yes,but how does it SOUND dammit ?
Jul 6, 2006 23:44:58 GMT
Post by rickcr42 on Jul 6, 2006 23:44:58 GMT
www.analog.com/library/analogdialogue/archives/40-06/class_d.html
OK.CMOS sucks as an output stage if SOUND QUALITY is any part of important which makes it inclusion as an example suspect but....
and this
looks more like a function generator block diagram than it does an audio amplifier.
And this :
looks like it would be a nighmare into a highly capacitaive load (Quads ?)
and this looks a little to smug,too "one sided" to be of any real use
www.analog.com/library/analogdialogue/archives/40-06/AD40-06_04.jpg
then there is this to consider :
Significant differences in power dissipation are visible for a wide range of loads, especially at high and moderate values. At the onset of clipping, dissipation in the Class D output stage is about 2.5 times less than Class B, and 27 times less than Class A. Note that more power is consumed in the Class A output stage than is delivered to the speaker—a consequence of using the large dc bias current.
Output-stage power efficiency, Eff, is defined as
At the onset of clipping, Eff = 25% for the Class A amplifier, 78.5% for the Class B amplifier, and 90% for the Class D amplifier (see Figure 5). These best-case values for Class A and Class B are the ones often cited in textbooks.
damn good thing my ears listen and not read or I might think 25% efficiency is somehow a BAD thing in a high end home system loudspeaker power amp which would be even more so after looking at this :
which even worse-
The differences in power dissipation and efficiency widen at moderate power levels. This is important for audio, because long-term average levels for loud music are much lower (by factors of five to 20, depending on the type of music) than the instantaneous peak levels, which approach PLOAD max. Thus, for audio amplifiers, [PLOAD = 0.1 × PLOAD max] is a reasonable average power level at which to evaluate PDISS. At this level, the Class D output-stage dissipation is nine times less than Class B, and 107 times less than Class A.
For an audio amplifier with 10-W PLOAD max, an average PLOAD of 1 W can be considered a realistic listening level. Under this condition, 282 mW is dissipated inside the Class D output stage, vs. 2.53 W for Class B and 30.2 W for Class A. In this case, the Class D efficiency is reduced to 78%—from 90% at higher power. But even 78% is much better than the Class B and Class A efficiencies—28% and 3%, respectively.
and worser yet (and YES I know "worser" is not a word but just another rickism,so ? )
These differences have important consequences for system design. For power levels above 1 W, the excessive dissipation of linear output stages requires significant cooling measures to avoid unacceptable heating—typically by using large slabs of metal as heat sinks, or fans to blow air over the amplifier. If the amplifier is implemented as an integrated circuit, a bulky and expensive thermally enhanced package may be needed to facilitate heat transfer. These considerations are onerous in consumer products such as flat-screen TVs, where space is at a premium—or automotive audio, where the trend is toward cramming higher channel counts into a fixed space.
pretty freakin' bleak,almost enough to make me want to chuck all my Class-A gear and make the switch until :
For power levels below 1 W, wasted power can be more of a difficulty than heat generation. If powered from a battery, a linear output stage would drain battery charge faster than a Class D design. In the above example, the Class D output stage consumes 2.8 times less supply current than Class B and 23.6 times less than Class A—resulting in a big difference in the life of batteries used in products like cell phones, PDAs, and MP3 players.
AHAA !!!!!!
GOTCHA DAMMIT !!!!!!!
what may pass for good with crap cell phones,PDAs and MP3 players,ALL of which will be used with power well below 1 watt anyway and ALL of which are not even close to a high quality program source has absodamnlkutely shit to do with Clas-D being a true high fidelity amplification format.The fact that ALL of these portables operate in the miliiwatt range means EVEN FULL CLASS-A OPERATION will have little effect on either battery drain in real world terms OR heat generation if properly heat sinked UNTIL you add it to energy hungry devices such as DSP chips and display drivers so what they are really saying is
"we are robbing the audio quality a bit so we can bring you more and more features and a shitload of lights to tell you they are on,so there"
more :
For simplicity, the analysis thus far has focused exclusively on the amplifier output stages. However, when all sources of power dissipation in the amplifier system are considered, linear amplifiers can compare more favorably to Class D amplifiers at low output-power levels. The reason is that the power needed to generate and modulate the switching waveform can be significant at low levels. Thus, the system-wide quiescent dissipation of well-designed low-to-moderate-power Class AB amplifiers can make them competitive with Class D amplifiers. Class D power dissipation is unquestionably superior for the higher output power ranges, though.
still waiting for the part where it says it SOUNDS as good which should be the main focus of anything meant to be listened to..........
so blah blah blah on and on and on and on yet nowhere does the claim of superior sound actually appear though it IS implied.
This and other such technical writeups ALL support my dual track theory that as sources and expectations standards are lowered by the "MP3 sounds as good as CDs and CDs sound WAY better than analog" crew any damn amp will sound OK because there is only so much you can do with a crap source (Garbage in/Garbage out ) so in the end everything meant for cramming more and more features into a smaller and smaller cell phone running longer and longer on smaller and lighter batteries will be ending up in some very expensive gear where "tricks" will be implemented along with a very pretty and very expensive chassis which will have all the professional reviewers touting how great the amps are until some idiot in his delusional world of reality decides to actually ask :
So how does it sound ? Doas it SOUND better than Class-A or just run more efficiently ?
no doubt in my mind that once the "experts" tout the Class-D revolution as THE next thing and every bit as good as other amp topologies the law making Class-A amps illegal will not be far behind in certain countries or in mine,certain states.
Hell,they are already trying to outlaw the "linear" power supply (that we ALL know sounds inherently better than switchers) because of its inefficiency so what do you think that crowd will make out of white papers and articles such as the above ?
