ART TUBE CHANNEL User Manual

TUBE CHANNEL

USER’S MANUAL

FEATURES......................................................................................3

OVERVIEW.....................................................................................3

W

HY USE AN EXTERNAL PROCESSING CHANNEL

D

ESIGN NOTES

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?...............................3

SETTING UP...................................................................................5

U

NPACKING

AC P
A

UDIO CONNECTIONS

I

NSTALLATION

S

AFETY PRECAUTIONS

P

OWERING UP

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OWER HOOKUP

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FRONT PANEL CONTROLS & INDICATORS ...........................7

P

REAMP CIRCUIT

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Gain Control..............................................................................7

Gain Switch................................................................................ 7

Phantom Power Switch...............................................................7

Tube Drive/Gain Reduction Display...........................................8

Preamp Output...........................................................................8

O

PTICAL COMPRESSOR CIRCUIT

.......................................................9

Slope Switch...............................................................................9

Speed Switch ..............................................................................9

Compressor Bypass Switch.........................................................9

Compressor Threshold and Output Controls.............................10

Compressor Threshold Control (outer control).........................10

Compressor Output Level Control (inner Control)....................10

Clip Indicator...........................................................................11

E

QUALIZER CIRCUIT

......................................................................11

Low Frequency Control............................................................11

Low Shift Switch.......................................................................11

Lo-Mid Frequency Control.......................................................12

Lo-Mid Shift x 10 Switch ..........................................................12

Hi-Mid Frequency Control.......................................................12

Hi-Mid Shift x 10 Switch...........................................................12

High Frequency Control...........................................................12

High Shift Switch...................................................................... 13

EQ Bypass Switch.....................................................................13

Master Output Level Control....................................................13

Phase Switch ............................................................................13

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Output Level VU Meter............................................................ 14

Power....................................................................................... 14

REAR PANEL CONNECTIONS.................................................. 15

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NPUT AND OUTPUT CONNECTIONS

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I

NPUT

O
L

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UTPUT

OOP INSERTS

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Preamp - Compressor Loop...................................................... 16

Compressor - EQ Loop............................................................. 16

Loop Connections.................................................................... 16

APPLICATIONS ........................................................................... 17

S

PECIAL EFFECTS

EQ T

....................................................................................... 19

IPS

.......................................................................... 18

What is the best way to use EQ?............................................... 19

TUBE REPLACEMENT...............................................................20

BLOCK DIAGRAM......................................................................21

A R T TUBE CHANNEL SPECIFICATIONS ............................. 22

WE’RE ON-LINE! ........................................................................ 23

WARRANTY AND SERVICE INFORMATION......................... 23

L

IMITED WARRANTY

S

ERVICE

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Features

The Tube Channel is a unique product. It contains three independent
award-winning circuit designs: one of the finest tube microphone
preamplifiers available, one of the finest optical tube compressors
available, and one of the most flexible EQs you’ve ever used -- all in
one unit. Developed in partnership with studio and live sound
engineers, the Tube Channel possesses a “sound” that is not available
from any other product on the market -- at any price! The Tube
Channel was designed and constructed with the best components,
assuring a lifetime of quiet, reliable performance. The Tube Channel
offers:- The award winning A R T “SOUND”! - A Tube-based
mic/line preamplifier- An Electro-optical compressor design

- A Tube-based semi-parametric, four-band equalizer- Hand-selected
preamp tubes- VCA-less compressor circuitry (i.e., transparent
dynamics control)- Unique tube drive and gain reduction metering

- VU output level metering- Bypassable compression and equalization
circuitry- XLR balanced inputs and outputs- ¼” TS unbalanced inputs
and outputs- A Custom extruded aluminum chassis

- ¼” unbalanced insert points between the preamp and compressor and
between the compressor and equalizer- +48V phantom

power- Phase reversal- Over 70dB of gain- Detented rotary controls­Compression and limiting ratios- Selectable release time settings­>90dB dynamic range- An Internal power supply- A three year
warranty- The Tube Channel was Designed and manufactured in the
USA

Overview

Why use an external processing channel?

The shortest signal path is the best way to get a signal to tape. In most
cases, the shortest path is: mic to preamp to compressor to EQ to tape
deck. The signal doesn’t even go through the mixer! This isn’t a new
concept, but it has become more relevant with the availability of
affordable mixing consoles. As their name implies, most affordable
mixers excel in signal routing and mixing capabilities. However, they
are not necessarily your best option for the actual recording of tracks.
While their onboard circuitry is nearly always clean and quiet, the
simple truth is that the Tube Channel has a better sounding and more

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flexible collection of circuits. Mixer manufacturers need to make
trade-offs to keep prices down while keeping performance up. Imagine
the price of your mixer if each channels’ EQ cost over $200 (and we’re
not talking about those of you who have one of those $250,000+
consoles!) The use of external processing (equalizers, preamps and
compressors) has sonic and practical benefits when you consider that
most recording is done one or two channels at a time. For those of us
on a budget, it just doesn’t make sense to spend a ton of money on a
“Cadillac” console when a budget mixer and a few pieces of external
gear is more cost effective. Even those engineers who regularly work
on “big” consoles use external EQs, compressors and preamps!The
goal of any recording is to get the sounds right before you commit
them to tape. The Tube Channel exists to help you get it right so you
don’t have to “fix it in the mix”.

