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Hi Samratsarkar,
I take the liberty to answer your question 😉
Gain does not depend on the rails voltage, it depends on the feedback divider's ratio. Referring to the schematic in post #2884:
Gain = R14 / R15 + 1 = 47K / 1K + 1 = 48
Gain(db) = 20 * log (Gain) = 20 * log (48) = 33.6 db
Cheers,
Valery
Hello friends, Finally I Test SR20, it sing 🎤. In First run bias 14mv, dc offset +/-1mv. Power feeding with +/-42v DC. With this setting I play music 🎶 2houre. Sound is nice and warm. In second run bias stable but DC offset shuffling on +2 to 2.5 mv (not more then 3 mv). Is it ok?
In both time O/P transistors little hot, but pair of BD139 is little hot compare of BD139/140. Any issue with that?
One more thing, Is SR20 need pro if yes which protector we use. Sorry Mr. Miles for throwing some questions 😃😂😂.
Regards
Gurpreet
In both time O/P transistors little hot, but pair of BD139 is little hot compare of BD139/140. Any issue with that?
One more thing, Is SR20 need pro if yes which protector we use. Sorry Mr. Miles for throwing some questions 😃😂😂.
Regards
Gurpreet
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Thanks Mr.Miles for FX100 PSU.But Today I m busy with second channel of SR20 DC offset 4-8mv. One time its go on 15mv. Is it ok.
Second issue with pair of BD139 and TIP147 more hot compare of TIP142 in both channels. Why ?
Can I use heat sink for both BD Transistors.
Above thing are normally Rise in mind
Because Discussion on SR20 - nothing. Sorry for selection on (may be ) words.
Regards
Gurpreet
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Sir without any input signal its 14-15mv.
With input signal its shuffling. Its going to 80-110mv. I m little confused with shuffling because no idea about biasing amplifiers. Now I m thinking about a small heat sink with pair of bd139, and bd139/140. Is that safe.
Regards
Gurpreet
thank you apexaudio but the volume of the source change the bias and as newbie I don't know which volume to use.
first put input of an amplifier to nearest Gnd point (to assure that input voltage is zero V) and than adjust bias. when you adjust it,connect input signal, disconnect voltmeter from an amplifier and listen what have you made, enjoy the sound.
During install heat sinks on BD's some resistance are burnt and a capacitor pop up( mark with red in blow pic.) on one board. After replaced faulted components bias stable but DC OFFSET SHUFFLING 10-20mv. Other measured volts also stable like
2.3v across capacitor 220nf,
.65 across resistance 68ohm
.58 across resistance 120ohm.
One more thing these results are with open and short input with GND
With bias 10mv and series with 100w bulb.
If we bias set on 15mv after some music played on full volume bulb little bright then bias checked its 100mv its going down too slow. Speaker 8ohm well work, 4ohm put stress on amp and bias get very hot immediately.
Any advice plz. .
Regards
Gurpreet
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