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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
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Reference Vacuum Tube Preamplifier
CSP3
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
IMPORTANT SAFETY
INSTRUCTIONS!
PLEASE READ THESE BEFORE
OPERATING THIS EQUIPMENT.
1. Read and Follow these instructions.
2. Do not plug your preamplifier in or
attempt to turn it on until you have
read and followed the steps in this
complete manual.
3. Never leave this preamplifier
powered ON while unattended or at
night when sleeping.
4. Do not use this preamplifier near
water or in damp locations.
5. Do not place this preamplifier near
any heat sources such as radiators,
heat registers, stoves, or directly
above other amplifiers that produce
heat.
6. Do not defeat the safety of the
three-prong power cord by
attempting to lift the ground. If
you only have two-prong outlets in
your home, have a licensed
electrician install a grounded outlet
near the preamplifier.
7. Protect the removable power cord
from being walked on or pinched at
either end.
8. Do not attempt to move this
preamplifier until after it has been
turned off and cooled down to
room temperature.
9. Unplug the preamplifier during
lightning storms or when unused
for long periods of time.
10. Refer all service to Decware or a
Decware authorized service tech.
Do not attempt to fix internal
problems. There are no user
serviceable parts inside.
11. WARNING HIGH VOLTAGES
PRESENT - This preamplifier stores
up to 500 volts in the capacitors.
Do not open the amplifier under
any conditions.
12. Never touch a vacuum tube while it
is operating. Some can reach
temperatures near 400 degrees F.
13. ALWAYS place preamplifier on a
solid sturdy clean and level surface
that can support its weight.!
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lightning flash with arrowhead, within
an equilateral triangle, is intended to
alert the user to the presence of uninstalled “dangerous voltage” within the
product’s enclosure that may be of risk
of electric shock to persons.
The exclamation point within an
equilateral triangle is intended to
alert the user to the presence of
important operating and maintenance (servicing) instructions in the
literature accompanying the appliance.
AVIS RISQUÉ DE CHOC ELECTRIC-NE PASOUVRIR.
WARNING- TO REDUCE RISK
OF FIRE OR ELECTRICAL
SHOCK, DO NOT EXPOSE THIS
EQUIPMENT TO RAIN OR
MOISTURE.
NO USER-SERVICEABLE PARTS
INSIDE. REFER SERVICING TO
QUALIFIED PERSONNEL.
To prevent the risk of electrical shock, do not remove
cover or bottom. No user serviceable parts inside.
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
Thank You!
_______________________________
By purchasing this preamplifier you are
helping to preserve the art of finely
crafted audio products with absolute
world class reference fidelity.
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Please Take a Moment!
_______________________________
The serial number and date of your
amplifier are recorded on the bottom.
Take a moment to write them down
here so you don’t have to move your
amplifier once it is installed.
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Serial Number:__________________
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Date (Month/Year): ______________
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Model Number: _________________
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Technical Assistance
_______________________________
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You can get help by calling us directly
or you by e-mail.
If you have any issues, check the web
site’s contact page for up to date e-mail
addresses and phone hours.
We also have a strong online support
forum that is very active. This can be a
handy way of getting help during off
hours or weekends when our office is
closed.
!
DECWARE/High Fidelity Engineering
75 S. Riverview Dr. East Peoria IL 61611
(309) 822 5255 www.decware.com
Table of Contents!
_______________________________
Safety Instructions 2
Thank You 3
Technical Assistance 3
Unpacking 4
Getting Started 4
What’s What 5
Connections 6
Input Connections 7
Connecting Subwoofers 7
Installing Tubes 8
Tube Matching 8
Tube Substitutions 8
Biasing your tubes 9
Tube life 9
Operation 10
Clipping 11
Headphones 11
Burn in 11
Design 11
Voicing 12
Maintenance 13
Specifications 14
Service 14!
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
Unpacking
Your Preamp should be carefully inspected upon receipt for any damages that may
have occurred in shipping. If you detect any issues please contact us right away.
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Getting Started
If you have taken delivery of your preamp during cold weather please allow it to
come to room temperature before you plug it in and try to use it.
You will need three pairs of high-quality interconnects and a power cord as well as
the supplied tubes.
On the following page you will see diagram of your preamp. Please familiarize
yourself with it as well as refer back to it frequently as you become familiar with
how this preamp operates.
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
What’s what
Here is a top view of the CSP3 layout.
