Hi Shel50
I agree with Rrog. It is totally your choice to mix and match brands in your gear or keep them all from the same maker. A lot of it will depend on how the music will sound with all the tubes and gear in place. Currently right now I have a XiangZheng 728A preamp. In this preamp I've got Sylvania JAN 6X4 tubes with the proper adapters, Tung Sol re-issue 12AT7s from New Sensor and vintage Tung Sol 12AU7s. It just worked out like that and I find the sound in my system to be ok but I'm noticing a bit more bass then I would like. I'm going to spend more time with this combination before changing stuff out. I've had a very good run with JAN Sylvania and GE tubes so in the future I may go for an entire run of JAN tubes in both preamp and amp. This has potential for being costly but I did like the sound of the music in my system when I had JAN Sylvania or JAN GE tubes from the 60s-80s in my system. So again it is a bit of trial and error as well as preference.
I don't know how the other tube guys deal with all the combinations. I've seen some systems with a Tube DAC or CD player then they have a tube phono preamp, tube preamp and then tube amps. If something goes awry sound wise all of a sudden where to you make changes?
