Help with audio amplifier

B

Brian

Guest
I bought a Radio Shack mini amplifier (277-1008) to learn about what makes
them tick. Mainly because it's such a simply amplifier. I've written down
all the components and was about to order a duplicate set to build an amp
from scratch, but wanted to ask a quick question before I did that.

When I turn the amp on, there's always an amount of static. What are some
ways to improve the sound quality? The amp IC that it uses is the 386D:

http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=
224207

Thanks for any help!
 
When I turn the amp on, there's always an amount of static. What are some
ways to improve the sound quality? The amp IC that it uses is the 386D:
Click to expand...
If that's the little handheld amplifier I think it is, I've tinkered with it
a few times...

1) That static you hear when you turn on the unit is likely due to a dirty
volume pot. Dust gets inside it and causes this.

2) The "386D" is just a plain old LM386 audio amplifier. These are very
plentiful. It can be configured in a variety of ways to get more or less
gain.

3) The only downside to this little amp is, the tiny speaker doesn't offer
much bandwidth. It has practically no bass at all. There's also no power
indicator, and I added an LED so I wouldn't accidentally leave the amp on
and drain the battery.

Matt J. McCullar, KJ5BA
Arlington, TX
 
Thanks for the help, Matt. I noticed that the traces were terribly dirty
and scraped up when I opened it up. If I continue to hear static, is
there anything else you would suggest to diagnose what is wrong?



"Matt J. McCullar" <mccullar@flash.net> wrote in
news:WGgmc.14705$Dc1.3151@newssvr31.news.prodigy.com:

When I turn the amp on, there's always an amount of static. What are
some ways to improve the sound quality? The amp IC that it uses is
the 386D:

If that's the little handheld amplifier I think it is, I've tinkered
with it a few times...

1) That static you hear when you turn on the unit is likely due to a
dirty volume pot. Dust gets inside it and causes this.

2) The "386D" is just a plain old LM386 audio amplifier. These are
very plentiful. It can be configured in a variety of ways to get more
or less gain.

3) The only downside to this little amp is, the tiny speaker doesn't
offer much bandwidth. It has practically no bass at all. There's
also no power indicator, and I added an LED so I wouldn't accidentally
leave the amp on and drain the battery.

Matt J. McCullar, KJ5BA
Arlington, TX
Click to expand...
 
The LM-386 is considered rather noisy by many... since it's audio
bandwidth is full range. You can add some tone controls to the circuit
that will tame down the hf noise and hiss you hear.

Radio Shack used to sell a neat pc board kit for the LM-386, which showed
the frequency responce and how specific parts would modify the frequency
response. If you were really serious about working with the 386, I can
scan and Email you a copy. Drop me a note through the radiowrench web
page if you want to reach me.

cheers

skipp

www.radiowrench.com


: Brian <ThisIsNotMyReal@ddress.com> wrote:
: I bought a Radio Shack mini amplifier (277-1008) to learn about what makes
: them tick. Mainly because it's such a simply amplifier. I've written down
: all the components and was about to order a duplicate set to build an amp
: from scratch, but wanted to ask a quick question before I did that.

: When I turn the amp on, there's always an amount of static. What are some
: ways to improve the sound quality? The amp IC that it uses is the 386D:

: http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=
: 224207

: Thanks for any help!
 
Skipp, sent you an email a couple of days ago to the nospam4me address on
your website. It was the only one I could find.


Skipp is from radiowrench dot com <gospamsomeoneelse@yahoo.com> wrote in
news:c7eho5$g0d$1@woodrow.ucdavis.edu:

The LM-386 is considered rather noisy by many... since it's audio
bandwidth is full range. You can add some tone controls to the circuit
that will tame down the hf noise and hiss you hear.

Radio Shack used to sell a neat pc board kit for the LM-386, which
showed the frequency responce and how specific parts would modify the
frequency response. If you were really serious about working with the
386, I can scan and Email you a copy. Drop me a note through the
radiowrench web page if you want to reach me.

cheers

skipp

www.radiowrench.com
Click to expand...
 
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