I actually popped the back off a couple days ago and noticed they were JJs. What about the ARS preamp tubes that are in it? When replacing, do you recommend those?
Ars jj in the first slot and 2 ARS Chamness in the other. You can play with the first tube if you like the sound of something else better. Warning though a lot of tubes are microphonic in the first slot, that's why we use JJ there.