Design Notes

The Tube Channel is a multi-purpose tool for audio engineering and
recording. Enclosed in a one rack space (1U) chassis are three
independent circuits featuring a tube-based analog preamplifier, a
VCA-less, optical compressor, and a semi-parametric, four-band, tube­based equalizer. Used as a direct recording channel, a mic/line
preamp, or a DI (direct) box, the Tube Channel is designed to work
seamlessly with any recording, sound-reinforcement, or electronic
instrument setup. A R T’s Tube Channel circuitry is a hybrid design
utilizing the latest, most advanced, solid-state and tube technology.
With a transformerless design, the Tube Channel maintains
exceptional signal integrity and extremely low noise. The compressor
circuit follows the preamp and the equalizer follows the compressor
(although you can change the order of the circuits by utilizing the
insert points). While the preamp is always active, the compressor and
equalizer may be individually bypassed. The preamplifier’s active
balanced solid-state input provides extremely low noise and excellent
CMRR. The ¼” input has a high impedance, which prevents the
loading of any device connected to it and makes the Tube Channel
perfect for DI or line level applications. The preamplifier’s second
stage 12AX7a tube runs on a regulated DC voltage providing an
additional 40dB of gain. Our design enables the tube to overload
before the input or output stage. This allows you to manipulate the
tube gain to meet different sonic requirements.The compression circuit
features a VCA-less design and utilizes optical (Vactrol) electronics
for superior musical performance. The compressor is soft knee by
design. Although it is capable of providing a thoroughly “squashed”

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signal, it was designed to excel in areas where transparent and musical
dynamics control is desired. The beauty of the optical design is its
ability to apply heavy amounts of compression without pumping and
breathing like VCA-based compressors. In many cases you will hear
the results of the compression without hearing the compressor.

The tube-based equalizer was designed to help “fix” the instruments
that give us the most headaches when we’re recording: kick, snare,
bass, toms, guitar amps, voice, etc. The two sweepable parametric
bands and selectable shelving bands have been optimized for musical
instruments. The two sweepable bands overlap each other and also the
high and low shelving bands, providing you with the ultimate in
flexibility. This EQ design gives you all the control you need to
effectively alter and dial in great sounds from even the poorest of
sources.

Setting Up

Unpacking

Your Tube Channel was packed with care at the factory. The shipping
carton was designed to protect the unit during initial shipment. Please
retain this carton for use in transporting the Tube Channel, or in the
unlikely event that you need to return your Tube Channel for
servicing.

AC Power Hookup

The Tube Channel has an internal power supply designed to operate at
100 to 125VAC, 50 to 60Hz. Units manufactured for use outside of the
United States have been modified to comply with the required
electrical specifications. Under no circumstances should the power
cable be altered. If the cable becomes cut or damaged, discontinue use
and have it replaced before operating the Tube Channel.

Audio Connections

Audio connections to and from the Tube Channel are balanced XLR
(Pin 2 = Hot (+), Pin 3 = Cold (-), Pin 1 = Ground) and unbalanced
¼” (Tip = Hot (+), Sleeve = Ground).

The insert points between the preamp and compressor and the
compressor and equalizer are ¼” (Tip = Hot (+), Sleeve = Ground)

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unbalanced connectors.

We recommend using only high-quality cables equipped with the
appropriate connectors.

Installation

The Tube Channel may be employed in a number of setups including:­Between a microphone and a mixer, digital multi-track recorder,

DAT machine, hard disk recorder, or analog recorder.- In a
mixer’s channel insert points.- Between a microphone and signal
processors.- Between electronic musical instruments (synthesizers,
guitars, basses, samplers, acoustic instruments with pickups) and

other gear.

Safety Precautions

Warning: To avoid the risk of shock or fire, do not expose this unit to
moisture. Do not remove metal panels or chassis parts. Removing any
chassis parts exposes dangerous high voltages. There are no user­serviceable parts inside. Refer all servicing to qualified personnel.
Note: If your power cord becomes damaged and must be replaced,
always replace it with the proper (3 prong) type.

