FUQ (eff -yu - cue) - FAQ's with an EDGE

Tagged As: Mesa Boogie Tube

Question:
I found some old tubes laying around. They are all mesa boogie tubes, but read differently. They are as follows : (1) Mesa 7025STR 12AX7A ECC83 (2) Mesa STR 12AX7A (3) Mesa STR SPAX7A (with black band around the tube). (4) Mesa 12AX7A They are all *AX7A, but can anyone tell me the differences between them? What is 7025? What is STR? What is ECC83 What is the diff b/t 12AX and SPAX? What is the difference between (E.g., a STR 12AX7A and a nonSTR 12AX7A), so on and so forth ...

Answer:
Mesa has never built a tube. They buy from other sources, and put their name on it. I'd have to see the tubes before I could tell what they really are. I don't know if others can tell you much about the coding, but I have a run of the mill Chinese that is marked Mesa and STR. Most of the lettering is worn off, even though I haven't handled it much ECC83 is the European designation for a 12AX7. A 7025 is (supposed to be) a 12AX7 selected for low noise and hum. A SPAX7A is (supposed to be) a selected 12AX7. AFAIK, the selection is done by Mesa (or whoever made their tubes), and I have no idea what criteria were used. STR is usually a designation one sees with Ruby tubes and, AFAIK, doesn't mean a damned thing. Chances are that they are all very similar tubes built to 12AX7 specs.