K3 audio filter board

[Mike Scott-7]

In the past I complained about harsh receiver audio characteristics similar
to some of the audio characteristics being posted recently. It got to the
point that I stopped operating as the listener fatigue was so apparent. The
effect seemed to be most apparent at CW filter bandwidths. I am apparently
sensitive to something that was present, either high frequency trash or 3rd
harmonic distortion. I have external rat shack book shelf speakers.

If you google audio fatigue you will eventually find that with some people
even a tiny bit of 3rd order harmonic distortion can cause audio fatigue, 60
or 70 dB down.

I have installed a beta version audio frequency low pass filter. It involved
cutting two traces and soldering in a very small board that contains two SMT
low pass filters for the two audio channels. The new board matches up with
appropriate tie points on the DSP board (I think it was DSP anyway) for
power, ground, two input and two output channels. I had to clear out some
vias that were supposed to be solder-free but which were not on my K3.
Except for clearing the vias the modification was straight forward. I should
have remembered that a stainless steel needle pushed into a via after
melting the solder with a soldering iron is the magic trick.

The K3 became a different radio after the modification that I am quite
pleased with. One of the problems we have is that no one who works at K3 can
apparently hear the problem, thus no hurry or they think we are crazy.

Mike Scott - AE6WA
Tarzana, CA (DM04 / near LA)
NAQCC 3535
K3-100 #508 / KX1  #1311


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[pd0psb]

The K3 became a different radio after the modification that I am quite
pleased with. One of the problems we have is that no one who works at K3 can
apparently hear the problem, thus no hurry or they think we are crazy.


Mike,

The problem is that meanwhile there is a lot of mix-up going on between hamradio and "hifi" enthusiasm. I've always seperated those but some don't. A lot of hamshacks are now filled with (semi) pro audio gear that is used for 10db s/nr SSB channels :-)

Because of this mix-up it is hard for Elecraft to seperate *serious* audio flaws from complaints about K3's not sounding like studio recordings.

The LPF board works wonderful in clearing out the last artifacts from DA conversion (and I think should become a regular upgrade) In the hamradio SDR/AD-DA era we encounter the same problems as in the first consumer digital audio products. This will clear out over time ;-)
The K3 has room for those improvements where other radios are "fixed" by current knowledge...

73'
Paul
PD0PSB