Powering Up

When the power switch is turned on, the VU meter will illuminate. It
is important to remember to turn the Tube Channel on before any
monitoring levels or power amps are turned on. The Tube Channel has
the ability to add over 60dB of gain to its input signal. This can cause
the Tube Channel to produce a “thump” on power up and power
down.Note: Like all tube-based equipment, the Tube Channel needs to
warm up before being used. Allow one to two minutes for the tubes to
reach proper operating temperature before using. If the Tube Channel
fails to power up when the power switch is turned on, check to see that
its power cord is plugged into an active outlet. If the unit still fails to
operate properly, turn it off and unplug it. Then consult your dealer or
A R T’s Customer Service department.

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Front Panel Controls & Indicators

Preamp Circuit

Gain Control

The Gain control sets the amount of input gain of the Tube Channel.

Turn the control clockwise to increase gain and counterclockwise to

decrease gain. Selection of the gain range is made with the +20dB

gain switch. You may control two ranges of gain with this control, +9

to +50dB and -11 to +30dB. When setting the Gain control, refer to

the 4 segment Tube Drive Array for a visual reference to the Tube

Channel’s internal signal levels (applied gain).

for the Tube Channel is when the second” warm” Light Emitting

Diode (LED) in the Tube Drive array is lit.

Gain Switch

Use the Gain switch to set the range of the Gain control. When the

switch is in the out (0db) position the gain range is -11 to +30dB.

Depressing the switch adds 20dB of gain. With the switch in, the gain

range is +9 to +50dB.

you’ll find using the Tube Channel with the +20dB gain switch in is

needed. Use the setting that best fits your application.

Note:

With most microphone applications

Hint:

the “sweet spot”

Phantom Power Switch

The Tube Channel can power any microphone needing +48 volts DC

phantom power. Consult your microphone’s documentation to see if

phantom power is required to power it. Phantom power is turned on

and off with this switch and supplies power to pins 2 and 3 of the XLR

input jack.

Note:

It is best to have phantom power turned off when connecting

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microphones to the Tube Channel.Note: Be sure to turn down or mute
the output of the Tube Channel when engaging or disengaging
phantom power. Additionally, when disengaging, allow 30 - 45
seconds for the power to completely dissipate. Most microphones will
make a sound like air leaking from a tire when phantom power is
disconnected, but some can make some very nasty low rumbles and
whines as well.Another Note: MOST dynamic microphones should
not be affected or damaged if they are plugged into the Tube Channel
when phantom power is turned on (we haven’t run across any).
However, if the mic doesn’t need it, don’t use it. Some things are best
left untested!

Tube Drive/Gain Reduction Display

Four LEDs display how the tube gain is affecting the input signal.
These LEDs are calibrated with the tube circuitry to give you an
accurate representation of the tube’s output signal (Note: these LEDs
measure the signal level before the output level control). Use this
meter as a visual guide for setting the Gain level. The first LED is
labeled “Cln”. The tube is producing a clean output when this LED is
lit. The next two LEDs are labeled “warm.” This is the optimal
operating range for the Tube Channel’s preamp. At this level, the tube
is producing an output signal that most would term “warm” (Whatever
you would like to call it is fine -- simmering, toasty, etc.) You’ll find
the output signal has an enhanced bottom to low mid quality with
smooth high frequency detail.The last LED is labeled “Clip.” This
LED will light approximately 6dB before audible distortion occurs. If
this light flickers, don’t panic. The unique design of the Tube Channel
allows the tube to distort well before any other gain stage. When a tube
goes into distortion it is a gradual process and tends to sound pleasing
for a range before it turns into a distortion box. After some use you’ll
find that the “sweet spot” of the Tube Channel is when this light
flashes fairly regularly. You may very well find a “clipped” level is
suitable for some applications.Note: Use the Tube Character Array to
aid in setting the Gain Control.

Preamp Output

The Preamp Output control sets the output level of the preamp section
of the Tube Channel. In most situations you’ll be leaving this control
set around 12 o’clock (or its “0” setting). The Preamp Output control
has a range of no output (from its fully counter-clockwise position), to
additional 16dB of gain (when turned fully clockwise).

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When setting up the preamp circuit, start with the Preamp Output at

its “0” level. Once you get the Gain control set the way you want it to

sound, use the Preamp Output control to set the level out of the

preamp circuit (much like using the master volume control on a guitar

amplifier). Use the Preamp Output control to add more gain when you

have the Gain control set low for a “clean” sound. Likewise, you can

use the Preamp Output control to decrease the level out of the preamp

circuit when you’re cranking the Gain control up for maximum tube

warmth.

Optical Compressor Circuit

Slope Switch

The Slope Switch selects the compression ratio for the compressor

circuit. In its “out” position, the compression ratio is an active 2.3:1.

