LM 386 + PDA+ PS = Noise
Posted: Sun Apr 07, 2002 7:12 pm
Hi
Regarding my earlier post on fade in/out
I decided to Kiv that for a while.. So I
built a quick kit of an LM 386 amp and
I had the following problem<p>Power Source= Cigaratte lighter
LM386 board is powered direct from 12++ volts
in the car. Power is smoothed using a 1000UF
and a 10UF capacitor<p>I plugged the PDA headphone output into the
circuit, voice/sound works fine<p>However when I plugged the PDA into a PDA
12 volt to 5 vdc power adaptor, all hell breaks
loose on the LM386 board..noise of every type
came out of the small speaker.<p>How do I clean up the whole circuit? I use
shielded cables from the headphone jack to
the Lm386 board.<p>One of my frieds say the reason is I am
getting all kinds of feedback and that my
12 Vdc -5vcd adaptor is noisy.. The gain
of my amp is too high and thus, I am hearing
all the horrible sounds when the PDA is plugged
into the dc-dc power supply<p>I am using a standard lm386 circuit and I can
cut the gain down, I know, but how do you put
in preventive electronic parts to chop the noise?<p>Regds
Allan
Regarding my earlier post on fade in/out
I decided to Kiv that for a while.. So I
built a quick kit of an LM 386 amp and
I had the following problem<p>Power Source= Cigaratte lighter
LM386 board is powered direct from 12++ volts
in the car. Power is smoothed using a 1000UF
and a 10UF capacitor<p>I plugged the PDA headphone output into the
circuit, voice/sound works fine<p>However when I plugged the PDA into a PDA
12 volt to 5 vdc power adaptor, all hell breaks
loose on the LM386 board..noise of every type
came out of the small speaker.<p>How do I clean up the whole circuit? I use
shielded cables from the headphone jack to
the Lm386 board.<p>One of my frieds say the reason is I am
getting all kinds of feedback and that my
12 Vdc -5vcd adaptor is noisy.. The gain
of my amp is too high and thus, I am hearing
all the horrible sounds when the PDA is plugged
into the dc-dc power supply<p>I am using a standard lm386 circuit and I can
cut the gain down, I know, but how do you put
in preventive electronic parts to chop the noise?<p>Regds
Allan