Here's the advertising bravo sierra from the Idiom Press website:
"The new SCAF-1 filter from Idiom Press makes your radio listener friendly, whether you are an SSB or CW operator. Using a modern but little known technology called SCAF filtering, the SCAF-1 is an active audio low pass filter offering user control of the filter cut-off frequency, yielding a stunning 96dB per octave roll-off of signals above the cut off frequency, and no white noise. It is the perfect partner for your crystal or mechanical filters. And, unlike most audio filters, there is absolutely NO ringing."
So, if it is so-o-o-o-o freaking magnificent, why am I selling it? Well, I found a better, more expensive unit and this is spare to my needs.
Truth be told, the unit comes in a handsome case, performs great as advertised, and can clear up a lot of the CW (and SSB) "fog of war" on a busy day on the bands.
Asking $75 + $10 shipping by U.S.P.S. Priority. Accept PayPal, U.S.P.S. MO, or check (for the agreed-upon amount and shipping ONLY), if the latter, but must wait until check clears.