Hi, cspiegs,
I don’t know anything about using a DBX expander but reading the manual it seems like a sophisticated tone control. You may be able to reduce the volume level of the frequencies associated with "noise" but you’re also reducing the output of music within that same frequency range. Not sure about the DNF 1201A either; it does look interesting but there’s probably a reason why you don’t see this type of gear sold anymore. The only true (optimal) vinyl noise reduction system that I’m aware of is the Sweet Vinyl SugarCube, but it’s a spendy piece of gear.
I’m not sure that records inherently have a lot of noise because of how they’re recorded; at least not the records I listen to. You didn’t mention if the noisiest records were purchased used or have had a fair amount of record play; perhaps with a lower quality tonearm and cartridge or before you began cleaning them with an RCM? Groove wear is permanent so once damaged will always sound damaged. Just throwing out possibilities.
I found that using a Herbie’s Way Excellent platter mat with my Music Hall turntables (Pro-Ject tonearms) helped to reduce background noise. That and certain cartridges can either highlight or downplay groove noise, especially cartridges with a micro-line stylus, which tend to trace sections of the groove that haven’t been abraded as much. The drawback with a micro-linear stylus is that it may take a bit more finesse in setup to get it tracking right. And it’s not a universal solution for worn, noisy records.
The other thing to consider is the phono preamp you’re using. Certain preamps can highlight the frequencies and dynamic contrasts associated with groove noise. While the phono stage in your Yamaha integrated may be fine, that amp appears to be designed more for home theater than vinyl playback. Vinyl was all but forgotten when that amp was popular. If you have a way to compare your phono preamp to another phono preamp you might find a different phono stage helps to reduce background noise. Speculation only.
Other than the Herbie’s mat I don’t have a definite solution to reducing groove noise, just a few things to consider. Perhaps someone with direct experience with your DBX expander, 2M blue cartridge, and Yamaha amp will chime in.
Regards,
Tom