[Elecraft] K3 Audio Low Pass Filter

[Bob Cunnings]

What is the point of insertion (in terms of the schematic) for this filter?

Bob NW8L

On Fri, Jul 3, 2009 at 6:09 PM, Brett Howard<brett at livecomputers.com> wrote:
> Its a low pass filter starting around 3.8Khz or so.  I have some before
> and after plots.  I just need to get around to posting them so I can put
> them up on the reflector.
>
> On Fri, 2009-07-03 at 19:45 -0400, Mike Harris wrote:
>> G'day,
>>
>> | All in all I'm quite pleased with the sound difference.
>> |
>> | ~Brett
>>
>> OK, that's couple of positive comments.  Is there any technical data on
>> the characteristics of this filter.  For example, does it in any way
>> respond to the "pink" vs. "white" noise thread of a few weeks ago.
>>
>> I've become rather more interested in this since reactivating my K2 and
>> running it side by side with the K3.  The K2 sounds so much nicer even in
>> the presence of a received S3 buzzy background noise.  If only the K2
>> power overshoot on 40M SSB didn't give my amp a hard time...
>>
>> Now to put this in context, there was a huge improvement in the K2 as soon
>> as I installed the analogue af CW filter years ago.  In SSB mode the
>> filter just introduces a low pass filter which takes the hiss out of the
>> audio and made it really smooth to listen to.
>>
>> I have played with the DSP bandwidth settings and replicated the K2 af
>> spectrum as displayed in Spectrogram to see if I can make them sound the
>> same but they don't.
>>
>> My agc and equalizer settings are nothing unusual or extreme.
>>
>> Regards,
>>
>> Mike VP8NO
>> K2 #1400
>> K3 #345
>>
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