Vt-747sp - Operation Manual (Version 1.0 - 2001)

DE S I G NAVA LONPURE CLASS A M USIC RECORDING SYSTEMS

VT-747SP

Operation Manual

Pure Class A Stereo Spectral Opto-Compressor Equalizer

© 2001 Avalon Industries Incorporated. Release 1.0.

AVALON DESIGNPU R E CL A S S A M U S I C RE C O R D I N G SY S T E M S

VT-747SP

Operation Manual

Avalon Industries, Inc., PO Box 5976, San Clemente, CA 92673

Tel: 949-492-2000 Fax: 949-492-4284 www.avalondesign.com

AVALON DESIGNPU R E CL A S S A M U S I C RE C O R D I N G SY S T E M S

Table of Contents

1.0 Introduction . . . . . . . . . . . . . . . . . . .41.1 Overview . . . . . . . . . . . . . . . . . . .41.2 Features . . . . . . . . . . . . . . . . . . . .51.3 Unpacking and Inspection . . . . . . .6

2.0 Quick Start-up . . . . . . . . . . . . . . . . .72.1 Quick Set-up Guide . . . . . . . . . . .82.2 Tips . . . . . . . . . . . . . . . . . . . . . . .92.3 Tutorial-Using it all . . . . . . . . . . . .9

3.0 Safety and Grounding . . . . . . . . . .103.1 Safety Instructions . . . . . . . . . . .103.2 Grounding Instructions . . . . . . . .103.3 AC Voltage Selection . . . . . . . . . .113.4 Fuse Replacement . . . . . . . . . . .123.4 Rack Mounting and Cooling . . . .123.5 Turn-on Procedure . . . . . . . . . . .13

4.0 Operation and Controls . . . . . . . . .144.1 Rear Panel Description . . . . . . . .174.2 Connections . . . . . . . . . . . . . . . .174.3 Unbalanced Operation . . . . . . . .174.4 Using the Vt-747sp . . . . . . . . . . .184.5 Six Band Passive Equalizer . . . .184.6 Using the Equalizer . . . . . . . . . . .184.7 Using the Side-chain . . . . . . . . . .19

5.0 Applications . . . . . . . . . . . . . . . . . .195.1.0 Typical Set-ups . . . . . . . . . . . .195.1.1 Recording . . . . . . . . . . . . . . . . . . .20

5.1.2 Stereo Mixdown (Buss) . . . . . . . . .20

5.1.3 Mixdown/Mastering - DAW . . . . . . .20

5.1.4 Mastering . . . . . . . . . . . . . . . . . . .21

5.2.0 Application Settings . . . . . . . . .215.2.1 Stereo Buss for Mixdown . . . . . . . .21

5.2.2 Stereo Buss with De-ess . . . . . . . .22

5.2.3 De-ess on Vocals . . . . . . . . . . . . .22

5.2.4 Stereo Keyboards . . . . . . . . . . . . .23

5.2.5 Extreme Compression Effect . . . . .23

5.2.6 Acoustic Piano . . . . . . . . . . . . . . . .24

5.2.7 Acoustic Guitar . . . . . . . . . . . . . . .24

5.2.8 Drum Overheads . . . . . . . . . . . . . .25

6.0 Compression Primer . . . . . . . . . . .25

6.1 Equalization Primer . . . . . . . . . . . .27

7.0 FAQs . . . . . . . . . . . . . . . . . . . . . . . .27

8.0 Trouble Shooting . . . . . . . . . . . . . .30

9.0 Service and Contact Information . .32

10.0 Technical Information . . . . . . . . .3310.1 Recall Sheet . . . . . . . . . . . . . . .3410.2 Block Diagram . . . . . . . . . . . . .35

11.0 Warranty . . . . . . . . . . . . . . . . . . . .3611.1 Returns . . . . . . . . . . . . . . . . . . .36

12.0 Safety Standards . . . . . . . . . . . . .36

Appendix A - Glossary . . . . . . . . . . . . .37

Avalon Vt-747sp Operation Manual

AVALON DESIGNIntroduction

1.0 Introduction

Welcome to Avalon and the world of highperformance Pure Class A music recordingsystems. The Vt-747sp is an extremelyversatile, pure Class A, vacuum tube/discreteTSP (Tube Signal Path) stereo opto-compressor and program equalizer.

