Duncan Twin Tube Blue SFX-11 User manual

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Two Channel Tube Overdrive / Distortion Pedal
SFX-11
Congratulations on your purchase of the Seymour Duncan
Twin Tube Blue™. You can start using your Twin Tube Blue right
away after reading the safety precautions below, and you’ll
immediately enjoy the versatility of having two channels of gain
and a wide range of great tones. However, you might want to
read through these instructions in their entirety rst, to gain
valuable information, which will enhance your enjoyment of your
Twin Tube Blue.
TM

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Safety Precautions
Hazardous voltages are present. For your protection, and to reduce the risk
of electric shock and danger to personal health, please observe the following
safety precautions when setting up and using your Twin Tube Blue. Most of this is
common sense, but please read it anyway.
Your Twin Tube Blue is designed to work with typical power systems utilizing a
three-prong outlet. To reduce the risk of electric shock, do not plug your Twin
Tube Blue into any other type of power system. Contact your facilities manager
or a qualied electrician if you are not sure what type of power is supplied
to your building or performance stage. Do not use your Twin Tube Blue with
ampliers or other gear that have two prong AC plugs. Do not overload wall
outlets, extension cords, or multiple power strips as this can result in a risk of re
or electric shock.
Never open the chassis. Do not attempt to tamper with or service your Twin Tube
Blue yourself. You’re just asking for trouble. Opening or removing the cover may
expose you to dangerous voltage or other hazards, which could result in serious
injury or death – not to mention damage to the Twin Tube Blue. Wouldn’t that
suck? Refer all servicing to qualied service personnel.
Do not block or cover the side vents on your Twin Tube Blue. Never push objects
of any kind through openings in the equipment. No drummer jokes, please.
Dangerous voltages may be present. Conductive foreign objects could produce
a short circuit that could cause re, electric shock, or damage to your Twin Tube
Blue.
Never place a Twin Tube Blue near a radiator or heat register. Failure to follow
these guidelines can cause overheating and affect the reliability of your Twin
Tube Blue.
Unplug your Twin Tube Blue from the wall outlet before cleaning. Do not use
liquid cleaners or aerosol cleaners. Use a damp cloth for cleaning.
Do not use your Twin Tube Blue near water - for example, near a bathtub,
washbowl, kitchen sink, or laundry tub; in a wet basement; near a swimming
pool; on stage with water effects or precipitation; and the like. Do not expose
the Twin Tube Blue to dripping or splashing liquids and do not place objects
lled with liquid on or near your Twin Tube Blue (yes, unfortunately, this includes
bottled malt beverage liquids). And for heaven sakes, don’t use it while you’re
sitting on the can… OK, enough of that.

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General Information
The Twin Tube Blue is designed for years of solid performance. One of the
secrets is the duo of type 6111 tubes. These sub-miniature triodes represent
the pinnacle of tube technology advancement. The 6111s were designed and
manufactured to meet the MIL-E-1 spec for reliability under conditions of severe
shock, vibration and temperature. They provide extremely long service life with
virtually no tendency towards microphonics (see USA Department of Defense
Standards, Test Methods for Electron Tubes). Also, unlike some “tube” stomp
boxes that only use the tubes as a clipping diode, the Twin Tube Blue employs
a 100% vacuum tube signal path with a high voltage power supply. This allows
the tubes to operate to their fullest potential and provides the most gain and the
smoothest tone. The result is the classic tube sound, smooth distortion, and low
order harmonics you expect from a great tube preamp.
Tube Life
The 6111 tubes will typically last many times longer than even the best 12AX7s.
For most Twin Tube Blue owners, this means you’ll never have to change your
tubes. However, nothing lasts forever. Should you nd your Twin Tube Blue in
need of new tubes (e.g., exhibiting erratically uctuating signal levels, spurious
increases in noise, sputtering, low level whistling, extreme loss in frequency
response), contact Seymour Duncan or your favorite authorized Seymour
Duncan dealer for your options.
Do not try changing the tubes yourself.
Changing tubes on the Twin Tube Blue is more complicated than plugging pins
into a socket and could be dangerous. Make sure a professional does the work.
Two channels means versatility. When coupled with (true) bypass, this effectively
provides three-channels: Rhythm, Lead and bypass. Separate gain and volume
controls allow Lead and Rhythm Channel levels to be independently set. The
meticulous internal layout minimizes cross coupling and unwanted circuit
interactions that can be a major problem in high gain-high impedance vacuum
tube circuits.

