Standard test conditions for power consumption in amplifiers is at 1/8 power with pink noise - not full sine wave. It's approximately what the amp draws when playing music with clipping just audible. Expect about 2X that with the amp "blasted". The big pro amps could never get safety agency certification if they had to claim current draw based on the absolute max that you could get on a test bench - and you never see that much for more than a few seconds in any real application anyway.
power levels
I am not that technical, so excuse my idiot questions! A power amplifier delivers 2000W RMS @ 4OhmsNeeds a power supply capable of delivering 80-0-80 12 Amperes for that channel let say.That means the MAIN power supply, (Transformer, or switching power supply) will draw 1/8 of the OUTPUT power of that amplifier from the mains supply 220VACOr most power amplifiers manufacturers measure amplifiers in peak power only?Or the Main transformer or Switching supply usually dont deliver the REQUIRED power to the amplifier. only peaksThanks
I am not that technical, so excuse my idiot questions! A power amplifier delivers 2000W RMS @ 4OhmsNeeds a power supply capable of delivering 80-0-80 12 Amperes for that channel let say.That means the MAIN power supply, (Transformer, or switching power supply) will draw 1/8 of the OUTPUT power of that amplifier from the mains supply 220VACOr most power amplifiers manufacturers measure amplifiers in peak power only?Or the Main transformer or Switching supply usually dont deliver the REQUIRED power to the amplifier. only peaksThanks
A 2x2000W/4 ohm amp needs a power supply that is more like +/-140V DC. Such an amp would draw around 40 or 50A off a 220V main with a full power sine wave output (80 to 100A from a 120V main). Try it some time - that's really what they draw if they can produce that kind of power. The breaker on the back panel will trip in a few seconds. It won't hurt a good touring grade amp - but a POS may go up in flames. For current consumption specs, they run the OUTPUT power to 1/8 power (which is typical useage) and see what the mains current is and that's what's reported. Peaks will actually be as high as 40 or 50A on each kick drum hit if it's driven to clipping but the average (or RMS) will be lower. For safety and overcurrent protection, that's the current that "matters". Your A/C may draw 25A when it's cooling and be protected by a 50A breaker. It draws hundreds or thousands of amps each time the compressor starts up (which is why the lights dim).
I feel that the 1/8 power spec is false advertising. If an amplifier is rated for 200W then the power draw should be based on delivering that much. This is tantamount to the old IHF music power spec that allowed 2W amplifiers to have a 100W specification.
Industry standard be damned, I won't go with it.
Industry standard be damned, I won't go with it.
You're free to build your amps any way you want. The problem isn't with 100W or 200W amps. Those come in under 16A current draw even with a continuous sine wave input. Even the old-school CS800 came in under 20A at full sine and 2 ohms per side. But then amps got "bigger". Double the power, and it takes a 30A feed. Double it again and it's 60A. I guess this made powering 500,000 watt concert systems "impossible" because you've exceeded the substation rating without even plugging in the lighting yet. And the actual current draw was always a small fraction of that. When amps started getting above a kW routinely, the industry decided to rate current consumption based on something that simulated real world usage instead of maximum power.
Unfortunately, what happened next was transformers and heat sinks shrinking to the point where you can't run a modern amp near full power for even 10 or 15 minutes anymore. The argument is always that "you don't need to". The ones that come closest cost thousands. Ones that can't even think about it go for a few hundred bucks.
Unfortunately, what happened next was transformers and heat sinks shrinking to the point where you can't run a modern amp near full power for even 10 or 15 minutes anymore. The argument is always that "you don't need to". The ones that come closest cost thousands. Ones that can't even think about it go for a few hundred bucks.
4kW of ClassAB sinewave output power will pull about 25Arms from a 240Vac mains supply.
4000W/ 0.68 = ~5.9kW of input power.
5.9 /240 ~25Arms.
But we all know that a transformer feeding a capacitor input filter does not draw sinewave current from the mains. It draws short spikes of current that flow for only 1% to 10% of the half cycle. The peak of these current spikes is ~ 5 to 10 times the predicted rms current.
I would expect to see current peaks approaching 200Apk from the 240Vac mains supply when the ClassAB amplifier is continuously outputting 4kW of sinewave power.
A two channel 200W into 4ohm ClassAB amplifier would pro rata draw near 20Apk from a 240Vac supply.
We plug these and much more into a 13A BS1363 socket outlet all the time and don't worry about it.
4000W/ 0.68 = ~5.9kW of input power.
5.9 /240 ~25Arms.
But we all know that a transformer feeding a capacitor input filter does not draw sinewave current from the mains. It draws short spikes of current that flow for only 1% to 10% of the half cycle. The peak of these current spikes is ~ 5 to 10 times the predicted rms current.
I would expect to see current peaks approaching 200Apk from the 240Vac mains supply when the ClassAB amplifier is continuously outputting 4kW of sinewave power.
A two channel 200W into 4ohm ClassAB amplifier would pro rata draw near 20Apk from a 240Vac supply.
We plug these and much more into a 13A BS1363 socket outlet all the time and don't worry about it.
Well, to be honest, that 200W amp will never be called upon to deliver that 200W continuously except on the test bench. So the question then is should we spec and built and pay for a test nebch spec or a music reproduction spec?
Be aware if you pay for a 200W continuous capability you pay for something that only the test bencher uses.
jd
very obviously correct.
I try to bring listeners/builders back to ground by repeatedly reminding them that the average power output to the speakers should be <= -20dB ref maximum power. i.e. a 200W amp ticks over with a 100mW of output and sounds quite loud with 2W of average output.
