Re-tubing and tube values

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akadave
Junior Member

Posts: 52

Re-tubing and tube values Mar 8, 2012 12:46:46 GMT -5

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Post by akadave on Mar 8, 2012 12:46:46 GMT -5

I ran into an issue when re-tubing my SR. The output tubes that shipped with the amp had a rating written on the base of the tubes of 21. Most manufacturers when selling matched sets of tubes will give a numerical rating to each for matching purposes. There seems to be some differences between manufacturers as to what this means. I purchased a set of JJ E34Ls that were rated a 45. I was unable to get the bias low enough to be able to use them (the multi-turn bias pot in my SR would only get them down to 57mA.)

What I would like to know is, do I have to buy the softest tube that a manufacturer makes in order to get them to bias in my SR? I dont want to kill my amp.

Thanks

Last Edit: Mar 9, 2012 12:47:53 GMT -5 by akadave

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benhur
Member

Posts: 108

Re-tubing and tube values Mar 13, 2012 16:19:20 GMT -5

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Post by benhur on Mar 13, 2012 16:19:20 GMT -5

Your best bet is to call Scott and order tubes. He has mentioned to me a few times that he'll match your ratings from set to set. I could see those JJ's being so much higher than the stock sino would be a problem. same kind of deal as running kt88 or 6550, gotta change a resistor so you can bias in the correct range.