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Old 25th August 2011, 03:36 AM   #1
Join Date: Jun 2011
Default Class D amplifier regulates the power flow?


Is it true that a Class D amplifier usually incorporates a compression algorithm which is variable ......and the level of compression depends on the music power that has recently been sent to the speaker.?

For example, it is known that SMPS's to supply class D amps are not rated to handle peak power therefore, the Class D amp DSP helps the SMPS out a little, by starting to compress the music when it knows that the SMPS has been flat-out for a longish while.........In this way, the power flow through the amp is staunched without the music suddenly sounding much quieter and different.

Since a typical music signal is likely to have peaks which are 100 times more powerful than the average power, its obvious that we're not going to have a genuine smps which is rated to handle that peak power we will compromise........and in order that we dont get caught out during say, a heavy metal guitar gig, and fry the power supply, the class D amp will itself effectively regulate the power, by means of compression of the music signal at suitable times.?
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Old 25th August 2011, 06:06 AM   #2
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No, it would not be a typical design feature but there might be some low cost low quality amps that does that.

A typical SMPS supply used to supply a class D amp should at least be able to supply the continuous RMS power consumption of the amp, not just the RMS output. Anything less implies a low cost low quality amp.

A typical music signal has peaks that are 12dB above average using the old RIAA recording standard guidelines, although with modern compressed music that might be as low as a 10dB delta from average to peak, so 10 to 16 times delta from average to peak would be normal, not 100 times (20dB).
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Old 25th August 2011, 11:31 AM   #3
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-the thing is, there may be some type of music which has the amp working at the ten-times average power for long continuous periods.

There needs to be some protection from this.....and if that protetion simply entails the smps shutting down, abruptly stopping the music....then that is bad, as one looks a fool on the best place to put the overpower protection is in the Class D amplififer. that you handle potential overloads gracefully, without abrupt shutddown
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Old 25th August 2011, 11:35 AM   #4
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As I said above, if the SMPS of the amp can't handle the RMS power consumption of the amp at least, then it's not properly designed from the start.

Last edited by Saturnus; 25th August 2011 at 11:39 AM.
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Old 25th August 2011, 02:27 PM   #5
AP2 is offline AP2  Italy
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This is the difference between a good amp and an amp designed for continuous use. eg. to professional power amp, the sound does not stop (only in exceptional cases). i mean for open-air theater or disco pubs. has a good amplifier circuits that limit the power output without introducing significant thd. it is obvious that in addition to protection circuits, the project must be suitable for intensive use.
the same difference that was on the class A-B amp. or class H.

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