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In Reply to: RE: I'm constantly amused posted by A.Wayne on November 09, 2015 at 08:00:10
It doesn't get any more textbook than this:
From Stereophile's measurements of the NAD M2.
Follow Ups:
Per JA's observations in the Stereophile test:
"Although it's convenient to refer to the NAD M2 as an integrated amplifier, it's actually something rather different: the M2 is a multiple-input D/A converter with an output stage that can drive a loudspeaker. "
Perhaps that is the direction others should go. Even then, note that the pretty wave has been filtered from high frequency noise.
I hadn't noticed that caveat on the graph, but JA says there is 100 mV of ultrasonic noise on the unfiltered output which would have fuzzed up the graph. Interestingly, I just re-read his comments on the Devialet and he said there is no ultrasonic noise on the output, which makes me wonder whether that is a benefit of the hybrid design or Devialet just includes aggressive filtering on the output.
@Dave K
The Devialet is the only class-D device i have heard not exhibiting the typical fuzzy high frequency ping usually encountered with other designs . Audible or not something is going on there ...@JA,
John thanks for the response and link
Regards
Go Rossi ......
Edits: 11/09/15
Stereophile's measurements of the NAD M2, whats causing the ringing ..?
Go Rossi ......
A square wave has an infinite number of harmonics. The ringing is what you get when you remove all the harmonics above a certain frequency. The NAD M2 is a digital device, and you're looking at a 1 KHz square wave at 96 KHz sampling, so there is a brick-wall filter response just under 48 KHz. The measurement I linked looks exactly the way a 1 KHz square wave is supposed to look when all harmonics above 48 KHz are abruptly cut off.
Similarly, the Devialet measurement looks exactly the way a 10 KHz square wave is supposed to look given the same digital filter response.
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