rogonzab
220 posts
Jan 24, 2013
4:34 AM
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Hi,
any of you know if I need to set the bias in order to change the tubes in my (new) Laney Cub 12r? Is a A/B class (does that matter?
I want to put 5751x3 and EH EL84x2.
THXS!!
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5F6H
1515 posts
Jan 24, 2013
7:17 AM
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The Cub is fixed bias, so ideally it would be a good idea. Reputable tube vendors often sell retube kits of selected tubes to drop straight into some common amps.
Alternatively, leave the EL84 it came with in there for now, rebiasing the ones you have will make as much, if not more difference than changing the tubes for another brand & rebiasing those to stock.
EL84 are pretty tough & take some abuse, there is a Russian 13.5W military tube (10% overrated), I don't recommend the "suck it & see" approach, but I know it happens, so if you are likely to do this these tubes might be a safer bet?
Preamps are cathode biased, no adjustment needed.
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Last Edited by on Jan 24, 2013 7:18 AM
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rogonzab
221 posts
Jan 24, 2013
7:50 AM
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THXS 5F6H!!
I was thinking that maybe I am going to low the gain more (I like a less distorted sound), something like this:
JAN Sylvana 12AY7 / JAN Phillips 5751 / JAN Phillips 5751.
That would be too much?
As you say, the power tubes is the last thing that I am going to change.
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5F6H
1516 posts
Jan 24, 2013
9:01 AM
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Well you never really know until you try.....EL84 don't need a lot of signal voltage so sometimes a lo mu tube, or even a 12DW7, feeding the power tubes works well. 5751 are great tubes but can be soft & round...more than one in a line up can be overkill...it really is a matter of trying all the options...good luck there are 178 combinations for you to try! :-)
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