AVALON VT-747 SP TWIN SIGNAL PATH OPTO-COMPRESSOR-EQUALIZER

The Avalon VT-747SP combines a creative STEREO tube-discrete Class A
spectral-opto-compressor with a musical six band program equalizer, L-R
output level and gain reduction metering and internal regulated power supplies
in a 2U space. Ideal for high performance DAW input signal conditioning, stereo
buss compression-EQ, stereo keyboards and analog mastering applications.

SPECTRAL-OPTO-COMPRESSION
The opto-compressor features a minimum signal path design utilizing sealed
silver relays for all signal routing and by pass functions. The optical attenuator
acts as a passive level controller with a Class A, variable gain make-up amplifier.
Full dynamic control from soft compression to hard-knee limiting can be achieved
with master threshold, ratio-compression, attack and release controls. Gain
reduction indication is a large analog VU meter. Low frequency and high frequency
contour parametric spectral controls can be routed into the side-chain path for
enhanced frequency dependent compression with variable frequency and threshold
levels. SC listen provides side-chain listen mode for monitoring.
SIX BAND PROGRAM EQUALIZER
The VT-747SP equalizer utilizes 100% discrete, Class A high-voltage transistors
for optimum sonic performance. The six band STEREO program EQ incorporates
the smooth characteristics of an all passive design. The frequency turnover, Q
and amplitude ranges have been carefully chosen for each band to provide the most
natural harmonic balance and lowest phase change while offering simple and
effective tone control. The EQ can be placed pre or post the opto-compressor for
enhanced effects.
TSP - TWIN SIGNAL PATH
The VT-747SP features TSP which gives you the choice of either tube tone
or the classic, Class A discrete transistor sound by exchanging, three (3)
high-voltage dual triode tubes with discrete amplifiers in the opto-compressor
and primary output stages.
INPUT-OUTPUT and METERING
Fully balanced DC coupled, Class A discrete amplifiers are utilized for the
input and output drive interface with+36dB input headroom. A high quality
analog VU meter indicates accurate gain reduction. Twin 60dB range LED
meters provide fast L-R output status of all levels.

VT-747SP FEATURES 
Stereo Class A opto-compressor with spectral control
Stereo Class A six band discrete passive program EQ
TSP twin signal path, vacuum tube bypass
Low noise -92dB
Fully balanced Class A input and DC coupled outputs
Stereo dynamic 60dB high resolution output meters
High quality analog VU meter for gain reduction
High headroom+36dB input before overload
Spectral side-chain monitor for pre listen
EQ pre-post selection for opto-compressor
Sealed silver relays for all signal routing
Internal discrete regulated power supplies
Military spec vacuum tubes for long life and low noise
 
VT-747SP SPECIFICATIONS
Circuit topology Three (3) dual triode vacuum tubes (Sovtek 6922),
high-voltage discrete Class A mode.
Input gain range Balanced, Class A, 20k ohms, -20dB to +16dB with
high gain switch
Maximum input level +36dB balanced XLR pin 2 hot
Maximum output level +30dB balanced 600 ohms, DC coupled, discrete
Class A 
Output type XLR connector, output trim gain -45dB to +6dB
Noise 20kHz unweighted -92dB
Distortion THD, IMD 0.5%
Frequency response -3dB 1Hz to 200kHz
Gain reduction meter High quality, illuminated gain reduction meter 0dB
to -20dB range 
Output meter Twin 20 segment LED VU meters with -27dB to +30dB range
Compressor type Optical passive attenuator
Make-up gain Variable 0dB to +10dB stereo tracking 
Threshold - Ratio Threshold variable -30dB to +20dB, ratio-compression
variable 1:1 to 20:1
Attack - Release Attack variable 2mS to 200mS, release variable 100mS
to 5 seconds
Side-chain spectral contour Variable threshold -15dB to +15dB, frequency
70Hz to 9kHz twin ranges
Equalizer type Discrete Class A, passive design optimized for full range
program material
Frequency bands (6) Variable amplitude LF +/-24dB 15Hz shelf response
Variable amplitude MF1 +/-8dB 125Hz selected Q response
Variable amplitude MF2 +/-4dB 500Hz selected Q response
Variable amplitude MF3 +/-4dB 2kHz selected Q response
Variable amplitude MF4 +/-10dB 5kHz shelf response
Variable amplitude HF +/-20dB 32kHz shelf response
AC power Internal toroidal 100v to 240v, 50-60Hz selectable, 70 watts
maximum
Dimensions 19 x 12 x 3.5 in (482 x 305 x 89mm)
Weight 22lbs (10kg)
Dimensions-shipping carton  21 x 18 x 8 in (533 x 457 x 203mm)
Weight-packed 26lbs (11.8kg)