The Vt-747sp is the most creative and flexiblestereo compressor available. With TSP (TubeSignal Path), the Vt-747sp uses three handselected vacuum tubes in the signal path forwarm tube tone or bypasses the tubes forclassic Class A discrete transistor sound. Alsofeatured on the Vt-747sp is a passive six-band graphic equalizer for gentle tone-shaping plus a two-band parametric EQ forcomplete spectral side-chain or musicalcontrol.

The Vt-747sp is hand built in the USA usingonly the finest active and passive electroniccomponents available. Many of these partshave been custom-manufactured exclusivelyfor Avalon. A "no compromise" approach inevery stage of design and production ensuresthat the Vt-747sp will give many years ofdependable high-quality service.

Please take a moment to read this manualand enjoy your Avalon experience!

1.1 Overview

The Vt-747sp combines a stereo tube/discrete Class A opto-compressor with amusical six-band program equalizer, as wellas Left/Right output level, gain reductionmetering and an internal regulated powersupply in a 2U space. Ideal for highperformance DAW (digital audio workstation)input signal conditioning, stereo busscompression/EQ, stereo keyboards andmastering applications.

The Vt-747sp features a minimum signal pathdesign utilizing sealed silver relays for allsignal routing and bypass functions.

Compression with the Vt-747sp is achievedwith twin optical attenuators that act aspassive level controllers together with a ClassA variable gain make-up amplifier. Fulldynamic control from soft compression tohard-knee limiting can be achieved withmaster threshold, compression ratio, attackand release controls. Gain reductionindication is a large analog VU meter. Lowand High Frequency (LF and HF) contourparametric spectral controls can be routedinto the on-board side-chain path forenhanced frequency dependent compressionwith variable frequency and threshold levels.An SC LISTEN switch provides side chainlisten mode for easy monitoring.

The Vt-747sp equalizer utilizes 100%discrete, Class A high voltage transistors foroptimum sonic performance. The six-bandstereo program EQ incorporates the smoothcharacteristics of an all passive design. Thefrequency turnover, Q and amplitude rangeshave been carefully chosen for each band toprovide the most natural harmonic balancewith lowest phase change while offeringsimple and effective tone control. The EQ canbe placed pre or post compressor forenhanced effects.

The Vt-747sp features TSP (Tube SignalPath) which gives you the choice of eithertube tone (utilizing three high-voltage dualtriode tubes), or the classic, Class A discretetransistor sound (utilizing discrete transistoramplifiers) in the primary opto buffers andoutput stages.

Fully balanced DC coupled, Class A discreteamplifiers are utilized for the input and outputdrive interface with +36dB input headroom. Ahigh quality analog VU meter indicatesaccurate gain reduction. Twin LED metersprovide a 60dB range with fast L-R outputstatus of all levels.

1.2 Features

� Class A optical compression

� 100% discrete Pure Class A operation

� Built-in side chain for spectral control

� Six-band discrete graphic passive EQ

� TSP (Tube Signal Path) with bypass

� EQ pre/post compression selection

� Twenty-two silver relays for signal routing

� True hard-wire bypass

� Low noise, better than -92dB

� High operating headroom +36dB

� Fully balanced operation, input and output

� 3 military-grade dual triode vacuum tubes

� High voltage, high current signal path

� Rugged stainless steel metric hardware

� 2U nineteen inch welded steel chassis

� Switchable AC power supply 100-240v

� 150W toroidal shielded power transformer

� Discrete soft-start DC power regulators


AVALON DESIGN Introduction

Inside view of Vt-747SP

1.3 Unpacking and Inspection

Your Vt-747sp was packed carefully at thefactory. Check to make sure that the shippingcarton contains the following items:

1. Vt-747sp2. Power cable3. Warranty card4. Operation Manual

Keep the packing materials in case you needto ship your unit for any reason.

Note: You must fill out and send in yourwarranty card in order to receive warrantyand technical support. If you have notalready filled out your warranty card pleasetake the time to do so now.