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POWER CORD
3A FUSE
POWER SWITCH
RIGHT OUTPUT
MONO OUTPUT
LEFT OUTPUT
RIGHT INPUT B
RIGHT INPUT A
LEFT INPUT A
LEFT INPUT B
RIGHT OUTPUT LEVEL
ADJUSTMENT
5Y3GT / 5U4G / 5AR4
6N1P / 6922
6N1P / 6922
6N1P/6922/6DJ8
LEFT OUTPUT LEVEL
ADJUSTMENT
RIGHT INPUT LEVEL
ADJUSTMENT
LEFT INPUT LEVEL
ADJUSTMENT
HEADPHONE JACK
HEADPHONE JACK
VOLUME
SOURCE SWITCH
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
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Connections
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The cables and jacks should be kept clean for optimal fidelity. The easiest way to
do this is to clean the male pins on your interconnects and headphone cables with
contact cleaner or 99% pure alcohol BEFORE you plug them into the preamp.
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Doing this will keep the insides of the jacks clean. A serious audiophile will do this
every few times the cables are removed and installed.
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Tube pins are equally important and should be cleaned every time a tube is
installed. Once again, this will keep the tube sockets clean which is critical for
maintaining top fidelity. Tube pins can be cleaned with 99% pure alcohol or a pencil
eraser.
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In addition to keeping tube pins clean, the smaller 9 pin tubes have thinner pins
that must be kept straight. If you notice the pins are bent they must be
straightened prior to inserting the tube into the socket. A simple way to accomplish
this is to have a tube pin straightener available from Decware.
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tube pin straightening tool from Decware
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
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Input Connections
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Your CSP3 can accommodate two line-level sources such as a CD player and a
Phono Stage for listening to LPs.
The switch to select inputs is on the front the preamp near the volume control. If
you require more than two sources we make a high-quality silver switch box that
can be used to extend the total number of sources to five.
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Your CSP3 contains a silver input selector switch and the switch box shown above is
also using silver switching and silver / Teflon internal wiring. This component is
called the ZSB and available on the Decware web site.
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Connecting Subwoofers
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The CSP3 can be built with your choice of two output jack configurations. You can
have two pair of stereo jacks OR one pair of stereo jacks and one mono jack.
The mono jack can be used to drive a center-speaker amplifier in a three-channel
setup, or a single channel amplifier in a mono set up; most commonly the jack can
be used to drive a powered subwoofer.
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
Installing Tubes
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There is nothing particularly special about installing the tubes other than making
sure they are the correct ones! In the case of this preamp, we ship it with (3) 6N1P
tubes which are all 9-pin tubes. It makes no difference which of the three 9-pin
sockets you put these tubes in.
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The large octal (8-pin) tube is the rectifier tube and can only fit in the larger socket
and only rotated a certain way so that the plastic dowel key in the center of the
tube socket lines up.
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Make sure tubes are OFF and COOL before you remove or install them. Contrary to
popular misinformation, you can touch the tubes without having to clean your
finger oil from the glass. Your finger oil will have no effect on the operation or the
life of the tubes.
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Tube Matching
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Matching the tubes is not required in the CSP3 preamp since the channels can be
individually adjusted; however it is nice to have the left- and right-rear 9 pin tubes
matched when possible so that you do not have to correct for channel imbalances
that might otherwise result.
The input tube at the front of the preamp actually serves both channels; meaning
the left triode section of the tube does the left channel and the right side does the
right channel. Again, while not required, it is nice to have this tube with matched
sections so the channel balance remains true without adjustment.
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Tube Substitutions
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Rectifier Tube - Used to convert high voltage AC to high voltage DC. The factory
supplied rectifier is either a 5U4 or a variation of it, such as the 274B from Valve
Art.
The CSP3 uses a 47uf 500V capacitor in the first section of its power supply, so
many 1940s rectifiers and remakes are not compatible since they want to see less
than 10uf 500V capacitors. When buying fancy rectifier tubes always be sure they
will be compatible with 47uf 500V capacitors.
The recommended rectifier tubes for this preamp are: 5U4G, 5AR4, 5Y3GT
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
Tube Substitutions cont’d.
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The front 9 pin tube can be substituted with the following: 6N1P, 6N5P, 6N23P,
6DJ8, 7DJ8, 6922, 6N11 Of all these tubes, the 6N1P is the warmest. The 6N5P
sounds just like it but has better focus and a touch less gain. The rest vary from
brand to brand.
The other two 9 pin tubes can be substituted with 6N1P, 6N5P, 6922, 6N11
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Biasing Your Tubes
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There is no biasing to adjust on the CSP3 preamp. All the tubes are cathode biased
which makes them naturally self adjusting and always in the optimal range.
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Tube Life
If the recommended 9 pin tubes are used the tube life will be whatever the
advertised lifespan is on the tube data sheet. In most cases this will be around
6000 hours for a new tube.
