Noise from a LM386N-1

[Fonny]

Evening all.
Wndering if anyone can help. I have a basic amplifier which I made from a
kit called a 'Super Snooper', distributed by Oatley Electronics in
Australia. It uses the LM386N-1 package to amplify minute noises via an
electret mic. It works fantastic and will even pick up the sound of my
watch ticking in the table next to it.
One problem. There is substantial hissing in the background. Is there any
way in which to reduce or eliminate this hissing? Another question. Is
there another amp chip, comparative to the LM386N-1 which will possible do
the same job, but with less noise. don't care if it costs more.
Thanks in advance to any replies
Rob Fonhof
Melbourne Australia

 

[Ban]

Fonny wrote:

Evening all.
Wndering if anyone can help. I have a basic amplifier which I made
from a kit called a 'Super Snooper', distributed by Oatley
Electronics in Australia. It uses the LM386N-1 package to amplify
minute noises via an electret mic. It works fantastic and will even
pick up the sound of my watch ticking in the table next to it.
One problem. There is substantial hissing in the background. Is
there any way in which to reduce or eliminate this hissing? Another
question. Is there another amp chip, comparative to the LM386N-1
which will possible do the same job, but with less noise. don't care
if it costs more. Thanks in advance to any replies
Rob Fonhof
Melbourne Australia

Rob, the main reason why you find this power amp inside the appliance is
certainly its low cost (0.19$). It will drive loudspeakers directly with up
to 1W power. Unfortunately the amp has a specialized pinout and can not be
replaced so easily with an ordinary opamp, even if you would use only
headphones and do not need the driving features. The bias scheme and the
gain adjustment have to be modified. Maybe when you post the circuit in ABSE
or elsewhere, somebody could be of more help.
--
ciao Ban
Bordighera, Italy

 

[Pooh Bear]

Fonny wrote:

Evening all.
Wndering if anyone can help. I have a basic amplifier which I made from a
kit called a 'Super Snooper', distributed by Oatley Electronics in
Australia. It uses the LM386N-1 package to amplify minute noises via an
electret mic. It works fantastic and will even pick up the sound of my
watch ticking in the table next to it.
One problem. There is substantial hissing in the background. Is there any
way in which to reduce or eliminate this hissing? Another question. Is
there another amp chip, comparative to the LM386N-1 which will possible do
the same job, but with less noise. don't care if it costs more.
Thanks in advance to any replies
Rob Fonhof
Melbourne Australia

Blimey ! I didn't think the LM386 was even still available ! It was fairly
rubbish when it was designed and is certainly no better now.

There's nothing that'll drop in to replace it.

Graham

 

[John Popelish]

Fonny wrote:

Evening all.
Wndering if anyone can help. I have a basic amplifier which I made from a
kit called a 'Super Snooper', distributed by Oatley Electronics in
Australia. It uses the LM386N-1 package to amplify minute noises via an
electret mic. It works fantastic and will even pick up the sound of my
watch ticking in the table next to it.
One problem. There is substantial hissing in the background. Is there any
way in which to reduce or eliminate this hissing? Another question. Is
there another amp chip, comparative to the LM386N-1 which will possible do
the same job, but with less noise. don't care if it costs more.

The only way I know to improve the noise performance is to lower the

gain of the LM386 and use a low noise opamp at the mic end to make
that gain back up. That way, by the time the signal reaches the LM386
and its considerable noise contribution, the signal is quite a bit
stronger, in comparison. But this would require a complete board
redesign or add on board.

 

[René]

On Sat, 7 May 2005 22:55:43 +1000, "Fonny" <Fonny@internet.com> wrote:

Evening all.
Wndering if anyone can help. I have a basic amplifier which I made from a
kit called a 'Super Snooper', distributed by Oatley Electronics in
Australia. It uses the LM386N-1 package to amplify minute noises via an
electret mic. It works fantastic and will even pick up the sound of my
watch ticking in the table next to it.
One problem. There is substantial hissing in the background. Is there any
way in which to reduce or eliminate this hissing? Another question. Is
there another amp chip, comparative to the LM386N-1 which will possible do
the same job, but with less noise. don't care if it costs more.
Thanks in advance to any replies
Rob Fonhof
Melbourne Australia

IIRC the std amplification (no feedback resistors added) is 20x - do
not ask more of it!
If adequate anti-oscillation ckt is added (the common 100n / 10 Ohm
network), I find the performance of ye olde amplifier (-1 type is 500
mW?) working adequate for simple tasks. Added amplification can be
added using a simple one transistor ckt as "frontend" (not always
opamps, 555's or Pics are required . Cleaning up the "frontend"
power with a RC ckt (560 Ohms, 220 uF or such) does help too.

--
- René