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#1
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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 |
#2
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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 |
#3
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I've got just the LM-386 circuit for you, with graphs. Email me direct
and I'll send you a scan. cheers skipp025 at yahoo.com : SpamHog wrote: : 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 |
#4
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Thank you Jack!
If you are going QRP there are now much lower ambient current devices than the LM386 Any specific device you would suggest? Texas Instruments / Analog Devices I'm heading there! BR + 73 Filippo |
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