Behringer Tube ultrafex T1954 User manual

TUBE ULTRAFEX®
T1954
www.behringer.com
Version 1.1 December 2001
Users Manual
ENGLISH

2
TUBE ULTRAFEX T1954
This s mbol, wherever it appears, alerts
ou to important operating and mainte-
nance instructions in the accompan ing
literature. Read the manual.
SAFETY INSTRUCTIONS
CAUTION: To reduce the risk of electric shock, do not remove
the cover (or back). No user serviceable parts inside;
refer servicing to qualified personnel.
WARNING: To reduce the risk of fire or electric shock, do not
expose this appliance to rain or moisture.
DETAILED SAFETY INSTRUCTIONS:
All the safet and operation instructions should be read before the appliance is operated.
Retain Instructions:
The safet and operating instructions should be retained for future reference.
Heed Warnings:
All warnings on the appliance and in the operating instructions should be adhered to.
Follo instructions:
All operation and user instructions should be followed.
Water and Moisture:
The appliance should not be used near water (e.g. near a bathtub, washbowl, kitchen sink, laundr tub, in a wet
basement, or near a swimming pool etc.).
Ventilation:
The appliance should be situated so that its location or position does not interfere with its proper ventilation.
For example, the appliance should not be situated on a bed, sofa, rug, or similar surface that ma block the
ventilation openings, or placed in a built-in installation, such as a bookcase or cabinet that ma impede the
flow of air through the ventilation openings.
Heat:
The appliance should be situated awa from heat sources such as radiators, heat registers, stoves, or other
appliances (including amplifiers) that produce heat.
Po er Source:
The appliance should be connected to a power suppl onl of the t pe described in the operating instructions
or as marked on the appliance.
Grounding or Polarization:
Precautions should be taken so that the grounding or polarization means of an appliance is not defeated.
Po er-Cord Protection:
Power suppl cords should be routed so that the are not likel to be walked on or pinched b items placed
upon or against them, pa ing particular attention to cords and plugs, convenience receptacles and the point
where the exit from the appliance.
Cleaning:
The appliance should be cleaned onl as recommended b the manufacturer.
Non-use Periods:
The power cord of the appliance should be unplugged from the outlet when left unused for a long period of time.
Debris and Liquid Entry:
Care should be taken that debris and/or liquids do not enter the enclosure through openings.
Damage Requiring Service:
The appliance should be serviced b qualified service personnel when:
- The power suppl cord or the plug has been damaged; or
- Debris or liquid has entered the appliance; or
- The appliance has been exposed to rain; or
- The appliance does not appear to operate normall or exhibits a marked change in performance; or
- The appliance has been dropped, or the enclosure damaged.
Servicing:
The user should not attempt to service the appliance be ond that which is described in the operating instruc-
tions. All other servicing should be referred to qualified service personnel.
This s mbol, wherever it appears,
alerts ou to the presence of
uninsulated dangerous voltage inside
the enclosurevoltage that ma be
sufficient to constitute a risk of shock.

3
TUBE ULTRAFEX T1954
FOREWORD
Dear Customer,
We thank ou for expressing our confidence in BEHRINGER products b purchasing the BEHRINGER
TUBEULTRAFEX. It is one of m most pleasant tasks to write this preface, as our engineering team has made
it possible to enhance the traditional tube circuitr design (particularl for our VINTAGER series of products),
and adapt it to meet the high sound qualit and d namics requirements of modern, pro-level audio technolog .
The fact that we are still fascinated b antique tube radios and amps as well as the fine and warm tonal
character that we usuall associate with them, are the reasons wh vacuum tubes have kept their ground even
in state-of-the-art circuit topologies used especiall in professional audio technolog or high-end devices. We
are particularl proud that we have found an extremel effective s mbiosis between solid-state and tube
technologies making them affordable to an bod interested in audio technolog . As alwa s, our top-priorit
concern when developing this device was the demanding end user, in other words: ou. It was our major goal
to meet our demands. Sure, it meant a lot of hard work to develop such a product, but the fun has made it all
worthwhile. The shine in the e es of the man interested musicians at the Music Fair 1997, when the saw our
VINTAGER models for the first time, was a lasting incentive driving our development efforts.
It is our philosoph to share our jo with ou, because ou are the most important member of the BEHRINGER
famil . With our highl competent suggestions for new products ouve greatl contributed to shaping our
compan and making it successful. In return, we guarantee ou uncompromising qualit (manufactured under
ISO9000 certified management s stem) as well as excellent technical and audio properties at an extremel
favorable price. All of this will enable ou to full unfold our creativit without being hampered b budget
constraints.
We are often asked how we can make it to produce such high-grade devices at such unbelievabl low prices.
The answer is quite simple: its ou, our customers! Man satisfied customers means large sales volumes
enabling us to get better conditions of purchase for components, etc. Isnt it onl fair to pass this benefit back
to ou? Because we know that our success is our success, too!
I would like to thank all people whose help on Project TUBEULTRAFEX has made it all possible. Ever bod
has made ver personal contributions, starting from the designers of the unit via the man staff members in our
compan to ou, the user of BEHRINGER products.
M friends, its been worth the trouble!
Thank ou ver much,
Uli Behringer

4
TUBE ULTRAFEX T1954
T1954
TUBEULTRAFEX®
Professional, multi-purpose sound enhancement s stem for high-end studio and stage applications
sOur new ULTRA-TUBE® circuitr warms up our music without unwanted noise
sA special Warmth control lets ou add the amount of tube sound ou want
sSelected 12AX7 tubes for outstanding, ultra-musical tube sound
sGives our music extra sparkle and makes our instruments or mixes stand out
sReleases untapped sonic resources and adds detail to instruments, vocals and mixed program material
sMultiband concept provides incredible bass power and high-frequenc transparenc
sNatural Sonic processor for ultra-musical sound improvement
sVSP (Variable Sound Processing) circuit for simultaneous enhancer and exciter processing
sSpecial LC coil/cap filter produces authentical vintage soft and tight bass sounds
sSurround processor provides real spatial enhancement and improved stereo imaging
sBuilt-in noise reduction s stem with precision LED displa to provide clear visual indication of operation
sServo-balanced gold-plated XLR and 1/4" TRS inputs and outputs
sUltra low-noise 4580 audio operational amplifiers for outstanding sound performance
sRela -controlled hard b pass with auto-b pass function during power failure (failsafe rela )
sHigh-qualit detented potentiometers and switches with authentic vintage st le knobs
sHuge back-lit analog VU meters and retro design
sBEHRINGER high-performance OT-1 output transformer retrofitable
sHigh-qualit components and exceptionall rugged construction ensure long life even under the most
demanding conditions
sManufactured under ISO9000 certified management s stem

