5881's in a tweaker 40 bad?

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bluesstrattone

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I'm curious to hear what that sounds like,
Also I have a pair of sed winged c 6l6s would like to experiment
With other tubes.
The amp is rated at 40 watts, and some tubes are rated for
20 or 30 watts, how would it take those kind of tubes ?
I don't remember the amps plate V.
Some have an idle bias point of 17 or 20 and the twk 40
Has a suggested bias of 60 plus.
So can any of these tubes work and be safe.
6l6, str,wgcstr, 5881, kt66 etc
Thanks for your input
 
Using EL34's in mine. Like it much better with these in the brit setting.
 
You should be able to use just about any 6L6, 5881 type of tube as long as the bias is set for the particular tube, and the voltages on the amp fall within the ratings of the tube. In fact, the manual lists 5881/6L6 for the output tubes, and the bias drawing posted by Egnater on this forum lists 6L6/5881/EL34. The Twkr has an adjustable bias. My 40 measured 438 VDC on the screen, and 442 VDC on the Plate, at approx 72 mV at the test point (roughly 34 mA per tube Plate current, 15 watts idle). Your voltages might be slightly different depending on which tubes that you have, and at what level your bias is set, but should be reasonably close. So, if the tubes can handle 450 VDC on the Plate and screen, they should work fine.

In the case of the 40, you can even use JJ 6V6 or GT 6V6-S, as their ratings are enough for this amp, but only these two types of 6V6 are rated to work, and only if the bias is set properly with these types. Using these 6V6, the amp will have less power and a little more of a 6V6 flavor, not quite like a real 6V6 and not far from the 6L6.

Other tube types have a higher current draw for the heater, the KT66 about 1.3A, and the EL34 is 1.6A, compared to .98A or less for the 6L6 and 5881. IMO, using EL34 or KT66 is pushing it just a bit, taxing the power trans too much (multiply the heater current difference x two tubes), but if the EL34 works, then the KT66 should also.
 
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