Still no luck in resolving my "squeal".
So far, I have removed C113 across pins 1 and 8 of the LM386 in order to
reduce it's gain. Big improvement to audio, at least to my ears.
The "squeal" at low audio levels existed before I removed C113 and
persists after removal.
I have now tried three different 10K pots - the two that were included
with the kit and a third new 10K pot (linear taper).
I have now tried three different small speakers, two are 4 ohm and the
third is marked 8 ohm.
And for good measure, combinations of these different 10K pots and
speakers.
All of this to no avail - I still get a "squeal" i.e. oscillation at
very low volume level for about five degrees or so of pot rotation from
full counter clockwise position turning clockwise to a higher volume
setting.
The "squeal" i.e. oscillation, disappears once the control has been
turned past this very low volume setting.
I am using a good quality HP / Agilent lab power supply and have tried
another with the same reuslts.
Still at a loss. There is something I don't quite understand about the
why of this behaviour. I guess it's back to basics and to prototype the
circuit to see if I can replicate the behaviour and if so then what I
need to fix it.
News at 11.....
cheers, Graham ve3gtc
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On 3/27/2017, "Michael Davis" <maddmd818@...> wrote:
I was going to mention speaker impedance. Mine did oscillate with a 4 ohm speaker, but not 8 ohm. I believe you said that there was no oscillation before removing the capacitor. Try adding an 8-16 ohm resistor in series with the speaker, or try a 16 ohm speaker, to see if the circuit change somehow affected what the audio amplifier load will be happy with.
Sent from Mike's iPad WA1MAD