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TUBE ULTRAFEX T1954
TABLE OF CONTENTS
1. INTRODUCTION..................................................................................................................... 6
1.1 The Design Concept ........................................................................................................................ 6
1.2 Before You begin ............................................................................................................................. 6
1.3 Control Elements ............................................................................................................................ 7
2. OPERATION .......................................................................................................................... 10
2.1 Introduction ................................................................................................................................... 10
2.2 The Position of the TUBE ULTRAFEX in the Signal Path ............................................................... 10
2.3 Basic Setting ................................................................................................................................. 11
2.4 Adjustment of the Bass Processor ................................................................................................. 11
2.5 Adjustment of the Noise Reduction S stem ................................................................................... 11
2.6 Adjustment of the Enhancer/Exciter S stem .................................................................................. 11
2.7 Adjustment of the Tube Stage ....................................................................................................... 12
2.8 Adjustment of the Surround Processor .......................................................................................... 12
3. APPLICATIONS ..................................................................................................................... 12
3.1 Sound Enhancement during Repla ..............................................................................................12
3.2 Sound Enhancement during Recording .......................................................................................... 12
3.3 Enhancing the Sound of Subgroups, Monitor and Effect Paths ...................................................... 13
3.4 Enhancing the Sound of Tape Duplication......................................................................................13
3.5 Enhancing the Sound of Instruments ............................................................................................. 13
3.6 Enhancing the Sound of P.A. S stems..........................................................................................14
3.7 Sound Enhancement in HiFi and Video ......................................................................................... 14
4. TECHNICAL BACKGROUND .............................................................................................. 14
4.1 The BEHRINGER TUBE ULTRAFEX ... ......................................................................................... 14
4.2 Ps cho-acoustic Background ....................................................................................................... 15
4.3 On Ps cho-acoustic Devices ........................................................................................................ 15
4.3.1 Frequenc correction .......................................................................................................... 16
4.3.2 Phase shifting ..................................................................................................................... 16
4.3.3 Artificial harmonics generation ............................................................................................16
4.4 The Bass Processor of the TUBE ULTRAFEX ............................................................................... 16
4.5 The Surround Processor of the TUBE ULTRAFEX ......................................................................... 17
4.6 The Vacuum Tubes of the TUBE ULTRAFEX ................................................................................. 17
4.6.1 UTC circuit .......................................................................................................................... 17
4.6.2 Tube histor ........................................................................................................................ 18
4.6.3 Design and functional principle of tubes .............................................................................. 18
4.6.4 Properties of tubes .............................................................................................................. 19
4.6.5 The best of both worlds ....................................................................................................... 20
4.6.6 Studio applications .............................................................................................................. 20
5. INSTALLATION ..................................................................................................................... 20
5.1 Rack mounting .............................................................................................................................. 21
5.2 Mains Connection ......................................................................................................................... 21
5.3 Audio Connections ........................................................................................................................ 21
5.4 Transformer-balanced Outputs (optional) ....................................................................................... 22
6. SPECIFICATIONS .................................................................................................................. 23
7. WARRANTY ........................................................................................................................... 24

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TUBE ULTRAFEX T1954
1. INTRODUCTION
In purchasing the new TUBEULTRAFEX T1954, ou have acquired an extremel efficient and universal sound
processor which combines the sound enhancement features of the ULTRAFEX series with the tube sound of
the BEHRINGER ULTRA-TUBE technolog . Since its announcement of the first ULTRAFEX model in ear
1990, it has caused a sensation. This high-end sound enhancement processor is based on our man ears of
experience and discoveries in the field of ps cho-acoustics. The TUBEULTRAFEX finds widespread applica-
tion throughout the world, in renowned studios, sound reinforcement s stems as well as in broadcast and TV
studios.The sound precision and flexibilit of the functions are the main outstanding features of this high-end
unit. The TUBEULTRAFEX is our state-of-the-art sound enhancement s stem offering a special combination
of sound improvement designs. The unit can be used wherever professional sound improvement is required.
The BEHRINGER TUBEULTRAFEX is the no-compromise answer when the situation demands a no-compro-
mise solution.
Advanced BEHRINGER technology
The philosoph behind BEHRINGER products guarantees a no-compromise circuit design and emplo s the
best choice of components. The TUBE ULTRAFEX uses high-qualit resistors and capacitors with ver tight
tolerances, high-grade switches, low-noise operational amplifiers (t pe 4580) as well other selected compo-
nents.
Additionall , the unit is manufactured in compliance with the ISO9000 certified management s stem.
1.1 The Design Concept
Compared to its predecessors, the TUBEULTRAFEX offers several advanced features and we have succeeded
in dramaticall refining the audio qualities. The unit now features our new UTC tube circuitr and a new L/C filter
switch which offers more power in the bass area. Beside that a new VSP (Variable Sound Processing) circuitr
has been added to allow ou to use simultaneous exciter and enhancer sound processing.
Since the introduction of the first ps cho-acoustic Processors, technolog in this field has made tremendous
progress. Although the fundamental principles of enhancer and exciter technolog have been well-known for a
long time, engineers have been able to refine and improve the essential components over and over again. The
BEHRINGER compan has also contributed considerabl to this development:
With the introduction of our Natural Sonic processor, we have set new standards. Previousl encountered
problems of restricted leveling range, plus increased noise level and audible distortion during signal process-
ing, are t pical shortcomings of conventional circuit designs. The were completel solved b the development
of new circuitr .
The BEHRINGER TUBE ULTRAFEX is equipped with different sound enhancement features which stand for a
new achievement in the histor of sound processors: The legendar BEHRINGER Natural Sonic principle in
combination with the Variable Sound Processing circuitr (VSP) and the integrated Noise Reduction s stem
offer presence and transparenc for our music without receiving unwanted noise. The Bass Processor addi-
tionall adds power to the bottom end. The innovative Surround Processor enables extra depth and width for
stereo signals. As a special feature the TUBE ULTRAFEX comes with the new ULTRA-TUBE technolog
(UTC) that adds warmth and translucenc to our music.
In the TUBE ULTRAFEX two selected 12AX7/ECC83 vacuum tubes are used. These triodes are capable of
handling a large d namic range with little microphon . In addition to that their relative ruggedness and above
average life span and ou can see wh its one of the most popular and reliable pre-amp tubes on the market.
These features also ensure ou their availabilit for man ears to come.
Failsafe rela s have been incorporated into the design of the BEHRINGER TUBE ULTRAFEX, which automati-
call and silentl b pass the unit in the event of power suppl disconnection or failure. These rela s are also
active at switch-on to isolate the TUBE ULTRAFEX until the power rails have settled, thus preventing the
possibilit of a potentiall damaging switch-on thump.
1.2 Before You begin
Your BEHRINGER TUBE ULTRAFEX was carefull packed in the factor and the packaging was designed to
protect the unit from rough handling. Nevertheless, we recommend that ou carefull examine the packaging
and its contents for an signs of ph sical damage, which ma have occurred in transit.
1. INTRODUCTION