Evidence to prove their side at the hearings is what
OK.CMOS sucks as an output stage if SOUND QUALITY is any part of important which makes it inclusion as an example suspect but....
and this
looks more like a function generator block diagram than it does an audio amplifier.
And this :
looks like it would be a nighmare into a highly capacitaive load (Quads ?)
and this looks a little to smug,too "one sided" to be of any real use
www.analog.com/library/analogdialogue/archives/40-06/AD40-06_04.jpg
then there is this to consider :
Significant differences in power dissipation are visible for a wide range of loads, especially at high and moderate values. At the onset of clipping, dissipation in the Class D output stage is about 2.5 times less than Class B, and 27 times less than Class A. Note that more power is consumed in the Class A output stage than is delivered to the speaker—a consequence of using the large dc bias current.
Output-stage power efficiency, Eff, is defined as
At the onset of clipping, Eff = 25% for the Class A amplifier, 78.5% for the Class B amplifier, and 90% for the Class D amplifier (see Figure 5). These best-case values for Class A and Class B are the ones often cited in textbooks.
damn good thing my ears listen and not read or I might think 25% efficiency is somehow a BAD thing in a high end home system loudspeaker power amp which would be even more so after looking at this :
which even worse-
The differences in power dissipation and efficiency widen at moderate power levels. This is important for audio, because long-term average levels for loud music are much lower (by factors of five to 20, depending on the type of music) than the instantaneous peak levels, which approach PLOAD max. Thus, for audio amplifiers, [PLOAD = 0.1 × PLOAD max] is a reasonable average power level at which to evaluate PDISS. At this level, the Class D output-stage dissipation is nine times less than Class B, and 107 times less than Class A.
For an audio amplifier with 10-W PLOAD max, an average PLOAD of 1 W can be considered a realistic listening level. Under this condition, 282 mW is dissipated inside the Class D output stage, vs. 2.53 W for Class B and 30.2 W for Class A. In this case, the Class D efficiency is reduced to 78%—from 90% at higher power. But even 78% is much better than the Class B and Class A efficiencies—28% and 3%, respectively.
and worser yet (and YES I know "worser" is not a word but just another rickism,so ? )
These differences have important consequences for system design. For power levels above 1 W, the excessive dissipation of linear output stages requires significant cooling measures to avoid unacceptable heating—typically by using large slabs of metal as heat sinks, or fans to blow air over the amplifier. If the amplifier is implemented as an integrated circuit, a bulky and expensive thermally enhanced package may be needed to facilitate heat transfer. These considerations are onerous in consumer products such as flat-screen TVs, where space is at a premium—or automotive audio, where the trend is toward cramming higher channel counts into a fixed space.
pretty freakin' bleak,almost enough to make me want to chuck all my Class-A gear and make the switch until :
For power levels below 1 W, wasted power can be more of a difficulty than heat generation. If powered from a battery, a linear output stage would drain battery charge faster than a Class D design. In the above example, the Class D output stage consumes 2.8 times less supply current than Class B and 23.6 times less than Class A—resulting in a big difference in the life of batteries used in products like cell phones, PDAs, and MP3 players.
AHAA !!!!!!
GOTCHA DAMMIT !!!!!!!
what may pass for good with crap cell phones,PDAs and MP3 players,ALL of which will be used with power well below 1 watt anyway and ALL of which are not even close to a high quality program source has absodamnlkutely shit to do with Clas-D being a true high fidelity amplification format.The fact that ALL of these portables operate in the miliiwatt range means EVEN FULL CLASS-A OPERATION will have little effect on either battery drain in real world terms OR heat generation if properly heat sinked UNTIL you add it to energy hungry devices such as DSP chips and display drivers so what they are really saying is
"we are robbing the audio quality a bit so we can bring you more and more features and a shitload of lights to tell you they are on,so there"
more :
For simplicity, the analysis thus far has focused exclusively on the amplifier output stages. However, when all sources of power dissipation in the amplifier system are considered, linear amplifiers can compare more favorably to Class D amplifiers at low output-power levels. The reason is that the power needed to generate and modulate the switching waveform can be significant at low levels. Thus, the system-wide quiescent dissipation of well-designed low-to-moderate-power Class AB amplifiers can make them competitive with Class D amplifiers. Class D power dissipation is unquestionably superior for the higher output power ranges, though.
still waiting for the part where it says it SOUNDS as good which should be the main focus of anything meant to be listened to..........
so blah blah blah on and on and on and on yet nowhere does the claim of superior sound actually appear though it IS implied.
This and other such technical writeups ALL support my dual track theory that as sources and expectations standards are lowered by the "MP3 sounds as good as CDs and CDs sound WAY better than analog" crew any damn amp will sound OK because there is only so much you can do with a crap source (Garbage in/Garbage out ) so in the end everything meant for cramming more and more features into a smaller and smaller cell phone running longer and longer on smaller and lighter batteries will be ending up in some very expensive gear where "tricks" will be implemented along with a very pretty and very expensive chassis which will have all the professional reviewers touting how great the amps are until some idiot in his delusional world of reality decides to actually ask :
So how does it sound ? Doas it SOUND better than Class-A or just run more efficiently ?
no doubt in my mind that once the "experts" tout the Class-D revolution as THE next thing and every bit as good as other amp topologies the law making Class-A amps illegal will not be far behind in certain countries or in mine,certain states.
Hell,they are already trying to outlaw the "linear" power supply (that we ALL know sounds inherently better than switchers) because of its inefficiency so what do you think that crowd will make out of white papers and articles such as the above ?
Evidence to prove their side at the hearings is what