulting http://www.pearce.uk.com |
Complete Fool
"Keith Gutless Wonder " ** An even dumber pommy turd than I thought. ........ Phil |
Measuring audio power ...
"Arfa Daily" It was just for interest then that I asked the question about whether 'real' meters read the power in the whole wave, or just one half. So when an amp says its output is 50w RMS, setting aside all the debate about whether RMS is valid, just taking it to mean what we all know the manufacturers want us understand by that, is it 100 watts of power contained in one half cycle, or one whole cycle. I'm sure you all know what I mean - I'm just not putting it very well ... ** The question is completely asinine. Comes from a TV repair tech - right ? ........ Phil |
Measuring audio power ...
"Phil Allison" wrote in message ... "Arfa Daily" It was just for interest then that I asked the question about whether 'real' meters read the power in the whole wave, or just one half. So when an amp says its output is 50w RMS, setting aside all the debate about whether RMS is valid, just taking it to mean what we all know the manufacturers want us understand by that, is it 100 watts of power contained in one half cycle, or one whole cycle. I'm sure you all know what I mean - I'm just not putting it very well ... ** The question is completely asinine. Comes from a TV repair tech - right ? ....... Phil It's funny how often you use that word, Phil. Did you originally find out its meaning, after how many times it had been said to you ? You may consider me, and my question stupid, and that's your self-perceived prerogative, but trust me pal, it's nothing to what I consider you to be ... Arfa |
Measuring audio power ...
"Arfa Daily the Con Man " It was just for interest then that I asked the question about whether 'real' meters read the power in the whole wave, or just one half. So when an amp says its output is 50w RMS, setting aside all the debate about whether RMS is valid, just taking it to mean what we all know the manufacturers want us understand by that, is it 100 watts of power contained in one half cycle, or one whole cycle. I'm sure you all know what I mean - I'm just not putting it very well ... ** The question is completely asinine. Comes from a TV repair tech - right ? It's funny how often you use that word, Phil. ** If the cap fits - dickheads have to wear it. You may consider me, and my question stupid, ** No - I said completely ASININE !! ONLY a complete technical nincompoop could imagine it even made sense. ....... Phil |
Measuring audio power ...
"Phil Allison" wrote in message ... "Arfa Daily the Con Man " It was just for interest then that I asked the question about whether 'real' meters read the power in the whole wave, or just one half. So when an amp says its output is 50w RMS, setting aside all the debate about whether RMS is valid, just taking it to mean what we all know the manufacturers want us understand by that, is it 100 watts of power contained in one half cycle, or one whole cycle. I'm sure you all know what I mean - I'm just not putting it very well ... ** The question is completely asinine. Comes from a TV repair tech - right ? It's funny how often you use that word, Phil. ** If the cap fits - dickheads have to wear it. You may consider me, and my question stupid, ** No - I said completely ASININE !! ONLY a complete technical nincompoop could imagine it even made sense. ...... Phil Asinine Oxford English Dictionary Adjective " of asses ; stupid " Asinine Funk & Wagnalls Practical Standard Dictionary Adjective " Pertaining to, or like an ass ; stupid ; silly When you can speak and understand the Queen's English, and not some *******ised four X-soaked antipodean version, please feel free to correct my understanding of english words. Until such time, stick to shooting dingos for your tea, or whatever it is you do. Arfa |
Measuring audio power ...
