I believe there was a firmware update. The FT-DX-3K can hit 4.2kHz if EQ'ed correctly, but the low end end suffers by dropping like a rock at 100Hz. If Yaesu allows for extended low-end response [to 40Hz] the DX-3K would really have an improved sound.
this might help you of course set you BPF to at least 3.0 then all these setting depends on your mic and your voiceif you have a deep voice you might have to notch the lows from 100 to 200 but here they are
menu 159-100
162-10
165-3
160-700
163- (-3)
166- 7
161-3200
164- 10
167-2
this might help you or you can use a starting point on Bob Heil's sight go to dsp settings and he has some settings for alot of rigs ,hope this help's
1. Make sure power is off.
2. Find the CS and TXW buttons just left of the Freq Dial.
3. Push and hold "CS" and "TXW" buttons in while powering the radio via the "ON/OFF" switch.
4. Select Menu# 104 and see that "TTBF" has replaced 3000WB.
5. If you wish to go back to 3000WB just do steps 1 to 4.
Guru anything I have this mod on my Ftdx1200 and process incoming audio with Waves), transmits in 4 KH smoothly Argentina greetings ... the end of the world !!!!