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Class D Switching Power Amplifiers and Power D/A conversion

Phase shift in class D amplifiers. How it affects the sound?
Phase shift in class D amplifiers. How it affects the sound?
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Old 3rd March 2021, 07:32 PM   #221
Mello4 is offline Mello4  United States
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Feedback is not a bandaid, it is a design method to make circuits more effective, controllable & reliable.


Feedback is also a naturally occurring reality, which we use every day with our movement as humans which is modified by our sensory feedback..

Last edited by Mello4; 3rd March 2021 at 07:39 PM.
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Old 3rd March 2021, 09:11 PM   #222
georgehifi is offline georgehifi  Australia
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Yeah well there two camps on that one, by some very noted designers.

Cheers George
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Old 20th March 2021, 11:26 AM   #223
maty tinman is offline maty tinman  Spain
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Default Icebrick IcePower Engine-400

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Old 25th July 2021, 02:13 AM   #224
georgehifi is offline georgehifi  Australia
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"-3 dB at 100 kHz giving very low phase shift at 20 kHz."

If that's what the low order switching noise output filter is doing.
I'd hate to see what kind of switching noise is on the 10khz square wave from the output of this amp, bet it looks like a buzz-saw with no resemblance to a 10k square wave. Probably much worse than this top pic.

Cheers George
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Old 29th July 2021, 09:14 PM   #225
Mark Tillotson is offline Mark Tillotson
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Out of band noise is out of band, get over it!! More seriously so long as the switching residual is much lower in power than the max signal, it is unlikely to be a problem (assuming EMI issues are addressed).

Last edited by Mark Tillotson; 29th July 2021 at 09:17 PM.
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Old 29th July 2021, 10:19 PM   #226
georgehifi is offline georgehifi  Australia
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If you saw a linear amp with this on it's square wave you' say it was broken, you get over it.
I've seen still working but "blued" Wilson tweeter voice coils because of this over time as he used to leave them on, I changed the diagram's for the customer with original new ones and they sounded great again, no need to tell you he flicked those D monoblocks that got "good" reviews on Stereophile, and went back to linear. And no the D's had no dc on the output or anything weird save for the switching noise oscillation
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Old 2nd August 2021, 10:02 AM   #227
phase_accurate is offline phase_accurate
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Yes, a linear amp with such an RF residual is broken (or being forced to drive a not so wisely chosen load). But that is a different story and doesn't mean that class-d amps are defective from the beginning.

The RF residual shown in your second last post would have a power of 15 Miliwatts into 8 Ohms approximately. Taking the tweeter's Le into account it would be even less. A decent tweeter shouldn't have any problems with even stronger residuals than that.

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Charles
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Old 2nd August 2021, 11:31 AM   #228
georgehifi is offline georgehifi  Australia
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"A decent tweeter shouldn't have any problems with even stronger residuals than that."


Well these did, those voice coils were nice a blue from heat, he was also the type to leave the amps on 24/7, and that RF residual may have been higher because the -3db point of his amps were a bit higher than those Anthem Statement M1's above Screenshot-2021-08-02-214358 — ImgBB .

Below is a pic of the FR of the offending amps and they were Nuforce Ref 9se V3 monoblocks

Cheers George
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Old 5th August 2021, 01:56 PM   #229
starkeyg is offline starkeyg
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Hello Georgehifi,

Yes, I can easily believe you saw a problem on a specific amp and speaker combination. Do not believe that means all class D amps are bad.

There have been fair number of marginal or even bad designs of other classes of amps which does nothing to say that all of those classes are bad.

IHMO there are bad and good in every class of amplifiers.

Greg
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