7
TUBE ULTRAFEX T1954
+If the unit is damaged, please do not return it to us, but notify your dealer and the shipping
company immediately, other ise claims for damage or replacement may not be granted.
Shipping claims must be made by the consignee.
The BEHRINGER TUBE ULTRAFEX fits into two standard 19" rack units of space. Please allow at least an
additional 4" depth for the connectors on the back panel.
Be sure that there is enough space around the unit for cooling and please do not place the TUBE ULTRAFEX
on high temperature devices such as power amplifiers etc. to avoid overheating.
+Before you connect your TUBE ULTRAFEX to the mains, please make sure that your local
voltage matches the voltage required by the unit!
The mains connection of the TUBE ULTRAFEX is made b using a mains cable and a standard IEC receptacle.
It meets all of the international safet certification requirements. Please make sure that all units have a proper
ground connection.
+Please ensure that only qualified persons install and operate the TUBE ULTRAFEX. During
installation and operation the user must have sufficient electrical contact to earth. Electro-
static charges might affect the operation of the TUBE ULTRAFEX!
Additional information ou will find in Chapter 5 INSTALLATION.
As a standard the audio inputs and outputs on the TUBE ULTRAFEX are full balanced. If possible, connect
the unit to other devices in a balanced configuration to allow for maximum interference immunit . The auto-
matic servo function detects unbalanced connections and compensates the level difference automaticall
(6-dB correction).
1.3 Control Elements
Fig. 1.1: The front panel of the TUBE ULTRAFEX
The BEHRINGER TUBEULTRAFEX has two identical channels and provides 2 switches, 6 rotar controls,
6control LEDs and 2 analog VU meters per channel. The Surround section is equipped with one switch, one
rotar control and one analog meter and has an effect on both channels.
1. INTRODUCTION

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TUBE ULTRAFEX T1954
Fig. 1.2: Control elements of the LOW BA D and HIGH BA D section
1The LOW MIX control of the low band determines the amount of signal used for sound enhancement
(from zero to six). Turn the control clockwise for a more strong and punch bass sound. The setting
depends on the application ou are addressing.
+Please note that the Bass Processor should be set carefully to avoid possible speaker damage.
Most near-field monitors are not capable of handling the bass produced by the TUBEULTRAFEX.
2The LC FILTER switch enables an additonal bass sound. The special L/C filter characteristic supplies a
more dr and punch bass sound.
3The R SE SITIVITY control adapts the sensitivit of the Noise Reduction s stem to the input level of
the program material. The Noise Reduction s stem cares for a noise-free performance during breaks in
our program material and removes noise during silent passages. For that the Enhancer/Exciter signal
is d namicall reduced if the input signal falls under the threshold of the NR SENSITIVITY. In combina-
tion with the Noise Reduction s stem ou also edit the sensitivit of the enhancer/exciter function when
using the NR SENSITIVITY control: The more ou turn the control clockwise the more the enhancer/
exciter function comes into action. To avoid pumping and to provide an optimum effect of the enhancer/
exciter function take care of a correct setting of the NR SENSITIVITY control. The three LEDs above the
NR SENSITIVITY control will help ou to find the right setting.
4In combination with the NR SENSITIVITY control these three CO TROL LEDs help ou to find the
perfect setting of the noise reduction s stem. The more LEDs illuminate the more effect signal passes
through the noise reduction s stem. When all three LEDs light up constantl the noise reduction s s-
tem is inactive. In quiet passages onl the first LED should light up. Loud signals should cause all LEDs
to light up.
5The TU E control sets the cut-off frequenc of the high pass filter. Using this control ou can select the
frequencies that are routed to the Natural Sonic processor. The cut-off frequenc can be adjusted within
a range of 1 to 8 kHz.
6The PROCESS control determines the function of the device. When turning the control in clockwise
direction, the exciter function is activated, which increases the signals transparenc and sharpness.
Consequentl , the TUBEULTRAFEX can be adapted to the program material, to suit the application on
hand as well as an personal sound preferences.
+Please note that ith classical music, acoustic instruments or ith output signals that already
include sufficient treble frequencies, the enhancer setting should be preferred. Ho ever,
hen processing, for instance, a slapped bass guitar, it is the exciter setting hich should
dominate.
7The HIGH MIX control of the high band determines the amount of signal used for sound enhancement
(from zero to six). It would depend on the application as to whether a high-qualit s stem is to be given
the finishing touch with the TUBEULTRAFEX, or whether maximum intelligibilit is to be achieved in a
relativel poor sound reinforcement s stem.
8The EFFECT I /OUT switch activates the complete signal process and tube circuitr . The
TUBEULTRAFEX features a hard-b pass function. As a result the inputs and outputs are connected
when the unit is switched off. With the EFFECT IN/OUT switch ou can compare the processed and the
input signal.
1. INTRODUCTION

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TUBE ULTRAFEX T1954
Fig. 1.3: Control elements of the surround and tube section
9With the SURROU D I /OUT switch ou can activate the surround section. Please note that this
switch has to be released if ou want to process two separate input signals. Otherwise there will be
undesired cross-talk between the two channels.
10 The SURROU D control determines the effect of the Surround processor. This function serves to im-
prove the intensit of the stereo effect and to enlarge the stereo basis dependent on the program
content. Therefore, this function can onl be used in conjunction with stereo program material.
11 The SURROU D METER enables ou to immediatel monitor the effect of the Surround Processor.
12 The WARMTH control adjusts the amount of upper harmonics added to the original signal.
13 The WARMTH METER allows ou to monitor the amount of added upper harmonics.
14 The POWER switch activates the TUBE ULTRAFEX. If the unit is switched off, it is b passed and the
input signal is connected to the outputs of our TUBE ULTRAFEX.
Fig. 1.4: The rear panel elements of the TUBE ULTRAFEX
15 SERIAL UMBER. Please take the time to have the warrant card filled out completel and return it
within 14 da s after the date of purchase, so as to be entitled to benefit from our extended warrant .
Alternativel , ou can register online at our website under www.behringer.com.
16 FUSE HOLDER/VOLTAGE SELECTOR. Please make sure that our local voltage matches the voltage
indicated on the unit, before ou attempt to connect and operate the TUBEULTRAFEX. In man units
the fuse holder can be installed in one of two positions, allowing ou to switch between 230 V and 115 V.
If ou wish to operate a unit outside Europe at 115 V, then a stronger fuse must be used (see chapter 6
SPECIFICATIONS). Blown fuses ma onl be replaced b fuses of the same t pe and rating.
1. INTRODUCTION