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Rectifier tubes are the first line of defense against power spikes and can fail as a
result of this for what would seem like no apparent reason. If rectifiers are used
that are not the recommended 5U4G, 5AR4, 5Y3GT then there is no guarantee how
long they will last. Using the approved rectifiers it is possible for one to last for up
to four or five years before it starts getting tired.
If a rectifier tube sparks internally when you first turn on the preamp, it is a sign
that the tube may fail in the near future when the preamp is first turned on.
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Always have a good working spare rectifier tube on hand at all times.
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
Operation and Setup
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To operate your CSP3, install the tubes, hook up the output jacks to the amplifier.
Once you are sure the amplifier and preamp are securely connected together with a
high quality interconnect cable between 1 and 5 meters in length you may plug
both units into the wall outlet.
Before you turn either piece on make sure that all of the controls on the CSP3 are
turned all the way down.
Turn on the CSP3 and let it warm up for one minute. Double check that all the
controls are down all the way, including the volume and that the interconnect cables
are securely installed into the output jacks of the CSP3 and the input jacks of your
amplifier.
Turn on the amplifier. The amplifier should come on and if has a gain control on it,
turn it up to the half way point. Your system is now on and at idle. Any noise or
hum that you hear is your system reference. Make a note of it so that later when
we connect our sources we can see if they added any noise or hum.
It is now time to connect your first source component to one of the input pairs on
the CSP3. You can do this while the CSP3 and your amplifier are on and at idle, but
be sure you haven’t turned any of the controls on the CSP3 up yet.
If you didn’t hear any hum or noise increase when you connected your first source
that means that A) your cables are probably good and B) there is no ground loop
between the components.
No add your second source if you have one and again listen for any increase in
noise or hum. If with either source you DO notice an increase in noise or hum then
it comes from cables or small ground loops between the components or both. The
key here: is the noise or hum acceptable? For example if you have to put your face
up to the loudspeaker to hear it, it’s acceptable. If however you can hear it from
the listening chair it is not acceptable and should be corrected before going any
further.
Once everything is connected and warmed up and you are happy that there are no
excessive amounts of noise or hum, you can set the controls on the CSP3 to match
your amplifier’s requirements:
1) turn up the input level controls all the way (clockwise). These are only adjusted
during headphone use and only with headphones that get too loud.
2) turn on your source and get some music playing.
3) turn up the main volume control on the CSP3 to half way.
4) slowly turn the output level controls up until you hear music playing at a normal
listening volume.
5) your preamp is now adjusted properly for your amplifier.
6) further experimentation can be made by adjusting the gain control on the
amplifier if it has one relative to the output level settings on the CSP3.
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
Clipping
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Clipping is another term for distortion during playback. The CSP3 has up to 30
volts of output with an industry standard 2 volt input signal without distortion and
can be adjusted to handle any input voltage via its variable input controls. Since
most amplifiers are set up to play at their full rated power with as little as 1/2 to 2
volts, it would be virtually impossible to clip the line level outputs of the preamp.
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Headphones
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Believe it or not the CSP3 was originally designed as a reference grade OTL
headphone amplifier. It wasn’t until later that we decided to make it also work as a
preamp and since no additional circuity was required it was the logical thing to do.
You can use any dynamic headphone between 32 and 600 ohms with your CSP3.
In fact there are several of the more efficient planar headphones that will also work
reasonably well.
If your headphones get too loud too fast, you can turn down the input level
controls.
The CSP3 can be built with either a pair of 1/4 inch headphone jacks, or a pair of 4
pin XLR jacks, or one of each. Also it can be built with dual 3 pin XLR jacks. Your
headphone cables are what determine what kind of jacks you need. Many people
will configure it with one 1/4 inch headphone jack and one 4 pin XLR headphone
jack which covers the most popular headphone cables.
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Burn-in
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When your CSP3 is new it will require about 200 hours of use to reach what we a
term “burned in” state which is to say a state where the sound is pretty much
where it’s going to be from then on out. During the 200 hour burn in period the
preamp and the tubes will season and you will hear the sound continue to improve.
The biggest differences happen in the first 20 hours.
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Design
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The CSP3 has a somewhat interesting design behind it. It is a dual triode driving a
pair of dual triodes where there is one for each channel. The pair that is being
driven is wired so each triode is in series (SRPP) giving it both massive output
levels but also low output impedance to drive long cable runs.
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
Design cont’d.
