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<blockquote data-quote="zako" data-source="post: 7658714" data-attributes="member: 629735">THD at rated RMS wattage is almost always 1%. If there is vendor literature that claims 0.05% THD or something similar at rated RMS wattage, they&#039;re almost certainly bullshitting you or their marketing people have no clue. This is because there also exists a test that measures THD at 1watt. This is usually &quot;the amplifier THD&quot;. That number is usually very low. A lot of manuals confuse the concepts and claim that the later number is the THD at the rated RMS wattage. A lot of posters confuse these things too. I have seen many times comments like: &quot;What, your amp has 1% THD? It&#039;s a piece of crap!&quot;Note that some companies that fancy themselves as being high end vendors provide RMS wattage only as measured up to 0.5% THD. I don&#039;t like that because this does not give you apples to apples comparison with amplifier watts measured at 1% THD. Moreover, there are also many amplifiers where once THD goes up, it _really_ takes off, so if the rating is 60watts at 0.5%THD, chances are good that you will get at best 70watts at 1% THD, an inaudible difference. A THD plot often looks like this:<a href="http://www.pasmag.com/images/stories/test_report_graphs/1304/precision_power/image1.jpg" target="_blank">http://www.pasmag.com/images/stories/test_report_graphs/1304/precision_power/image1.jpg</a>So just because someone measured RMS wattage up to half percent THD, it&#039;s not necessarily cleaner than amps with similar wattage up to 1% THD.</blockquote>

[QUOTE="zako, post: 7658714, member: 629735"] THD at rated RMS wattage is almost always 1%. If there is vendor literature that claims 0.05% THD or something similar at rated RMS wattage, they're almost certainly bullshitting you or their marketing people have no clue. This is because there also exists a test that measures THD at 1watt. This is usually "the amplifier THD". That number is usually very low. A lot of manuals confuse the concepts and claim that the later number is the THD at the rated RMS wattage. A lot of posters confuse these things too. I have seen many times comments like: "What, your amp has 1% THD? It's a piece of crap!" Note that some companies that fancy themselves as being high end vendors provide RMS wattage only as measured up to 0.5% THD. I don't like that because this does not give you apples to apples comparison with amplifier watts measured at 1% THD. Moreover, there are also many amplifiers where once THD goes up, it _really_ takes off, so if the rating is 60watts at 0.5%THD, chances are good that you will get at best 70watts at 1% THD, an inaudible difference. A THD plot often looks like this: [URL="http://www.pasmag.com/images/stories/test_report_graphs/1304/precision_power/image1.jpg"]http://www.pasmag.com/images/stories/test_report_graphs/1304/precision_power/image1.jpg[/URL] So just because someone measured RMS wattage up to half percent THD, it's not necessarily cleaner than amps with similar wattage up to 1% THD. [/QUOTE]

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