I have an EAR 834p phone preamp (with the ""Thorsten modification", if that matters) - I am beginning to experience some distortion which I'm thinking may be associated with a tube beginning to fail. There are three in the unit, all of them 12AX7 (ECC83). I admit knowing very little about the nuts-and-bolts of this.
I have two questions which I was hoping someone could help me with:
1) I know this is subjective, but what would be the "best" tubes to use as replacements, and where to obtain them? The ones that are currently installed are Telefunken ECC83/12AX7. The originals (I believe) which I also have are marked DPF (?) ECC83, two have the marking N8AN8, and one A9AN8.
2) What is a good new or used (via eBay, I suppose) tester for these? I'd be looking for something relatively inexpensive, as I don't currently own any other tube-based components (although I plan to get a couple of amps when I can). Understand too, I am unsure how to interpret the readings, so I will be back to ask about that, as well...
Thanks very much for any input.