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TUBE ULTRAFEX T1954
17 AUDIO I . These are the audio inputs of our TUBEULTRAFEX, available both as balanced 1/4" TRS
connectors and XLR connectors.
18 AUDIO OUT. These are the audio outputs of our TUBEULTRAFEX. Matching phone jack and XLR
connectors are wired in parallel. These outputs can be transformer-balanced b retrofitting the optional
output transformer OT-1. The reference level is +4dBu and the maximum level comes to +21dBu.
2. OPERATION
2.1 Introduction
The BEHRINGER TUBE ULTRAFEX combines the legendar sound enhancement possibilities with the musi-
cal tube sound of the UTC technolog .
The BEHRINGER UTC technology
The BEHRINGER TUBE ULTRAFEX uses our newl developed UTC technolog , a development resulting from
two ears of intensive research work b our engineering team. This technolog overcomes the problems
related to tube circuitr (see Chapter 3) and generates upper harmonics even at low levels to give our record-
ings more warmth and power.
The BEHRINGER Natural Sonic Processor: sound enhancement of classical and pop music
The BEHRINGER Natural Sonic principle is based on frequenc -selective phase shifting in conjunction with
program-dependent equalization and pulse enlargement. An automatic and natural correction during signal
processing offers a qualit of sound enhancement that has been almost inconceivable until now. Program-
dependent control permits the musical and unobtrusive transparenc required for classical music material,
et also provides the necessar brilliance for pop recordings. Owing to its d namic control, and in contrast with
conventional units, the circuitr does NOT introduce an additional noise, non-related harmonics or distortion.
The VSP (Variable Sound Processing) circuit
The new VSP (Variable Sound Processing) circuit used for the first time in the TUBE ULTRAFEX, allows for
variabl fading over from enhancer to exciter mode. Using the PROCESS control clockwise, the exciter circuit
comes in additionall to provide a variable and carefull adjusted processing of high frequencies. The result is
an increased brilliance and transparenc . Fading over from one effect to the other can thus adapt the effects
perfectl to the respective program material.
Built-in Noise Reduction system
Due to ph sical reasons, exciters and enhancers principall increase noise of the processed program mate-
rial. Therefore, we have incorporated a switchable noise reduction s stem which is capable of automaticall
fading out an additional noise.
Bass Processor
The TUBE ULTRAFEX is equipped with a separate Bass Processor which allows for sound enhancement in the
lower frequenc band. The newl developed, switchable LC filter produces a more dr and substantial bass
sound. Processing the bass range means an optimum completion of high-frequenc processing and opens up
new dimensions in the field of sound processing.
Surround Processor
A switchable Surround Processor has also been integrated into the TUBE ULTRAFEX. With this processor the
intensit of the stereo effect can be dramaticall improved (see chapter 4.5 for additional information).
2.2 The Position of the TUBE U TRAFEX in the Signal Path
The perfect position for inserting the TUBE ULTRAFEX in the signal path depends on the terms of reference:
The stereo structure of the TUBE ULTRAFEX suggests to connect the device with the subgroup or main
inserts. If our mixer does not have inserts ou can also position the TUBE ULTRAFEX between the Main Mix
output and a recording device. Moreover the use between signal processors and a mixer makes sense.
Of course, ou can also use the channels of the TUBE ULTRAFEX independent of each other. So ou can
process two mono signals independentl .
2. OPERATION

11
TUBE ULTRAFEX T1954
2.3 Basic Setting
We recommend setting the controls as indicated in the following section. This will give ou a better idea of
switch and control functionalit :
sSet the SURROUND IN/OUT switch to position OUT and the L/C FILTER switch to position OFF. Turn the
TUNE controls to center position and all other controls full CCW. Set the EFFECT IN/OUT switch to
position IN.
sYou ma find that getting to know a dual channel processor like the TUBEULTRAFEX is easier when ou
concentrate on one channel first. If ou have a mixer connect the TUBEULTRAFEX to the insert of one
channel onl . See also the Chapters 2.1 and 3 for the right connection.
2.4 Adjustment of the Bass Processor
Apart from processing the upper harmonic ranges, users of the BEHRINGER TUBEULTRAFEX have access
to an innovative Bass Processor.
The numerous stages of processing during the recording, reproduction, cop ing and effecting processes,
increasingl dela the phase of the bass frequencies, when compared to the remaining frequenc ranges. This
is wh the low-frequenc range suffers from a loss in power and fundamental bass definition.
With the help of frequenc -selective phase shift combined with sub-bass boost, the Bass Processor of the
BEHRINGER TUBEULTRAFEX is capable of compensating for this loss, giving the program material new
bass presence. Using the MODE switch, ou can select between two different bass sounds.
Be extremel careful when using the Bass Processor: excessive use of the Bass Processor might lead to
speaker damage. The amplified sub-bass frequencies ma well place a heav load on the amplifier and the
woofers. Therefore, carefull adjust the Bass Processor and observe the power rating of our s stem!
2.5 Adjustment of the Noise Reduction System
With the SENSITIVITY control ou can now adjust the noise reduction s stem.
The noise reduction s stem prevents noise from becoming audible during pauses and soft pieces in the
program material. The enhancer/exciter signal is reduced d namicall when the signal drops below the value
set b the NR SENSITIVITY control. The NRSENSITIVITY also controls the sensitivit of the enhancer/exciter.
When the NRSENSITIVITY control is turn clockwise more harmonics are added b the enhancer/exciter
section. Turn the control counter-clockwise with lower signals and further clockwise for loud signals.
Use the three LEDs above the control to monitor the effect to avoid pumping or other side effects.
When more LEDs light up the enhancer/exciter is increasingl active. When all three light up the Noise
reduction s stem is inactive. When none light up the effect signal is muted, the enhancer/exciter is inactive.
Tr to set it up so that at soft pieces onl one LED lights up and all three light up at loud pieces.
+When the NRSENSITIVITY control is turned so far counter-clock ise that no LEDs light up, the
effect signal is muted and the settings for the enhancer/exciter are inactive. When this hap-
pens, simply turn up the NRSENSITIVITY until the LEDs light up.
2.6 Adjustment of the Enhancer/Exciter System
Now ou can start processing the high frequencies. Turn the HIGHMIX control clockwise and notice how the
high frequencies become more pronounced and transparent. When ou turn the TUNE control, the frequenc
at which the effect begins is changed, the PROCESS control changes the wa the effect operates. When set
to ENHANCER onl frequencies that are present in the original signal are used, when set to EXCITER artificial
harmonics are generated based on the frequencies present in the signal. When the control is turned clockwise
the sound gains brilliance but also sharpness. Use the exciter on instruments which do not have an abundance
of upper harmonics i.e. bass guitars, to give them more brilliance and Punch. Use the enhancer, to boost high
frequenc information that is alread present.
Because the effect of an enhancers/exciter is impressive at first, there is a danger of overdoing the effect. We
recommend that ou make frequent A/B comparisons (IN/OUT) between the original and the processed sig-
nals. Rule of thumb: sound-enhancing effects should be missed when absent instead of directl audible.
2. OPERATION

