audioguru, question on preamp/amp

[crivoli]

Question 1:
I built the circuit on the LM386 datasheet with the amp at a gain = 20. Everything works fine.
I then adjusted the gain to 50 and it works correctly.
When I adjust the gain to 200 the speaker just squeals horribly.
I have built this circuit before and used a gain of 200 with no problems. Any idea of what I could be doing wrong?

    LM386 datasheet: http://cache.national.com/ds/LM/LM386.pdf

Queation 2:
I hooked up a preamp circuit using a LM741 and send the output to the amp I built with the LM386. Needless to say the output to the speaker is very bad quality.
Is there anything special I need to do with the output of the preamp before it goes to the input of the audio amp?

I have attached the LM741 preamp schematic

Thanks all
-newb

View attachment 39039

 

[audioguru2]

Hi Crivoli,
An amplifier has positive feedback squealing when it has a microphone that can hear its speaker. Turn down the volume, reduce the gain or separate them.

An amplifier (especially with a very low power output like an LM386) produces very bad quality when its output clips because its volume or gain is too high.

You don't show parts values for your preamp.
You don't show a pretty big (1000uF) supply bypass capacitor.
The preamp doesn't have a volume control so it might be clipping.
What is the input from?

 

[trigger]

Also need to take precaution on the input capacitor, as it will affect the input signal.

 

[crivoli]

i believe I solved this problem with your help... Thanks a ton.

I seperated the mic and speaker and I also changed somve values of what I was using.

Please check my other post on a "Simple AM receiver"

Thanks again.