Yes don't go all crazy with tube swapping but...well researched substitutions can make a world of difference. I have a Modwright PS 9.0 that came with Sovtek 5ar4 tube. That one blew after a week. I replace it with the same tube...6 months and another blow. I put one last Sovtek in it and worked but sounded like crap. Edgy grainy unlistenable. I'm new to tubes so I started asking Mr. GoogleI settled on NOS Tung Sol 5R4GY which sound so much better. This was not an expensive tube and I learned what rolling could do. Next I popped for more expensive NOS Phillips 5R4GYS and bang Jackpot! Now lets see how long this one lasts
Rectifier Tube Rolling in a Modwight LS 36.5DM
I was hoping to get advice, I have been rolling Rectifier tubes in my two box preamp I am blown away how different tubes change the sound ,I own two sets of Mullard GZ37/CV378 a set of GE 5U4GB both vintage early 1960's and a set of stock Sovtek 5AR4 also have a NOS set of 6H30 DR I am trying in the clean box , both the Mullard's and Dr tubes only have about five hours of run in time but the sound seems defused on the top end ok on the bass the GE Tubes are good in the mids but soft on the highs and bass so far the stock Sovtek seems to sound best ,Dan says try 5R4-GY Tubes, any one tell me about the Mullard's in this preamp I am getting frustrated, thanks