Decware SE34I.5 Owner's Manual

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Decware High Fidelity Engineering Co., East Peoria IL, USA www.decware.com

MANUAL NO. 01 REV. DATE: 10/2015

MODEL SE34I.5

aka Rachael

ZEN TRIODE INTEGRATED

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DESCRIPTION!

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The Zen Triode Integrated is a 5~6 watt per channel - single-ended-triode amplifier
using easy to find EL34/6CA7 output tubes. It has zero negative feedback for unlimited
sound-stage depth and superior imaging. It features tube rectification, proprietary
Decware transformers, a self-biasing circuit with a bias meter for each output tube.
Like the famous SE84C 2 watt Decware amplifier, this is a purist built product with the
absolute minimum number of parts and solder nodes. Between the input and output
jacks there is only 1 capacitor, 2 resistors and our premium output transformers made
from the finest US gain oriented silicon steel. (see section on transformers)

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DUAL VOLUME VS. SINGLE VOLUME CONTROLS!

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When you purchase the “Integrated” configuration of this amplifier you will have the
option of setting it up with ONE or TWO volume controls. Here are the pros and cons of
each:

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Single volume control - Pros: Ease of Use, stereo image is always centered.
Cons: No way to adjust balance
Dual volume controls - Pros: Ability to adjust balance
Cons: slightly more difficult to use.

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The main question one would have is why not simply have a volume control and a
balance control? Reason: That puts two controls in the signal path instead of one. In
an amplifier with only two resistors and one capacitor, adding additional parts, like
these controls, in the signal path is audible. Remember, less is more and the goal is to
preserve transparency - one of this amplifiers strongest traits.

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Dual volume controls have another advantage besides half as many parts in the signal
path when compared to a volume and balance control. With dual volume controls you
can turn up one speaker by itself to a desired listening level and then turn up the other
channel to match. Meaning you can make the second channel higher or lower without
effecting the first channel. The advantage to doing this is that you can hear once you
get close to a match between the channels, the sound stage lock-in when you hit the
right spot. Since your room is non-symmetrical and your speakers are in reality not
matched to within 5% of each other, having the volume exactly perfectly centered
between the channels is never the perfect spot. You’ll hear it when you try it. And
you’ll notice a small window when you get close to matched where you can actually
adjust the sound stage to your room a bit better.

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Decware High Fidelity Engineering Co., East Peoria IL, USA www.decware.com

O W N E R S M A N U A L

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TUBES - output!

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The SE34I.4 uses a single EL34/6CA7 output tube per channel. These are the larger
ones on either side of the power transformer. They are run with lower voltages for
increased life and better tone. NOTE: The EL34 is a true pentode and has no internal
connections between the suppressor grid and cathode like the vast majority of audio
tubes (6550, KT88, KT77, 6L6, 6V6 to name a few). That means other than directly
heated triodes like 2A3’s, 300B’s for example, the EL34 is the only popular audio tube
that can be wired as a TRUE TRIODE. We find the EL34 wired this way in our circuits to
sound excellent.

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Due to the unique opportunity with EL34’s we developed what has come to be known
as the Hazen Grid Mod, aka Christmas Comes Early Mod (CCE Mod for short), 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 normal.

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While the CCE circuit will have no effect on the following tubes, they are still wonderful
sounding alternates that can be used in your amplifier, each with it’s own sound, all
about the same power in this particular circuit. They are: 6L6G, KT77, KT66, KT88,
6550, 7027, 6CA7. These are all plug in compatible alternates to the EL34 in this
amplifier and require no adjustments.

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Decware High Fidelity Engineering Co., East Peoria IL, USA www.decware.com

O W N E R S M A N U A L

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TUBES - input!

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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.

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TUBES - rectifier!

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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.

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There are also some compatible substitutes that you can try which include 5Y3GT and
5AR4. The 5AR4 is an indirectly heated rectifier with a soft start up so it may be a bit
more expensive than the 5Y3GT and 5U4. A popular rectifier tube that many people try
to substitute is the 274B. There are different manufactures and different types of 274B
rectifier tubes. Of the ones we’ve examined, they all required no more than a 10uf
capacitor in the first section of the power supply. Very few tubes amps today use that
small of a value. The SE34I.4 uses a 47uf capacitor in this location which can cause a
vintage 274B to arc on start-up and thus reduce it’s life. We have found a tube labeled
274B by Valveart that we do not find to be a real copy of a 274B but rather a beefed up
5U4, which happens to work well and look great so it is often shipped as the stock tube
in this amplifier.

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Decware High Fidelity Engineering Co., East Peoria IL, USA www.decware.com