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There are precious few parts in the circuit and it is wired point to point with no
circuit boards but even that’s not what sets this preamp so far apart from similar
circuits. The CSP3 features a very simple single node power supply that feeds all
three tubes from the same point. The power transformer is rated for a 170
milliamp load which is what you would see with a 40 watt power amplifier, yet it
only draws 10 milliamps! That makes the power supply of the CSP3 literally 17
times larger than required and that much more expensive.
The reason for this is multi-pronged. A) the power supply has bottomless current
and over twice the voltage it needs to operate with zero sag and therefore requires
zero regulation. B) it will last virtually forever which makes it easy to carry our
lifetime warranty.
As a headphone amp or a line-stage, this artifact-free liquidity is well appreciated
and solely the result of this power supply.
For line stage use we made the output level of each channel adjustable relative to
the master volume control to make it compatible with literally any size or type of
audio amplifier.
Besides being able to adjust the gain structure with these output level controls to
effect the voicing, you can also do a great deal of voicing with tubes.
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Voicing
The CSP3 can be voiced through gain structuring and through tube rolling. To voice
by gain structuring you simply experiment with the relative settings between the
volume control and the output level controls. For example, having the volume
control higher in it’s range and the output level controls set lower will sound one
way while doing the opposite will sound another way. If your amplifier has a gain
control, the same can be done between the output controls of the CSP3 and the
gain control of the amplifier.
To voice with tubes, we recommend starting with rectifiers. Get yourself three or
four different compatible rectifiers to try and settle on a favorite. After the rectifier
tube you can then experiment with different input tubes, which is the single 9 pin
tube in the front. There remaining two 9 pin tubes are almost always best kept
stock (6N1P).
Focusing on the input tube location, you will find the 6N1P warmer, the 6922 less
warm but more focused and the 6DJ8 to be more detailed in the top end and lighter
in the bass. Of course there are many more tubes than this to try, but these are
the three basic starting points.
For headphone users, voicing can mean the difference between liking and disliking a
pair of headphones.
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
Maintenance
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There is no real maintenance on the CSP3 other than to keep it and the jacks clean.
The best tool for dusting your CSP3 is a 2 inch paint brush. If you have to really
clean it, remove the tubes and spray some windex (window cleaner) on a cloth rag
and wipe the surfaces clean. When dry, clean and re-install the tubes.
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Tubes should be replaced every couple years on average, but it is dependent upon
use.
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Since tubes wear out slowly it is hard to hear when to change them. The trick to
knowing their condition is simple; Keep a complete set of new tubes on hand and
every 6 months install them to see if the sound improves. If it does its probably
time for new tubes. If the sound doesn’t improve then put the new tubes back in
the boxes and try again in 6 months.
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You can think tube replacement for your CSP3 in 3 levels:
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1) The first tube to replace is the rectifier. If it’s getting tired a new one will sound
cleaner and more robust.
2) The second level is the input tube in front. Replace it with another of the same
type and see if the sound gets better.
3) The third and final level is the output tubes which are the remaining two 9-pin
tubes. These are usually purchased and replaced in matched pairs.
It is possible for only one of the three levels to require new tubes, or all three
levels.
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NOTE: the level controls and and the volume controls are designed to be used, so it
is good to periodically turn them throughout their full range before the preamp is
turned on just to work the dust out of them. This is especially true if the preamp
has sat for any length of time (months) without use.
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OPERATION MANUAL MODEL : CSP3 - CLASSIC STEREO PREAMP! REV 1 MAR 2018
Specifications
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Weight 16 lbs
Dimensions 8.5” H x 7.25” W x 14.75” D
Circuit Triode Class A OTL
Input Voltage Adjustable
Noise/Hum -80dB
Input Impedance 100k Ohms
Output Impedance <600 Ohms
Feedback None
Rectification Tube 5U4
Signal Tubes 6N1P / 6922
Biasing Cathode Bias - no adjustments needed
Resistors 1% metal film and carbon composition
Signal Caps Film and Foil
Filter caps F&T 500V 47uf x 2
AC Cord Fused IEC 3A fuse and removable cord included
Consumption 65 watts
Input jacks RCA
Output jacks RCA
Headphone jacks dual 1/4”, 4 pin XLR or 3 pin XLR
Warranty lifetime to original owner, 90 days on tubes
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Service
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For service please contact us by phone or by email. You can find both on the
contact form of our web site, www.decware.com
We can help you troubleshoot your system and help you determine what is causing
the issue that you’re having. Everyone can save themselves a lot of trouble by
having a spare set of known good replacement tubes on hand. Most problems are
tube related. For example, noise or hum problems could be a tube. Channel
balance issues are likely a tube. Sound quality issues are likely a tube.
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