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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: RE: OHMS LAW..... posted by jea48 on July 15, 2012 at 10:35:42:
RE the first part, I agree that, yes such a measurement should tell where the transformer stands with heavy load current.
Re the last long sentence, the 3 hour continuous draw current capability is moot.
Music is not a sine wave, nor is it continuous. Unless the amp is Class A, the transformer will never see a full rated load continuous load current.
If the amplifier was Class A, then the transformer might see 1/2 the load current represented by the power amp load rating into a given nominal impedance, with some increase above that for the brief moments when the current draw of the Class A power amp slightly exceeded the draw of 1/2 of full rated power.
With almost any other power amp, the current draw will average out to less than 1/3 full rated power current draw, and more typically, 1/8 of full rated load current draw.
UL, which are known to be severely conservative in their testing and ratings, uses the 1/8 power point of full rated load, and the current draw at that point for the "average" power draw from the line for most modern power amps, with the exception of a Class A type power amp.
Switching amps are even less current draw that that criteria.
If you use the SU-2 with a power amp that at full rated power output into a given load, draws at or less than the continuous current rating of the transformer (per Signal), there is not going to be a problem. No way.
Even with 10% THD clipping point (which sounds absolutely terrible to any one with audiophile/music lover pretensions), the power draw is still only a moderate fraction of the full rated power current draw for the power amp.
Music has a crest factor, so does a sine wave. The crest factor is the ratio of the peaks to the RMS value of the signal.
For a sine wave, it is 3 dB. For even the most highly compressed Rock/DubStep/Reggae whatever, the crest factor is going to be no worse than 10 dB, and is usually higher. That means for a 1000W power amp, the average RMS signal power is going to be 100W when the amp is clipping.
10% THD clipping only raises that average to maybe 120W.
Old school rock and roll has a higher crest factor, as does jazz, classical, etc. A ballpark figure for most other music that is not heavily compressed and clipped during mastering is around 15-25 dB crest factor, which puts our hypothetical 1000W power amp, clipping when it reaches an average power of from 31 to 4 watts.
Not exactly burning up the wires, eh?
Jon Risch
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Follow Ups
- RE: OHMS LAW..... - Jon Risch 21:15:26 07/15/12 (1)
- RE: OHMS LAW..... - jea48 08:01:43 07/16/12 (0)
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