AVALON DESIGNIntroduction

Vt-747sp contents and packaging

2.0 Quick Start-up

The following chapter is designed to help youget started using your Vt-747sp right awaywithout having to read the entire manual.Make sure however to take time to read themanual at a later date as there are manysafety aspects and features of the Vt-747spthat will not be discussed here.

If you are familiar with this type of equipmentyou can also familiarize yourself with yourVt-747sp and the functions with the QuickSet-up Guide on page 8.

Note: The Vt-747sp is an extremely highperformance piece of musical equipment.Every setting has great potential formusicality. Do not be afraid of turning theknobs or faders to their full extremepositions.

Hook it up, turn it on and play:

1. Check on the rear of your unit that thepower supply is set for your local ACvoltage. (120V in U.S.) Refer to Chapter 3page 11 for details.

2. Plug in the AC power cable and connectyour Vt-747sp to your stereo source. (XLRtype connectors pin 2 is hot.) You can usethe Vt-747sp in mono, however, the Leftand Right will always work together as onededicated stereo pair.

3. Turn on the power and allow 60 secondswhile the soft-start procedure commences.You may hear a relay click at about 45seconds. During the soft-start procedure,the Vt-747sp is in hard-wire bypass modeand will pass signal, but the controls willnot work. For optimum performance,allow 30 minutes for the Vt-747sp tofully warm up.

4. With all switches in the disengaged or non-illuminated position, run a signal throughthe Vt-747sp. Use the output control on theright hand side of the unit to check basicoperation.(see figure 2.0 below)

5. Now you are ready to start pressingswitches, turning knobs and pushing EQfaders!

The Quick Set-Up Guide on the followingpage gives a brief description of the switchesand controls on the Vt-747sp.


AVALON DESIGN Quick Start-up

figure 2.0 Quick Start up

Keyboard or Stereo Source

Right and Left Outputs

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AVALON DESIGNQuick Start-up

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2.2 Tips

Unity Level - The Vt-747sp is calibrated sothat unity level is +4dBu.

INPUT - Use the input control as a gaincontrol, not a level control. This will drive thetubes and/or transistors harder for differenttone.

OUTPUT - Use the output control as theoverall level control.

TSP (Tube Signal Path) - Pressed in(illuminated) is tube mode. Pressed out (non-illuminated) discrete Class A mode.

EQ > COMP - Inserts the six-band graphicEQ before (pre) the compressor in the signalpath.

SIDE-CHAIN - Engages the built-in side-chain. Use the SIDE CHAIN THRESHOLDand the corresponding frequency bands tocompress specific frequencies.

SC LISTEN - To monitor the signal throughthe side chain.

GR (Blue LED) - Fast-acting LED illuminateswhen peak gain reduction begins to occur.

EQ - Six-band graphic EQ parameters:Low to high (left to right)

+/-24dB 15Hz shelf +/-8dB 125Hz selected Q+/-4dB 500Hz selected Q+/-4dB 2kHz selected Q+/-10dB 5kHz shelf+/-20dB 32kHz shelf

2.3 Tutorial - Using it all

The following is a tutorial that will quickly getyou familiar with all of the functions of theVt-747sp.

Start by plugging a stereo source (CD player,stereo keyboard, Submix output, etc.) intoyour Vt-747sp. If possible, run directly out ofthe Vt-747sp to powered monitors bypassingthe console or mixing board. Choose amusical selection, loop, patch, sample orinstrument with wide dynamic range so youcan experiment with the compressor.

Set push button switches to their off or non-illuminated position.

1. INPUT - Set to 5. (Adjust OUTPUT so thatoverall signal level is at a comfortablemonitoring level.

2. GAIN +10dB - Press in and out to get a feelfor the sound of the high gain switch. Leaveit non-illuminated.

3. EQUALIZER - (Located on right side ofpanel) press in equalizer switch andfamiliarize yourself with the six bandequalizer. Adjust the two outside bands halfway between unity and maximum, and thefour mid-bands to half way between unity andminimum. Toggle the EQUALIZER switch inand out.

