There was one early change to a few resistors that would/could become slightly noisy. This was done several years back after the first production models hit the market. I think you're good to go with any serial number above about 2650 or so. Of course, Jim White was good about updating the units that did have issues. They too would be fine.
There has been no other changes that I am aware of except Aesthetix did change tube types to help cure a noisy tube problem that seemed to be fairly common for a while.
The Calypso is a great preamp for it's cost even new.
I certainly wouldm't be afraid of a unit several years old.
There has been no other changes that I am aware of except Aesthetix did change tube types to help cure a noisy tube problem that seemed to be fairly common for a while.
The Calypso is a great preamp for it's cost even new.
I certainly wouldm't be afraid of a unit several years old.