When I put my 897D in narrow CW mode (with the Collins 300Hz filter), it sounds like the gain is way too high somewhere. Noise in the passband sounds clipped and rumbly, and the received signal has a lot of harmonics in it. It sounds like something is loose inside the chassis and rattling with a loud signal, but it's the same with headphones or any external speaker.
With the 2.3k SSB filter, things sound great. I do not hear any evidence of overdrive.
I can improve the audio by turning RF gain -way- down until the signal is almost gone, but then I lose the ability to pull signals out of the mud because the background noise is still everywhere. Right now the filter performs nowhere near as well as my DX-70 with the cheap ceramic filter when it comes to working weak stations.
Does anyone have a schematic or any experience with this situation? I am thinking there's a gain adjustment somewhere that's out of control. Or maybe the filter itself is no good. I've had the latter for years and never really thought much of it but I've been working with the rig more lately and it's starting to become annoying.