This means that for every 2.3dB over the threshold the input signal

rises, the compressor’s output will change by 1dB. This is a very mild

and musical compression ratio, which is ideal for smoothing all types

of signals.In its “in” position, the compression ratio is greater than

6:1. This is typically called “soft limiting” as it allows only a 1dB

change in signal level for any signal reaching over 6dB of the set

threshold. This setting is ideal for applications where exceeding a set

level is not desirable (i.e., mixing, popping bass, digital recording,

etc.).

Speed Switch

The position of the Speed switch selects the release characteristics of

the compressor circuit. The “out” (“fast”) position allows the

compressor to recover quickly once the signal falls below the

threshold. The “in” (“auto”) position allows the compressor to adjust

itself depending on the characteristics of the input signal. Use the

“fast” setting when the signal has repetitive, consistent characteristics

(kick drum, snare, vocals, etc.). Use the “auto” setting when the signal

has varying characteristics (long decaying notes alternating with quick

notes, mix material, etc.).

Compressor Bypass Switch

A Bypass switch is included on the compressor circuit to enable you to

remove the compressor from the signal chain. When set to its “in”

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(bypass) position, signal is allowed to pass from the preamp circuitry
to the equalizer circuit with no compression. The LED will glow red
when Bypass is engaged. This informs you that the compressor is
bypassed. In its “out” (Norm) position, the compressor is active.

Use the Bypass switch when setting the compressor’s output level to
achieve unity (no boost or cut) gain. Unity gain is achieved through
the compressor when the active level is the same as the bypassed level.
Toggle the switch between active and bypass while adjusting the
compressor output level. Once the levels are the same (use your ears
and the VU Output Level meter), you’ve reached the unity setting for
the compressor.

Compressor Threshold and Output Controls

The compressor’s Threshold and Output controls are ganged together
on a dual concentric pot. The outer control is the Threshold level and
the inner control is the Output level.

Compressor Threshold Control (outer control)

The Threshold control sets the point at which the compressor circuit
will act on the input signal. Turning this control counterclockwise
lowers the threshold (adding more compression to a signal). Turning
this control clockwise raises the threshold. Setting the Threshold
control is dependent on the Preamp Output control (or the output of
the device plugged into the compressor return insert point). The
easiest way to set the threshold control is to start with the control fully
clockwise. After setting the Preamp Output control, slowly turn the
Threshold control counter-clockwise (lowering threshold) until you see
the yellow (0dB) Threshold LED light in the gain reduction display.
Now adjust the control (either lower or higher) until you have the
amount of compression you desire. Use the Gain Reduction meter as a
visual guide to the amount of compression applied.

Compressor Output Level Control (inner Control)

The Compressor Output level control sets the output level from the
compressor circuit. Typically, the output level of a compressor is used
to add gain to compensate for the amount of compression applied to a
signal. The output level is set to achieve unity gain (no change in level
when compressor is active or bypassed). See Compressor Bypass

Switch for more details on achieving unity gain.

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When the control is fully counter-clockwise, the output is attenuated

by –20dB. Turning the control clockwise increases the level to a

maximum of +20dB of gain. While you can use the compressor to add

gain to a signal, it is better to add gain before the compressor for the

best signal to noise ratio. If you want to use the compressor to add

more gain, refer to the output level VU meter, or the meter on your

recorder or mixer to make sure you won’t clip the next piece of

equipment in the chain.

Clip Indicator

The Clip LED is located in the equalizer circuit. It will illuminate 6dB

before the headroom of the circuit is exceeded. When this Clip

indicator lights, the level into the equalizer is too high. Turn down

either the Preamp Output control, the Compressor Output control or

the output level of the device plugged into the compressor return insert

point.

Equalizer Circuit

The equalizer circuit in the Tube Channel is a tube--based, semi-

parametric, four-band equalizer. Each of the bands overlap, giving you

the ultimate in flexibility. The “Q” (or bandwidth) of each of the filters

is purposely wide to provide a very musical sound.

Low Frequency Control

The Low Frequency control adjusts a shelving filter with a selectable

corner frequency of either 40Hz or 120Hz. The low shelving filter

affects all frequencies below the corner frequency when applying boost

or cut. In other words, cutting at 40Hz also cuts 30Hz, 20Hz, etc. The

Low Frequency control has as range of +/- 12dB. Two ranges are

selected with the Low Shift Switch: 40Hz or 120Hz. 40Hz is great for

enhancing sub-low frequencies such as those in bass guitars and kick

drums. Cutting 40Hz can also help to “clean up” mixes that sound

muddy or “loose” in the low end. 120Hz is generally the low-end for

vocals, guitars and toms. Boosting 120Hz can add “weight” or “beef”

to a week vocal and cutting it can “thin out” a signal that takes up too

much room in the low end.

