Tube rolling question

My phono preamp uses four 6922 type tubes.  Is there any problem with using two different types simultaneously.  So, for example, can I use two 6922s and two 7308s at the same time?  Thanks.
Wild guess in the L/R positions, yes.
Not a lot of info to go on there..

NO with both left (6922) and both right (7308). 
They would work, but there will most likely be a sonic, and a gain difference..

I'm guessing the 6922 and 7308 are options or equals, there is a difference.. I didn't look up the specs on the valves..

keep the differences in tubes symmetrical by channel

(i.e. always same combo in each channel)