Sipi

Svojevremeno je vise ljudi kupilo ovakve hladnjake pa ako je nekom pretekao jedan komad (ili tri) voljan sam da ga/ih kupim.

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Ko ovo prouci nece vise imati problema sa brujanjem/zujanjem - stvarno je kvalitetno dokumentovano i objasnjeno, sve varijante su pokrivene.

Link :
http://www.audiosyst...com/publish.htm

sekcija :
Hum, Buzz, and RF Interference

Sadrzaj:
Audio Interfacing for Non-Audio Professionals This is the Power Point for part of a tutorial workshop I presented to the 2005 IEEE-EMC Symposium. It includes Bill Whitlock's groundbreaking work on balanced interfaces, and shows why when a cable shield is connected only at one end to prevent shield current, the connection point should always be at the sending end.
Pin 1 Revisited Neil Muncy called our attention to the Pin 1 problem (the improper termination of the shield of audio wiring to the circuit board rather than to the shielding enclosure) in his classic 1994 paper, reprinted in the June 1995 Journal of the AES. When he wrote his paper, most commercially available audio gear had pin 1 problems. It was, indeed, difficult to find equipment without it -- even the most prestigeous consoles had serious pin 1 problems! Over the next decade, the better manufacturers redesigned their products to correct their mistake, but sadly, many have not done so. This is the first installment of a two-part article published in the SynAudCon Newsletter.
Pin 1 Revisited -- Part 2 This is the second installment of a two-part article published in the SynAudCon Newsletter.
Shield-Current-Induced Noise - Part 1 Current flowing on the shield of balanced audio cables will be converted to differential mode voltage on the signal pair by imperfections in cable construction. This is Part One of a series about this matter that I wrote for the SynAudCon Newsletter.
Shield-Current-Induced Noise - Part 2 This is Part Two of a two-part article published in the SynAudCon Newsletter. It also includes recommendations for the termination of audio cables.
Power and Grounding For Audio and Audio/Video Systems -- A White Paper for the Real World This White Paper was commissioned by New Frontier Electronics (the SurgeX people) so they would have something to pass out to contractors and other users of their excellent power products.
RF Susceptibility of Condenser Microphones Many modern condenser microphones have problems in the presence of strong VHF and UHF transmitters, like FM and TV broadcast stations, 2-way radios, and cell phones. This is an article published in the SynAudCon Newsletter. You can download a much longer and more detailed AES paper that David Josephson and I wrote in 2003 from the AES website.
Understanding How Ferrites Can Prevent and Eliminate RF Interference to Audio Systems This applications note has been significantly revised and expanded since its first posting earlier this year. Even if you've read the earlier version, you should get this one. It has also been turned into an AES Paper for the New York convention in October 2005.
The Effects of Cable on Signal Quality I first studied the loading of output stages of microphones and line level equipment by cable capacitance in 1988. On the basis of that work, I wrote this applications paper for Sound and Video Contractor in 1990.
Termination, Impedance Matching, and the Maximum Power Transfer Theorem in Audio Systems This Tech Topic is the first writing I did for SynAudCon, back in 1982. Back then, folks were slapping 600 ohm resistors on everything that sat still long enough, and this was my contribution to giving the practice a decent burial. Like the special technique that scares away elephants, It appears to have been at least partially successful -- when's the last time you saw a 600 ohm resistor (or an elephant)? There's also some nice tutorial material here on how transformers and passive equalizers work.

Posto filmove uglavnom pustam sa laptopa a analogni audio izlaz daje jedva par stotina mV javila mi se potreba za preamp-om koji ce da ima pojacanje od oko 5 puta, sa niskom izlaznom (oko 25 Oma, ukljucujuci i R9/R20) i visokom ulaznom impedansom (oko 200k) da ne zvuci naporno i da ne idem do prodavnice po delove. Medjutim, rezultat je ispao mnogo bolji nego sto sam se nadao (sije AD797 lako, a to nije lako) pa ga zato i objavljujem. Kao i obicno, na zvucni karakter uticaj ima izbor spreznih kondenzatora, ja sam koristio Siemens stack-foil i Vishay MKP X2 - na izlazu je bolja WIMA MKP10 ali nisam imao pri ruci veci od 2u2. U opstim crtama, zvuk je tacan, definisan, a nezan bez brljanja.

Topologija je krajnje jednostavna - naponski pojacavac sa zajednickim emiterom (snazno degenerisan) plus izlazni buffer (emitor folover sa Ic=10mA). Na bazi Q1 je nnesto manje od 4V a na kolektoru oko 15-16V. Preamp je jako brz pa sam mu limitirao band (R8, C4) na oko 2MHz (-3dB). Pojacanje je 5 V/V sa R1=270R odn. 3V/V sa R1=470R (nije potrebno nista drugo menjati ako R1 ostane u tom opsegu vrednosti). Upotrebljiv swing na izlazu je oko 7-8V peak sto je recimo, skoro dvostruko vise od napona potrebnog da se F5 potera na punu snagu. Tranzistori Q1-Q4 mogu biti i BC550C ali je vazno da budu "C" varijanta (hfe oko 500 - od toga zavisi radna tacka i ulazna impedansa)

Za napajanje je uzet vec poznati shunt reg. na 32V. Kroz Q6 tece oko 65mA, preamp trosi oko 20mA po kanalu.

Evo je sema i slike prototipa :

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Link:
http://www.diyaudio....tml#post2501579

Covek prodaje punu kutiju, sasvim solidni elektroliti i jako jeftino ih daje - koliko nas ima zainteresovanih i imamo li nacina da platimo (PayPal) ?

Sve cesce se @ ("At" sign) koristi u medjusobnom obracanju kroz forumsku komunikaciju na pogresan nacin.

Znak @ predstavlja predlog engleskog jezika "at" i znaci ka, na, u tj. odredjuje usmerenost neke akcije.

Pravilno:
@Radojica:
molim te reci mi....

Nepravilno:
Kao sto je rekao @Radojica....

Dovoljno je samo: Kao sto je rekao Radojica....

@ ispred nick-a stavljamo samo da bi oznacili kome je poruka koju pisemo upucena.