This +20dB overhead allows for voltage peaks ~ 10times the average signal level.
I have no objection to that philosophy. What I do object to is the implication that an amplifier can deliver a certain amount of power. If indeed one can get 200 W from an amplifier but only for 5 seconds, that should be in the specification. I don't buy a 100 W light bulb and expect only to run it for 20 seconds else it will burn out. I believe in full disclosure.
Yes, I expect my amplifier to meet it's power specification without suffering any damage for as long as the output (or any other) devices stay at or below their maximum design operating temperature.
Similarly I expect to be able to drive a resistive load of half the specified impedance and preferably one third, for as long as the semiconductors stay within their design operating temperature.
I arrange to do power testing in one to two seconds, by using 20dB switches in the test signal. The smoothing capacitors have already sagged to their long term power voltage.
Similarly I expect to be able to drive a resistive load of half the specified impedance and preferably one third, for as long as the semiconductors stay within their design operating temperature.
I arrange to do power testing in one to two seconds, by using 20dB switches in the test signal. The smoothing capacitors have already sagged to their long term power voltage.
What I would like to see, especially in pro amplifiers, is a rated duration at 1/8, 1/3 and full power at all useable impedances. It would make the decision as to how much capability X dollars is actually buying. Of course, this is exactly the kind of thing most of them don't want you to know. When building my own, I shoot for being able to operate at 1/3 power indefinitely which is what the old FTC spec was supposed to "enforce". It has since changed to 1/8 power. Some touring grade amps have 2 ohm FTC specs (at the 1/8 power level), but it would also be nice to know how long it will go at 1/3.
And of course, most of them have no FTC spec at all. So you have no idea if it will run for two seconds or 5 minutes at full whomp before shutting down.
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It's simply a case of deceptive advertising. I won't buy such a device. If I want an amplifier for a specific purpose, I may end up building one. It's cheaper and more suited to the job.
These companies are run by a combination of people who don't know what they are doing and people who think they can sell anything. Sorry, I'm not buying into any of that. The Detroit automakers were like that (and probably still are) and it cost them dearly. When the Japanese started making stuff, they brought honesty to the market and the domestic producers had red faces.
These companies are run by a combination of people who don't know what they are doing and people who think they can sell anything. Sorry, I'm not buying into any of that. The Detroit automakers were like that (and probably still are) and it cost them dearly. When the Japanese started making stuff, they brought honesty to the market and the domestic producers had red faces.
For a 200W (or even 400) it's quite practical for DIY anyway. I'm using one in my living room. You can buy 2kVA 60-0-60 toroids and enough heat sink to dissipate 1500W. It just costs money. And it won't fit in 2U, but it might in 4U. For amps in the 4-13kW range that can run full blast indefinitely, forget it. You could build it and it would weigh 200 pounds and take 6U and have a loud fan or four. Useless for HT or mobile PA. A compromise that can run 1/8 power for hours or 1/3 for a few minutes gets down to something practical - like a CA18.
Power Transformer Sizes
Well.
I think that some manufacturers uses over sized transformers into there amplifiers ( the Old amplifiers I mean 90s)
As an example:
I have one Amplifer delivers 700W RMS @4 OHms per channel
the Toroidal transformer in that amplifier can drive at least 2.5KW RMS from its size, the thick wires used.
Another amplifier CLAIMS 600W RMS @2 OHMS with 1/2 size of that amplifier.
I think some manufacturers gives RMS power, and some gives Peak Power
And from what I understand now, that ANY amplifier will NEVER draw the maximum current from the 220VAC line.
Well.
I think that some manufacturers uses over sized transformers into there amplifiers ( the Old amplifiers I mean 90s)
As an example:
I have one Amplifer delivers 700W RMS @4 OHms per channel
the Toroidal transformer in that amplifier can drive at least 2.5KW RMS from its size, the thick wires used.
Another amplifier CLAIMS 600W RMS @2 OHMS with 1/2 size of that amplifier.
I think some manufacturers gives RMS power, and some gives Peak Power
And from what I understand now, that ANY amplifier will NEVER draw the maximum current from the 220VAC line.
Maybe. Maybe 'audiophiles' that think they need an amp that can run 200W indefinitely don't know very well what they're doing either.
jd
I agree; anyone that needs that much power must be deaf or trying to fill a stadium with sound. My complaint was not whether a high power amplifier has legitimate use, but that the specifications lie. If you can put out 200W only for 10 seconds, then say so. Otherwise I presume a power rating to be for continuous operation.
I have used a 300W amplifier in continuous operation; it was a Kenwood I still have. But not to run a loudspeaker. Where I worked we needed 120V 50 Hz power and of course our mains are 60 Hz. So a nice amplifier with an audio oscillator and an output transformer gave us what we wanted without firing up a monster gasoline generator.
I have used a 300W amplifier in continuous operation; it was a Kenwood I still have. But not to run a loudspeaker. Where I worked we needed 120V 50 Hz power and of course our mains are 60 Hz. So a nice amplifier with an audio oscillator and an output transformer gave us what we wanted without firing up a monster gasoline generator.
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Maybe. Maybe 'audiophiles' that think they need an amp that can run 200W indefinitely don't know very well what they're doing either.
jd
You have to take into account the dynamic range of different types of music.
I have built amps with +/- 40volt rails and been shocked just how quickly the music clipped on transients.
I now use +/-60 volt rails and that performs much better.
Music can be quite flat and then a drum or percussive instrument cuts in and a huge spike appears on the waveform.
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