OK, The following were my actions.
- I unplugged all non-2 channel components (and all 2 channel components not related to streaming).
- Rerouted and further separated all cables
- Unattached TV cable
- Ran an ethernet across the room to ensure no interference
- Attached ferrite to power cords for conditioner
- Changed USB cable back to my old cable
- Disconnected my iFi DC Blocker+ from my preamp
Still got fluctuating frequencies at upper mid range
My next steps were to change speaker cables and bring my secondary speakers upstairs and try them.
Then I thought... listen without my hearing aids... suddenly the fluctuating frequencies were gone. My top of the line Signia hearing aids!! Also explains why it has always kinda been there. Have contacted my audiologist. Could be an expensive fix, but at least I got to the bottom of it.
Thank you everyone for you help and advise. @audphile1 The DAC may need to wait. If I need new HA’s, it will be $6K. I do like the LTA recommendation. As always, you provide excellent advise.