Low Shift Switch

The Low Shift switch selects the corner frequency of the Low

Frequency control. In the “out” position the corner is 40Hz. In the “in”

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position the corner is 120Hz.

Lo-Mid Frequency Control

The Lo-Mid control is a dual concentric pot (there are two controls-­one outer and one inner). The outer control is used to select a
frequency while the inner control is used to apply +/-12dB of gain.
The Lo-Mid control can cover two frequency ranges depending on the
position of the Shift x 10 switch. These ranges are 20Hz to 200Hz and
200Hz to 2KHz.

Lo-Mid Shift x 10 Switch

The Lo-Mid Shift x 10 switch determines the range over which the Lo­Mid frequency control will cover. In its “out” position, the range is set
at 20Hz to 200Hz. In its “in” position the range is set at 200Hz to
2KHz.Note: You’ll notice the Low Frequency and Lo-Mid Frequency
controls overlap (meaning they cover the same frequencies). This is
intentional and is one of the powerful features of the equalizer circuit.

Hi-Mid Frequency Control

Like the Lo-Mid Frequency control, the Hi-Mid control is a dual
concentric pot (there are two controls--one outer and one inner). The
outer control is used to select a frequency while the inner control is
used to apply +/-12dB of gain. The Hi-Mid control can cover two
frequency ranges depending on the position of the Shift x 10 switch.
These ranges are 200Hz to 2KHz and 2KHz to 20KHz.

Hi-Mid Shift x 10 Switch

The Hi-Mid Shift x 10 switch determines the range over which the Hi­Mid Frequency control will cover. In its “out” position the range is set
at 200Hz to 2KHz. In its “in” position the range is set at 2KHz to
20KHz.Note: The Lo-Mid and Hi-Mid Frequency controls overlap in
the 200Hz to 2KHz range. This feature allows either or both controls
to be used in this range. This is extremely useful if you want to cut at
200Hz and boost at 350Hz.

High Frequency Control

The High Frequency control adjusts a shelving filter with a selectable
corner frequency of either 6KHz or 18KHz. The high shelving filter
affects all frequencies above the corner frequency when applying boost
or cut. In other words, cutting at 6KHz also cuts 7KHz, 8KHz, etc.

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The High Frequency control has as range of +/- 12dB. The two ranges

are selected with the High Shift switch. 6KHz is great for adding top

end to guitars, snare drums and vocals. Cutting 6KHz can also help to

“take the edge off” brittle or harsh sounding instruments. 18KHz may

be used to add “sizzle” to cymbals and is generally referred to as the

“air” band. While there aren’t very many instruments that contain

18KHz information directly, many instruments and mixes contain

upper harmonics, which can add extra definition and “space” when

boosted. Cutting at 18KHz can decrease hiss and noise.

High Shift Switch

The High Shift switch selects the corner frequency of the High

Frequency control. In the “out” position the corner is 18KHz. In the

“in” position the corner is 6KHz.Note: The High Frequency and Hi-

Mid Frequency controls overlap. This feature gives you the ultimate in

flexibility. For example, on cymbals try boosting 18KHz with the High

control while cutting 20KHz with the Hi-Mid control for a very bright,

yet noise--free result.

EQ Bypass Switch

A Bypass switch is included in the equalizer circuit to enable you to

remove it from the signal chain. When set to its “in” (bypass) position,

signal is allowed to pass from the compressor circuitry to the output

jacks with no equalization. The LED will glow red when Bypass is

engaged. This informs you that the equalizer is bypassed. In its “out”

position, the equalizer is active. Use the EQ Bypass switch when

setting the Tube Channel’s output level to achieve unity (no boost or

cut) gain through the equalizer circuit. Unity gain is achieved when

the active level is the same as the bypassed level.

Master Output Level Control

The Master Output level control sets the output level of the Tube

Channel. When the control is fully counterclockwise, there is no

output. Turning the control clockwise increases the level of the output

to a maximum of +10dB of gain. When setting the Output Level

control, refer to the VU Output Level meter or the level meter on your

recorder or mixer.

Phase Switch

The Phase switch is provided to reverse the phase of signal leaving the

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Tube Channel’s XLR Output jack. The Phase switch also reverses the
polarity of the ¼” Output jack. In the Normal (out) position, the signal
is in-phase. In the Reverse (in) position, the polarity of Pins 2 and 3
(and the Tip of the ¼” jack) are reversed and the signal is changed to
180 degrees out of phase with the input signal. In multiple microphone
applications, the placement of the microphones can affect the phase of
a signal. If two microphones pick up the same signal from different
locations, the result can be a hollow or frequency “shifted” sound. In
some cases it may sound as if an instrument disappears if it happens to
be 180 degrees out of phase. Depressing the Phase switch can remedy
this problem. Likewise, if a microphone cable is wired incorrectly, the
signal will be also out of phase.Note: In single microphone
applications, switching the phase will produce no audible change in
the output signal.

