i'm running the Tascam US-428 here with no problems.

A friend of mine used to have the 1641, and I seem to remember him having trouble with the later version drivers (Mostly with Logic and Garageband), he reverted to an older version driver and it helped (if I remember correctly).

Have you tried reverting to an older driver ?
It looks like 1.03 was the previous one to version 2.0.
Might be 32 bit only though, not sure if that is going to be a problem.

http://tascam.com/product/us-1641/downloads/

Hopefully this helps.

- Jay


MacPro 5,1/12 core@3.46GHz -- OS X 10.15.7 -- ATI 7970 -- 32 Gig RAM -- Crucial 500GB OS SSD -- Samsung EVO 1TB Audio/Sample SSD -- BIAB 2024 -- Logic Pro X -- Cubase Elements 14 -- Too many plugins