You are using the wrong type of cable. You need a TRS to TRS cable. The cable you are using is sending a line level signal from the mono out to a mic level input on the Focusrite and overloading the input on the Focusrite.
Does the same thing happen if you use headphones? Are you using direct monitoring (the control nearest you)? Is input 1 working as expected? If so then it looks like you have a faulty U-44.
Not total hogwash. The big issue with the Neumann capsule copies is the tensioning and consistency. According to David Josephson, Neumann's tensioning method is a closely guarded secret and, certainly when he made those comments, the Chinese capsules often sounded nothing like the Neumann ones...
Do you have Intel graphics in your system as well as Nvidia? I had a few odd graphics glitches until I set my default graphics adaptor to the Intel one instead of the Nvidia one.
To my ears, Sennheiser HD600s sound close enough to the Tannoys to allow me to make similar mixing decisions on either. The Sony 7506s have a reputation for sounding very bright - some people like them but they don't sound like Tannoys.
As I understand it, once he's got it configured, it doesn't need to be connected to a computer again so the disappearance of Firewire doesn't matter. That's how I use my Focusrite Saffire Pro26io these days.
Audio interfaces have had built-in DSP since the days of the Turtle Beach Multisound in the early 1990s. Not all of them, of course, but a significant number have DSP in the interface.
I would have to say that some amps do have a sound. Unfortunately the first amp that we used the NS10s with in the studio, a Teac AX75 had a slightly bright sound that made the NS10s sound even worse than they really were. The amp and speakers came as part of a recording package from Thatched...
I think the sound of a Scully or Studer might actually be too subtle for most people wanting analogue "warmth". A Portastudio comes much closer to the sound of tape that people who've never used decent tape machines expect.
The best thing to do would be to stripe one of the tape tracks with timecode and then feed that timecode to Reaper so that the drums play in Reaper while your other tracks play from the Portastudio. If you want the tape sound on the drums then I would record the drums in stereo (or even 3...
I've transferred some mixes recorded at RAK. There were 8 versions of one song as far as I remember which would all have been done in the same studio on the same gear. The first couple of versions were done by the writer (who was also a co-producer) and, to be honest, they sounded like demos...
Terry Witt ships worldwide and does good work from what I've heard.
https://www.terrysrubberrollers.com/
Sweetbeat's suggestion of Athan is also good - they've been making replacement rollers for many years.
The next thing to do is to get a new reel of tape that doesn't shed. Stop trying to...
Sadly it seems to be a trend with some people who buy old tape machines. There has been a very similar and frustrating thread on the SOS forum very recently. Mind you - I also steer clear of Tapeheads these days because it is full of people who pose as experts yet have little idea of what they...
One of Tannoy's adverts in the 1970's claimed that something like 80% of UK studios were using Tannoy speakers (although not always in Tannoy cabinets). You probably see as many Tannoy speakers in studio shots as you do NS10s but they tend to be hiding in the background rather than sitting on...
Before you do anything more, clean the tape path thoroughly and then try a brand new tape. I still reckon that your problem is a bad tape. Trying to make your own demagnetiser is likely to only make things worse - possibly irretrievably worse. If you accidentally magnetise the heads badly enough...