Tensors with serial numbers 108-066999 used a different circuit board that had less memory and a mono analog signal path.  We plan to offer an upgrade board for longer looping times and stereo input/output.  Unfortunately, we are waiting on some key components to arrive before we can start production.  Due to the current supply chain issues (as of May 2022) we do not have a shipping estimate.  The upgrade will be user installable when its available, and we will announce it on our newsletter and social media.