Tube Biasing: do I have to?

They're already receiving some bias Voltage, just not the the correct amount (probably).

If they're overbiased, they'll wear out more quickly and maybe even glow red and blow. If they're underbiased they won't sound as good as they should.

Why wouldn't you adjust the bias?
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I'm glad Jjwa asked because I am in the same quandry. I just bought a used tube integrated amp. The second day I had it I blew the fuse. I took the unit in to find out why it blew, and the techie said that the four 6550 tubes were not in the same place the previous owner had them and therefore some of the tubes ran too hot and blew the fuse.

I want to buy a new set of Svetlana KT 88s and will need to bias the new tubes, but my half-a-manual doesn't tell me how to do this... What are my options???

Uppermidfi - find out! The info is out there on the net somewhere. If you are going to use this arcane technology, it behooves you to learn its ways. There are some very good discussions of biasing output tubes on the FAQ sections of this and other forums.

Bias procedures will vary from amp to amp. You guys would do well to list your specific amp including the model, and or do a search (here, google, and AA) using the amp's name and "bias procedure" (or something of that nature). As already indicated, some amps have an auto-biasing circuitry and do not need to be adjusted with tube swaps. Others which require biasing will require a decent digital volt meter and the basic knowledge of how to use it. The actual procedure, as I said, will vary according to the amp.

If you want your manualy biased amp to run properly and not risk tubes, fuses and or very lackluster performance you do indeed have to bias your output tubes. I would furthermore recommend you check the bias at least once a month or so, and more frequently if you are breaking in brand new tubes.

Marco

The arcane technology john mentioned happens to be the most maturated aspect of high end audio.Study your audio history and you will understand that cd's are still in the thumb SUCKING stage... emphasis on sucking.There are many engineers out there that are slowly realizing that digital cannot offer the many characteristics that a well designed tube stage offer.The young pro audio camp loves digital and that is understandable since they have 30 to 40 less years of analog in their brains than the old fart contingent.Find out the bias #'s that your manufacturer intended for your tubes and if your unit does not autobias then ask the vendor like THE TUBE STORE to bias them for those specs.Good luck