12
TUBE ULTRAFEX T1954
Remember, less is more. Used with care an exciter can greatl improve the intelligibilit while extreme set-
tings can become sharp after a while.
+When exposed to high sound pressure level (as in a recording studio) the ears can sho signs
of fatigue, resulting in a decreased sensitivity to high frequencies. Take regular breaks hen
you are using this, or any other sound equipment.
2.7 Adjustment of the Tube Stage
With the settings ou have achieved so far a considerable sound improvement can be made. You ma not
know this, but ou have alread benefitted from the tube stage of the TUBEULTRAFEX. Even when the
WARMTH control is turned full counter-clockwise, subtle and hardl noticabl warmth and musicalit is
added to the signal. You can now drasticall increase the effect b turning up the WARMTH control.
Increasing amounts of upper harmonics generated b the new UTC circuitr are then added to the signal. This
leads to more musical and transparent hights which combine perfectl with the enhancer/exciter effect, which
can perhaps even be reduced a little in favour of the warm tube sound. You can monitor the amount of warmth
that is added with a glance at the WARMTH meter.
2.8 Adjustment of the Surround Processor
Sound qualit during signal transmission is given top priorit toda . The signal is processed with the help of
reverb devices, compressors, exciters, denoisers etc. to produce a compact, low-noise and transparent sound.
However, the fact that hearing impression depends largel upon the positioning of the instruments within the
stereo panorama is often enough neglected. Using the Surround Processor of the TUBEULTRAFEX, the
intensit of the stereo effect can be dramaticall improved. The program material gains in liveliness, loudness
and transparenc . As in a cinema with its special acoustics, the listener has the impression that the orchestral
instruments are placed all around him. The Surround Processor enlarges the stereo basis dependent on the
program material, without audibl colouring the sonic image.
The function of the Surround Processor is based on the derivation of a special signal, which is generated from
the difference of the left an right channel. This signal is then dela ed program-dependentl and mixed with the
original signal. The difference between the two channels is the stereo substance whose ambience and spatial
information is improved b dela ing the signal.
Due to the described function, the Surround Processor is principall useful onl with stereo program material.
3. APPLICATIONS
3.1 Sound Enhancement during Replay
For this application, the BEHRINGER TUBEULTRAFEX follows the master or multi-track recorder, i.e., in-
serted between tape machine and mixer (or amplifier). Of course, a cassette recorder, or similar, can also be
used as signal source.
If a companding noise reduction s stem is used in this situation, it should precede the TUBEULTRAFEX.
3.2 Sound Enhancement during Recording
The sound enhancing effect can be increased b using the BEHRINGER TUBEULTRAFEX not onl during
repla but during recording. This method of sound processing is recommended, in particular, if the subsequent
storage medium is of poor qualit . When doing tape duplications, the enhancer signal added during the record-
ing will compensate for the loss in qualit which occurs when several generations of copies are made from the
master tape.
In this scenario, insert the TUBEULTRAFEX directl after the master output of the mixer into the recording
path of the master or multi-track machine.
In particularl difficult cases, we recommend using the TUBEULTRAFEX both during recording and repla .
3. APPLICATIONS

13
TUBE ULTRAFEX T1954
3.3 Enhancing the Sound of Subgroups, Monitor and Effect Paths
For this application there are several options:
1. If our mixer features subgroup outputs with insert points, ou can process the subgroups separatel .
2. You can also combine monitor and effect paths and route them via the BEHRINGER TUBEULTRAFEX to
a free input channel. The respective signals have to be taken pre-fader, the respective channels must be
muted. It will be useful to insert the TUBEULTRAFEX as the last component in the chain of effects devices.
The summed signals will then be routed through the TUBEULTRAFEX, and sent back to the master via the
effect returns.The channels need be muted. Set up the mix as usual with the faders and determine which
monitor or effect send controls the signal portions to be routed to the BEHRINGER TUBEULTRAFEX.
With the help of the effect return control ou can adjust the amount of the sound enhancing signal which
is added to the summed signals. Be sure that the channels are muted for this kind of application, since the
combination of original signals via the summed, as well as the effects path, ma lead to phase cancella-
tions (comb filter effect).
3.4 Enhancing the Sound of Tape Duplication
Even under the most favourable of conditions, presence, liveliness and transparenc of the program material
will suffer during each cop ing process. These losses are particularl obvious when cop ing cassettes while
simultaneousl using a noise reduction s stem.
With the BEHRINGER TUBEULTRAFEX, losses during tape duplication can be avoided or compensated for.
Provided that the original is of good enough qualit with onl low noise levels. It is even possible to produce
super copies which sound even better than the original.
For this purpose, the TUBEULTRAFEX is inserted between the line outputs of the source machine and the
inputs of the target machine. Machines with post-head listening control (setting tape) allow ou to check the
qualit of the cop while duplicating the tape.
+If the tape noise is fairly high, a different strategy is required, since the TUBEULTRAFEX can
effectively process the frequency ranges in hich the most predominant noise portions can be
found. We recommend attenuation of noisy high frequencies, either ith an equalizer or 
better still  ith a single-ended noise reduction system. The TUBEULTRAFEX ill process
those frequencies ith all their natural clarity - but ithout the tape noise.
We would like to point out in this section that we offer an extremel powerful noise reduction s stem  the
DENOISER SNR2000. The noise produced b magnetic tapes or an other signal sources can be dramaticall
reduced with the BEHRINGER DENOISER SNR2000. Not onl the noise produced b mixers, effects devices
etc., but also b s nthesizers, guitars etc., can be effectivel reduced. Copied tapes and cassettes will benefit
from low noise and high d namics.
The TUBEULTRAFEX when used in conjunction with the DENOISER SNR2000 will prove an ideal combination
for sound enhancement. Please contact us for further information or visit our website at www.behringer.com!
3.5 Enhancing the Sound of Instruments
The bandwidth of most electronic musical instruments is limited b its sampling rate. The BEHRINGER
TUBEULTRAFEX can improve the sound, so that s nthesizers, samplers and drum machines have a more
natural and transparent sound.
With the TUBEULTRAFEX even tin details within the sound of acoustic musical instruments such as guitars
etc., can be emphasized without affecting the overall sound of the instrument. Drum instruments such as
toms, bass drums etc., benefit from a punch and thus achieve a more powerful, precise and defined sound.
Please note that low-level signal sources such as microphones, guitars etc. should pass through a pre-
amplifier before the processing stage, since the TUBEULTRAFEX is a line-level device.
3.6 Enhancing the Sound of P.A. Systems
If used in P.A. and other sound reinforcement s stems for background or live music, the BEHRINGER
TUBEULTRAFEX offers astounding advantages:
3. APPLICATIONS