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Explanation of Controls
1 Rhythm Gain – Inter-stage gain control for the Rhythm Channel. Provides varying
degrees of overdrive, from clean tube tone to crunch.
2 Rhythm Channel Status Indicator – When lit, it indicates that the Rhythm
Channel is active or staged for activation if the unit is bypassed.
3 Rhythm Volume – Master volume control for Rhythm Channel. Positioned at the
end of the gain chain, it regulates the loudness relative to the other channel, and to
the bypassed sound.
4 Lead Gain – Inter-stage gain control for the Lead Channel. Provides varying
degrees of overdrive, from bite to super hot lead tones.
5 Lead Channel Status Indicator – When lit, it indicates that the Lead Channel is
active or staged for activation if the unit is bypassed.
6 Lead Volume – Master volume control for Lead Channel. Positioned at the end
of the gain chain, it regulates the loudness relative to the other channel, and to the
bypassed sound.
7 Bass – Controls low frequency content in both channels with greatest effect in the
range of 40 Hz to 200 Hz.
8 Treble – Controls high frequency content in both channels with greatest effect in the
range of 2 KHz to 20 KHz.
9 Channel Selector – Selects between the Lead and Rhythm channels. It is possible
to pre-select the gain or volume for a channel when in bypassed mode. This allows the
exibility of transitioning from bypass to either channel without having to step through
different sounds.
Top Panel
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2
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7
5
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10
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10 On/Bypass button – Selects between true bypass and whichever channel has
been selected by the Channel button.
11 Active/Bypass status indicator – When lit, it indicates that the Twin Tube Blue
is engaged and operational. When dark, it indicates that the unit is in bypass mode
and that the guitar signal is passing straight through unaltered.
Explanation of Controls
Back Panel
1 Input Jack – Plug your guitar in here
2 Output Jack – Provides the output signal. Connect to the input of a guitar amp,
power amp or other device here.
3 Power Jack – This is where you connect the provided wall-mounted power supply
(“wall wart”) to the Twin Tube Blue. Note: it is a 16 VAC/600mA unit. Do not try to
substitute a DC power supply or another AC supply with a different voltage value
or current rating. If you lose your transformer or if it breaks, contact an authorized
Seymour Duncan dealer for a replacement. As an alternative, for North America and
Japan, you can order a 16 VAC/600mA transformer from Digi-Key (www.digikey.
com). The part numbers for each common voltage is as follows:
North America: 120 Volt/60Hz – Digi-Key part # MT7123-ND
Europe and Asia: 230 Volt/50Hz – Seymour Duncan part # 352301-230 (no
known off-the-shelf replacements available)
Japan Only: 100 Volt/50Hz – Digi-Key part # MT7127-ND (note: this
transformer is rated by the manufacturer as 20 Volt/450mA output with 120 Volt
input, but will produce the proper output voltage and current when coupled to a
100 Volt mains supply)
2
1
3

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Explanation of Controls
You may be wondering why the Twin Tube Blue uses a 16-volt AC transformer
instead of a common 9-volt DC adaptor or even a battery. The Twin Tube Blue relies
on an internal transformer to obtain the high voltage the dual triodes require. The
transformer cannot work on DC voltage. One alternative would be to run the tubes
on low voltage in “starved plate mode.” Here, the tubes are used like a clipping diode
and do not actually amplify. Though starved plate voltage is used in some inexpensive
tube stomp boxes, it is not true tube amplication. The circuitry in the Twin Tube Blue
enables the tubes to work like the tubes in the preamp section of a high quality tube
amplier. Another alternative would be to supply a dedicated AC power cord and an
internal high voltage transformer or a DC-to-DC switching converter. However, these
options would make the Twin Tube Blue larger, heavier and more costly. With the Twin
Tube Blue you are getting true tube tone AND tube amplication with minimal size,
weight and cost.

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The ¼” mono instrument cable that leaves your guitar’s jack plugs into the Twin
Tube Blue’s jack marked “Input.” The cable that exits from the “Output” jack on
the Twin Tube Blue goes to the next effect in the signal chain, or to the amplier.
When rst activating the Twin Tube Blue, start with the Rhythm Channel Volume
and Gain control knobs in the full counter-clockwise position. Then, start rotating
the knobs clockwise until the desired volume level and overdrive are achieved.
Next, with the Lead Channel Volume and Gain control knobs in the full counter-
clockwise position, depress the Channel Selector switch. This mutes the Rhythm
Channel and activates the Lead Channel. As with the Rhythm Channel, start
rotating the knobs clockwise until the desired volume level and distortion are
achieved, relative to the Rhythm Channel and to the bypassed sound of the Twin
Tube Blue.
Experiment with different Volume and Gain settings. Some of the coolest tones
are achieved with a little discovery. Because of the Twin Tube Blue’s incredible
amount of gain and distortion in the Lead Channel, be aware that extreme settings
can result in uncontrollable feedback. And, as always, musicians and audience
members are best advised to use ear protection when exposed to loud volume.
Here are some sample settings to get your started:
Basic Operation
Tune your Strat® to E at and let it rip. Sweet and soulful and
downright nasty at the same time, all at your ngertips.
Austin Texas Crunch
Example Settings

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Basic Operation
With a semi-hollow and humbuckers, you can feel the connection
between guitar and tubes. You can push it just hard enough to
break up, while most of your notes are clean and clear.
Memphis Boogie
Dirty blues will hit your amp hard, if you’ve got the chops. This will
dirty up your Strat®, but you’d better hit hard and dig in if you want it
to get greasy.
Chicago club

