IIRC, the 6DZ7 channel separation was specified at 50 dB. If the driver tube is also shared between the two channels, this may be somewhat lower, but for most non-crtical purposes this si still plenty "good enough".
That's not bad. Super duper high dollar phono cartridges can barely make 35db channel sep.
I can see a SE layout with a 5R4-GY behind a 6DZ7 behind a 12AX7A.
You find some of the mostest coolest stuff to post, for sure.
Thanks!