Despre amplificatoare cu tuburi => discutii generale

[Усилитель]

Capacitors

In my younger days I used to think people who worried about capacitors were crazy, but in 1980 engineer Walt Jung along with Dick Marsh published the best articles I've seen to date about picking capacitors (read picking capacitors part 1 and picking capacitors part 2) where they explain exactly how and why some capacitors are much better than others.

Making a long story short, while electrolytic capacitors are superb for power supplies, their high dissipation factors and mysterious recovered voltage effects make them poor for coupling high-quality audio signals.

Most solid-state designs use electrolytic coupling capacitors because they are much smaller and much less expensive than good (film) capacitors in the values needed, typically 10 ~ 220 µF at 15V or less. Electrolytics like this sell for pennies apiece and are the size of pencil erasers, while film capacitors in these values sell for about ten dollars each and are about the size of a baseball — and there may be dozens in even the simplest amplifier.

Solid-state equipment usually uses polarized electrolytic capacitors to decouple DC, and that's bad. Not only are electrolytic capacitors far from optimum for coupling audio, they need a polarizing voltage which is usually absent in these designs. Most of these designs hope that no one notices, since the DC voltages aren't enough to blow up the capacitors when the DC voltages are backwards from what the capacitor needs, but it's still suboptimal.

In contrast, because of the much higher voltages and lower capacitance values needed, tube amplifiers almost always use much better film (or 50 years ago, paper) capacitors for audio coupling.

Tube amplifiers usually use coupling capacitors rated between only about 0.022 ~ 0.47 µF, but usually rated at 600 volts! Film (usually polyester or polypropylene and less commonly polycarbonate or Teflon) capacitors abound in these ranges.

Whether designers want to or not, the voltages and impedances involved usually sentence solid state designs to electrolytic capacitors, while tube amplifiers usually can use film capacitors.

As Jung and Marsh observed directly, for all they know, a big reason people may prefer tube amplifiers is precisely because they usually use much better capacitors for the audio signal path.

[daniels]

 

[sesebe]

1 oră în urmă, Усилитель a spus:

Capacitors

In my younger days I used to think people who worried about capacitors were crazy, but in 1980 engineer Walt Jung along with Dick Marsh published the best articles I've seen to date about picking capacitors (read picking capacitors part 1 and picking capacitors part 2) where they explain exactly how and why some capacitors are much better than others.

Making a long story short, while electrolytic capacitors are superb for power supplies, their high dissipation factors and mysterious recovered voltage effects make them poor for coupling high-quality audio signals.

Most solid-state designs use electrolytic coupling capacitors because they are much smaller and much less expensive than good (film) capacitors in the values needed, typically 10 ~ 220 µF at 15V or less. Electrolytics like this sell for pennies apiece and are the size of pencil erasers, while film capacitors in these values sell for about ten dollars each and are about the size of a baseball — and there may be dozens in even the simplest amplifier.

Solid-state equipment usually uses polarized electrolytic capacitors to decouple DC, and that's bad. Not only are electrolytic capacitors far from optimum for coupling audio, they need a polarizing voltage which is usually absent in these designs. Most of these designs hope that no one notices, since the DC voltages aren't enough to blow up the capacitors when the DC voltages are backwards from what the capacitor needs, but it's still suboptimal.

In contrast, because of the much higher voltages and lower capacitance values needed, tube amplifiers almost always use much better film (or 50 years ago, paper) capacitors for audio coupling.

Tube amplifiers usually use coupling capacitors rated between only about 0.022 ~ 0.47 µF, but usually rated at 600 volts! Film (usually polyester or polypropylene and less commonly polycarbonate or Teflon) capacitors abound in these ranges.

Whether designers want to or not, the voltages and impedances involved usually sentence solid state designs to electrolytic capacitors, while tube amplifiers usually can use film capacitors.

As Jung and Marsh observed directly, for all they know, a big reason people may prefer tube amplifiers is precisely because they usually use much better capacitors for the audio signal path.

Ți-ar prinde bine sa nu mai citești toate timpeniile de pe net. 

Stiu articolul. L-am citit și studiat acum citiva ani. Cea mai mare parte de acolo o reprezinta doar timpenii haudiofile sau generate de audiofilie. 

Editat Aprilie 15 de sesebe

[Усилитель]

Acum 48 minute, sesebe a spus:

Ți-ar prinde bine sa nu mai citești toate timpeniile de pe net. 

eu sunt prost si nu stiu care e tampenie si care nu.....

articolul nu prea inghite electroliticii ...pe unde merge semnal.......( decat in surse...) ....cred ca nici tu nu le pui in filtrele din boxe...

deci intre tranzistoare dece ar fi bune....? 

[Marian]

7 hours ago, Усилитель said:

a big reason people may prefer tube amplifiers is precisely because they usually use much better capacitors for the audio signal path.

Multa audiofilie aici 

[sesebe]

Am și electroliticii în filtrele de la boxe. 

Daca tu preferi sa ari cu 10 autoturisme înhămate la plug doar ca să nu folosești un tractor și preferi sa sapi gradina cu un briceag tocmai pt detaliile înflorate create de el în loc de o sapa, n-ai decit. 

Mai exista și oameni normali pe lumea asta nu doar sadomasokisty audiofili. 

[sonic11]

Iar divagatia cu condesatorii...dai in masa ca toti fac acelasi lucru.

Unde sunt capacitati mici se poate folosi polipropilena, stirofex.....etc, dar unde avem nevoie de zeci sau sute de microfarazi nu ne apucam sa plantam o padure de conzi polipropinena!?

 

[daniels]

Acum 13 minute, sonic11 a spus:

dar unde avem nevoie de zeci sau sute de microfarazi nu ne apucam sa plantam o padure de conzi polipropinena!?

sunt cei pt pornire motor, f buni in filtre.

[Ovidanie]

Totusi, pentru semnal audio, cel mai nefavorabil mod in care poate lucra un electrolitic: cu semnal mic si lipsa polarizarii.
 

[sonic11]

Acum 34 minute, daniels a spus:

sunt cei pt pornire motor, f buni in filtre.

Unii au greturi cand aud de asa ceva...

Apoi si aia sunt de doua feluri, electrolitici si uscati

Eu nu as pune doar din considerente de estetica treaba o fac cu succes.

Editat Aprilie 16 de sonic11

[ionut120v]

Acum exista cu polipropilena de care doriti,  cel din margine are 50 uF la 500v doua din alea sunt in ghargerul solar unul la intrare si altul la iesire, personal nu am electrolitici pe forta in sistemul solar  si voi va plangeti ca nu aveti ce pune in audio, cele ceramice nu sunt bune pentru audio deorece au fenomenul de electrostictiune, vibreaza in camp electric variabil.

Electroliticii imbatrinesc repede si au dispersie mare a rezistentei.

 

Pentru amplificatoare DC coupled este nevoie doar de 2 condensatori pe semnal unul in bucla de reactie si unul la intrare de valori relativ mici 1-2 micro.

Editat Aprilie 17 de ionut120v