My fully original Stereo 70 has a bad EL34 tube. It still has these four '60 Philips Miniwatt:
I've only a couple of questions:
1) I would like to replace the bad tube only. Is it a big heresy, to use the amplifier with 3 vintage tubes and one new and from a different brand?
2) I can easily find EL34s from JJ-Electronics and Electro-Harmonix. Which one do you think is the better one, in my situation?
Thank you in advance