The CHRISTMAS COMES EARLY MOD
by Steve Deckert
to the creative mind of Mr. Hazen, my top solder guru, we have stumbled
into a modification that can be applied to most Decware amplifiers. In
all the years of typical mods and tweaks, we have never come
across a more dramatic improvement in sound quality. It eclipses
all of the usual attempts to make something nearly perfect even better.
Things like; cryo treated tubes, coupling cap or resistor upgrades,
silver wire, tube dampers etc., etc. The mod actually improves the
coherency of true pentodes to a degree that you wouldn't even think
it's the same tube.
are two unique pentodes that can be found in many Decware amplifiers.
These are the Russian 6P15P-EV and the EL34. What makes
these pentodes different from other tubes is that the suppressor grid
is not internally connected to the cathode. These two tubes can be
wired as either pentodes or triodes. And the suppressor grid can
the RCA transmitting tube manual on air-cooled tubes from 1938:
In all radio tubes. electrons striking a
positive electrode may, if moving at sufficient
speed, dislodge or "splash
out" other or secondary electrons. In diodes and
triodes, such secondary electrons produced
at the plate usually do not cause any
trouble because no positive electrode other than the plate itself
is present to attract them.
These electrons, therefore, are eventually drawn back to the
plate. In tetrodes, the
(operating at a positive potential) offers a strong attraction to
secondary electrons when the plate
voltage swings lower than the screen voltage. This
effect limits the permissible plate swing
for tetrodes because the major portion of
the space current then goes to the screen
rather than to the plate. The plate swing limitation can be
substantially removed when a fifth electrode, known as the suppressor,
is placed in the tube between the screen and the plate. Such five-electrode
types are called pentodes.
The suppressor in a pentode is usually
connected to the cathode, or to a low positive or negative voltage,
depending on the tube
application. Because of
negative potential (in any case) with respect to the
plate, the suppressor retards the flight of
secondary electrons and
diverts them back to the plate, where they
cause no undesirable effects. Thus, in
pentodes, the plate voltage
may swing below the screen voltage."
though it is stated that diverting secondary electrons back to the
plate causes no undesirable effects, we have found this to be somewhat
false with respect to sound quality based on the rather dramatic
improvement that results from modifying HOW the spray is diverted back
to the plate.
this; a piece of wire connecting the suppressor grid to the cathode
sounds familiar, but replacing the wire with a non-polarized film cap
creates a condition that makes the tube sound better. You hear a
dramatic increase in clarity. This kind of clarity can only
be from better linear timing with less delays from
shifting phase angles throughout the frequency spectrum, or so one
would think based on the resulting sound. Phase angles are largely
a factor of the amplifier design more so than the tube itself, however,
when the tube is inserted into the amplifier, they become one in the
same. It can only be assumed that by manipulating the
suppressor grids potential against the cathode that we have improved
how the tube functions based on what we're hearing. We're still
discussing theory's to explain exactly what is happening that would
remove hardness and smearing in the playback. Certainly it has
been an eye opening experience to the importance of the suppressor grid
and its effect on the sound. Over a piece a wire, the film
cap has several components, AC, DC, it's size and rate of charge, and
may even have a damping effect on the grid itself.
PART II - MEASUREMENTS OF THE MOD
Can be read here: Christmas
Comes Early Mod Part II
result of doing this is an improvement in coherency that has to be
heard to be believed. On our first test we took a well seasoned SE34I
(EL34 based single ended triode amp) and found the difference to be
larger than any single thing we could have done. For example, pure
silver-wound output transformers would not have made as big an
improvement. Switching the coupling caps to V-Caps or Audionote would
not have made as big a difference. Spending hundreds on N.O.S. tubes
would not have made as big a difference nor would any anything else I
know of. The midrange being always the first to reveal true success was
next test was to see what happened on our pentode wired EL34 push pull
amp called The TORII MK II, and again the same results were observed.
The final test was to do our original Zen Triode amp with the Russian
6P15P-EV tubes, and again, simply amazing. In every case an
increase in performance was seen and dynamics improved with head
shaking improvements in clarity and imaging.
bring the point home, during the test on our Torii MK II, one channel
was done and tested on a single speaker against the stock channel.
Starting with the stock channel, as you might expect when listening to
only one speaker, the sound seems to come directly out of the speaker.
When the modded channel was tried, the single speaker virtually
disappeared. Any time you can make a single speaker disappear
you're on to something.
hearing what we had done to the above mentioned amplifiers with this
mod we could only look at each other and say that "Christmas came early
this year (it's only MAY)!"
we're calling it the "Christmas comes early mod" or CCE mod for short.
As of May 2009 all Decware amps that use either of these tubes are
manufactured with this mod standard.
NOTE: This mod can be done on The Torii Mk II and
all of the Zen Triode amplifiers except for the Mini Torii. Cost is
$100.00 plus return packing and shipping.
If you would like to get the Christmas comes
early mod, just pack your amp so it can't be damaged and fill out the RA form here
on the web site. Print it out and include it with your
amp. We will contact you a few days after it arrives.