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Vintage threads from the first ten years

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1/27/1997 5:17 PM
Mike L tubes
I recently purchased Bassman amp. It came stock with the 6L6GC tubes in  
it. I came across some NOS 6L6WGB and was going to install them in the  
Bassman. Upon further investigation I found out that the plate voltages  
are much higher in the GC's than in the WGB's. If I install these tubes  
do I have to make any mocifications to the amp for them to work or is all  
that is required is re-biasing.
1/24/1997 12:17 PM
Josh Cecil
As far as I know if the tubes are compatable all that you have to do is adjust the bias  
to keep the tubes from running too hot. The higher voltage tube at the same bias will  
likely cause the tube to run hot. You can always call fender and ask if they know some  
good modifications or other tubes that work well.
1/27/1997 12:23 AM
john Martin

Tube wise, a good candidate for the Fender 75 and 135 models, would be some NOS 7581A. They can take a bit more voltage than many other 6L6 substitutes. I find them good for bass amps, but a little harsh for guitar amps. They will make your amp roar, however. These have also been known to work in 70's Ampegs in place of the 7025 tubes.  
In my personal opinion they should have not used the 6L6 in these higher voltage ultralinear versions of the Bassman and Twin amps. I believe it was just a manufacturing cost issue. The 6CA7 or 6550 tube would be a better design choice.  
JM out
1/25/1997 7:07 PM
Just re-bias it!
1/30/1997 11:16 PM

the 6l6wgbs should be ok. always check bias current when changing tubes. maximum ratings in tube manuals are generally conservative especially for u.s. tubes. 6v6 tubes are rated 70 to 85 or so volts less than what a fender deluxe reverb operates at. your 6l6wgbs should be ok if you watch your current draw. is this a blacface or silverface? good luck.

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