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zbrujic

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  1. Melvin Van Peebles (August 21, 1932 – September 22, 2021).
  2. Šteta je da ovaj tekst ne bude i kod nas na forumu (sa v-engine): It's wintertime again and we are seeing many threads on issues with static so I decided to re-post a blog entry I wrote on the subject (with some updates). Most old timers here know this info and have their own methods of dealing with things, but I thought I'd throw my $0.02 in (again) for the sake of discussion:Where does static charge come from?All matter is made of atoms. Atoms have a nucleus of positive change surrounded by electrons with negative charge. Loosely held electrons can transfer from one material to another, creating materials with opposite net charges. The ability of a material to surrender its electrons or absorb excess electrons is a function of its conductivity. Good conductors like copper have a rigid molecular construction that doesn’t allow its electrons to move about freely. Non-conductive materials (insulators) like plastics and glass ceramics are easily disrupted and take on a charge with minimal friction, heat, or pressure. Some materials tend to give up electrons and become positively charged while others tend to collect electrons and become negatively charged. The comparative tendency of a material to charge positive or negative is represented in the “Triboelectric Series”. If you look up one of these charts, you will see PVC and related polymers like to take on a negative charge. So when a vinyl record becomes in contact with, then is separated from, a material like a paper sleeve, it can become negatively charged. Without getting into physics and Coulomb’s Law, suffice it to say that nature likes to balance charges so positively charged particles like dust are attracted to this negatively charged insulator. Hence, you end up with a dirty record with non-structural audible deficiencies.How does one minimize static issues?Handling is very important.* The surface area of contact, pressure, and speed of separation affect the amount of charge transferred. Hence, it is recommended that records are removed slowly from sleeves and sleeves of a neutral insulating material (polyethylene or polypropylene but NOT PVC) are used. Sometimes these sleeves contain or are treated with antistatic agents (discussed below).One can also increase the charge on a record chemically, by using the wrong cleaning agent (a negatively charged detergent or acid for example). This is why most preservationists (e.g. Library of Congress) recommend non-ionic detergents for cleaning records and frown upon SDS/SLS containing dish soaps which leave negative charges behind. How a record is dried after rinsing can also have an effect. Wiping with a cloth can transfer charge for example.Simply putting a charged vinyl record on a grounded turntable will not dissipate the charge. The record (a PVC-PVA copolymer) is non-conductive, which is why it holds a static charge. So one option to reduce static charge is to make the record more conductive. Formulators of vinyl compositions have included various compounds in their mixes to deal with charges. For example, carbon blacks are included that help evenly distribute the charges. Positively charged antistat compounds have also been added to vinyl mixes and become incorporated into the pressed record. While these compounds can help with normal handling, there is a limit to how much charge they can neutralize. Furthermore, negatively charged compounds are produced when the vinyl is subjected to heat, UV light, and air pollution. PVC breakdown is autocatalytic: the products (mainly HCl) promote further breakdown (and negatively charged compounds). The vinyl formulations include scavengers and stabilizers to help with this (without them, hot pressing of vinyl would not be feasible) but again, they can become exhausted over time. Hence, additional measures are often necessary to reduce charge build-up on a vinyl record.Water can be conductive so a well humidified room works to help balance charges within a space. It also reduces the risk of electrostatic discharges (ESD) that can damage equipment.