12au7

I just bought an RCA 12AU7A tube to replace the one in my dbx 367 which gave up.

It doesn't work. No audio being passed or metered. I checked connections.

Is this a wrong tube for the dbx367?

6SN7 & 12SN7. any of you guys who build or tinker have any opinions?

I know the au,at & 6sn7 are lower gain than their counterparts.

Any thoughts on the way they sound?

Thanks