AudioBanter.com - View Single Post - ARC SP-11 preamp versus SP-15

said:

I have compared it to a couple of ARC units and IMO it sounded better,
but then I'm biased.

In class A, no doubt ;-)

Yes, but the manufacturer in question uses very large values of cap so
that a DC offset can swamp the output stage long enough to cause an
output tube to pull a lot of current long enough to shorten its life.

Nope.
Imagine what happens when the amp is switched on (or off), or a loud
thump from switching or a loud bass drum is processed by the amp.
The time constant of a typical RC combination of 0.5 uF and 100k in
the grid path of a power tube is 20 s.
However, one can't neglect the grid current that will occur at or
above a grid voltage of 0 V, thereby draining the charge of the
coupling cap very fast.
If the impulse at the grid is in the opposite direction, which is
likely with a positive going signal at the anode of the driver tube,
the power tube will be cut off and no danger of excessive current
through it is present.

The fix is to replace the cap in question, of course, but you paid for
a manufactured product, not a kit...

The cap will survive things like that, unlike any DC coupled solid
state amplifier and/or the connected speaker.............

--
Sander de Waal
" SOA of a KT88? Sufficient. "