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Basic Operation
Explode into modded tube amp territory. No additional overdrive
pedal needed with this setting. There’s enough gain on tap for
searing leads and loads of sustain.
Searing lead
strat is a registered trademark of fmic with which seymour duncan is not affiliated

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Detailed Step-By-Step Instructions
1. Plug in the cable of the provided 16 VAC power supply to the distortion box
then plug the “wall wart” end into a 120V wall outlet or power strip. You should
see the green LED on the Rhythm channel light up. All other status indicators
will be dark. When rst powered up, the Twin Tube Blue will always default to
bypassed mode with the Rhythm channel staged in waiting mode.
2. Turn both master volumes fully down (counter-clockwise). Set the Bass and
Treble controls at 12 o’clock.
3. Connect a good quality, shielded ¼” cable from the output jack to the input of
your amplier.
4. Connect another good quality, shielded ¼” cable, rst to the output jack on
you guitar, and then to the input jack of the Twin Tube Blue. Note that the tubes
in the Twin Tube Blue may require two to three minutes to warm up and begin to
produce sound.
5. Press the “On/Bypass” button to activate the Rhythm Channel. Turn the Gain
control up about half way. Slowly turn the Master Volume up as you pluck a string.
Fine-tune the Gain setting to achieve the level of overdrive and saturation you
want. Set the Master to achieve the playing volume you want.
6. Press the “Channel Selector” button to switch to the Lead Channel. Repeat the
previous process of setting up the Gain and Master Volumes.
7. Adjust the Bass and Treble controls as desired. Note that they inuence both
channels. We have “pre-voiced” the two channels to provide what we feel is a
balanced tone when switching from Lead Channel to Rhythm Channel and to
facilitate using one common set of tone controls.
8. Balance your wet to dry levels by working with the Volume control(s) on your
amp and the Master Volumes on the distortion box.
9. Never open the chassis. There are no user serviceable parts inside and
tampering with the high voltage tube circuits could result in serious injury or death
– not to mention damage to the unit.

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Specifications
Description – The SFX-11 is a two-channel guitar preamp employing premium
subminiature type 6111 vacuum tubes. The 6111 is manufactured to meet the
stringent MIL-E-1 specication for reliability and is optimized to provide long
service life under conditions of severe shock, vibration, high temperature and high
altitude. The tubes are congured with a high voltage power supply for maximum
dynamic range. True bypass capabilities are provided to allow uncolored feed-
through.
Gain:
• Before level compensation
Rhythm channel – 74dB
Lead channel – 98dB
• After level compensation
Rhythm channel – 52dB
Lead channel – 76dB
(Gain measured at 500Hz).
Nominal output level
• Rhythm channel – 0.4 Vrms (-5dBu)
• Lead channel – 0.5 Vrms (-4dBu)
(Nom. output level measured with 100mV 500Hz input signal and all
controls set to 12 o’clock).
Max. output level before clipping – 2 Vrms (+8dBu)
(Max. output measured with all controls set fully up).
THD @ 1 Volt RMS output – 3%
Harmonic spectrum @ 1Vo – predominantly 2nd harmonic with minor amounts
of 3rd harmonic @ > 20dB below.
Noise @ output:
• Rhythm channel - < 3 mV (< 3 dB hum content)
• Lead channel - < 10 mV (< 3 dB hum content)
(Noise measured with all controls set fully up and input shorted).
Power consumption – 10.4 W
External dimensions – 7.50 X 6.62 X 1.96 in. (190 X 168 X 50 mm)
Weight – 3.15 lbs. (1.43KG)

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Designed and Distributed by:
Seymour Duncan / Basslines
5427 Hollister Ave.
Santa Barbara, CA 93111-2345 USA
tel: [phone]
fax: [phone]
www.seymourduncan.com
PN: 501070-150 Rev A
The SFX-11 is made in China. Designed and tested in USA. Printed in China. © 2009
Seymour Duncan offers the original purchaser a one-year limited warranty on both labor
and materials (except tubes) starting from the day this product is purchased from an
Authorized Seymour Duncan Dealer. The warranty on the tubes is 90 days. We will repair
or replace this product, at our option, if it fails due to faulty workmanship or materials
during this period. Defective products should be returned to your USA dealer, international
distributor, or sent direct to our factory postage prepaid along with dated proof of purchase
(e.g., original store receipt) and a RMA number clearly written on the outside of the box.
Please call our factory for issuance of an RMA number.
This warranty does not apply to damage to this product or an instrument caused by misuse,
mishandling, accident, abuse, alteration or faulty installation. Product appearance and
normal wear and tear (worn pain, scratches, etc.) are not covered by this warranty. Seymour
Duncan reserves the right to be the sole arbiter as to the misuse or abuse of this product.
Seymour Duncan assumes no liability for any incidental or consequential damages, which
may result from the failure of this product. Any warranties implied in fact or by law are
limited to the duration of this express limited warranty.
Limited Warranty