The level below which an expander begins functioning.
"The CDs and cassette tapes I ordered arrived yesterday. Thank you! I was amazed at the clarity you were able to produce from a 36-year-old reel-to-reel tape. Again, thanks! I think my grandmother, father, and uncles will be very happy to be able to listen, once again, to the tribute to my grandfather from so long ago. God bless."