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iFi,
a couple questions regarding "Power Matters" mW bumps-
1. are the 10V, 5.5V, 2V numbers actually "Vrms" ? I'm always confused by what vendors spec/report/how.
2. I'm assuming the mW numbers are cumulative values (total output) for: Left channel + Right channel?
(ie. in your Normal mode 1900 mW , 16Ohm, would deliver 950 mW to Left channel + 950mW for Right. = 1900)
Lastly:
the Ohm's law math numbers "added up" in your earlier specs for the various Volts at 16ohm, 32, 64ohm, etc.
today at the new 5.5V (16 and 32 Ohms) and 2V values (8 and 16 Ohms), plugging into Ohm's law for values given the mW numbers do compute with what you reported above.
but for the 10V value:
at 64 Ohms, does compute (=1562 mW)
but at 16 Ohms, math says = 6250mW. not the 4000 mW reported.
Can you explain my bad math or the specific power adjustments?
thank you.
Hi,
1. The Volt are Volt RMS and can be sustained indefinitely (well, until battery is empty if not on an extra high-power USB Port) into the impedance listed.
2. The numbers are per channel.
Further comments:
So 10V into 64 Ohm can be sustained with sinewave testing.
Limitations in terms of power supply current and heat-sinking mean if we use a much lower impedance the protection circuitry will limit available current for sinewaves.
We test maximum power with sinewave bursts, which simulate music with a 20dB crest factor. This is a realistic test for what is possible with for example, well-recorded classical music.
Under those tests into 16 Ohm (and 8 Ohm where indicated) we get the stated results into the stated load.
So in Turbo mode with 16 Ohm load we run out of peak current before we run out of voltage, so only 4,000mW maximum power (for musical peaks), but 10V into higher impedances.
We can output continuous power in Turbo mode and Normal of around 1,500mW into any load low enough to draw enough current.
So Turbo and Normal mode would give each 1,560mW continuous (sinewave) power into 16 Ohm, in Turbo mode we also get 1,560mW continuous into 32 Ohm and 64 Ohm, for even higher impedance we run out of voltage before we run out of current.
Bty, in practice the continuous sinewave figure is not useful. Music is not a continuous sinewave, but rather something like this:
If you draw a "zero" line into this, the power used by the music is the area "under the curve",meaning between zero line and the curve.
You can see many high and narrow spikes, but the average power is low.
Compare to sine:
So a steady sine wave power rating does not help to understand what will happen with music.
Thanks
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