Output Level VU Meter

A backlit, average reading, VU meter is provided to accurately
monitor the output level of the Tube Channel. The “0” level is
calibrated to +4dBm with a 600 ohm load on the output (using either
the XLR or ¼” connector).

Use the VU meter for a visual reference to the signal level leaving the
Tube Channel.

Note: When using the Tube Channel into a mixing console or
recorder, always reference the meter on the mixer or recorder when
setting output levels. All meters are not necessarily calibrated the same
and it is always best to look at the level entering the last piece of
equipment in the chain.

Power

The Power switch supplies and removes power from the Tube
Channel. The Tube Channel should be turned “on” only after all
monitor levels are turned down, or off, to protect against any
“thumping” caused by high gain settings. Likewise, the Tube Channel
should be turned “off” after turning all monitor levels down.

The Output Level VU meter will illuminate when power is turned on.

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Rear Panel Connections

Input and Output Connections

The Tube Channel’s XLR connectors follow the AES standard: Pin 1

= Ground, Pin 2 = Hot (+), Pin 3 = Cold (-). The unbalanced ¼”

phone jacks are typical Tip = Hot (+), Sleeve = Ground.

Input

One input jack per channel should be used at a time. However, because

of its design, the Tube Channel can be hard-wired without having to

disconnect the XLR inputs when using the ¼” jacks. If no load is

placed on the XLR input (no instrument or microphone connected) the

¼” jack will function as if there was nothing connected to the XLR

input. However, it is still preferable to disconnect any unused cables to

avoid pick up of extraneous noise, hum, or RF interference.

Output

Both balanced and unbalanced output connections may be used

simultaneously. This is particularly useful when using the Tube

Channel as a direct box for instruments or line level signals.Note: If

you experience a hum when using both output connectors

simultaneously (one to the console and one to an instrument amp), a

ground loop may be the problem. To remedy this problem, disconnect

the ground wire (pin 1) from the XLR cable plugged into the Tube

Channel’s output (or use a ground-lifted audio cable). This interrupts

the ground path and therefore breaks the loop.

Loop Inserts

Two signal loops are provided to connect external equipment to the

Tube Channel, to use only specific individual circuits, or to take direct

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signal paths from specific sections. The connections are unbalanced
¼” (Tip = Hot (+), Sleeve = Ground). Both of the “send” jacks may be
used without interrupting signal-flow through the Tube Channel. The
“return” jacks break the signal-flow when a jack is inserted.

The loops may also be utilized to “re-patch” the compressor and
equalizer circuits in a different order (i.e. signal flow = preamp to
equalizer to compressor).

Preamp - Compressor Loop

A loop is provided between the output of the preamp circuit and the
input of the compressor circuit. The Preamp Send jack is located
directly after the Preamp Output level control. This jack may be used
to send an unbalanced signal directly to an input of a recorder, mixer
or other piece of outboard equipment.

The Compressor Return jack is located directly before the Threshold
Control of the compressor circuit. This jack may be used to connect
the output of a piece of equipment to the input of the compressor
circuit in the Tube Channel. Since there is no input level control to the
compressor in the Tube Channel, the piece of equipment in the insert
loop should have level matching capabilities (i.e., an output level
control).

Compressor - EQ Loop

A loop is provided between the output of the compressor circuit and
the input of the equalizer circuit. The Compressor Send jack is located
directly after the Compressor Output level control. This jack may be
used to send an unbalanced signal directly to an input of a recorder,
mixer or other piece of outboard equipment.

The EQ Return jack is located directly before the input of the
equalizer circuit. This jack may be used to connect the output of a
piece of equipment to the input of the equalizer circuit in the Tube
Channel. Since there is no input level control to the equalizer in the
Tube Channel, the piece of equipment in the insert loop should have
level matching capabilities (i.e., an output level control).

Loop Connections

To use only the preamp of the Tube Channel: Plug a mic, instrument,
or line level signal into either of the Input Jacks. You can use either of

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the following for an output: Plug the output from the Preamp Send

jack into the input of the next piece of equipment, - or - bypass the

compressor and equalizer circuits and connect either of the Output

Jacks to the input of the next piece of equipment.

To use only the compressor circuit of the Tube Channel: Plug a line

level signal (or a send from a mixer) into the Compressor Return Jack.

Connect the output from the Compressor Send jack into the input of

the next piece of equipment (or the return of a mixer).

To use only the equalizer circuit of the Tube Channel: Plug a line level

signal (or a send from a mixer) into the EQ Return Jack. Connect

either output from the Tube Channel into the input of the next piece of

equipment (or the return of a mixer).

