from my experiences, the rectifier does impart it's own sound signature thru the wa6
and wa6SE. these are not gain tubes but act as the stage where AC voltage/current
is changed to DC voltage/current. (an inverter does the opposite) i think the sound we
can distinguish is due not to the quantity, but the manner in which the electrons are
being moved from the anode plates to the cathode plates. thus plate structure, size,
composition, heat dissipating ability, plate resistance and other variables are important.
as much impact as the rectifiers may have, the tubes in front impart more distinguishable
sound signature for the wa6/6SE from my experience. these twin tubes are duo triodes
with two separate sections that act as a drive/gain section and power/output section.
most of these duo/dissimilar triodes were made for televisions of the 40's to the 70's.
the most popular were the 6sn7 variants which have two sections that are equal and
are not dissimilar like the 6de7. these 6sn7 were made for small tv monitors of the 40's
but as soon as the screens got bigger engineers needed a more powerful section that
could power the larger area of the screen. thus the 6de7 and many others were created.
for power and dynamic clarity these newer triodes are fine but i think the craftsmanship
and material used in the 40's resulted in better tubes like the 6sn7. these
earlier 6sn7 give a more refined, balanced and ethereal sound quality, which
works for acoustic music the best. woo audio seems to be selling the adapter
for the 6sn7 on the wa6. BUT, these adapters will not work for the wa6SE
without further modifying the amount of voltage reaching the cathode sect.
instead of changing the amp internal circuitry, a resistor can be used in the
adapter itself for the modification. i don't think wooaudio has worked on
making these available yet.
as good as these duo triodes are, the better( or simply more expensive) amps
make use of two separate tubes for the drive/gain and power section. because
the 6sn7 lacks power to make speakers function at their best most amp builders
use the 6sn7 for the drive section only, with a separate more efficient tube for
the power section.this allows for more tube rolling combinations and flexiblility.
but for most headphones, except the k1000 and k340, the wa6 and wa6SE works
fine with just the 6sn7 performing both functions, mainly because the output
transformer picks up for the less than ideal power section of the 6sn7.
a good example of using separate driver tube and power tube is the wa22 and
the wa5. but don't get discouraged, these duo triodes sound great on the wa6
and wa6SE.
the main difference between the transformer-coupled and otl is that one uses
transformer in the output section to change the impedance, voltage and
current to drive lower impedance cans which require more current than voltages.
the otl doesn't use transformers but instead usually uses capacitors and
output tubes in series to function as the transformer. transformers are thought
to impart more distortion than capacitors and thus the otl amps. this may be
more relevant if transformers were still made in the 50's or if the amp was to be
used solely for speakers, but wooaudio makes their own hand-wound
transformers to their liking. i hope i haven't caused any more confusion and
that some of this helped in making your choice.