**One can also rinse their “charged up” records with water, which efficiently dissipates the charge. Unfortunately, the best rinses leave no audible residue so distilled or deionized water is required. As the conductivity of water is directly related to the amount of ions in solution, these types of water preparations have no lasting effect after the record is dried.One can wipe the record surface with something conductive. This is how most antistatic brushes work as carbon fiber is electrically conductive. Hair is on the positive side of the Tribolelectric series so some recommend natural (e.g. horsehair) fiber brushes. Some brushes contain radioisotopes (mainly Polonium 210) that emit alpha particles (positively charged helium atoms) that ionize oxygen and nitrogen atoms in air to balance charges. Polonium brushes aren’t cheap and they need to be replaced annually as the isotope decays but in the right hands they can be effective. High voltage ionizers like the handheld Zerostat or desktop emitter devices work similarly through air, but can be difficult to get consistent results in practice or are rather cumbersome. Either way, brushes and ionizers are transient solutions since they only balance charges on the record at that very moment: the method often needs to be repeated after the record contacts and is separated from another surface (e.g, each time it is taken out and played).For a longer-lasting, inexpensive solution, one can treat records with an antistat, in a manner similar to what is done in industrial settings (hospitals, electronic parts manufacturers, flammable liquid handling facilities, etc.) for treating hard surfaces. These solutions have been adapted for home use in products like antistatic sprays, fabric softeners, and hair conditioners. The most common ingredients are quaternary ammonium compounds (“quats”). Typically these are in the form of surfactants containing the positively charged ammonium head group with long carbon chain “tails”. Many commercially sold antistatic record cleaners, groove lubricants, and record conditioners consist of these compounds. Antistatic sprays or sheets made for other household purposes are not recommended for use on vinyl as they can contain additional chemicals that can leave residues or damage your records (e.g. oils or solvent propellents). They are useful for treating carpets, furniture, and cables within the listening space however. You can also easily and cheaply make your own quat antistat solution and there are threads describing this (I adapted the use of Hepastat 256, for example). The quats balance charge and like most detergents, even after rinsing, some molecules are left behind on the surface (presumably via hydrophobic interactions with the carbon tail). This molecular layer is thought to trap water molecules and make the surface more conductive. They also reduce friction as the stylus moves across the record (which is why quats are included in “groove lubricants”). Most quat surfactants have antimicrobial properties, which is another useful property in record cleaning. When used properly, the quats do not form a residue or have any audible effect. In fact, according to patent filings, they have been included as antistats in proprietary vinyl formulations for years. They are also frequently incorporated in “anti-static record sleeves”.So there really is no excuse to live with excessive static charge on vinyl records. They can be handled, treated, and stored in ways that practically eliminate the issue and allow for a more enjoyable playback experience. Happy, noise free, listening!*Side note 1: One can measure surface charge with an electrostatic voltmeter. These are routinely used in the printing industry (I got mine from a friend at Xerox). The highest readings I often observe are from brand new records. Clearly there are few static control measures employed in the production/packaging plants.**Side note 2: Most of the electrostatic discharge shocks you feel (like when rubbing across a carpet and touching a doorknob) are in the 3000-5000V range. No wonder ESD is such an issue in industrial settings.
  3. Posle dugo vremena - izdanje iz ovog veka
  4. зато што промена висине ручице због промене VTA ефективно резултира променом ефективне дужине Uh! Preteruješ. Očekivano
  5. Slutio sam da mi nema radija bez spoljne antene
  6. Verujem ja vama, pričali su mi i drugi da im je u kolima dab značajno bolji od fm-a, ali kod mene u sobi to zaista nije slučaj. Malopre otkrih i da jedan od ovih mojih tranzistora ima info displej i na njemu stvarno piše 64kbps za RBg3.
  7. Probao sam u međuvremenu dva DAB radio-aparata sa sopstvenim teleskopskim antenama. U oba slučaja maksimum "jačine" signala koji postižem je oko 2 od 3 "linije". Šuma nema, a ni prekida. Međutim, ovo što čujem na Radio Beogradu 2/3 je izuzetno zatvorenog zvuka i jadne dinamike. Nešto poput "neambicioznog" MP3-ja. Svakako mnogo lošije od FM signala (koji, na žalost, ima dosta šuma). Može da posluži samo za govorne emisije. Istina, jeftini su to aparati, koristim phones izlaz... Ali, isti aparat značajno bolje zvuči preko FMa. Zna li se, u kakvom kvalitetu se emituje taj DAB+ signal iz Beograda? Edit: Je li moguće, nalazim na nekom forumu, da je samo 64kbps?
