My SVTIII - Pro came with a total of 5 tubes. I am in the process of replacing the preamp tubes. 4 are easy - Sovtek; 7025; 12AX7WA 1 is mysterious that i need help identifying: Hot Rods; 95-126-01; Made in Germany; 9306; SLM Electronics are printed on the tube. Is this another 12AX7? Also, regarding the "WA" at the end of the 12AX7, what does this mean? Can any other similar tube be used in its place? Thanks!