[Elecraft] Back to the KAF2

[Dale Boresz]

Wolf,

I can appreciate your feelings regarding the hiss, which is particularly 
noticeable when using high-quality headphones. However, there's a 
relatively easy way to restore the "KAF2 Sound" while retaining the 
utility of the KDSP2 module. I removed the components from the KAF2 
which make up the eliptical filter which is responsible for taming the 
hiss. Those components are: R11, R12, R13, L1, L2, and C1 - C4. I 
mounted the components in a 'dead bug' configuration (against the 
surface of a blank pc board with the component leads up in the air), and 
wired them together to duplicate the filter.

Since I didn't care about the turn-on thump, I removed the two FET's Q5 
and Q6 from the KDSP interface board (not the DSPx module, but the board 
into which it plugs), and used the pads to connect the filter as follows:
- the (S)ources are connected to the inputs of the filter (R11, and R12)
- the (D)rains are connected to the outputs of the filter (across R13)

That's it. It works great, and sounds just like the KAF2 when neither of 
the filters are selected.

Regarding the 'artifacts' of the DSP - welcome to DSP. I've never heard 
a DSP unit without those artifacts; they're just part of the package. I 
also have an ICOM 746PRO and the effects of the DSP are very similar 
sounding. I'll admit they're not necessarily pleasant, but the DSP can 
make the difference between some copy and no copy at times. I'll happily 
trade the significant reduction in noise for a bit of rhaspiness on the 
cw note. To me, under noisy band conditions, there is much less 
listening fatigue with the KDSP on, than with it off.

If you decide to try this and have any questions, I'll be happy to help 
however I can.

73,
Dale / wa8sra

Wolf-Ruediger Juergens wrote:

>Hello,
>After using the KDSP over the month i decided to remove the KDSP and plug 
>back the KAF2 in my K2. The always present noise (hiss) in the headphone 
>makes me angry. Also the artifacts with weak signals...
>
>73 Wolf, DL2WRJ
>  
>