Changing the 6550 power tube in a Audio Research Ref 6SE Preamp

This is the preamp I have. While I have done tube rolling with other brands of equipment, I do not do it with Audio Research. Their  tube choice is very specific and designed to get a very specific sound. That is the sound I want and is compatible with the rest of my system (also, Audio Research).

While buying the tubes from Audio Research is more expensive I typically do. They do much more extensive testing than other tube suppliers. In addition, I want to support this great company.

I always keep and extra set of tubes around for each of my components. Then when swapping out tubes I’m all set... and if I needed to trouble shoot a tube I could. Since my Phonostage, Preamp and DAC/CD player all use the same 6550 tubes that are changed more frequently, I bought an extra quad from ARC.

I replaced Sovtek 6550 with EH from Upscale Audio, ARC grade. Sounded great. No problemo. 

I have the ARC Ref 5SE.  I use a new production Tung-Sol 6550.  I preferred that to the SovTek 6550 although the difference was negligible and probably just due to the SovTek having to many hours on it.  Surprisingly, I also preferred the new production Tung-Sol to a very expensive NOS Tung-Sol 6550 from the 1950s.  Anyhow, you can feel free to try different manufacturers of 6550s and will probably hear small differences between them.

Thanks to one & all !

It seems the consensus is: Yes, non-SovTek 6550 tubes are safe to uses and will have unique sonic characteristics.  

If I am unsatisfied, I can always return to the SovTek 6550 (from ARC or else ware) should others seem inferior (in my system).

Well, time to get shopping...

@inagroove I highly recommend Upscale Audio. Bought enough tubes from them over the years. Just get the ARC grade.