Thank you all.
Thanks to your advice, I have finally succeeded in producing audio amplifiers. I attached my final circuit and it worked pretty well.
The output was loud enough to hear 5~10 meters away from amp.
I'm satisfied with this result. As you guys recommended, I bought
additional transistors(2n2222, 2n2907) and used them.
First, I put all of them instead of to92 series, but it worked poorly.
So I experimented all combinations of four transistors and found out
the best combinations of TR which works weell as in my circuit.
In addition, mic output was louder than I expected and it made
very horrible sound with high tone.(beep sound?) So I substituded
mic gain resistor 100k to 47k. Then beep sound(?) only occured at
maximum volume set. Why is the mic input have larger gain when I
make a wind(air?) in mouth like whisling than make an usual voice?
Is it related with frequency difference? Let me know how to analyze
overall gain and bandwidth of my circuit. What do you think of the important spectification for audio amp(eg.idle power, bandwidth)?
Thanks to your advice, I have finally succeeded in producing audio amplifiers. I attached my final circuit and it worked pretty well.
The output was loud enough to hear 5~10 meters away from amp.
I'm satisfied with this result. As you guys recommended, I bought
additional transistors(2n2222, 2n2907) and used them.
First, I put all of them instead of to92 series, but it worked poorly.
So I experimented all combinations of four transistors and found out
the best combinations of TR which works weell as in my circuit.
In addition, mic output was louder than I expected and it made
very horrible sound with high tone.(beep sound?) So I substituded
mic gain resistor 100k to 47k. Then beep sound(?) only occured at
maximum volume set. Why is the mic input have larger gain when I
make a wind(air?) in mouth like whisling than make an usual voice?
Is it related with frequency difference? Let me know how to analyze
overall gain and bandwidth of my circuit. What do you think of the important spectification for audio amp(eg.idle power, bandwidth)?
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Congratulations on a working prototype.
Some mikes are more sensitive at some frequencies than others, thus more output for a whistle input. My $2 mikes sound like **** but my $150 used KSM27 mikes have pretty flat frequency response.
Power amps without feedback as this design may have greater gain at one frequency than another. Whistle is about 1000 hz?
For amps I like harmonic distortion <0.4 % and power out >50 W so it can be louder than the vehicles driving by my house. I live 15 M from the street corner. I run 1/4 W average output but musical forte peaks can hit 50 W. My vacuum tube ST70 amp is rated at 1% HD and sounds a bit fuzzy. The Apex AX6 board I built sounds better, clean. Power bandwidth should be at least 40-14000 hz for high fidelity. Piano goes down to 40 hz as does 16' organ stop. 32' organ stop is 20 hz but most LP's don't have that on them. My ears stop at 14000 hz after completing Army service. Children can hear 20000 hz.
I can get better output transistors than 2n2222 out of junk televisions or CRT displays sitting on the curb on garbage day. Heat sinks, too. But I have a dirty work area in the garage where I can disassemble old stuff and discard the excess. That is the best way to get low Cob bjt >20 W driver transistors in the US. Every fast driver TO220 or TO126 transistor I've bought from distributors shipped as heat sinkless F package.
Some mikes are more sensitive at some frequencies than others, thus more output for a whistle input. My $2 mikes sound like **** but my $150 used KSM27 mikes have pretty flat frequency response.
Power amps without feedback as this design may have greater gain at one frequency than another. Whistle is about 1000 hz?
For amps I like harmonic distortion <0.4 % and power out >50 W so it can be louder than the vehicles driving by my house. I live 15 M from the street corner. I run 1/4 W average output but musical forte peaks can hit 50 W. My vacuum tube ST70 amp is rated at 1% HD and sounds a bit fuzzy. The Apex AX6 board I built sounds better, clean. Power bandwidth should be at least 40-14000 hz for high fidelity. Piano goes down to 40 hz as does 16' organ stop. 32' organ stop is 20 hz but most LP's don't have that on them. My ears stop at 14000 hz after completing Army service. Children can hear 20000 hz.
I can get better output transistors than 2n2222 out of junk televisions or CRT displays sitting on the curb on garbage day. Heat sinks, too. But I have a dirty work area in the garage where I can disassemble old stuff and discard the excess. That is the best way to get low Cob bjt >20 W driver transistors in the US. Every fast driver TO220 or TO126 transistor I've bought from distributors shipped as heat sinkless F package.
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