Going thru a piece here and 1 original transistor was labeled a BC549 and another a BC549C further up the audio chain. So it looks like the difference in the pieces the C version has more gain then the 549. Looking around the 549 have been superseded to mostly 549C pieces. Also needed are BC 238 & BC239 pieces but these aren't made and go to the BC549, which then goes to the 549C. Now the original pieces238, 239 and the 549s are available from over in RU land. These are the equivalents to American designed pieces I am guessing, just a Russian version of them. Prices are good and the pieces aren't made in China where a lot of counterfeit pieces are being produced at. The Russian tubes have a good reputation these days so the SS parts from over yonder should be acceptable, I am guessing.