To place the equalizer circuit before the compressor circuit: Connect

the Preamp Send to the EQ Return. Connect the unbalanced Output to

the Compressor Return. Use the Compressor Send as the main output

to the input of the next piece of equipment.

Applications

The main application of the Tube Channel is as a processing channel

for a microphone, instrument or line level source. To use the Tube

Channel as a mic or line preamplifier only, simply press the Bypass

switches to bypass the compression and equalizer circuitry. Plug a

microphone directly into either input and set the input and output

controls to provide an appropriate level into the next stage of your

system.The Tube Channel is ideal for use as a DI box. Plug the

instrument into either input and use the XLR, 1/4, or both outputs to

connect to your recorder, board, or PA system. Experiment with

different input level settings for different textures.

In most cases the Tube Channel offers superior performance to the on-

board preamp on your console. To use the Tube Channel instead of

your on-board preamp, simply connect the output of the Tube Channel

to the line input of your mixer’s input channel. Note: you can connect

the XLR output jack of the Tube Channel to the XLR input of your

mixer, however most affordable mixers do not allow you to bypass

their internal preamp when using the XLR jack. You will cause no

harm to either unit when doing this but you will probably experience

slightly higher noise. This is due to the fact that you are now

preamplifing your mixer’s preamp.

17

Note: Be certain that you do not connect the Tube Channel’s XLR
Output to a mixer input that has Phantom Power applied.

The Tube Channel has enough gain to be used in front of a power
amplifier. To use the Tube Channel as a instrument preamp, simply
plug the instrument into the Input jack and connect the Output jack to
the input of the power amplifier.See Loop Connections for further
hook-up options and for using single circuits in the Tube Channel.

Special Effects

For industrial, metal, or just “flavor” textures, experiment with the
Tube Channel. Overdriving the preamp, compressor and equalizer
circuitry can add interesting textures when blended with vocals and
other instruments. Placing signals purposely out of phase can also
yield interesting results. No harm will come to the Tube Channel with
this type of experimentation. However, be sure to have output and
monitoring levels turned DOWN before “testing” the sound.
Remember, you have a great amount of gain available in the Tube
Channel!

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EQ Tips

What is the best way to use EQ?

There are two schools of thought on EQ: 1) Use as much as you need

to make things sound good. 2) Don’t use any EQ. Most people follow

the suggestion of “if it sounds good, it is good.” You need to use your

ears and judge for yourself as their are no steadfast rules for EQing.

Here are a few pointers to guide you.Always tweak the instrument you

are EQing while listening to it in the mix. EQ’ing an instrument when

it is soloed doesn’t give you a good representation of how it will sound

when mixed with other instruments. You’d be surprised at how bad a

killer guitar track can sound when it is isolated from the rest of the

mix. Remember, what makes it killer is how it sounds in relation to

the other instruments! Always keep the big picture in mind.Most

people think of EQ as boosting only (“we’ll just add a little EQ...”).

Many times a “bad” sounding instrument can be fixed by simply

isolating the bad frequency and pulling it out. After you determine

approximately where the “problem area” is in the instrument (highs,

lows, mids), isolate the track and boost one of the mid bands. Slowly

sweep through the frequency range. When the really nasty sound

jumps out at you (you’ll know it when it happens) turn the boost back

to “0” (12 o’clock). Now put the track back into the mix and cut the

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frequency. You’ll have to adjust the level of the instrument depending
on how much you cut, but you should find that with the “problem
area” pulled out, the instrument works better in the mix.When
recording EQ’d instruments you want to make sure you have good
representation of frequencies on tape. Always monitor “off” tape when
recording. This ensures that what you’re hearing is what is on tape.
When recording things like kick drums, make sure you have enough
low end “thud” and high end “click” (if applicable) before you record.
Recording guideline: You can always boost or cut frequencies after
they’ve been recorded, but you can’t add frequencies that weren’t’
recorded! Always be prepared for the drummer who says he loves the
John Bonham kick drum sound (lots of low end power and ambiance)
you got when recording but during the mix decides he wants to sound
like Metallica (more click than punch).If you get the sounds right
when you record the tracks you shouldn’t be spending a lot of time re­EQing during the mix. During mixing you should be concentrating on
the blending of tracks and the dynamics of the song. If you find
yourself EQing everything, take a break and come back to it later.
Start mixing with a group of instruments (the whole drum kit or
guitars and bass) instead of listening to individual tracks. Mixing is
the time for tweaking -- not applying a sonic re-design. Once again, “if
it sounds good, print it!” Trust your ears -- nevermind where the knobs
are pointing.

