mmjuz píše:No jak myslíš....
No teda by mne fakt zajimalo, a) jakej mas zesik b) jestli jsi nekdy koukal na schema treba marshallskyho konce. Zkus se do nej podivat, predstavit si tekouci proudy a rict mi, kteryma soucastkama konkretne potece ten drastickej proud, pokud 2 ze 4 vyndas (a kde se tam vzal).
Ja uz jsem to Vobrstakovi rikal a psal, tak to ale radsi napisu i sem.
Pokud se bavime o tride AB, tedy napr. klasickym EL-34 konci (treba Marshall JMP), tak predpeti se privadi na mrizku koncovy lampy. Je to mekky zdroj, ale jelikoz na mrizce nepotrebujes zadnej extra proud, nehne se ti predpeti, i kdyz vyhazes lamp kolik chces (taky se to nazyva fixed bias - viz nize). Pak uz ti tam ale vlastne zbyva anodovy napeti, to je taky stejny, i kdyz jich vyndas hafo, no a zhaveni, to je taky porad stejny. V zesiku tridy A (Vox) je to jinak - tam mas proud definovanej jednim spolecnym katodovym odporem, pokud zmenis pocet lamp, hnes proudem ostatnima, takze tam pri zmene lamp musis hybat i hodnotou katodovyho odporu. Takhle ma treba prepinani 15W/30W udelany Matchless DC30, kdy pri prepnuti prepinace odpojis 2 lampy, ale soucasne zmenis hodnotu katodovyho odporu.
Takze zpatky k AB /treba JMP nebo Bugere/.
Pri vyndani 2 lamp a hrabnuti do strun ti bude hrat zesik trochu jinak, trochu se zmeni barva, ale ne moc dramaticky. To se da korigovat korekcema, je to v poho. Pokud bys chtel podobny frekvencni prubeh, jako predtim, muzes se na nej dostat zmenou vystupniho vinuti z trafa pomoci prepinace vyst. impedance. Podle mne to ale neni nutny, ten zvuk z 333-XL po vyndani dvou lamp se mi vic libi s ponechanim prepinace ve stejny poloze (odpovidajici ohmazi bedny).
Australan Rob Tognoni prepina impedanci na Bugere, ale on pouziva 6260 v crunch zvuku, tam uz ten dalsi narust vysek je asi zbytecnej.
Abys nemel pocit, ze si to tady taham z paty, tak jednak jsem to pouzival uz pred x lety na Marshallech, jednak mam mj. taky jednu Bugeru 333-xl, ktera to ma takhle rada a hraje na 2 flasky prijemne.
No a bylo by dobry vlozit nazor nekoho, kdo ma mezinarodni kredit, abys mne neosocil, ze si to taham z fusekle. Nevim, jestli znas zesiky Londonpower, je to velmi draha studiova zalezitost. Jejich tvurce, Kevin O'Connor je fakt machr nejvetsi. Urcite se tim prolouskas, kdyby neco nebylo jasny, tak rekni, prelozim. Takze Kevin ma tenhle nazor:
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Removing tubes from a multi-tube fixed-bias output stage is never a
problem. You can remove any number of tubes, and yes, that means you can
take one tube out of a two-tube amp; one, two, or three out of a four
tube stage, et cetera. This sounds heretical to techs stuck in the mire
of convention, but it is something that has been known since tubes were
invented.
The even-number tube extractions reduce power symmetrically. Neither the
tubes nor the transformer will be damaged. Power will be reduced and so
will frequency bandwidth - you will lose some bass and some treble. This
is the point that switching the impedance selector to a less-than-load
setting is supposed to correct, but it is completely subjective whether
you should. The only 'should' of the matter, is do I like it this way,
or do I like it that way?
In the end, you can pull tubes to reduce power, unless the amp is
cathode biased - then you have to split the bias resistor. In any case,
you do not have to worry about the impedance selector either.
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Proste mam pocit, ze tady uz v x-tym postu resime furt to samy dokola a uplne zbytecne.
Kdyztak se ale ptejte...