[Elecraft] K3 Audio Low Pass Filter

[Brett Howard]

Not sure as I don't have a schematic...  Somewhere I wrote down the amp
that was used....  I'm sure that we could ask for it I just hadn't
gotten around to it.  It is an active filter though...

~Brett

On Sat, 2009-07-04 at 17:35 -0400, Gregg W6IZT wrote:
> What are the values of the components for filter?
> 
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Mike Scott
> Sent: Saturday, July 04, 2009 1:21 PM
> To: Elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K3 Audio Low Pass Filter
> 
> >G'day,
> >What about - how did it perform?
> >...does it in any way respond to the "pink" vs. "white" noise thread of a
> few weeks ago.
> >Mike VP8NO
> 
> Mike,
> I am still evaluating but I believe the LP filter took the harshness out of
> my audio. I had been one of people with a complaint about harsh audio and so
> far I like it. I seem to have distortion products above the intended audio
> passband that this filter cuts out. That extra stuff made it fatiguing for
> me; other people don't hear it. I understand that some people can be
> fatigued by odd order harmonic distortion even when the distortion is way
> down.
> 
> I am not set up to compare with another radio and I can't do an A-B test as
> the filter is hardwired in. I plan to live with this set up for a while and
> maybe put in larger coupling caps to bring up the audio warmth. Perhaps I
> will replace with 100 uF SMD devices like the current production caps.
> 
> The filter is a 4th order Chebyshev low pass filter with a -6dB shoulder
> somewhere around 4.5 KHz judging by looking at a plot. It is flat below 3.2
> KHz and low ripple, so, nothing to do with pink noise. Maybe Wayne will get
> around to putting a pink noise filter into the DSP.
> 
> I am experimenting with the following Rx EQ settings from another post to
> simulate a pink noise filter:
> 1 +0
> 2 +8
> 3 +2
> 4 -1
> 5 -1
> 6 -3
> 7 -5
> 8 -10
> 
> 
> 
> Mike Scott - AE6WA
> Tarzana, CA (DM04 / near LA)
> NAQCC 3535
> K3-100 #508 / KX1  #1311
> 
> 
> 
> 
> 
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