On Sun, 25 Jun 2006 20:01:55 GMT, "Arfa Daily"
wrote: It was just for interest then that I asked the question about whether 'real' meters read the power in the whole wave, or just one half. So when an amp says its output is 50w RMS, setting aside all the debate about whether RMS is valid, just taking it to mean what we all know the manufacturers want us understand by that, is it 100 watts of power contained in one half cycle, or one whole cycle. I'm sure you all know what I mean - I'm just not putting it very well ... Arfa The specification for power - often mistakenly called RMS power - is actually for average power. If you look at a sine wave that has been mathematically squared, which you need to do to get power, you will see that one complete cycle comprises two upward humps. The average of one of those humps, which corresponds to half a cycle, will do just as well as the average of two for establishing power. Obviously if you are using music rather than sine waves it is quite likely that those two humps will not be the same size, a quite normal situation where the signal is bigger one way than the other. In that circumstance, you do need the average of both those humps, not just the one. So for music, you really need full-wave rectification, while for sine waves, half wave is every bit as good. d -- Pearce Consulting http://www.pearce.uk.com |
Spineless creep
"Phil Allison" wrote in message ... "Keith Gutless Wonder " ** An even dumber pommy turd than I thought. ....... Phool Whereas I was right on the money first time with you - see the Subject Line.... |
Measuring audio power ...
"Arfa Daily" wrote in message ... "Phil Allison" wrote in message ... "Arfa Daily the Con Man " It was just for interest then that I asked the question about whether 'real' meters read the power in the whole wave, or just one half. So when an amp says its output is 50w RMS, setting aside all the debate about whether RMS is valid, just taking it to mean what we all know the manufacturers want us understand by that, is it 100 watts of power contained in one half cycle, or one whole cycle. I'm sure you all know what I mean - I'm just not putting it very well ... ** The question is completely asinine. Comes from a TV repair tech - right ? It's funny how often you use that word, Phil. ** If the cap fits - dickheads have to wear it. You may consider me, and my question stupid, ** No - I said completely ASININE !! ONLY a complete technical nincompoop could imagine it even made sense. ...... Phil Asinine Oxford English Dictionary Adjective " of asses ; stupid " Asinine Funk & Wagnalls Practical Standard Dictionary Adjective " Pertaining to, or like an ass ; stupid ; silly When you can speak and understand the Queen's English, and not some *******ised four X-soaked antipodean version, please feel free to correct my understanding of english words. Until such time, stick to shooting dingos for your tea, or whatever it is you do. I think if that clueless **** tried to shoot a dingo it'd have *him* for tea...!! In fact, I *know it*..... *Australia's Finest*.....!! (Ya hafta fekkin' larf, don'tcha? :-)) |
Measuring audio power ...
"Don Pearce" wrote in message ... On Sun, 25 Jun 2006 20:01:55 GMT, "Arfa Daily" wrote: It was just for interest then that I asked the question about whether 'real' meters read the power in the whole wave, or just one half. So when an amp says its output is 50w RMS, setting aside all the debate about whether RMS is valid, just taking it to mean what we all know the manufacturers want us understand by that, is it 100 watts of power contained in one half cycle, or one whole cycle. I'm sure you all know what I mean - I'm just not putting it very well ... Arfa The specification for power - often mistakenly called RMS power - is actually for average power. If you look at a sine wave that has been mathematically squared, which you need to do to get power, you will see that one complete cycle comprises two upward humps. The average of one of those humps, which corresponds to half a cycle, will do just as well as the average of two for establishing power. Obviously if you are using music rather than sine waves it is quite likely that those two humps will not be the same size, a quite normal situation where the signal is bigger one way than the other. In that circumstance, you do need the average of both those humps, not just the one. So for music, you really need full-wave rectification, while for sine waves, half wave is every bit as good. d -- Pearce Consulting http://www.pearce.uk.com Thanks Don. Useful input. Arfa |
Measuring audio power ...
Don Pearce wrote:
If you really want to measure power accurately, use a resistor as the load, and measure its temperature. d lol I like that way -- Dave www.davewhitter.myby.co.uk Music is Art - Audio is Engineering Steam is Fun |
PISS OFF - TV TECH MORON
"Arfa Daily the Con Man ****wit " ** The question is completely asinine. Comes from a TV repair tech - right ? I said completely ASININE !! ONLY a complete technical nincompoop could imagine it even made sense. **** OFF - YOU BRAIN DEAD POMMY MORON FROM HELL !!! ........ Phil |
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