Posted this on another forum. Not Bottlehead related but I trust the knowledge of the guys on this forum. Here goes ...
Got a pair of "matched" EL34 tubes from a reputable online dealer for a Marshall JTM45 clone I built about a year ago.
Install the tubes in the amp. Go to adjust bias and the tubes are 9ma apart. Shut the amp down. Swap the tubes/sockets, fire amp back up and the bias problem follows the tubes. "Hot" tube is still "hot" in the other socket, and "cold" tube is still "cold". Same 9ma difference. My conclusion is that the tubes are not matched. End of story.
Am I missing anything?
Thanks