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TUBE ULTRAFEX T1954
1. In audio s stems for announcements and background music, the TUBEULTRAFEX is placed in a similar
wa to recording and tape duplication - directl before the power amp. The intelligibilit and range of our
s stem will be improved and the sonic image will become clear and transparent, even at low volume levels.
Problems caused b background noise fluctuations, room acoustics (reflections), and speaker setup can
be solved more easil .
For instance, in discos or clubs ou do not need to constantl readjust the high frequencies as the place
becomes increasingl crowded; ou will be able to protect our speaker s stem and the hearing of visitors.
Background music in bars and restaurants can be heard easil . It does not anno our guests because its
volume had to be turned up too far.
2. The sound of an P.A. s stem will be improved b using the TUBEULTRAFEX. For example, the vocals of
music groups or speech transmissions will be considerabl more transparent and intelligible, the instru-
ments can be distinguished more easil . The bass will gain in depth and power.
3. The TUBEULTRAFEX will increase the speaker s stems acoustic performance and its abilit to penetrate
a room, particularl in places with difficult acoustics. The s stem also needs less effective amplifier power,
since the subjectivel heard volume level increases. Powerful and detailed sound reproduction can also be
achieved in weak s stems.
3.7 Sound Enhancement in HiFi and Video
Of course, the BEHRINGER TUBEULTRAFEX can also find applications in the fields of hifi and video. The unit
is simpl placed between the signal source (cassette recorder, tuner, VCR etc.) and the power amplifier. We
recommend using the tape monitor inputs most pre-amplifiers provide, thus the TUBEULTRAFEX can be
switched into an signal source.
4. TECHNICAL BACKGROUND
4.1 The BEHRINGER TUBE U TRAFEX ...
sincreases presence and transparenc . The program material will sound livel and natural again.
simproves the intelligibilit of speech: voices become clearl articulated, text easil intelligible, the transpar-
enc of the vocal increases.
sprovides a distinct sound improvement, particularl for instruments pla ed in a percussive st le - slapped
bass guitars or drums will sound incredibl funk .
sprovides better stereo imaging: the sound becomes more differentiated, the positioning of the speakers is
much easier, et the signal remains full mono-compatible.
sdoes not require an decoding process, since sound enhancement with the TUBE ULTRAFEX is not cre-
ated independentl of the signal itself, and remains available even during numerous processing or cop ing
stages. Even digital recordings or CD repla ing will gain from the use of the TUBE ULTRAFEX.
sincreases the listeners awareness. Even with low sound pressure levels, the TUBE ULTRAFEX avoids
listening fatigue.
sfinds useful application in hifi s stems b providing better resolution of the sonic image, due to its suitabilit
for the studio and its outstanding specifications. In particular, the processing of old analog recordings
(disks and tapes) proves to be ver efficient with the TUBE ULTRAFEX.
sproduces a more powerful and fuller bass which does not sound mudd . All recordings will benefit from the
dr  and precisel defined bass contouring.
sproduces an improved spatial enhancement and stereo effect intensit with the Surround Processor without
audibl colouring the sonic image.
4. TECHNICAL BACKGROUND

15
TUBE ULTRAFEX T1954
4.2 Psycho-acoustic Background
The term ps cho-acoustics refers to the ps chological aspect of hearing  in contrast to the ph siological
transfer of impulses (transmission of nervous impulses). Ps cho-acoustics examines the effect of sound on
the listener and the reasons for certain sonic impressions. How a sound is interpreted is influenced b a lot of
factors, most of them can hardl be measured et are fairl important. For instance, those portions which are
responsible for the spatial localization of a sound. Nevertheless, the determine the qualit of a recording to an
extraordinaril large extent.
There are also portions of the audio spectrum which we perceive as presence or naturalness. If this kind of
information is missing, the recording suffers from a loss in freshness, liveliness and spatial transparenc .
Furthermore, natural harmonics are essential components of the sound. Often enough, the onl represent a
minor portion of the signal and are easil lost. It´s the harmonic structure that makes a tone colour unique.
Without this structure, different instruments would not be distinguishable. When comparing acoustic musical
instruments, for instance acoustic guitars, ou will note that even two instruments from the same series have
a different sound. Numerous factors determine the sound of an instrument: the design and materials to name
but two, but with such bearing on the eventual sound produced b that instrument.
From a ph sical point of view, a guitar produces a tone b means of a vibrating string which, in turn, sets air in
motion. The subsequent propagating sound waves reach the ear and are identified b the brain as a tone. Since
the string vibrates within itself, the tone consists of not onl the fundamental oscillation but also innumerable
upper harmonics which are based on the fundamental wave.
The complex vibrations of the string are transferred to the bod which, in turn, is also set in motion. The
combination of string and bod produces the sound of the instrument. For example, certain harmonics ma be
amplified due to resonance effects in the bod , while other frequencies ma be canceled due to the properties
of the wood.
This phenomenon creates complex sounds and is underlined b the fact that a combination of harmonics can
produce additional tones, known as interference or residual tones. All of these tin sound portions contribute to
the sound of certain instruments. The human ear, which is highl sensitive, can detect even minimum changes
in the harmonic structure of a sound.
B experiencing the CD qualit of 32-bit converters etc., we have made considerable advances toward the
naturalness of sound, et still recordings do not sound like the music in a concert hall. Wh is there a
difference?
Here, the ke word is intelligent hearing: the visual contact with the musicians enables us to concentrate our
attention on a certain instrument which results in an intensification of the sonic experience. The listener sitting
in front of a speaker s stem lacks this spatial experience and at the same time the visual feedback aspect of
listening to live music. The perceived positioning of instruments is made even more difficult since the disper-
sion of the sound is not homogeneous, i.e., widel panoramic, but usuall reduced to two sound sources.
In particular, the loss of upper harmonics during the transmission of the sound additionall affects the per-
ceived positioning of the instruments and the transmission of room ambiance. The reason for this loss in sound
qualit is the inadequac of the sound recording and reproduction processes.
Each link in the transmission chain  from the microphone via mixers, effects devices, tape recorders ampli-
fiers etc., to the loudspeakers  causes a loss in sound qualit . Each time the sound is processed, it
becomes audibl less natural.
4.3 On Psycho-acoustic Devices
Although the ps cho-acoustic effect of enhancers and exciters etc., has been known for several decades, the
function of these devices has been deliberatel surrounded in m stique, to increase their appeal.
However, it is fairl clear that all devices in this field are based on certain technicall repeatable methods of
functioning. Basicall , three principles appl :
sSound improvement b means of d namic frequenc correction.
sThe generation of a wider sound with the help of phase shifting with respect to dela times.
sThe enrichment of the program material with artificiall generated harmonics.
Independentl of each other, each of these methods produces a certain effect which is perceived as a subjec-
4. TECHNICAL BACKGROUND

