Hello,
I just build a LM4780 amplifier, using the reference PCB from national.com. The sad thing is that it goes into oscillation after 30-60 seconds after powering it on. Sometimes even faster with the source in. The oscillation occurs with source in or without it.
The only thing I changed from the difference layout were the Ci1 and Ci1, because I was unable to find 68uF, I used 47uF, but I don't think this is the problem.
Any advices are appreciated.
I just build a LM4780 amplifier, using the reference PCB from national.com. The sad thing is that it goes into oscillation after 30-60 seconds after powering it on. Sometimes even faster with the source in. The oscillation occurs with source in or without it.
The only thing I changed from the difference layout were the Ci1 and Ci1, because I was unable to find 68uF, I used 47uF, but I don't think this is the problem.
Any advices are appreciated.
How do you know it's oscillating? Is it low frequency (motorboating) or high?
The 47uF shouldn't make a significant difference. If it's a reference design (is it the one in the datasheet?) the chances are you've built it wrong. If this is the case it can be very hard to find your error, you check it and check it but you don't see it.
w
The 47uF shouldn't make a significant difference. If it's a reference design (is it the one in the datasheet?) the chances are you've built it wrong. If this is the case it can be very hard to find your error, you check it and check it but you don't see it.
w
here's the sound:
http://www.swooms.com/doc/oscillation.wma
So you are telling me the reference design is wrong ? To be honest, I used press and peel, but it wasn't that good, so I have to aid it with a marker. If it's the PCB to blame, I will post pictures soon.
This makes me very sad, first time I tried using a strip-board, and it was a failure. This is the second attempt...
http://www.swooms.com/doc/oscillation.wma
So you are telling me the reference design is wrong ? To be honest, I used press and peel, but it wasn't that good, so I have to aid it with a marker. If it's the PCB to blame, I will post pictures soon.
This makes me very sad, first time I tried using a strip-board, and it was a failure. This is the second attempt...
so, after I changed the resistor, the amp works ok, .... 
)) maybe wonderful is the right word, I just love how it sounds. And I am using some not so good Sony speakers (can't wait to change the tweeters) but still it sounds wonderful.
Yesterday I spent many hours with making the case. It lacks the upper part and left, but I have some perforated metal, and I will install it soon. Here are the pictures:
LM4780_AMPLIFIER
I also have to paint it, or cover with some textile don't know
)) maybe wonderful is the right word, I just love how it sounds. And I am using some not so good Sony speakers (can't wait to change the tweeters) but still it sounds wonderful. Yesterday I spent many hours with making the case. It lacks the upper part and left, but I have some perforated metal, and I will install it soon. Here are the pictures:
LM4780_AMPLIFIER
I also have to paint it, or cover with some textile don't know
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