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2. Texnologia kartwn hxoy

Se ayto to tmhma dinetai mia basikh perigrafh ths texnologias toy chfiakou hxoy, me skopo na boh8hsei sthn katanohsh twn ennoiwn poy 8a xrhsimopoih8oun parakatw sto keimeno. Gia kapoion poy 8elei na ma8ei perissotera, kalo 8a htan na symboyleytei ena biblio gia chfiako hxo h chfiakh epejergasia shmatos.

O hxos einai analogikos, mporei dhladh na labei opoiadhpote timh se mia synexh klimaka. Oi ypologistes einai chfiakoi, doyleuoyn dhladh me diakrites times. Oi kartes hxoy xrhsimopoioun mia syskeyh gnwsth ws Metatropeas Analogikou Shmatos se Yhfiako Shma (Analog to Digital Converter (A/D h ADC)) gia na metatrepei ta plath (voltages) ths analogikhs hxhtikhs kymatomorfhs se chfiakes h ari8mhtikes times, oi opoies mporoun na apo8hkeytoun sth mnhmh. Paromoia, enas Metatropeas Yhfiakou Shmatos se Analogiko (D/A h DAC) metatrepei ari8mhtikes times se analogikh tash h opoia me th seira ths odhgei ena megafwno, paragontas hxo.

H diadikasia ths metatrophs toy analogikou shmatos se chfiako, gnwsth ws deigmatolhcia, eisagei kapoio sfalma. Duo paragontes ka8orizoyn poso kala to deigmatolhpthmeno shma antiproswpeuei to arxiko. O ry8mos deigmatolhcias einai o ari8mos twn deigmatwn poy phrame ana monada xronoy (synh8ws ekfrazetai se deigmata ana deyterolepto h Hertz). Enas xamhlos ry8mos deigmatolhcias antiproswpeuei me ligoterh akribeia to analogiko shma. Euros deigmatolhcias einai to euros twn timwn poy xrhsimopoieitai gia na antiproswpeuei ka8e deigma, syxna ekfrazetai se bits. Oso megalutero einai to euros deigmatolhcias, toso akribestero 8a einai to chfiako shma.

Oi kartes hxoy xrhsimopoioun synh8ws euros 8 h 16 bit deigmatwn me ry8mous deigmatolhcias apo 4000 mexri 44,000 deigmata to deyterolepto. Ta deigmata ayta mporoun na periexoyn ena kanali (mono) h duo (stereo). Sun8esh FM (FM Synthesis) einai mia palioterh texnikh gia paragwgh hxoy. Basizetai sto syndyasmo diaforetikwn kymatomorfwn (p.x hmitonikh, triangle, square). H FM synthesis einai aplousterh sthn ylopoihsh se hardware apo ton D/A metatropea, alla einai pio duskolh ston programmatismo ths kai ligotero eyelikth. Polles kartes hxoy parexoyn FM synthesis gia logoys symbatothtas me palioteres kartes kai logismiko. Dinontai synh8ws epishs kai polles anejarthtes gennhtries hxoy h fwnhs.

H sun8esh me bash pinakes kymatomorfwn (Wavetable Synthesis) syndyazei thn eyelijia toy metatropea D/A me thn ikanothta pollaplwn kanaliwn ths FM synthesis. Me ayto to sxhma oi chfiopoihmenes fwnes mporoun na apo8hkeuontai se eidika afierwmenh mnhmh, kai na paizontai, na syndyazontai, kai na metaballontai me mikrh epibarynsh ths CPU. Oi kartes hxoy teleytaias texnologias yposthrizoyn oles wavetable synthesis. Oi perissoteres kartes hxoy parexoyn th dynatothta gia mijh (mixing), syndyasmo shmatwn apo diaforetikes phges eisodoy ka8ws kai elegxo ths sta8mhs enisxyshs twn shmatwn (gain levels). MIDI einai ta arxika toy Musical Instrument Digital Interface, to opoio einai ena ka8ierwmeno prwtokollo toso hardware oso kai software gia na epitrepei thn metaju twn moysikwn organwn epikoinwnia. Ta shmata poy stelnontai se ena MIDI kanali (bus) mporoun na apo8hkeytoun san MIDI arxeia gia th metepeita epejergasia (editing) kai anaparagwgh (playback). Polles kartes hxoy parexoyn MIDI interface. Aytes poy de dinoyn, mporoun na paizoyn MIDI arxeia xrhsimopoiwntas tis on-board dynatothtes ths kartas hxoy. Ta MOD arxeia einai ena koino format gia tragoudia poy syn8etontai se ypologisth. Ta arxeia ayta periexoyn plhrofories gia tis notes poy 8a paixtoun ka8ws kai chfiopoihmena deigmata twn organwn (h fwnwn). Ta MOD arxeia prohl8an apo ta computers Amiga, alla paizoyn me to katallhlo logismiko kai se alla leitoyrgika, symperilambanomenoy toy Linux.


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