Tube Replacement

The Tubes in your Tube Channel should last for many years. They are
hand-sorted for performance. In the event that you need to replace
them, A R T suggests that you do so with tubes available from A R T.
These are matched to the Tube Channel and will yield consistent sonic
results. You can replace the tubes with other brands, however A R T
has no responsibility for the resulting sound quality. They may sound
better, they may sound worse. The choice is yours. Please realize that
unauthorized alterations to the Tube Channel will result in voiding the
warranty.

20

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A R T Tube Channel Specifications

Dimensions 5.25"D x 19"W x 1.65"H
Weight 8.0 lb.
Maximum Gain

XLR to XLR 81dB

¼” to ¼” 63dB
Phantom Power +48v DC (switchable)
Compression Ratio 2.3:1 (comp)/ 6:1 (lim)
Attack Time 6.5ms
Release Time 200ms (fast), 70ms-1sec (auto)
EQ Frequency Bands:

Low Shelf: 40Hz/120Hz Selectable

High Shelf: 6KHz/18KHz Selectable

Low-Mid Sweepable: 20Hz to 200Hz/ 200Hz to 2KHz

High-Mid Sweepable: 200Hz to 2KHz/ 2KHz to 20KHz

“Q” 1.1

Gain/Frequency Band: +/- 12dB
Equivalent Input Noise -129dBu (XLR to XLR, ‘A’ wghtd)
Dynamic Range >90dB (no weighting)Input
Impedance 1.67k ohms (XLR), 1M ohm (¼”)
Output Impedance 600 ohms (XLR), 300 ohms (¼”)
Maximum Input Level +15dBu (XLR), +21dBu (¼”)
Maximum Output Level +27dBu (XLR), +22dBu (¼”)
CMRR 90dB (typical)
THD <0.1% (typical)
Tubes Two Hand-Selected Tubes

(12AX7A/12AT7)

Power Requirements 100-125 VAC, 25W (Export units

configured for country of
destination)

A R T retains a policy of constant product improvement. A R T reserves the
right to make changes in design or make additions to or improvements upon
this product without any obligation to install the same on products previously
manufactured. In other words, specifications are subject to change without
notice.

Designed and manufactured in the United States of America.

Applied Research and Technology, Inc. [phone] (Phone)

22

215 Tremont Street [phone] (FAX)

Rochester, NY 14608 USA

We’re on-line!

For Product information, questions, applications, tips, answers and

general discussion with A R T employees look for A R T on the

Internet.. Email us at [e-mail] out our Web Page at:

http://www.artroch.com

Wa rranty and Service Information

Limited Warranty

Applied Research and Technology, Inc. will provide warranty service

for this unit in accordance with the following warranty

statement.Applied Research and Technology, Inc. (A R T) warrants to

the original purchaser that this product is free from defects in

workmanship and materials for a period of three years from the date of

purchase. A R T will, without charge, repair or replace, at its option,

defective product or component parts upon prepaid delivery to the

factory service department or an authorized service center,

accompanied by proof of purchase date in the form of a valid sales

receipt.EXCLUSIONS: This warranty does not apply in the event of

misuse or abuse of the product or as a result of unauthorized

alterations or repairs. This warranty is void if the serial number is

altered, defaced or removed.

A R T reserves the right to make changes in design and make

additions or improvements upon this product without any obligation to

install the same on products previously manufactured.A R T should

not be liable for any consequential damages, including without

limitation damages resulting from the loss of use. Some states do not

allow limitation of incidental or consequential damages, so the above

limitation or exclusion may not apply to you. This warranty gives you

specific rights and you may also have other rights, which vary, from

state to state.For products purchased outside the United States, service

will be provided by an authorized distributor of Applied Research and

Technology, Inc. products.

Service

The following information is provided in the unlikely event that your

unit requires service. Use this procedure to return units in the United

23

States only. For service outside the United States, please contact your
authorized A R T distributor.1) Be sure the unit is the cause of the
problem. Check to make sure the unit has power supplied, all cables
are connected correctly, and the cables themselves are in working
condition.2) If you find the unit to be at fault, write down a description
of the problem, including how and when the problem occurs.3) Call
the factory for a Return Authorization (RA) number.4) Pack the unit
in its original carton or reasonable substitute. The packing box is not
recommended for a shipping carton. Put the packaged unit in another
box for shipping. Print the RA number clearly under the address.5)
Include with your unit: a return shipping address (we cannot ship to a
P.O. Box), a copy of your purchase receipt, a daytime phone number
and the description of the problem.

6) Ship the unit to:

Applied Research and Technology, Inc.
215 Tremont Street
Rochester, NY 14608
Attn: Repair Department
R.A.# _______________

7) Contact our Customer Service department at [phone] for
your Return Authorization number or questions regarding your repair.
Customer Service hours are Monday through Friday 9:00AM to
5:00PM Eastern time.

©1998 Applied Research and Technology, Inc.

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