Wow, that’s interesting. Am following this.

Dear MC,

thank you very much for the great input. I performed the test and you are right both recordings do sound equally awesome now. I have to investigate further, what was going on earlier. Maybe I am just nuts and trick my brain into hearing things.

Keep up the great work.

Check the Settings dialog for USB errors counting up when using the hub.

BF Pro FS manual chapter 8.1.

Correct.

No. It has never been a problem in those interfaces, if there were issues they came from a different side (mostly OS). It does exist for USB 3, though. But I agree that in your case it would have been nice to see if there is a relation.

Some further investigations yielded the following observation: the distortion is linked to the presence of a tethered iPhone on the USB tree.

Moreover when connecting to the internet via the tethered iPhone and using a messenger (Telegram) every time I hit enter I see a peak centred at 1khz in the Digicheck analyser.

I don't hear anything but there clearly is some kind of signal in the system.

I can do a screen recording demonstrating this if desired.

Mods: pls feel free to move or remove this post if deemed OT. In that case pls inform me where to report.

Thx Kai - already moved the device off the monitors hub to another hub.

Problem is I can't directly connect the BFP to the MBP as my BFP was delivered with a faulty USB-C cable (connector is bend and doesn't plug into the USB-C port).

The device was ordered as "B-Ware" at a big German reseller. It was otherwise in perfect condition but I noticed the problem with the cable immediately and raised a ticket with them. They promised to send a new cable but so far nothing happened. Just shot the reseller another email.

Hence I have to use a USB-hub for the time being and can't investigate if the above mentioned tethering phenomen persists when the BFP is connected directly to the Mac.

IMHO time for USB to PC isolation... as using INTONA gear and then proper grounding of the audio gear

If you are at that point, why not use balanced power lines - the ultimate solution.
A (big) transformer balances both phase and null relatve to ground for all audio devices.
This way floating PSU’s stray currents result in a voltage closer to ground level and causes largely reduced negative effects.

Switched Mode PSU‘s don’t care about power line resistance or even line voltage. They just compensate.

Power amps with unregulated PSUs might loose some RMS power, but peak power practically only depends on the low load line voltage.

Most households are feed with under-voltage lines.
A balancing lines transformer can compensate or even improve on this, as secondary can be a bit higher than primary.

Additionally, bigger toroidal transformers have very low internal resistance, way below the smaller ones inside the power amps.

The power lines balancing makes a lot of power lines garbage “invisible” for the connected devices, no need for extra filtering (except over-voltage protection).