I have bought a VAc CLA-1 preamp

Perhaps this manual may help, it is for CPA-1/CLA-1.
If not, try to contact VAC. Kevin Hayes is always very helpful.

Cheers,
John

Siemems/Amperex 7308-6dj8
Shuguang triple-mica 12ax7 select-Doug's tubes
Mazda/Radio Technique French military triple-mica 12au7
The first pair are expensive.The "select" are about $13/ea and the Mazda tube will run about $60/pr.
Of course there are always the Golden Dragon/VAC tubes.These come "gold-pin "and "standard".The GPs are more linear/more detailed and Stds are warmer.Maybe GPs in the phono and Stds else-where.

I use Mazda 12AU7 tubes from the 60's.Great tube,dynamics galore.
Costly though.I paid $180 for a matched pair.