Re:Bassman Rectifers, what does it all mean?
The Sovteks and the Rubies were probabaly amde in the same plant. Ruby
doesn't make tubes they silkscreen them. Could be you got a bad one
could be their grading isn't that good.
Randy please explain to me the part about the re-biasing. Output tubes
are biased at idle. Low current highest voltage. You're trying to reach
a happy medium between tube shut-off and tube saturation. The rectifier
has no effect on the idling voltage or current. Only the max output.
Since there is a fairly wide range of idling current that a 6L6 is happy
with it would seem to me difficult to make a pronouncement as to the need
for re-biasing. It's a subjective call at best. We could say Randy
Likes his re-issue Bassman best with a 5AR4 rectifier. FJM finds that a
5U4GB works fine also. It's a pretty complex issue anyway. The values
of the components in these amps are all over the scale. The main
difference in all these different rectifying schemes for Bassman re-issue
is the max output of the rectifying source. Fender specs both tubes for
the re-issue. Some people love over or under biased amps. There really
is no just right only an it won't catch on fire and die within these
If the method you're using to bias the amp is the Groove Tubes method I
can see how you could get the idea that there is an ideal idle current.
If you use the current bypass method that Ken Fischer of Trainwreck amps
uses it starts to look a lot more subjective. If the idling current is
set at not less than 10ma and not more than 50ma I'd say you were ok. My
Bassman idles around 35ma right in the middle. These figures are for
6L6's running class AB fixed bias. FJM
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