We took this a step further with what we call the Hazen Grid Mod, aka Christmas
Comes Early Mod, where we couple the suppressor grid to the cathode through a
capacitor adding great clarity to the tube by reducing stray electrons that typically
bounce of the plate and reattach themselves in a different location due to the potential
on the suppressor grid. This pushes this popular tube up the fidelity later even higher
and as a result handles stray electron bounce better than expensive directly heated
triodes like the 300B. Another advantage to using this output tube configuration is that
it’s quiet.
Directly-heated triodes are generally noisy in that some hum is expected unless great
expense is taken in the power supply which is seldom done. The result is an amplifier
with less than black backgrounds when you listen to music.
TUBES - input
The smaller 9 pin input tubes in this amplifier are dual triodes configured as an SRPP
stage to give maximum voltage swing with the least number of parts. The only
alternative is to use two gain stages with an additional coupling capacitor. Since the
amplifier design only has one coupling capacitor, we certainly would hate to DOUBLE
the quantity in this otherwise extremely transparent amplifier. The tube used is our
favorite Russian NOS military grade 6N1P-EV. (In Russian that reads 6h1n-EB, which is
what is printed on the tube) Alternately you can use 6922’s which are a touch less
warm but slightly more dynamic. Using 6DJ8’s may or may not work depending on the
brand and condition of the tube. This is because the voltages used are on the max
end of what a 6DJ8 likes to see. Alternately, you can also use the Russian 6N2P-EV
for more gain, a more open and lively sound. There are two grades of this tube (as
there is for the 6N1P) and the easy way to tell the military grade from the consumer
grade is the pins. The better tubes have shiny plated pins, while the consumer grade
are un-plated and dull looking.
With the 6N2P the difference in sound between the two grades is pretty obvious. The
better grade has more definition and is tighter. These tubes are also quiet. The
consumer grade is more musical sounding, but typically noisier. The consumer grade
usually requires you to have two or three pairs on hand to find one pair that is quiet
enough to use and enjoy - but they are inexpensive.
TUBES - rectifier
The rectifier tube in this amplifier is located directly in front of the power transformer.
DO NOT TOUCH IT WHEN IT IS ON as it will be HOT and could burn your hand. The
amplifier typically ships with a 5U4G rectifier tube. There are many different brands of
5U4 type rectifiers both in New Old Stock (NOS) and in current production. Each will
have a subtle effect on the sound of your amplifier. Each will also sound different.
O W N E R S M A N U A L
Decware High Fidelity Engineering Co., East Peoria IL, USA www.decware.com
