Mullard Tube
Can I replace a power tube in a guitar amplifier without matching it to the existing power tubes?
I just bought a vintage amp and it has 3 Mullard EL34's but is missing the fourth. I have read that if i get a fourth and don't get it matched it will compete against the existing tubes. I eventually want to get a 4th matched tube and the other 3 tested but i want to turn the amp to make sure it is functioning properly as it is before investing in new tubes. Is it okay to play through it at low volumes with just the 3 tubes and/or can i get away with putting in a cheap EL34 in the empty slot to play for a little while before getting the 4th matched Mullard?
Most high end audio products using tubes require matched tubes for two reasons:
1. Sound quality
2. Electronic reasons.
The best case scenario - the mismatched tube will be relatively close to the installed tubes, and you'll have some distortion and poor sound quality.
Worst case scenario - the mismatched tube will be so far out of spec with the other tubes that it will lead to a lot of distortion, feedback, etc, and it will permanently damage some of the other electronic components in the amp.
Best advice - see if there is someone local who has a spare set of tubes that you can borrow to do your initial tests, then invest in a set of matched tubes afterwards.
If you really want to cheap out and not buy all four tubes, at least buy matched pair, and replace two of them. They are generally used in pairs - but you will need a schematic and someone with experience to tell you which two are paired with each other.
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