I was told the 303/300 & 306/200 had analog volume controls
I think? you can tell from my last link pic that the 303/300 doesn’t have analog vc. There are some reviews that say it has, but I think they got it wrong.
You can see from this pic for it to have analog vc it would have to go after the OPA2604 lp filter, but all there is a two transistor buffers, the valve stage and the muting relays before the output rca’s/xlrs’
http://mycollins.net/Cary-05.jpg
And the 200 definitely did have digital vc.
Cheers George