In my research, it seems there has only really been one change, which had to do with resistors. There were some noisy stock tubes reported for awhile, and that now seems fixed. There were also some hum problems reported with Ayre amps, but Ayre changed their grounding scheme and took care of that, I don't believe the Calypso changed anything with regards to the hum when used with Ayre. I would be interested to hear from anyone more knowledgeable on whether there were additional changes or versions, and maybe what serial number started the resistor change.
Aesthetix Calypso How many versions?
I've seen some people advertising their for sale Calypsos as being the "latest version with the ultra quiet resistors" Why, how many versions does this model have? Or are they all the same? Should I look for the latest version or does it not matter? It seems like the "newest model" ones sell faster, so should I get the newest model so I can resell it quicker if I don't like it?