2 vs 8 tubes in preamp, sound difference?

It's ALL about the design.  

All about the design and implementation - Tube regulation tube rectification, etc.

My ARC SP9 mkll has two tubes in it. One for the preamp and one for the phono section. It was my daily driver until recently, but now maybe once a week.

All the best.

JD

You only need enough. Having more tubes is no better than having more woofers.....in the right configuration and application, it could have some benefit.... but could also just be more, and maybe too many..

Absolutely not! The fewer the tubes the better. The finest sounding amps are SET with one output tube per side. That goes double or preamps.