16
TUBE ULTRAFEX T1954
tive enhancement within the sound.
These methods are described in more detail in the following:
4.3.1 Frequency correction
The boosting or cutting of certain frequenc ranges is the simplest form of sound modification. Equalizers can
correct the sonic image in order to produce a sound that is more pleasing to each taste.
So-called treble boosters achieve this effect b emphasizing the high frequencies, which the listener per-
ceives as a transparent sonic image.
Within the BEHRINGER TUBE ULTRAFEX, an frequenc correction is combined with a frequenc -dependent
phase shift, which results in a sound that is warmer and more musical.
4.3.2 Phase shifting
The term phase shift describes the displacement of a signals phase in relation to its point of origin. As a matter
of principle, the phase shift produces a dela within the signal.
If the dela ed signal is added to the original signal, the resultant signal becomes wider. Below time dela
values of 20 msec. the brain perceives the dela ed arrival of the two signals as the arrival of one signal, which
results in the desired pulse enlargement effect, sometimes called 3-D effect b other manufacturers.
The effect produced b so-called chorus units is based on the same principle of phase shift and signal dela .
Here, several dela ed signals are added to evenl intensif this effect.
The BEHRINGER TUBE ULTRAFEX is equipped with a frequenc -selective phase shift circuit that comprises
several stages. Due to the program-dependent dela ed signal, the sonic impression becomes more vivid, as
with an orchestra, where the musical liveliness is the result of inaccurate entries b musicians.
4.3.3 Artificial harmonics generation
B 1955 an American, Charles D. Lindridge, had alread invented the first EXCITER (a unit that EXCITES
upper harmonics), when he presented a unit for improving the sound of music and speech. He enriched signal
sources with artificiall generated upper harmonics and found that both sound qualit , transparenc and per-
ceived positioning of musical instruments could be considerabl improved using this effect. He was granted an
American patent on his circuit design under the number US 2 866 849.
Compared to modern technolog , Lindridges circuit was an thing but full developed, however, it featured
man of the aspects found in toda s modern circuit designs.
Ps cho-acoustic discoveries and greater knowledge, gathered over the ears, have allowed for new and im-
proved circuit designs, through the use of advanced technolog .
4.4 The Bass Processor of the TUBE U TRAFEX
Apart from processing the upper harmonic ranges, users of the TUBE ULTRAFEX have access to an innovative
Bass Processor.
The numerous stages of processing during the recording, reproduction, cop ing and effecting processes,
increasingl dela the phase of the bass frequencies, when compared to the remaining frequenc ranges. This
is wh the low-frequenc range suffers from a loss in power and fundamental bass definition.
With the help of frequenc -selective phase shift combined with sub-bass boost, the Bass Processor of the
TUBE ULTRAFEX is capable of compensating for this loss, giving the program material new bass presence.
Using the MODE switch, ou can select between two different bass sounds.
Be extremel careful when using the Bass Processor: excessive use of the Bass Processor might lead to
speaker damage. The amplified sub-bass frequencies ma well place a heav load on the amplifier and the
woofers. Therefore, carefull adjust the Bass Processor and observe the power rating of our s stem!
4. TECHNICAL BACKGROUND

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TUBE ULTRAFEX T1954
4.5 The Surround Processor of the TUBE U TRAFEX
Sound qualit during signal transmission is given top priorit toda . The signal is processed with the help of
Reverb devices, Compressors, Exciters, Denoisers etc. to produce a compact, low-noise and transparent
sound. However, the fact that hearing impression depends largel upon the positioning of the instruments
within the stereo panorama is often enough neglected. Using the Surround Processor of the TUBE ULTRAFEX,
the intensit of the stereo effect can be dramaticall improved. The program material gains in liveliness, loud-
ness and transparenc . As in a cinema with its special acoustics, the listener has the impression that the
orchestral instruments are placed all around him. The Surround Processor enlarges the stereo basis depen-
dent on the program material, without audibl colouring the sonic image.
The function of the Surround Processor is based on the derivation of a special signal, which is generated from
the difference of the left an right channel. This signal is then dela ed program dependentl and mixed with the
original signal. The difference between the two channels is the stereo substance whose ambient and spatial
information is improved b dela ing the signal. Due to the described function, the Surround Processor is
principall useful onl with stereo program material.
4.6 The Vacuum Tubes of the TUBE U TRAFEX
4.6.1 UTC circuit
Our engineering team has made it possible to enhance the traditional tube circuitr (particularl for our TUBE
ULTRAFEX) and adapt it to meet the high sound qualit and d namics requirements of modern, pro-level audio
technolog . The fact that we are still fascinated b antique tube radios and amps as well as the fine and warm
tonal character that we usuall associate with them, are the reasons wh vacuum tubes have kept their ground
even in state-of-the-art circuit topologies used especiall in professional audio technolog or high-end devices.
We are particularl proud that we have found a highl effective s mbiosis between solid-state and tube tech-
nologies making them affordable to almost an bod in audio technolog .
IN
OUT
WARMTH
Fig. 4.1: UTC (ULTRA-TUBE Circuitry)
A closer look at developments and trends in audio technolog shows that tubes are enjo ing a renaissance
toda , in a time when even amateur musicians are free to use digital effects processors and recording media,
and ever more affordable digital mixing consoles are becoming a natural part of the equipment of man semi-
4. TECHNICAL BACKGROUND

18
TUBE ULTRAFEX T1954
professional studios. Manufacturers tr with ever new algorithms to get the most out of DSPs (Digital Signal
Processors), the heart of an digital s stem.
Still, man audio engineers, particularl old hands often prefer using both old and new tube-equipped devices.
As the want to use their warm sound character for their productions, the are read to accept that these little
darlings produce a higher noise floor than modern, transistor-based devices. As a consequence, ou can find
a variet of tube-based microphones, equalizers, pre-amps and compressors in toda s recording and master-
ing environments. The combination of semiconductor and tube technologies gives ou the additional possibilit
of using the best of both worlds, while being able to make up for their specific drawbacks.
4.6.2 Tube history
Due to man patent litigations, it is difficult to determine exactl when the tube was born. First developments
in tube technolog were reported between 1904 and 1906. It was a research task of that time to find a suitable
method for receiving and rectif ing high frequencies. On April 12, 1905, a certain Mr. Fleming was granted a
patent for his hot-cathode valve which was based on Edisons incandescent lamp. This valve was used as a
rectifier for high-frequenc signals. Robert von Lieben was the first to discover (probabl b chance) that the
anode current can be controlled b means of a perforated metal plate (grid)  one of the milestones in the
development of amplification tubes. In 1912, Robert van Lieben finall developed the first tube for the amplifica-
tion of low-frequenc signals. Initiall , the biggest problem was to produce sufficient volume levels, which is
wh resonance step-ups (though impairing the frequenc response) were used to maximize the attainable
volume. Later, the objective was to optimize the electroacoustic transducers of amplifiers in such a wa that a
broad frequenc band could be transmitted with the least distortion possible.
However, a tube-specific problem is its non-linear amplification curve, i.e. it modifies the sound character of the
source material. Despite all efforts to ensure a largel linear frequenc response, it had to be accepted that
tube devices produce a bad sound. Additionall , the noise floor generated b the tubes limited the usable
d namics of connected storage media (magnetic tape machines). Thus, a one-to-one reproduction of the audio
signals d namics (expressed as the difference between the highest and lowest loudness levels of the program
material) proved impossible. To top it all, tube devices required the use of high-qualit and often costl trans-
ducers and sophisticated voltage supplies.
With the introduction of semiconductor technologies in the field of audio amplification, it soon became clear
that the tube would have to give wa to the transistor, as this device featured an enormousl enhanced signal-
to-noise ratio, required a less complex power suppl and ielded an improved frequenc response. Plus,
semiconductor-based circuits can be realized much more easil - for less mone .
Two decades later, the introduction of binar signal processing meant the beginning of a new era of recording
media that provided plent of d namic response and allowed for the loss-free cop ing of audio signals. As
digital media were enhanced, however, man people began to miss the warmth, power and liveliness the
knew from analog recordings. This is wh purists still toda consider digital recordings as sterile in sound.
4.6.3 Design and functional principle of tubes
Tubes can be roughl classified according to the number of electrodes the use. There are tubes with two,
three or five electrodes usuall referred to as diodes, triodes or pentodes.
Fig. 4.2: Diode
The diode contains two electrodes in a vacuum glass bulb that have electrical connection to the outside. The
vacuum allows for a free movement of electrons. When one of the electrodes is heated up (= thus becoming a
cathode), it begins to emit electrons. When a positive DC voltage is applied to the other electrode (= anode),
the negative electrons start to migrate from the cathode to the anode. With reverse polarit between cathode
4. TECHNICAL BACKGROUND

