[Elecraft] [K3] K3 Rev C +AF filter

[Eric Tichansky]

Julian, G4ILO wrote:
> I don't see what purpose an audio filter board would serve, given that we
> have a crystal filter followed by DSP filtering and then RX equalization
> already. Any high frequencies that can get past that lot must be at a pretty
> low level already.
>
>   

At least from my perspective and hearing, this LPF module would knock 
down and eliminate the 12 kHz related beat notes noticeable on CW.  
Otherwise, I've had to drag around outboard audio filters + cabling, 
etc. anytime I take the K3s anywhere to guest OP.  I could have opted 
for a passive filter and bastardized my headphones, but chose a pair of 
AF-1 active filters until Elecraft had an "official" fix for the 
problem.  Therefore, the LPF module is not just an audiophile 
enhancement, but hopefully a resolution to a real problem, at least for 
those that have high frequency and sensitive hearing.

- no3m