• Professional 31-band stereo graphic equalizer for live and studio applications
• Revolutionary FBQ Feedback Detection system instantly reveals critical frequencies and can also be used as audio analyzer
• Ultra-low noise 4580 operational amplifiers for highest signal integrity
• Dedicated mono subwoofer output with adjustable crossover frequency
• Additional sweepable high and low-cut filters for each channel remove unwanted frequencies, e.g. floor rumble, hiss etc.
• Highly accurate 12-segment LED input/output metering and input gain controls for easy level setting

• Relay-controlled hard-bypass with an auto-bypass function during power failure (fail-safe relay)
• Servo-balanced inputs and outputs with 1/4" TRS and gold-plated XLR connectors
• “Planet Earth" switching power supply for maximum flexibility (100 - 240 V~), noise-free audio, superior transient response plus low power consumption for energy saving
• 3-Year Warranty Program*
• Conceived and designed by BEHRINGER Germany

Innovation

The ARX AFTERBURNER? is a unique Multi Mode compressor/limiter
designed for use in any professional audio dynamics control application.
Multiple Modes
The Afterburner can be set up and used in three different ways:
In Two channel mode, it performs as two independent compressor/limiters,
with 'industry standard' variable Threshold, Ratio and Output gain. In stereo
mode, our New Adaptive Stereo Link circuitry provides increased stereo
imaging accuracy when linking both channels as a stereo pair. A single front
panel switch puts the Afterburner into its alternative Mono mode, setting it up
as a Single channel, Dual Band compressor/limiter, with separate dynamics
control of both Low and High frequencies, opening up a whole new range of
gain control techniques.
Enhance Switch
In any mode, the Afterburner features an 'Enhance' switch, which provides
frequency restoration to preserve the spectral balance of the audio signal,
compensating for the sagging Low and High frequency response of compressed
program material. Think of it as a 'smart' loudness control.
 
Features
Switchable Modes - Stereo; Dual Channel Single band; or Single Channel
Dual Band (Low and High)
Low and High frequency compression in Single Channel mode
'Enhance' switch restores spectral balance of compressed signal
New Hard/Soft knee compression switch
New Adaptive Stereo Link circuit for accurate stereo imaging
New Above/Below Threshold LEDs enable at-a-glance compression
confirmation
Balanced XLR and Jack Inputs and Outputs
Sidechain Insert points
Intuitive user-friendly layout
Flawless performance
 
New Above/Below Threshold LEDs enable at-a-glance compression confirmation
New Hard or Soft knee compression option
New LED metering provides accurate Level status, with separate Gain Reduction
metering in easy to read 'wide scale' meters. There is also comprehensive LED
indication of all operating functions and status in any mode.
Balanced Inputs and Outputs
On the rear panel, each channel has true differential Balanced inputs and outputs,
on both XLR and TRS jack connectors. As well, each channel has a TRS jack
Sidechain access insert point, for applications such as De-essing (when used with
an external equalizer such as the ARX Multi Q or EQ 260).Other features include a
true Hardwire bypass switch for each channel, and passive RFI filters on the inputs.
Universal AC Power
AC power range is a universal 100 to 120V or 220 to 240V AC, and is connected to
the unit via a removable power lead and standard 3 pin IEC connector, with built-in
fuse and voltage change switch.
With its smooth compression, intuitive user friendly layout, high density precision
circuitry, and extensive user-variable operating parameters, the unique ARX Afterburner
is equally at home in Studio, Installation, Broadcast and Sound Reinforcement
environments. It can provide great sounding dynamics control effects that are not
available with any other device.
 
T E C H N I C A L  S P E C I F I C A T I O N S
Input Impedance Balanced 20 Kohms, Unbalanced 10 Kohms
Input Headroom + 22 dB
CMRR >60 dB, 20 Hz-20 KHz
Output Impedance Balanced 300 ohms, Unbalanced 150 ohms
Output Level (Max) + 22 dB
Frequency Response 20Hz to 20KHz ±0.2dB
Signal to Noise ratio -93 dB Unweighted, -99 dB 'A' weighted
Distortion .02% THD @ 0dB,1KHz
Dynamic Range 115 dB
Sidechain Insert Impedance 10 Kohm
Filter Section
Filter Type Phase corrected 6dB/octave
Summed Filter Response ±0.2dB through crossover region
Dividing Frequency 250 Hz
Enhance Section
Low Enhance 50 Hz, High Enhance 10 KHz
Power Requirements 100/120 V AC, 220/240 V AC
Weight 5 lbs/2.2 Kg
Dimensions 19“W x 1?“H x 6“D, 482 x 44 x 155mm
Input/OutputConnector type XLR, Balanced Jack
Sidechain Insert Connector TRS Jack

