Hi Guys,
I have built a non-inv amp (LM3886), the issue is that I forgot to place a resistor from the non inverting input to ground. It worked but was really noise and the output was at a 35V potential(same as power supply Voltage). No mater what I did I couldn't figure out what was wrong specially with the very loud hum. Then I placed a 22k res. there and all is good!! no dc at all on the output.
what is the purpose of this resistor?
Now its very quiet but get a bit hot for my taste even at rest, I have a 3inch x4inch aluminum plate a a heatsink. Would this be normal?
Please reply with any thoughts at all.
Thank you very much in advance for yoru time.
God bless.
I have built a non-inv amp (LM3886), the issue is that I forgot to place a resistor from the non inverting input to ground. It worked but was really noise and the output was at a 35V potential(same as power supply Voltage). No mater what I did I couldn't figure out what was wrong specially with the very loud hum. Then I placed a 22k res. there and all is good!! no dc at all on the output.
what is the purpose of this resistor?
Now its very quiet but get a bit hot for my taste even at rest, I have a 3inch x4inch aluminum plate a a heatsink. Would this be normal?
Please reply with any thoughts at all.
Thank you very much in advance for yoru time.
God bless.
avenger said:
No experience with the 3886 but every 3875 I've built got hot even at low volumes during the first 10 hours or so. For whatever reason, after that "break in time" they all cooled off and operated at a much lower temp. Can't explain why but since it has happened over and over again I guess it is real.
Maybe something similar with the 3886?
wow, great,
at least mine is not the first to do that.
You had mentioned the oscilation, I will take a look with the scope, but what should it look like? what should I look out for?
Actually I think its oscilating because just now it was making a scrachy noise with the audio and it was a lot different than before and the temp. started to increase alot..I had to shut it off for a few minutes.
Thank you in advance.
Sim, eu sou portugues e vivo nos EUA. sou natural de Ponta Delgada, ilha de Sao Miguel nos Acores.
Continuacao de uma boa noite.
at least mine is not the first to do that.
You had mentioned the oscilation, I will take a look with the scope, but what should it look like? what should I look out for?
Actually I think its oscilating because just now it was making a scrachy noise with the audio and it was a lot different than before and the temp. started to increase alot..I had to shut it off for a few minutes.
Thank you in advance.
Sim, eu sou portugues e vivo nos EUA. sou natural de Ponta Delgada, ilha de Sao Miguel nos Acores.
Continuacao de uma boa noite.
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