I did the upgrade by swapping out boards.
My recall = The major change was the addition of a low pass filter to eliminate a “leak through” of the D to A clock.
At the time, there were complaints by several users that there was a high frequency noise in the K3 that was tiring when using the K3 for long periods.
Also improved the low freq response of the audio – don’t remember the complaint.
As a pilot & motorcyclist of more than 40 years, my hearing at high frequencies is limited; so I did not see a significant difference between the 2 DSP boards. If I had been in my 20s or 30s, I probably would have noticed the change.
When I went to work at that age, I would hear the TV monitors 15 kHz singing until a bit into my shift when I became accustomed to the sound.
I would recommend contacting Elecraft service to determine if the upgrade is worth the cost.
73 George AI4VZ
I think the enhancements were audio related. If you have no complaints, it may not be worth it.
From what I remember, comments have been a mixed bag.
I have an older K3, s/n 1312 (10/2008), and I'm thinking about purchasing the K3DSPUPGD, trying to find out if it's worth it or not. wondering if I will notice a change in the receiver performance or audio. Having a hard time finding reviews on that enhancement. Your input is appreciated.