So, I have a new tube amp, (NAD thread posting soon, once I'm sure I'm keeping it!) and one that is apparently rather tube-hungry by nature. I got it used, and it's definitely not sounding like it did the first time I played it in the store a few months ago... rather dull and woolly rather than smooth and complex.
So, I'm thinking it might be time to replace the tubes so I can really get an idea of what it sounds like.
1) It's got 3 12AX7s and 4 EL84s, as well as a 5u4 rectifier. I assume the rectifier tube is fine, but how do I tell which tubes to replace? I know that power tubes last longer than preamp tubes, so I'm gonna have to replace the EL84s, but what about the 12AX7s and 5u4?
2) Is the replacing something I can do myself?
3) What is 'biasing,' and will I have to have it done? Apparently this amp is 'cathode biased', whatever that means.
4) With 4 EL84s, can I use two matched pairs, or should I try to dig up a matched quad? They don't seem to be nearly as easy to find...
5) Finally, how much should I expect to pay for tubes, and how much for the biasing/replacement if it needs to be done by a tech?
Make? Model? The answers to your questions depend on the answers to my questions.