[Elecraft] K3 Audio Low Pass Filter

[Brett Howard]

Its installed in the speaker outputs.  So it doesn't modify the
headphone circuits but I use it via speaker at home most of the time...
I should take a look and see if the headphone output had that 11-12khz
stuff on it...

~Brett

On Fri, 2009-07-03 at 18:21 -0600, Bob Cunnings wrote:
> 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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