4. COMPRESSOR - Press in COMPRESSORswitch and turn the main compression controlsto the following: COMPRESSION - fully clockwiseTHRESHOLD - fully counter clockwiseATTACK - fully counter clockwise (Fast)RELEASE - fully clockwise (Slow)


AVALON DESIGN Quick Start-up

5. EQ->COMP - Press in to insert the EQbefore (pre) the compressor in the signalpath.

6. Press in TSP. This will engage the tubesso that you are now in tube mode.

7. Press in SIDE CHAIN and SC LISTEN. Youare now monitoring the signal going throughthe side chain. You can use the side chainlisten function as a parametric EQ on theprimary audio path.

8. Adjust the side chain parameters to thefollowing settings:Both LF and HF side chain threshold fullycounter clockwise.LF frequency set to 300 Hz.HF frequency set to 1k6 Hz.

9. Press out the SC LISTEN switch (disengaged).

Now you have full compression, with fastattack and slow release, and two differentfrequencies going into the side chain that arebeing compressed more than the overallstereo signal.

Make yourself familiar with all of the functionsin the Vt-747sp. The combinations, colors,and tones are endless. For more details oneach specific control or switch, please refer toChapter 4 - Operations and Controls.

3.0 Safety and Grounding

The following chapter describes how tosafely install your Vt-747sp for optimal sonicperformance.

3.1 Safety Instructions

This unit contains voltages that can causeserious injury or death. Do not operatewith the covers removed.

Improper connection of the equipment-grounding cable can result in a risk of electricshock.

Check with a qualified electrician orserviceman if you are in doubt about yourelectrical power or ground connection. TheVt-747sp is for use with an AC supply asselected by the AC voltage selector (locatedwithin the AC inlet on the rear of the chassis).Voltages are 100-120-220-240 VAC +/-5%,50-60Hz, at 60 watts.

3.2 Grounding Instructions

Always connect the Vt-747sp to a groundedAC power circuit.

If the unit should malfunction or become"live", the chassis ground will provide the pathof least resistance for electric current toreduce the risk of fatal shock.


AVALON DESIGNSafety andGrounding

This product is equipped with an ACpower inlet and must be connected to athree-wire grounded plug.

The AC power cable must be plugged into anappropriate outlet that is correctly installedand grounded in accordance with all localelectrical safety codes and ordinances.

If hum or ground-buzz is induced into thesystem, remove the rear-mounted GROUNDLINK. This ground-link isolates the ACchassis ground from the audio ground. Whenthe LINK is removed, the AC ground remainsconnected to the chassis via the AC inletconnector and provides a direct path for anyelectrical fault or dangerous condition.

Warning! No ground adapter should everbe used with this unit.

3.3 AC Voltage Selection

Before connecting the Vt-747sp to the ACsupply, check the OPERATING VOLTAGElocated on the rear of the chassis in theAC inlet connector.

Voltages available are 100-120-220-240VAC+/-5%, 50-60Hz at 60 watts. (USA uses 120V)

To change the AC voltage for your location:

1. Make sure there is no AC power cableconnected to the AC inlet.

2. Insert a small flat-head screwdriver tip intothe voltage selector cavity. Carefully lift-openthe hinged cover from left to right.

3. Rotate the selector wheel to show thecorrect voltage for your location, then pushthe wheel firmly into the mounting tabs.

4. Press the voltage selector cover snap-shut,check correct AC voltage in window.

5. Connect grounded AC power cable.


AVALON DESIGNSafety andGroundingAVALON DESIGN

3.4 Fuse Replacement

The fuse on the Vt-747sp is located within theAC plug assembly on the back of the unit. A fusecan blow if the AC selection is not selectedproperly or if there is a sudden surge of AC toyour Vt-747sp.

Your Vt-747sp uses a 250V, 1 amp slow blowfuse.

To change the fuse:

1. Make sure there is no AC cable connectedto the AC inlet.

2. Insert a small flat-head screwdriver tip intothe voltage selector cavity. Carefully lift-openthe hinged cover from left to right.

3. Pull fuse casing (labled with an arrow)straight out.

4. Replace fuse in casing. Insert casing intocasing slot. Close AC voltage selector cover.

3.5 Rack Mounting and Cooling

The Vt-747sp is designed to be mounted in astandard 19" equipment rack. As vacuumtubes and Class A circuitry can generate heat,it is highly recommended that an additionalrack space above and below the unit be keptempty to allow for adequate cooling. AvalonDesign has developed 1U ventilation panels(VP-1) specifically to keep your rack-mountedgear cool.