Front Panel Controls
Hardwire bypass IN/OUT switch
Threshold, Ratio and Output Gain controls
Above/Below Threshold LEDs
12 segment LED Output Level display
Numbered marker panel for labelling compressor assigns
7 segment LED Gain Reduction display
Enhance switch and status LED
Adaptive Stereo link switch and status LED
Dual/Single channel mode switch and status LEDs
Rear Panel Connectors
Balanced Inputs and Outputs, on both XLR and TRS jack
connectors. In Single channel (Mono) mode, use Channel
1 Inputs and Outputs only
Sidechain Insert TRS connector on each channel
AC input connector, with voltage switch and fuse.
 

The AD2055 combines 100% discrete, pure class A signal amplifiers with state-of-
the-art passive and active filter topologies. The AD2055's unique circuitry delivers
very high resolution transient detail at the operational extremes of real world equalization
demands. The AD2055 auto-bias DC servo loop control eliminates the need for all
interstage capacitor coupling. The AD2055 breathes life into all musical performances!
 
AD2055 FEATURES
Pure Class A, 100% discrete design
Smooth musical detail and sonic excellence
Minimum audio signal path
Dual mono operation
Transparent active and passive filter design
High headroom +30dB Very low noise -94dB
Fully balanced inputs and outputs
DC coupled, no transformers in audio path
Switched frequencies in high and low bands
Mid bands use X10 frequency for extended range
Wide bandwidth -3dB 1Hz to 450kHz
Low distortion less than 0.5% THD and IMD
All signal routing with sealed silver relays Conductive
plastic potentiometers for low noise
External 150W toroidal power supply 100% discrete
power supplies for audio path
Long lasting, stainless steel hardware
 
SONIC EXCELLENCE
The Avalon AD2055 Pure Class A music equalizer is the most powerful, low noise
parametric equalizer available today. Designed to optimize absolute signal integrity
and musical performance, the AD2055 combines the best of active and passive filter
topologies with sonic excellence unequaled by lesser designs. The AD2055 is the
perfect solution for two buss music-program equalization, special instrument EQ and
FX applications and ultra high performance mastering studio's.

Features include state-of-the-art, balanced 100% discrete, Pure Class A signal amplifiers,
practical user features and rugged hardware designed to deliver true high performance
audio for many years. 

PASSIVE-ACTIVE FILTER DESIGN
Avalon equalizers feature the unique combination of both active and passive filter EQ designs.
This special combination enables the AD2055 to deliver high speed transient detail at the
operational extremes of real-world equalization demands. The passive high and low bands offer
alternate musical tone range to the full function active parametric mid bands. Passive equalizers
have long been a favorite with music lovers around the world.  Full bodied, powerful (up to +/-32dB,
64dB range !) and sweet frequency selections are the benefits of the passive high-low EQ bands.
The full bandwidth twin mid bands provide variable frequency selection (X10 frequency multipliers
for very wide range), variable Q (width) and amplitude control.

MINIMUM SIGNAL PATH DESIGN
Avalon's advanced true symmetry design offers high-voltage, large headroom, extended bandwidth
and very low noise. The use of 100% discrete, Pure Class A signal amplifiers give the serious music
professional unlimited sonic character and a natural harmonic detail that enhances the program
material and becomes one with the music itself. The Avalon AD2055 breathes life!

AD2055 SPECIFICATIONS
Circuit Topology  High-voltage 100% discrete, balanced and symmetrical
Class A 
Output Gain Range  Unity Gain 
Maximum Input Level  +30dB balanced XLR pin 2 hot 
Maximum Output Level  +32dB balanced 600 ohms, DC coupled, high-current
discrete Class A 
Input / Output Type  XLR type, pin 2 hot balanced 
Noise 20kHz Unweighted  -94dB (EQ in) 
Distortion THD, IMD  0.5% (typical 0.05% at +6dB 1kHz) 
Frequency Response -3dB  1Hz to 450kHz (input band limited) 
Equalizer Type  Passive high and low bands plus two fully parametric mid
bands 
Bypass  Hard-wire relay bypass for equalizer in-out 
Low Band F1  Passive, amplitude to -32dB to +32dB shelf or peak-dip curve 
F1 Frequency Range  Switched 10 position 18Hz, 25, 30, 50, 72, 100, 150, 215,
300, 450Hz 
Mid Band F2  Active, amplitude to -16dB to +16dB peak-dip curve 
F2 Frequency Range  Variable 35Hz to 450Hz (x10) 350Hz to 4k5Hz, Q (width)
0.3 to 3.0 
Mid Band F3  Active, amplitude to -16dB to +16dB peak-dip curve 
F3 Frequency Range  Variable 160Hz to 2k0Hz (x10) 1k6Hz to 20kHz, Q (width)
0.3 to 3.0 
High Band F4  Passive, amplitude to -26dB to +26dB shelf or peak-dip curve 
F4 Frequency Range  Switched 10 position 1k5Hz, 2k5, 3k5, 5k, 7k2, 10k, 12k5,
15k, 20k, 25kHz 
AC-DC Power  External AC supply, 150w toroidal transformer, 4 pin cable 90v
isolated, 
(B2T Power Supply Included)  100-240v selectable 50/60Hz, 150w max 
Dimensions  19 x 3.5 x 12 in (482 x 88 x 305mm) 
Shipping weight  30lbs (13.6 kg) 

