Mikruskes sukurtos, ideja liko ta pati su tom pacom bedom. Ir straipsny apie tai gana aiskiai parasyta. Nori garsiai ir lengvai darais D klase, nori graziai ir kokybiskai A. Pramone del lengvai ir garsiai ir del to, kad mulkiam D klase galima pakist kaip desra ir kisa ta D kur reikia ir kur nereikia, juk gamint reikai pigiai o parduot brangiai. Tau gi telieka atsirinkt kas yra kas. On 05/02/2013 07:25 PM, psw wrote: > 2006 metų straipsnis, D klasės progreso prasme, jau akmens amžius, > sukurti nauji elementai, čipai, moduliai, technologijos. Su dabartiniais > komponentais, jei viskas daroma korektiškai, tai straipsnyje paminėtų > bėdų beveik nebus. Dabartiniai net nebrangūs D klasės moduliai jau labai > perspektyvūs. > Blogesnis damping faktorius paprastam D klasės stiprintuve gali būti > visai neaktuali problema, nes nevisada reikia didelio dampingo. D klasės > schemoje, įvedus neigiamą grįžtamą ryšį (NGR), dampingas didėja. Su NGR > mažinama išėjimo filtro darbo priklausomybė nuo apkrovos varžos, > gerinamas filtro tiesiškumas ir impulsų sinchronizavimas. Gerai padaryti > ir neperlenkti su NGR nėra paprasta, todėl jis ne visada bus pilnai > naudojamas pigesniuose variantuose. > > Visos neigiamos nuomonės apie D klasę sudarytos remiantis senų teorijų > prielaidom, kad gali būti tos ar kitos problemos, kurios dabar jau > išspręstos arba buitiniuose variantuose net neaktualios. Iki šiol > buitiniai D klasės stiprintuvai daugiausiai buvo paplitę ten, kur > reikia, kad būtų efektyvu ir nebrangu, todėl dažnai su visom dėl pigumo > nesutvarkytom problemom. Dėl sudėtingų konstrukcinių ir techninių > niuansų, D klasė buvo labai nedraugiška DIY mėgėjams, kas automatiškai > "programavo" neigiamą iki to nepriaugusių mėgėjų nuomonę. Bet jau yra > aukštos klasės pilnai padarytų modulių, manau, greitu laiku situacija > pasikeis. Artimiausiais metais (nes jau pribrendo), pasipils > vidutinės-aukštesnės klasės naminiai stiprintuvai, bus "mėsos" gausiems > palyginimams ir daug kas "praregės". :)) > > > On 2013.05.02 09:49, Signalizacija wrote: >> The whole reason for existence of Class D is efficiency. >> >> ... >> >> If Class D were perfect, it would have swept the world and there would >> be no other class in common usage. I'll tell you about the three major >> problems of Class-D amplifiers in a moment, but first, here's a >> question: how do you make an efficient radio transmitter? Answer: start >> with a Class-D audio amplifier. Yes, the high frequencies involved in >> Class-D amplification readily propagate as radio waves, potentially >> causing interference with radio receivers and other equipment. You might >> think that the solution would be to enclose the amplifier in a >> substantial steel housing. But that's not where the problem manifests >> itself — it's in the cables. The filter that is supposed to remove the >> high-frequency components and leave only the audio signal is quite >> shallow in slope — 6dB or 12dB per octave — so there's quite a lot of RF >> energy still getting out. Clearly, manufacturers take care to improve >> the situation and remain within allowable limits, but it is a problem >> inherent to Class D. >> Class D without the filter. Lab Gruppen's 'Class TD' technology extends >> Class D with a claimed sonic performance equivalent to Class AB, but >> with Class D's superior performance in terms of efficiency and low >> weight. >> >> The second problem of Class-D is that the last thing the signal sees >> before it reaches the loudspeaker is the filter. A passive filter made >> from capacitors and inductors expects to see a certain load on its >> output. Even just looking at the resistance of a loudspeaker and >> ignoring its capacitance and inductance, loudspeakers come in 2(omega), >> 4(omega) and 8(omega) nominal impedances, and the filter will work >> differently according to the impedance of the loudspeaker. Taking >> capacitance and inductance into account, the impedance will vary >> according to frequency. So the filter design is suddenly very much more >> complex: an amplifier that performs differently for different speakers >> is going to be a problem. >> Thirdly — not finally, but enough for now — a Class-D amplifier has a >> relatively poor damping factor. The damping factor is the ratio of the >> impedance of the loudspeaker to the output impedance of the amplifier >> (it's a little more complex than that, but let's not get bogged down >> with details). In simple terms, it's a measure of how well the amplifier >> can control the movement of the diaphragm of the loudspeaker. A good >> amplifier doesn't just give it a push and hope for the best; it senses >> where the diaphragm is from moment to moment and controls its position. >> To do that, a high damping factor is desirable, and, as mentioned above, >> a simple Class-D amplifier has a low damping factor. >> >> Clearly, advanced technology can be applied to ameliorate these >> problems, but because of them Class-D amplification is used mainly in >> applications where efficiency, weight and small size are important. >> These include live sound, in-car audio and compact portable systems. >> >> Clearly, there is more to know. For instance, it's important to know >> that the switching frequency must be very high to achieve the necessary >> resolution. A switching frequency of around 300kHz, which is around 15 >> times the highest audio frequency of general interest, is typical. The >> dynamic range and signal-to-noise ratio of the Class-D amplifier are >> controlled by the switching frequency — the higher the better. Clearly, >> the greater the rate of pulse generation, the more closely the pulse >> width will be in proportion to the instantaneous signal level. However, >> the drawback of increasing the switching frequency is that the amplifier >> will be less efficient. Optimum efficiency would be achieved if the >> transistors could switch instantaneously, so that they were in either >> their fully on or fully off states, where almost no power is consumed. >> But in the real world it takes a little time for the voltage to swing, >> and during that time some power is dissipated. So the more often the >> swings take place, the more opportunity for waste. Even so, the >> efficiency of a practical Class-D amplifier can be better than 90 >> percent, which is significantly better than a Class-AB design (78.5 >> percent at best and typically closer to 50 percent). >> >> http://www.soundonsound.com/sos/jun06/articles/loudandlight.htm >> >> On 05/02/2013 08:25 AM, Dainiushas wrote: >>> tu čia stebuklines pasakas kažkokias seki. šiaip jau >>> >>> On 2013.05.02 07:56, Signalizacija wrote: >>>> Dar karta kartoju. Klausai , kalusyk, bet nerikia kist D klases kai >>>> kazkokio stebuko. Pats aiskiai parasei, geris gabarituose ir energijos >>>> panaudojime. Deja tuo tas geris ir baigiasi. >>>> >>>> >>>> On 05/01/2013 09:17 AM, spakainas wrote: >>>>> Ale tu žiūriu vis nepasimokai, negana o.autos'uose grybą pjauni, tai >>>>> dar >>>>> ir kitur ateini pasišiukšlint. >>>>> >>>>> 2013.04.30 22:52, Signalizacija rašė: >>>>>> Nu maladiec, kad pacitavai kazkoki reklamini straipsniuka >>>>>> Klausykis savo lengvo ir ekonomisko stepro, ziurek lcd plastmasini >>>>>> vaizda, apsikabines gumine bobike :) >>>