AVALON DESIGNSafety andGrounding

Avalon units with VP-1 vent panels


AVALON DESIGNSafety andGroundingAVALON DESIGN

Be sure that the ventilation slots (located onthe top and bottom of the unit) are notobstructed and air is allowed to flow easilythrough the chassis. If the unit is not rack-mounted, be sure to place supports under theunit to allow air to pass underneath. Neverleave any obstruction on top of the unit (suchas papers or books) blocking ventilation slots.Also, be sure that the heat sink mounted onthe rear panel of the chassis has adequateclearance from the equipment enclosure andany adjacent equipment. In electronicequipment, excessive heat is the cause ofmost component failures . A little extraprecaution to ensure proper ventilation canhelp avoid many premature equipmentbreakdowns.

Always use all four front panel-mountingholes when mounting the Vt-747sp in a rackenclosure. If not shipped in its originalpacking, the Vt-747sp should be transportedin a floating-type shock-mounted flight case.

Although the Vt-747sp is well shieldedagainst moderate electrical and magneticfields, care should be taken to avoid areasthat are in proximity to large motor or powertransformers. Locations near sources of highRFI (radio frequency interference) such ascomputers or digital effects devices shouldalso be avoided.

Because of the microphonic nature ofvacuum tubes, areas of extreme vibration orsound levels should also be avoided.

3.6 Turn-on Procedure

The Vt-747sp is designed with a "soft-start"feature that slowly brings the unit to life whenthe unit is powered on. This feature ensuresthat there is no strain on the electroniccomponents when it is activated. It takesapproximately 60 seconds for the unit to runthrough the "soft-start" turn-on procedure.

When the Vt-747sp is switched off or duringthe "soft-start" turn-on procedure, it is in hardwire bypass mode and the unit will passsignal utilizing a hard wire relay but none ofthe controls will operate.

Allow the unit to warm up for at leastthirty minutes prior to use. This allows thecomponents time to come up to temperatureand stabilize before recording begins.

It is recommended that the unit be turnedoff during periods of "non-use" greaterthan 4 hours.

4.0 Operation and Controls

The following chapter describes the details ofyour Vt-747sp and how to operate eachfunction.

INPUTContinuously variable control trims input levelof signal source. This control will drive thetubes harder while in tube mode to get moretube tone into the compressor. In discretemode (TSP disengaged) the transistors aredriven harder to achieve more classicdiscrete transistor sound. The input has+36dB of headroom before overload. You canuse this control at minimum and maximumlevels for different sounds and colors.

GAIN +10dBBoosts the signal by +10dB. This switchenables more flexibility for another set ofsounds and colors, and for matching low levelsources. (e.g. keyboards, synthesizers, etc.)

TSP (Tube Signal Path)Illuminated switch IN swaps three (3) tubesinto the audio path from discrete Class Atransistor-based amplifiers.

THRESHOLDThis control sets compressor threshold level.Continuously variable from -30dB to +20dB.

EQ > COMPSwitches six-band passive equalizer before(pre) the compressor. This gives flexibility toachieve different sounds. Putting the EQbefore the compressor will give the signal amore squashed and narrow sound than if theEQ follows the compressor.

LF SIDE-CHAIN THRESHOLDControls the increase of compression for theLF specified frequency range. As theThreshold is turned counter clockwise (mademore negative), the frequency set with the LFSide-Chain Threshold Hz will be compressedharder than the compression of the overallprogram. (Operates in the reverse of a stan-dard EQ +/- control.)

HF SIDE-CHAIN THRESHOLDControls the increase of compression for theHF specified frequency range. As theThreshold is turned counter clockwise (mademore negative), the frequency set with the HFSide-Chain Threshold Hz will be compressedharder than the compression of the overallprogram.

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Operation andControls AVALON DESIGN

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VU METER (0dB calibration screw)Recessed screwdriver adjustment for setting0dB on the VU meter. The VU meter indicatesthe amount of gain reduction in dB.