Features
Four Independent Compressor Channels
Channels 1 and 2, 3 and 4 are stereo linkable
7 LED Gain Reduction metering
Balanced XLR Inputs and Outputs
Sidechain Insert points
Intuitive, user friendly layout
Flawless performance
 
The sheer amount of effects and signal processors necessary for today's standards
of audio production puts a great strain on the available space in equipment racks,
both in the studio and on the road.So, ARX would like to introduce the ARX Quadcomp.
An all-new upgrade of the classic award-winning ARX Quadcomp?, the very first four
channel 1 RU compressor.You?ll notice that we haven?t strayed very far from our
original design concept. The Quadcomp  is still four variable ratio Compressor/ Limiters
neatly housed in a compact all steel 1 RU package. However, all new low noise/low
distortion circuitry, better metering plus XLR inputs and outputs put the Quadcomp
in a class of its own.
More Control, Less Space
On the front panel, each channel has the 'industry standard' individual controls for Threshold,
Compression Ratio and Output, plus a new 7 LED Gain Reduction display for accurate visual
indication of the amount of gain reduction being applied to the program, and an IN/OUT
hardwire bypass switch.In addition to this, each channel has a blank numbered panel to write
on for easy confirmation of compressor assigns.
Precision Circuitry
Internally, each compressor uses Class A VCAs and true 2 pole averaging RMS/DC converters
for low distortion and accuracy, plus program dependent attack and release time, which
automatically determines optimum compressor response.
Balanced Inputs and Outputs
The rear panel has true differential Balanced XLR Inputs and Outputs for each compressor.
Each compressor has a TRS jack Sidechain access insert point, for frequency sensitive
compression, De-essing, etc. in conjunction with an external equalizer (such as the ARX EQ260).
Compressor pairs 1 and 2, 3 and 4 also have rear panel mounted Stereo Link switches for accurate
stereo tracking. When switched IN, the first channel becomes the master and controls all the functions
of the second except Output gain.
Universal AC Power
AC power range is switchable 100 to 120V, or 220 to 240V, and is connected to the unit via
a standard IEC connector, with built-in fuse and voltage switch.
Whatever the application ? Channel insert, Bus insert, Master Outputs, Monitor outputs,
Crossover outputs, the Quadcomp II?s unique High Density design, precision Low Noise circuitry
and clean uncluttered layout make it a truly useful audio tool for all applications.

T E C H N I C A L S P E C I F I C A T I O N S
Input Impedance
Balanced 20 Kohms, Unbalanced 10 Kohms
Input Headroom + 20dB
CMRR >50dB, 20 Hz?20 KHz
Output Impedance
Balanced 300 ohms Unbalanced 150 ohms
Output Level (Max) + 20 dB
Frequency Response 20Hz-20KHz ±0.5dB
Signal to Noise ratio
-93 dB Unweighted, -98 dB ?A? weighted
Distortion .015% THD @ 0dB,1KHz
Dynamic Range 108 dB
Attack and Release Times Program dependent
Metering
7 LED display: ?1, 2, 3, 6, 12, 18, ?24 dB
Sidechain Insert Impedance 10 Kohm
Power Requirements
100/120 V AC or 220/240 V AC
Weight 5 lbs/2.2 Kg
Dimensions
19“W x 1?“H x 6“D, 482 x 44 x 155mm
Input Connector type Balanced XLR
Output Connector type Balanced XLR
Sidechain Insert Connector TRS Jack

Front Panel Controls
Hardwire bypass IN/OUT switch
Threshold, Ratio and Output Gain controls
7 LED Gain Reduction display
Marker panel for labelling compressor assigns
Stereo link status LEDs
Rear Panel Connectors
Input and Output balanced XLR connectors
TipRingSleeve Sidechain insert connectors
Channels 1 and 2, 3 and 4 Stereo link switches
IEC AC mains connector with inbuilt fuse and
voltage change