[Elecraft] K2 AF noise level?

[Darwin, Keith]

Hey 'Crafters,
 
I'm debating between the KAF2 or an outboard audio filter for my K2.
Possible choices are the SCAF-1 and an Autek QF1A.
 
My goal is to greatly reduce the hiss that is there in the headphones
when the narrow CW filters are engaged.  I'd also like to add some CW
selectivity.  A notch would be great too.
 
KAF2 has the benefit of being integrated into the rig but doesn't offer
lots of flexibility.  The others are external but give you more control
over the filtering.
 
How well does the KAF2 kill the hiss?  I assume it does great for that.
Does it add any noise back in?
 
- Keith KD1E -
- K2 5411 -