What differences between Conrad-Johnson PV10.11.12

Could anyone let me know the differences between these model?

Thinking of purchasing of the these used.
The PV 10 is c-j's entry level pre. The PV 12 is the upgrade/relpacement for the PV 11. C-J's website can give you all the details.
I own the PV11. From what I understand the PV10 & 11 have a similiar line stage, but the PV11 has bypass caps in it and is more refined. The PV-12 is different than the other two. I have read that the PV-12 lost some of the magic of the PV-11. Many prefer the PV11 over the PV12. Both are discontinued. The CJ PV10(b) is still available, and the "b" version is similar to the PV12 line stage, from what I understand. If you can find a PV11, I'd go for it. I compared it to a Quicksilver preamp, and it soounded much better to me, plus the phono stage is excellent, even cleaner than the line stage. Hope this helps.