It’s All About The Glass

As can be seen here with the photo turned upside down, there are four tubes in the Skylark; a pair of 6BQ5, a 6C4 and a 6EU7. Going from left to right, the 6EU7 serves as the power tube and its faint red RCA marking is barely legible. Next is the phase inverter, a 6C4 bearing the yellow script “made in USA for Ampeg by Sylvania 939 JFO”. The first 6BQ5 in the lineup sports the “RCA electron tube” marking while its partner 6BQ5 makes do with “RCA USA”. The tubes are old but after warming up a bit, still kick out a toneful 4 or 5 watts.