I need an Audio Detective

Try a different antenna.

@jr96aolcom

This is one of those situations that will drive many audio-enthusiasts crazy. It really depends on how much work you want to put into this. You could simply keep the DAC off (along with all LED lighting) while listening to your tuners. That would be the easiest solution here.

Or, you could unplug all audio interconnect cables from the DAC (with the unit powered ON), and see if that makes a difference, and report back your findings. It’s very possible you *might* be able to reduce this RFI using ferrite on some of the DAC cables (which ones will need to be determined). One tuner (the Magnum) might be more sensitive to this RFI vs your other tuners.

Hmmm, an audio-enthusiast that still values OTA (over the air) FM listening. I'm impressed. 

Love my tuners got into in a big way a few years ago

Magnum Dynalab MD108t SE

Mcintosh MR71 fully restoted

Mcintosh MR 78 with RM mods

Tandberg 3001 A

@jr96aolcom

For over 25 years I was Chief Engineer of a number of both FM and AM radio stations. I was always on the hunt for a tuner that provided to me at home (to monitor the audio quality of the FM station’s I engineered) the same performance of our station’s modulation monitors (which sample RF directly from the station’s transmitter output - no multipath of any sort is introduced). I found that one day in the Yamaha T-85 (I also owned a MR 78 at one point in time). If you’ve never tried one...

I was actually able to confirm the audio performance of the T-85 by installing a few (at different transmitter sites), and hooking them up to an A-B audio switch (A being the station’s modulation monitors, and B being the T-85). With audio levels matched, I could easily switch back and forth between the two, and the T-85 always sounded almost exactly like the modulation monitors. Just in case you were interested.

One last thing; for outdoor FM antenna reception, many times I used lower loss Belden 9292 (RG-11) over various RG-6 cables. It’s harder to terminate (as RG-11 connectors require a special crimping tool), but can help with fringe reception.

Belden 9292

@erik_squires 

Erik has it right, disregard my first post.