[Sinker]

What's the going rate for re-rubing and biasing an amp?

[Sinker]

Part Deux:

How important is biasing? Can I buy my own tubes and replace them myself? Will my amp have that 'not biased' sound? If I buy a 'matched pair' of 6L6 power amp tubes, will that negate the need for biasing?

Do I have an inappropriate bias towards not spending too much money on this old amp?

[Major Tom]

Originally Posted by Sinker

Part Deux:

How important is biasing? Can I buy my own tubes and replace them myself? Will my amp have that 'not biased' sound? If I buy a 'matched pair' of 6L6 power amp tubes, will that negate the need for biasing?

Do I have an inappropriate bias towards not spending too much money on this old amp?

I don't know the going rate, but it depends on a couple things - if it has a bias adjustment pot in the amp, it is a lot easier, and less time consuming for the tech. If not, resistors have to be changed out, which takes more time, especially on a PC board type amp. I would guess $50 -100 plus tubes.

You can change out the tubes yourself - preamp tubes do not require any bias adjustment - no sense having someone else do that. As far as the biasing for the power tubes...getting a matched pair does not negate the need for bias adjustment. You can change power tubes without adjusting the bias, the results will vary. If the setting is too "hot" (too much current), the tubes won't last as long, and/or may not sound their best. If its too "cold", the tubes will last longer, but not sound their best. There is a "correct" bias setting, but they will operate in range well outside of that, many like to tweak the bias hotter and report the tubes sound better there.

When you buy a set of power tubes - they are rated on a 1-10 scale usually, called "hardness" rating or whatever. Different suppliers methods vary. Get a set that is rated 4,5, or 6 - these middle rated tubes are closest to the "norm", or theoretical specs for that tube type. First, if you don't have it biased, they are more likely to be in the middle of the bias range. If you do have it biased, in the future, just get the same type tubes and rating, you should be good without any rebiasing.

More than likely you will be ok without a re-bias, unless it was set for some really "cold" tubes, which might be an extremely hot setting for the replacements. If the plates ( the large vertical metal pieces) glow with the replacements, the bias is way too hot - get it changed, they won't last long like that!