Odd noise after TMC2100 upgrade

Hi there
I've got a custom made 3D printer (Summoner v3.0) and yesterday I tried the TMC2100 drivers.
At a constant velocity you can't hear it. But when it's executing a new line/instruction, it makes an noise like an old HDD (that crrrt sound).
I've opened the Repetier software and enabled the echo mode (that's how I managed to see that only when a new instruction is executed the printer makes a short crrt sound)
No step skipping, no high-pitch noise. The drivers get a bit hot (0.7-0.8V on ref). Steppers are cool.

On this printer I've went through A4988, DRV8825 and now the TMC2100.
The reason for this upgrade is, of course, the noise reduction.
I'm running the drivers in stealthchop mode (16 uStep, with 256 interpolation). The motherboard is a RAMPS 1.4. Printing at 30-40mm/s.

I've tried playing with speeds, accels, jerkXY, feedrate, only one stepper (even with only one stepper active, the issue is still there), dry run (no PID interference), feedrate (at 25% you can really hear the independent crrt noise)
Some say the 8bit ucontroller might be the issue (the driver is controlled with a 16 ustep resolution, not 256) but that does not make much sense. The 24V supply solution is only for high pitch noise.

Any piece of advice is greatly appreciated.

I found the TMC2100 almost noiseless in spreadcycle mode and never bothered with stealthchop at all.
There was more noise coming from the belts on the pulleys....

I wonder if stealthchop is in conflict somehow.... maybe something with the stepper motors or something somewhere....

So I am guessing you cut or de-soldered cfg1, if you have a spare TMC2100 Stepstick maybe you should try it unmodified, so its in spreadcycle mode....
Just pull all three jumpers from the Ramps and drop it in, set vref of course
Just to see, might be worth the experiment.....