Which Audiologic dac was the first to go 24 bit?

Rcprince is correct.
I'm keeping my M34 DSM in original form (except for special tubes) to me it sounds absolutely fantastic,
(mine was Jerry's own personal unit a while back)
Newer is not always better, just different, sometimes worse, depending on ancillary equipment & preferences.

Hey Jeffcott go for it, thanks for the offer !!

Thanks Gary, you said it better than I could !!
BTW, the RCA 12AU7's are sounding primo.
The other side is running a pair of Cryo'd Russian 6H23N-EB's, life is good.

I've been using an Orchid balanced between my CEC & Audio Logic Dac with excellent results, like to try a couple others for comparison.