KX1 speaker output with superimposed oscillation
Posted by
wb2srf on
Sep 04, 2007; 6:52pm
URL: http://elecraft.85.s1.nabble.com/KX1-speaker-output-with-superimposed-oscillation-tp452289.html
Hi Paco,
Sorry to read that it did not work for you.
LM386 amplifiers can do strange things when over driven. There is a lot
of available gain.
If the amplifier is operating properly, the Idle DC voltage with no audio
signal on the output pin 5 should be half of the DC voltage measured on
the power supply pin 4 if not you may have a leaky coupling capacitor on
the input circuit or a bad IC internal circuit throwing off the bias.
I have also found at times from building my own equipment that a de
coupling capacitor with short leads is needed across the power supply
pins 4 and 6 to keep it stable at high output levels especially if the
impedance of the power supply is not low enough. I use a 10uF tantalum
capacitor when connecting it is very important to observe the correct
polarity.
Also the RC network connected between the output pin 5 and ground is
required to keep the amplifier stable at high frequencies at different
loads.
GL 73,
Bob Johansen WB2SRF
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