I just finished building this
I left the number 1 and 8 pins open. I also am using an audio output transformer on the input side of the amp Sometimes there is a high pitched squeal coming out of the speakers and sometimes it is quiet. Anyone know what the noise is or how to fix it? Thanks Richard
Squealing in a LM386 circuit means either that you’re driving in too much current, or your speaker ohms are not what you think they are.
And I’m scared that I knew that off the top of my head. Been a long time since I used those brain cells.
Thanks Bob
I have a 9 volt battery to power the amp, but will probably use 12 volt to power it when I’m done.
I’m trying to decide between a 4 ohm and 8 ohm speaker.
If I use 12 volt to power the amp I will use a 8 ohm speaker.
I think you should not tie pin 1 to pin 8 directly. This is used for wave generation. use a cap to control gain.
Go to national.com for the spec and examples on the LM386 usage.
Richard Eberwein said:;)
I left the number 1 and 8 pins open.
Dan I did tie pins 1 and 8 together ( no caps no resistors), and it made a world of difference in the volume. I found the cause of the squeal. After twisting the battery wires the squeal went away. Here is a picture of the amp and a parts list:
(http://farm7.staticflickr.com/6055/6403595869_aa08b9988c_z.jpg)
1 Audio transformer… RS#273-1380—2.69 1 LM 386----------------RS#276-1731—1.69 1 Retention contact----RS#276-1995— .59 2 47uf capacitors…RS#272-1027…2.98 … $7.98
