I don't think I have ever seen a dsp noise filter that had a setting 
specifically for AM.

Even if one did, it would still tinker with the bandwidth of your 
receiver audio in one or more frequency ranges, just is it does with 
SSB, since that's part of how it limits noise in the first place.

The higher the DSP filter level setting, the more narrow the 
bandwidth. You keep increasing the DSP level to the point where you 
hear audio that sounds no better than, and usually worse than, audio 
from a cell phone.


If you can do it, try to borrow one for a test before you buy one. 
Although external DSP filters have been around for at least nearly 20 
years now, they don't appear to be getting any cheaper.






Mike Duke, K5XU
American Council of Blind Radio Amateurs