19
TUBE ULTRAFEX T1954
and anode, a current flow is not possible because the unheated anode emits more or less no electrons. This
design was used, for example, as a rectifier in the power supplies of amplifiers. The magnitude and velocit of
the flow of electrons depend on the cathodes temperature, the material it consists of, and the magnitude of the
anode voltage. When the electrons hit the anode the produce heat that is dissipated b using large anode
plates.
Fig. 4.3: Triode
The triode has an additional metal grid between anode and cathode. B appl ing a negative voltage, this grid
can be used to control the internal resistance of the tube, and hence the anode current. When the grid bias
voltage (voltage between cathode and grid) becomes negative, the current flowing to the anode is reduced
because the negativel charged grid repels the arriving electrons. As a consequence, there are less electrons
to reach the anode. When the bias voltage shifts towards zero, the flow of electrons accelerates. When it finall
becomes zero or even positive, the grid current begins to flow which considerabl reduces the current flowing
to the anode and can possibl destro the tube. Triodes are most commonl used in pre-amps, often in pairs
arranged in one tube (twin triode).
Fig. 4.4: Pentode
In a triode the capacitance between grid and anode is a problem with regard to high frequencies and large
amplification factors. For this reason, the pentode has a positivel charged screen grid between the control grid
and the anode. However, the positive charge of the screen grid attracts electrons emitted from the anode plate
when it is hit b arriving electrons. To prevent this electron emission, a decelerating or suppressor grid is
placed between anode and screen grid. As it is negativel charged it blocks the electrons, so that the cannot
reach the screen grid. Pentodes are most commonl used in power stages.
4.6.4 Properties of tubes
In general, the saturation (overdriving) of both transistor and tube-based circuits results in various t pes of
distortion. These phenomena are quite complex in the real world, but for the sake of a straightforward math-
ematical description we are going to classif them as linear and non-linear distortion. Linear distortion is
produced b frequenc -dependent amplification or attenuation processes such as occurs in all kinds of filters
and equalizers. Linear-distortion signals have the same frequenc portions both on the input and output sides,
but with different phase positions and amplitudes. Non-linear distortions have additional harmonics and distor-
tion components that were not contained in the original input signal.
For example, when the simplest of all oscillations, a sine wave with a fixed frequenc f, is overdriven, new
oscillations with frequencies of 2*f, 3*f, etc. (integral multiples of the original frequenc ) are produced. These
new frequencies are referred to as upper harmonics grouped as odd and even harmonics.
Unlike the transistor, saturated tubes mostl produce even harmonics which are perceived b the human ear
as more pleasant in sound than odd harmonics. Another important aspect lies in the fact that tubes produce
distortion more graduall than transistors, which is wh we speak of the saturation of a Tube Stage. When
4. TECHNICAL BACKGROUND

20
TUBE ULTRAFEX T1954
ou overdrive a transistor ou get a sudden square deformation of the sine signal applied at the input, which
produces an extreme harmonic spectrum at the output.
Non-linear distortions are measured with a distortion factor that consists of the total harmonic distortion [k] and
partial harmonic distortions [kn]. The latter are defined as the ratio between the voltage of a single harmonic and
the voltage of the distorted overall signal. Thus, the content of even harmonics is expressed as k2, k4, ... and
that of odd harmonics as k1, k3, ... .
U
U
kn
n=
Formula for calculating partial harmonic distortion
The total harmonic distortion is the root of all squared distortion factors of the second and third degrees. Since
the higher harmonics have onl little impact on the measured results, the can be neglected.
kkk=+
2
23 2
Formula for calculating total harmonic distortion
In tube circuits the distortion factor k2 is used to describe an effect which the human ear classifies as pleas-
ant. Also the frequenc bands in which distortion occurs pla an important role because the human ear
differentiates ver clearl , in particular, in the frequenc range of human speech.
4.6.5 The best of both orlds
Despite man efforts neither manufacturers nor developers have succeeded so far in simulating these positive
properties of the tube b means of other devices. Additionall , the natural capabilities of the tube to act as a
soft limiter can onl be mimicked with highl sophisticated circuitr . Toda s studio technolog requirements
are therefore met b a combination of both high-grade semiconductor and tube technologies. In this context,
tubes no longer serve their original purpose as amplifiers, but are used for the detailed shaping of sound.
4.6.6 Studio applications
In a recording studio tubes do not perform the same task as the do in an overdriven guitar amp, where the
considerabl higher saturation of the tube(s) leads to a full and often deliberate modification of the input signal
(in man cases combined with a heav increase in noise floor levels). In the studio more subtle effects are
needed. Here, tube circuits add life to the signals tonal character and increase its power to make itself heard.
Often, tubes also increase the signals perceived loudness (in relation to the unprocessed signal), i.e. the
perceived loudness goes up although the volume level remains the same. This is because the d namic range
of the applied audio signal is limited b the tube circuit, while the amplitude of the signal with the lowest
loudness is raised. Thus, increasing tube saturation produces a slight compression effect over the entire
d namic range.
A similar effect can be perceived when analog tape is saturated. This saturation effect also compresses the
recorded audio material and produces additional harmonics.
5. INSTALLATION
Your BEHRINGER TUBEULTRAFEX was carefull packed in the factor and the packaging was designed to
protect the unit from rough handling. Nevertheless, we recommend that ou carefull examine the packaging
and its contents for an signs of ph sical damage, which ma have occurred in transit.
+If the unit is damaged, please do not return it to us, but notify your dealer and the shipping
company immediately, other ise claims for damage or replacement may not be granted.
Shipping claims must be made by the consignee.
5. INSTALLATION