Pascal Pincosy wrote on Tue, 12 December 2006 01:27 |
BTW Bob, in the comment about 100 amps at 120 volts mains, Jens was refering to an amp from Studio R in Brasil called the X12, which is an 11,000 watts RMS Class-H amplifier that pulls up to 68 amps 220v (so I'd guess about 125 amps @120v) at its peak current draw.
You would probably need a revised distro to run an amp like this with a 2 Ohm load, maybe up to 100 amps @ 120v per circuit Though I think 50 amps per circuit @ 120v would be fine for almost all applications not involving a 2 Ohm load and a Drum & Bass/Hardcore show.
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13,200 Watts @ 1.5 ohms, IEC, 500ms, 136A @ 115V, 68A @ 220V. These are all maximum ratings. The EIA ratings are considerably lower.
As quoted from Meyer;
"When an amplifier is rated in RMS watts, this is a shorthand way of saying “average watts obtained by the RMS method.” If you use a signal other than a sine wave, you must use a meter reading ‘true’ RMS voltage to obtain the correct average power.
So what about peak power? Peak power is a special case where Ppeak = Epeak * I peak. For a sine wave, this is always twice the average power. A major problem with using this rating, however, is that many power amplifiers cannot maintain peak power for more than a few milliseconds.
The standard method of testing a power amplifier to see if the power supply can maintain continuous peak power is to connect all channels of the amplifier into load resistors, drive the amplifier’s input with a square wave and monitor the peak voltage at the outputs. Almost all power amplifiers will ‘sag’ in output power under this drive condition.
Now, having a power amplifier produce twice the continuous sine wave power is hardly necessary for music reproduction, but sometimes music signals produce short-term square wave or large sine wave-like waveforms. So how long should a power amplifier be able to maintain reproduction of a square wave or sine wave at full amplitude?
Recently Meyer Sound measured a well-known dual 18” subwoofer system that came with a power amplifier. The amplifier’s power supply rail when it was not being driven sat at 160 volts. Using this rail voltage, we could calculate the instantaneous peak power for a 4 ohm (resistive) load to be:
E2/R = 1602/4 = 6,400 watts per channel
Thus, we could claim this amplifier has well over 12,000 watts of peak power. This is a very impressive power rating to publish, but is it at all meaningful? Meyer Sound engineers drove the system with a single, drum note of 40 milliseconds in duration. The power amplifier rail voltage plummeted from 160 volts to 80 volts while playing the note. This 80-volt drop in output level acts as a compressor on the audio. The transducers used in this system were very non-linear, producing a large amount of second harmonic distortion."
These are incredible amplifiers Jens is talking about and they would probably work quite well from a 230V 30A source. Note that the published EIA rating for the amp indicates it will draw 19.3 amps and produce 6600 watts per channel under a 2 OHM load. I look at this as a real world figure. That's the point I'm trying to make here. Jens also makes a deal out of 115v and lives in a country where 230V is standard.