"Phil Allison" wrote in message ...

Bugera is an alias for Behringer - used for marketing their valve amps.

Based on what Phil says... The name suggests what the amp will do to its
owner.

Even without his analysis, viewing the description of how the Infinium system
works would have made my hair stand on end.

Tubes deteriorate slowly, so there's no point in continuously checking the
tube bias. It should be sufficient when the amplifier is turned on, or the
user initiates a rebias cycle. And, as Phil points out, how do you keep the
biasing system from being "confused" by the audio signal?

I'm not an expert on tube output-stage design. But it should be obvious that
the correct idle current for one tube type is not necessarily optimum for
another. The promo indirectly acknowledges this by pointing out the mixed
tubes will produce "interesting" harmonic and IM distortion. And if the tubes'
characteristics are sufficiently different, you might even wind up with a
"healthy" (not!) level of DC through the output transformer's primary.

The guy can't even pronounce "potentiometer".

I wonder what David Hafler (who came up with a simple and cheap way of
biasing Dyna amps) would have to say about this...

I posted the following, but it hasn't been approved yet. (I expect it to be
censored.)


Bugera? The name "says it".

I'm a degreed EE and hold an Amateur Extra license (KA3QXL). Most of this is
utter baloney. Tubes deteriorate slowly, so there's no need to reset the bias
more often than the start of a session. And you don't want to be doing it
while amplifying a signal!

As for mixing tube types... Yes, you'll get "interesting" distortion -- along
with the potential (joke intended) of amplifier damage due to mismatched tube
characteristics.

This is a bad, bad, bad idea.