If you are going QRP there are now much lower ambient current devices than
the LM386 -- secondly, if you go to Texas Instruments website you can
download their FilterPro software -- you can program gain and Q into the
devices. Analog Devices also has some good interactive filter design
software.

Jack

"SpamHog" wrote in message
om...
I would like to build a minimalistic
AF chain for small HF receivers,
that would limit the audio passband
to either 300-2800 Hz or 700-900 Hz.

The LM386 audio amplifier has a tempting inverting input.
Did anyone try to design it into a 1-device
audio filter + power amplifier?

I looked around, pored over the applications sheet,
but found no examples.

I did this playing with TAA611's many years ago. Then I did find
rather clear indications on how to lower the high frequency cutoff -
but nothing similar with the LM386.

Any hints?

Or,
why isn't this done
as a matter of course,
as I
perhaps mistakenly
think it should?


73 de n1jpr/i2

http://filippo.ru.ru
http://webfools.net/filippo/desert-ratt.html