I just wanted to get some peoples opinions on class D amplifiers. I like them but id like to know what others felt about them 🙂
Hello,
Class D amplification involves the complete destruction of the original analog signal and the reconstruction. It use the PWM technology to reach an efficiency greater than 90% (very good). We are far from Pass SoZ 🙂 . To get a good bandwidth with those king of amplifiers, device must switch at least 1 MHz. Needless to say the problems related to RFI and EMI emissions. In conclusion? I found that the sound quality of those amplifiers is very poor. The only advantage is the efficiency.
Class D amplification involves the complete destruction of the original analog signal and the reconstruction. It use the PWM technology to reach an efficiency greater than 90% (very good). We are far from Pass SoZ 🙂 . To get a good bandwidth with those king of amplifiers, device must switch at least 1 MHz. Needless to say the problems related to RFI and EMI emissions. In conclusion? I found that the sound quality of those amplifiers is very poor. The only advantage is the efficiency.
Are these amps legal in your country? I'm not sure but in my country these amps are banned because of RF polution.
I don't think RF emissions are greater than the law permits (at least in Canada). Those amplifiers are based on the same principle of switching power supplies.
More to this than you might believe
You can ALWAYS design something so that it is legal. I find it very hard to believe that a technology is illegal -- it is wiser to make specifications as to pollution. The same technology is used in switching power supplies, motor drives etc.
The best way to make a class D amp is to build a high-powered DAC. Most amps need analog at the input regardless of whether the source is analog or digital to begin with. You can think of this difference as the difference between analog and digital computers.
TacT makes a really good class D amp. TI bought the technology and recently introduced some very cool technology (improvements on same). I don't see any competitors for TI at the moment but lots of work is going on in this space. LCAudio and B&O are doing interesting work. Apogee and Tripath (analog) also. Cirrus might be one to watch as well.
You can ALWAYS design something so that it is legal. I find it very hard to believe that a technology is illegal -- it is wiser to make specifications as to pollution. The same technology is used in switching power supplies, motor drives etc.
The best way to make a class D amp is to build a high-powered DAC. Most amps need analog at the input regardless of whether the source is analog or digital to begin with. You can think of this difference as the difference between analog and digital computers.
TacT makes a really good class D amp. TI bought the technology and recently introduced some very cool technology (improvements on same). I don't see any competitors for TI at the moment but lots of work is going on in this space. LCAudio and B&O are doing interesting work. Apogee and Tripath (analog) also. Cirrus might be one to watch as well.
Bwoca,
Is there an paper at http://www.intersil.com/, about the ic HIP4080, with some theory about class D amps. It's about efficiency, distortion etc.
For low frequency class D amps are a very good choice. You can achieve the high power levels neede at these frequencies with high efficiency and little heatsinks.
For the rest of the audio band, since you don't need big power to achieve high sound pressure levels, they are not the best choice, because THD in this class of amp increases if you don't use high switching frequencies. Typically you need 20 times (or more) the higher audio frequency that you are working on the switching circuit to achieve low THD levels.
Regards
Is there an paper at http://www.intersil.com/, about the ic HIP4080, with some theory about class D amps. It's about efficiency, distortion etc.
For low frequency class D amps are a very good choice. You can achieve the high power levels neede at these frequencies with high efficiency and little heatsinks.
For the rest of the audio band, since you don't need big power to achieve high sound pressure levels, they are not the best choice, because THD in this class of amp increases if you don't use high switching frequencies. Typically you need 20 times (or more) the higher audio frequency that you are working on the switching circuit to achieve low THD levels.
Regards
I have built a 2oow mono amp based on this chip, I think it is great as sound to price ratio is great, obviously you can get better sound, but not for the same price🙂 My reason for starting this thread was to get others opinions on the matter 🙂
International rectifiers and crystal have made a set of mosfet+digital driver for a class D amp. It´s the newest thing out with very cheap prices.
http://www.irf.com/e/w010514.html
take a look.
http://www.irf.com/e/w010514.html
take a look.
About IRF and Cirrus
But performance of the Cirrus/IRF solution does not even begin to touch what TI are claiming. Disappointing, but they will be back with better stuff soon I hope.
Petter
But performance of the Cirrus/IRF solution does not even begin to touch what TI are claiming. Disappointing, but they will be back with better stuff soon I hope.
Petter
class-d amplifiers
hi.
poor quality?? i dont think so , please take a look at :
http://www.cadaudio.dk/pwmaudio.htm to give you an idea.
audiophiles living in copenhagen area are welcome for a listening experience, we have a stereo set of class-d / digital amplifiers set up.
bye k madsen
ps. unlike some of the others these are real world items 🙂
ps. "Class D amplification involves the complete destruction of the original analog signal and the reconstruction"....
like in a cd?? or other digital recording ??🙂
[Edited by km on 06-04-2001 at 07:03 PM]
hi.
poor quality?? i dont think so , please take a look at :
http://www.cadaudio.dk/pwmaudio.htm to give you an idea.
audiophiles living in copenhagen area are welcome for a listening experience, we have a stereo set of class-d / digital amplifiers set up.
bye k madsen
ps. unlike some of the others these are real world items 🙂
ps. "Class D amplification involves the complete destruction of the original analog signal and the reconstruction"....
like in a cd?? or other digital recording ??🙂
[Edited by km on 06-04-2001 at 07:03 PM]
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