New Tube Color Code Question

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May 12, 2024
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I've read several of the threads on this forum and elsewhere about the tube color codes, but I haven't seen my questions addressed yet. I have a new Triple Crown TC-50 head that was delivered with EL-34 tubes marked STR 447 BLU (I assume this is blue). I have read that some of you have measured voltages of the various color code tubes, so in theory there are differences. But Mesa's official position is that the tone differences between different colors is not significant and the colors are just for matching. I don't know that these allegedly small differences will mean anything to me until I've been using my amp for a while.

My questions:
1. I want to switch to 6L6 tubes. Do all tubes marked BLU have the same voltage characteristics? If not, what color code 6L6 has similar voltage characteristics to a blue EL-34? Or should I even care?
2. Is there a chart somewhere explaining the meaning of STR 447? I read one thread that mentioned that this indicates country of origin, among other things. It would be nice to know where my tubes are coming from, and whether that makes a quality difference.

Thanks for any help!

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