problema nga talaga kapag di nasisira sis
Sa VAS stage ng amp mostly merong ceramic cap na nakakabit from base to collector ng transistor, it is there to protect the circuit from oscillation.
amps when driven hard or is fed with transients like mic having feedback or some cables breaking at some point tend to misbehave...some amps are able to recover quickly, but still some oscillate first, these oscillations can either be of the audible type if form of distortions or the sound become very harsh to the ear, or in the rf region, you can only look at them with the oscilloscopes...another symptom of this is some unexplained heating up of the amplifiers....just because you don't hear it doesn't mean it does not happen...that is why preventing your amps from clipping is a step in the right direction and a good practice...
most amps have led power indicators, use them, siguruhin na hindi sumasagad yung output level...maraming circuit na pang monitor ng clipping....one exapmle...http://sound.westhost.com/project23.htm
^yup, lamp nga yun at protection nga sa tweeter. sonic guard ang tawag ng peavey sa ganung protection scheme.
forgot to comment on this. those 5w/10w resistors most probably form a PAD or attenuator to match the sensitivities of the mid and hi drivers to that of the woofer. tweeters may have sensitivities at around 110dB@1w@1m while woofers maybe at around 98dB@1w@1m. without an attenuator on the tweeters, the sound would be "top" heavy, kaya nag-iinsert sila ng attenuator to match the equivalent sensitivity of the tweeter to that of the woofer.
^oscillation talaga ang tinutukoy ko.. kung yung amp ay hindi stable, yung transient sa pag-on ng mic ay pwedeng mag-initiate ng oscillations. very long unbalanced mic cables can cause a system to go into oscillation. kasi yung unbalanced mic cables mababa noise rejection nya unlike balanced mic cables. and those noise can trigger oscillations. likewise faulty/loose connectors. pag nag-oscillate yung system, hindi mo maririnig yung oscillations pero maririnig mo ang effect nito sa music/voice na lumalabas sa sound system mo. these are just what i experienced anyway, and i don't know if it is applicable on the case of sir 2010 insider.yes, may mga compensation caps sa vas stage ng amps, pero minsan sa mga DIY diagrams, binababaan nila ng husto yung value kung i-cocompare mo sa original na diagram. case in point would be the spec-2 clone in the other thread. andaming parts na magcocontribute sa stability ang tinanggal sa clone kung i-cocompare sa original diagram. in other cases din, binababaan nila yung value ng cap na nakaparallel sa feedback resistor to extend the hi-frequency response.i may be wrong though, and i am not an expert on amp design.
korak sir, sa mga diy mangayyari ang oscillation kase hindi sinsasama ang mga caps na maliliit sa pagkabit kase tumutunog at ok pa rin naman kahit wala ang mga yon. Perro kung alam mo ang purpose nun siguradong ikakakabit yon.I have 1 experience with very old sansui amplifier na pinarepair sa shop ko, flustrated na ang technician ko kase nagnormal na ang mga boltahe sa mga test point kaso ang output untiunting umiinit. Mga pinalitan na transistors ay iba na ang number sa original dahil di namin mahanap sa tindahan yong ganong number. Nung pinasa na sakin at inimbistigahan ko ang circuit design napansin kong walang caps sa VAS. nung nilagyan ko ng 100pf ayon nagnormal. So naiisip ko na ang rason bakit nagkaganun ay dahil sa mga pinalit naming transistors baka fake yong iba kaya nagoscillate sya.Thx nga pala kay sir tony sa knayang expluination about miller cap
pasend n rin po sa email q.. benedictoarwin@yahoo.com thanks po 70wats lang meron aq
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Topic: SMG 300 WATTS SCHEMATIC (Read 11816 times)