To calibrate the VU meter: Power unit on andallow 30 minutes before making this adjust-ment so that components can warm up tooperating temperature. While there is no signalpresent, adjust the trim pot so the needle onthe VU meter lines up with zero (“0”).

COMPRESSION RATIOSets the compression ratio. Continuouslyvariable from 1:1 to 20:1.

Note : With opto-compressors, the Thresholdand Compression Ratio are interactive andare effected by one another.

COMPRESSOR Switches the compressor in the signal pathwith a sealed silver relay. (Hard-wire bypass)

VU METER Analog VU meter indicates gain reduction.The VU meter’s needle is speed sensitive formeasuring attack and release of the signal.

EQUALIZERSwitches the six-band passive graphicequalizer in the signal path with a sealedsilver relay. This EQ is designed for subtlesweetening and shaping. It is very simple andeasy to use. The frequency turnover, Q andamplitude ranges have been carefully chosenfor each band to provide extremely smoothmusicality. Pushing the faders up from centerdetent will boost and pushing the faders downwill cut.

OUTPUTContinuously variable output control. Thiscontrols the overall program level of the Vt-747sp.The Vt-747sp is calibrated so that 0 on theLED output meters accurately shows +4dBu.

ATTACKVaries attack time of compressor from 2ms(FAST) to 200ms (SLOW).

RELEASEVaries release time of compressor from100ms (FAST) to 5 seconds (SLOW).

LF SIDE-CHAIN THRESHOLD HzSweep variable peak/dip frequency setting forSide-Chain parameter. (60Hz to 1kHz)

SIDE-CHAINActivates the two-band parametric spectralSide-Chain controls.

GR (Blue LED)Fast-acting blue light indicates peak gainreduction.

HF SIDE-CHAIN THRESHOLD HzPeak/dip variable sweep frequency sidechain parameter. (600Hz to 10kHz)

SC LISTENTo monitor the signal going into through the SideChain before it is effected by the compressor.

MAKE-UP GAINVariable 0dB to +10dB control to add gainafter compressed signal. (Only acts when thecompressor switch is in.)

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Operation andControlsAVALON DESIGN

LOW-BASS EQUALIZER BANDControls low-bass frequency range:+/-24dB 15Hz shelf

MID-BASS EQUALIZER BANDControls mid-bass frequency range:+/-8dB 125Hz peak/dip

LOW-MID EQUALIZER BANDControls low-mid frequencies0+/-4dB 500Hz peak/dip

MID-RANGE EQUALIZER BANDControls mid frequency range:+/-4dB 2kHz peak/dip

HIGH-MID EQUALIZER BANDControls high-mid frequency range:+/-10dB 5kHz shelf

HIGH-RANGE EQUALIZER BANDControls high frequency range:+/-20dB 32kHz shelf

AC Power SwitchTurns the power on and off. You must allowapproximately 60 seconds from the time youturn on the power switch for the Vt-747sp tocomplete the entire soft start turn-on proce-dure. For more details on the soft start pro-cedure please refer to Chapter 3.5 Turn-onProcedure.

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Vt-747sp production at Avalon

4.1 Rear Panel Description

LINE INPUT (Left and Right)Female XLR-3 connectors. Balanced input forline level signals to +36dB maximum. (pin +2 hot)

LINE OUTPUT (Left and Right)Male XLR-3 connectors. Balanced DC coupled,capable of +30dB into 600 ohms. (pin +2 hot)

GROUND LINK2-terminal barrier strip. Provided to isolatechassis ground from audio ground. To liftground, simply unscrew both phillips-headscrews and remove the metal strip held by thescrews.

AC INPUT & FUSECombination IEC socket, voltage selector andfuse location. AC voltage is factory set asordered. To change the factory voltage setting,refer to the AC Voltage Selection section of thismanual in Chapter 3 (page 11), or contact yourauthorized Avalon dealer.

For instructions on changing the fuse, see

Chapter 3.4 Fuse Replacement (page 12).

4.2 Connections

The LINE INPUTS are an electronicallybalanced Class A circuit with a nominal 20k ohminput impedance. (Can be used unbalanced byshorting pin 3 to ground on the cable connector.)The connectors are female XLR-3.

