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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: BIAS QUESTION posted by BCR on December 23, 2015 at 13:49:25:
Tubes do not have an intrinsic bias. What I think you are referring to is a 'bias point', a number assigned by the seller in the tube matching process. A 'bias point' of 60 would be OK if your amp manufacturer recommends a bias setting of 60 for your amp. If the recommendation is less you would be over-driving your tubes and could expect early tube failures and the consequences if any. If the recommended bias more then you will have no issues. However if the max recommended setting is 60 then you have no flexibility. FWIW I would rarely use a max bias setting of 60 even if recommended by the manufacturer- you can get very similar performance at a lower bias setting and longer tube life. I slightly lower setting might sound a bit cooler in tone, but not much.
FWIW when I buy tube set's I usually ask for tubes that have a 'bias point' of about 45. That will work in most of my amps. Under 35 can often be a problem (too little) as can over 55 (too much).
BTW, FWIW, if you are going to run tubes at a '60' bias keep your eye on the tube plates for reddening of the plates. That is a precursor of problem to come. In answer to your question the bias of 20 on your old tubes would be normal - I assume you can bring them up to the manufactuers recommended setting range by rotating the pots.
Hope that helps a bit.
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Follow Ups
- RE: BIAS QUESTION - Chuck Y 14:41:35 12/23/15 (1)
- RE: BIAS QUESTION - BCR 14:51:21 12/23/15 (0)
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