I had planned to add the KAF2 after building my K2 in 2000. Then I happened to hear a K2 with one installed and was not impressed. Later it dawned on me why: my high-frequency hearing is already compromised, thanks to spending a lot of time firing weapons in the military (soldiers don't wear ear protectors). I had a "built in" filter to attenuate high frequencies, Hi!
Later I had a chance to work with the Elecraft AF1 "mini-module" outboard audio filter. The AF1 includes an analog low pass filter with a variable cut-off point to attenuate the higher frequencies, and it has a separate, analog, active, tunable "peaking" filter. I use that frequently with the K2. The active "peaking" filter in the AF1 does the same thing as the APF in the K3, frequently pulling signals near or below the noise level up into the clear. Indeed, using them side by side it's hard to tell performance of the AF1 peaking filter apart from the APF. I guess that's a complement to the APF, since the APF strives to replicate in DSP a filter like the AF1 peaking filter. The AF1 is an extra little box on the operating table but I find it a valuable addition to the K2 for copying CW. Ron AC7AC -----Original Message----- The KAF2 has a very nice low pass filter in it. It removes essentially all hiss, and just sounds nice. I don't find the rest of the filter to be very effective. The DSP is very effective, but lacks the hiss reducing low pass filter. There is a solution to this. Think about it. I built the KAF2 low pass filter onto my DSP board. Best of both worlds. 73, Fred - kt5x K2 # 0700 K3 # 0144 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
