I'm back with an update.

I turned the lights off,
I put Ferrite beads on both ends of each related cable into or out of the interface and computer,
I have the power conditioner set & running properly,
I have the gain at noon on the preamp,
I created a Faraday Cage for the interface, (as best could be expected given cables in n out ), using a foiled lined freezer bag,
I turned the monitor screen off,
AND
I used a "terminated" XLR cable.

Net result a TINY drop in the level of the problem.
I tried to filter the noise out using ReaFir...
it takes a block at -108dB to filter out the sub hump and a block at -102dB to do the same for the peaks.
Those dB levels are according to ReaFir.

With those settings there's quite a bit of "noise" between the hump & peak when the line & HiZ buttons are engaged and quite a bit more when the 4K button is brought in...all expected as a matter of signal increase and colour (interesting to "SEE" the colour of the Heritage 4K thing...a low mid through to upper mid curve and harmonics after the peak). basically some EQ and distortion.
a) bass before Reafir
b) bass IN ReaFir &
c) bass post ReaFir

I filtered the noise from the guitar bus and the bass as they had the most pronounced readings - caused by the HiZ preamping the vocal wasn't as severely affected.

Attached Files (Click to download or enlarge) (Only available when you are logged in)
bass in ReaEQ before ReaFir.png (23.43 KB, 56 downloads)
bass in ReaFir.png (21.94 KB, 56 downloads)
bass in ReaEQ post ReaFir.png (23.11 KB, 56 downloads)
KATYASKAZAZhzC.mp3 (7.13 MB, 1 downloads)
Song with "noise" intact
KATYASKAZAZhzCfiltered.mp3 (7.13 MB, 1 downloads)
Song with noise "filtered"
Last edited by rayc; 09/19/21 01:54 AM.
Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe