[Elecraft] K3 Audio Response - Version 3.33 Firmware

[Steve Ellington]

I've just been listening all evening with a big smile on my face :*)  This 
is beautiful. Having the LF audio seems to make the entire spectrum sound 
better. Even QRN is more pleasant to listen to. Thanks Elecraft! What took 
so long? Why was bass chopped off in the first place?

Steve
N4LQ
N4LQ at carolina.rr.com
----- Original Message ----- 
From: "Paul Christensen" <w9ac at arrl.net>
To: <elecraft at mailman.qth.net>
Sent: Friday, September 18, 2009 10:40 PM
Subject: [Elecraft] K3 Audio Response - Version 3.33 Firmware


>I have attached links to three .JPG images of the K3's audio response as
> measured at
> the headphone jack with SpectraPlus FFT software.  Response passband was
> normalized for both modes.  SSB
> is measured through the 6K filter, and CW through the 8-pole 2.8 kHz 
> filter.
> However, V3.33 SSB was taken with Fc = 1.35.
>
> It would have made more sense to capture the responses such that three SSB
> plots would overlay on one graph and three CW plots on a second, but that
> took too much time in waiting for the firmware to load between plots.
> Still,  you can see radical differences between firmware versions in the
> kinks below.  Rx Band-1 EQ seems operational now too :-)).
>
> http://216.229.20.37/images/K3-V325.jpg
> http://216.229.20.37/images/K3-V330.jpg
> http://216.229.20.37/images/K3-V333.jpg
>
> As you can see, CW with V3.25 has the strongest low-end response relative 
> to
> 1 kHz, but that can be compensated for with the first two EQ bands.  Even 
> as
> it is, if you draw a horizontal line mid-way through the V3.33 plots, that
> represents roughly +/- 2.5 dB from 20 Hz through 3.5 kHz.  Not too shabby
> for a
> communications receiver.
>
> As a further experiment, I just added 3 dB to Rx bands 1-3 and the 
> response
> is now essentially +/- 0dB between 20Hz and 3.5 kHz in SSB through the 6K
> filter and Fc = 1.35.  You can lay the ruler flat on the response.
>
> http://216.229.20.37/images/K3-V333-EQ.jpg
>
> Paul, W9AC
>
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