Bob Brown (N1CVX) posed an interesting question in his entry in my site's visitors' book. He wrote: "Would be especially interested in hearing some of your observations regarding the K3 vs. K2. Like you, I have both - but find myself lately gravitating back to the K2. Among other things, the audio seems 'cleaner' (the noise level seems lower), and the push-button crystal filters are simply easier to use. And, of course, the receive power requirements aren't really in the same ballpark (K2 clearly wins there). Though I feel like I should like the K3 more, I find myself reaching for the K2 ever more. Perhaps, I simply haven't figured out the K3 (one difference: running with AGC off in the K3 significantly reduces noise - and if the RF gain is at about 12 o'clock, I've not yet seen the K3 overload; K2 AGC off is a bit trickier in my experience)."
I'm not really the guy to ask about running with the AGC off. I'm not one of those people who tries to work someone down in the noise right next to someone else who is 40 over 9. I just tune around and try to work what I can hear. I did try turning the AGC off once and hurt my ears, so I turned it back on again and never repeated the experiment.
However, unlike Bob I have never felt the urge to revert to using my K2. I find the K3 audio cleaner and crisper. I put that down to the flatter (and wider, in the case of SSB) filters. I also find the razor-sharp selectivity of the K3 better in CW and digimodes to the gentler slopes of the K2's filters. I should point out that I have never had the opportunity to try the K2 DSP module. My K2 has the original analog audio filters, but I rarely used them.
The K2 certainly uses less energy on receive than the K3, but I'm not too bothered about it, and the K3 is still more efficient than many of its oriental competitors. As for the ease of use of the filters, I prefer the K3's rotary Shift and Width controls to the K2's buttons, that forced you to cycle through three different bandwidths when you wanted to go back one.
Perhaps there is something in the suggestion that the K3 sounds noisy when receiving a lot of signals at once, like at the sharp end of a pileup. There is an interesting thread on the Elecraft reflector right now in which some people have described the K3 audio when receiving a number of signals of similar strength as sounding like "a sea of mush". I haven't heard it myself, but I wonder if this - as well as Bob's observations - is the difference between digital and analog? It sounds reminiscent of the arguments that audiophiles had when CDs started to become popular. They were sure they could hear detail in a vinyl recording that was inaudible in the CD equivalent.