  8. Jon Hassell https://www.theguardian.com/music/2021/jun/27/jon-hassell-avant-garde-us-composer-dies-aged-84
  9. Još od pre više od godinu dana (možda i dve) imam taj problem s juno-om i master karticom (intesa). Bez rešenja. Banka ne "vidi" da je bilo ikakvog pokušaja transakcije.
  10. Koristim Cyrus, ali ne i njegovu phono sekciju. Ali, to s glasnoćom jako zavisi od konkretne ploče. Ovde je, konkretno, bio problem u kratkotrajnim peak-ovima. Sam "osećaj" glasnoće možda i ne mora biti "podignut". (Ostaje i pitanje da li bi pri ripovanju bilo dobro trażiti neki kompromis i pristati na izvesnu meru clippinga, kako bi se dobio koji db glasnoće snimka) Ima, pak, ploča koje i u tim peak-ovima ne idu iznad, možda, +3db. A da li će gram biti glasniji od CDa zavisi i od proizvoda phono gaina i izlaznog napona zvučnice, a oba faktora variraju od setupa do setupa. Kad sam ovde... Kada, npr. Ortofon kaže da je izlazni napon za 1kHz 0.5mV pri 5cm/s, na šta se konkretno misli? Naiđoh na nečiju tvrdnju da, mislim da je za Denon zvučnice govorio (tvrdi da to Denon ima negde napisano), da je reč o lateralnoj kretnji, dakle mono. To bi onda značilo da je "kanalna" brzina 3.54m/s. Dalje, jesu li te brzine "rms"? Verujem da jesu (možda pogrešno). Ako jesu, onda imamo 5cm/s maks kanalnu brzinu. I dalje je malo u odnosu na standardne nivoe glasnoće. DIN standard po horizontali ima valjda 8cm/s rms (ćak 11.3 u maximumu). Evo ga još koji decibel glasnoće Je li neko naleteo na neki sajt gde je ovo autorittivno objašnjeno?
  11. E, da je samo Tascam. Ne naiđoh ni na jednu zvučnu kartu kod koje to nije problem. Ploče znaju biti preglasne u peakovima: http://www.audiomisc.co.uk/HFN/LP2/Gallery.html Usput, uspeo sam večeras da ripujem najglasniju ploču preko ulaza (u miksetu) kod kojeg je, izgleda, max input level čak +30dbu.
  12. Znao sam da to "balanced" mora da ima neke veze i da ono što ceo život znam kao "stereo jack" ovde to nije. Znači, ništa od ripa ni s ovim Tascamom. Ipak, ostaje saznanje da bi trebalo tražiti nešto s max input nivoom od preko, recimo, 5-6Vrms. Mislim da imam još jednu igračku s kojom bih mogao da probam...
  13. Tek sam se ovih dana pokušao pozabaviti ripovanjem preko tog linijskog ulaza na Tascamu. Ispostavilo se da sam pogrešno rekao da imam Tascam "US 2x2". Trebalo je "US 1x2", ali, prema specifikacijama (ovde) ovo ne pravi razliku. Na "IN 2" ulazu (6.3mm jack), kad je preklopnik na "Line", trebalo bi da imam to "zasićenje" na 7.75V. Iz Phono-out sam signal doveo u taj Line In. Stereo jack, 6.3mm (to je, valjda, ono TRS); zapravo adapter 3.5-6.3mm. Međutim, na laptopu dobijam samo desni kanal, čak i kad svičujem kanale. Probao sam i drugi "3.5-6.3" adapter - isto. Je li ja pogrešno shvatam da je taj ulaz stereo? Interesantno je i da kada u softveru tog Tascama postavim "Mono input", dobijam na laptopu i levi kanal, ali su dva kanala ista (mono). Postoji li neko razumno objašnjenje za ovo? Ima li veze s onim "balanced" iz specifikacija? I, da, sudeći prema nivoima tog jednog kanala, na ovom ulazu je moguće izbeći clipping (korišćenjem potenciometra za taj ulaz).
  14. Baš to malopre dogovorih, jednu takvu probu (neki dab "tranzistor" s built-in teleskopskom antenom ).
  15. Prvo da vidim da li kupovati dab tuner
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