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Big Bad Bob Big Bad Bob is offline
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Default Tube mono-block amp with SIX 6L6 outut tubes

On 12/28/18 09:16, bitrex wrote:

All amps of that scale should have active protection
circuitry/monitoring of currents, biases, and temperatures via
microprocessor to avoid potentially catastrophic faults.


I think it works ok without "all that". fuses where needed of course,
to avoid things catching on fire. But tubes are amazingly strong at
absorbing conditions that transistors would melt under. Sure the plates
turn pink [like when half of a push-pull transformer melts away] but if
you don't push them to the edge of physics they generally take it ok and
survive getting a new output transformer. Or if a single tube fails in
multi-pair configuration, the others will take up most of the slack
without too much bad behavior. You'll probably hear the bad quality
sound at high volumes, but without extended operation "that way" the
other tubes should survive.

the more you have paralleled, the less impact a single tube failure will
have on the other tubes.

Even briefly overvolt or overcurrent on a typical transistor, and you'll
be replacing it VERY soon. I made the mistake of designing a circuit
that operated close to the maximum Vceo (these 60V transistors should be
able to handle 45-50V right?), and the transistors never lasted long
under load (replaced 3 times, and 3 blown fuses that were supposed to
protect them). Replaced with transistors that had twice the Vceo and no
problem.


--
(aka 'Bombastic Bob' in case you wondered)

'Feeling with my fingers, and thinking with my brain' - me

'your story is so touching, but it sounds just like a lie'
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