The OUTPUTS are a low impedanceelectronically balanced circuit which terminatesto a male XLR-3 connector. (Can be usedunbalanced by shorting pin 3 to ground on thecable connector.)

All XLR connectors are wired:Pin 1 groundPin 2 high (+)Pin 3 low (-)

Input Impedance: 20k Ohm Output Impedance: 600Ohm

4.3 Unbalanced Operation

The Vt-747sp can also be used in unbalancedmode by grounding pin 3 on the cable inputand output pins.

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Operation andControlsAVALON DESIGN

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AVALON DESIGN

4.4 Using the Vt-747sp

The opto-compressor of the Vt-747sp hasthe standard features of a typical outboardcompressor plus a few other unique featureslike no other compressor. Basic operation isas follows:1. Engage the COMPRESSOR push-button.This will insert the compressor into the signalchain.2. Set ATTACK to FAST.3. Set RELEASE to FAST.4. Set COMPRESSION to 20:1 (fully clockwise)5. Set THRESHOLD to –30dB (fully counterclockwise)6. Test compression by introducing signal.Needle should move rapidly for any substan-tial input signal. Turn up the INPUT GAIN ifneedle is not moving.8. Fine tune controls for desired effect.

4.5 Six Band Passive Equalizer

The six band graphic equalizer is extremelysmooth and musical. The six frequencybands and corresponding Q settings havebeen carefully chosen to provide the mostnatural harmonic balance and lowest phasechange while offering simple and effectivetone control.

The following is a description of the six fre-quency bands.

From Low to High (left to right)1. +/- 24dB 15Hz shelf response2. +/- 8dB 125Hz selected Q response3. +/- 4dB 500Hz selected Q response4. +/- 4dB 2kHz selected Q response5. +/- 10dB 5kHz shelf response6. +/- 20dB 32kHz shelf response

4.6 Using the Equalizer

The equalizer section of the Vt-747sp hasbeen designed to be easy to use.

Engage EQ push-button (illuminates "IN") toinsert the EQ in the signal path.

All six faders have a center detent. When allfaders are set to center detent the EQ iscompletely flat.

Pushing a fader up from the center detentboosts the corresponding frequency bandand pushing a fader down from the centerdetent cuts the corresponding frequencyband.

Because of the passive design, the equalizeron the Vt-747sp is smooth and musical. It canbe used to subtly shape and color while stillkeeping the signal musically balanced(program equalizer.)




ApplicationsAVALON DESIGN

4.7 Using the Side-chain

Inserting an equalizer into a compressor’sgain reduction control path is commonlyknown as side-chaining . This effect allowsfor spectral control of the compression at thespecified frequencies. The most frequentapplication of this technique is known asde-essing. De-essing is the removal ofexcessively pronounced "S" sounds fromvocal recordings. You can de-ess with theVt-747sp and any other frequencies whereyou need a little more compression than theoverall program.

To insert the two-band spectral EQ into theSide Chain:1. Set the compressor to full compression tobegin. (described in previous section)2. Engage the SIDE-CHAIN switch3. Set the HF and LF Threshold controls to-15dB (fully counterclockwise)4. Press in the SC LISTEN to monitor5. Sweep the LF and HF frequency controlsto find the desired signals to send into theSide-Chain. 6. Depress the SC LISTEN switch (non-illuminated)so that the signal you were emphasizing withthe SC LISTEN is now routed into the gaincontrol section of the compressor.

5.0 Applications

The first thing to remember is that there areno specific rules . The Vt-747sp wasdesigned to be extremely flexible and filledwith endless colors, textures and tones.TRUST YOUR EARS!

5.1.0 Typical Set-ups

The following setup diagrams are a fewtypical ways (not the only ways) to insert theVt-747sp in the audio chain during arecording project. Much of the power in theVt-747sp lies within its flexibility. You can usethe Vt-747sp in every stage of the recordingor mixdown process:

Figure 5.1.1 - Recording to direct to DigitalAudio Workstation (DAW) or tape machine.

Note that the Vt-747sp is a line level unit only.It does not have microphone preamplifiers(mic pre’s). You must use mic pre’s Such asthe two-channel Avalon AD2022, beforeinserting the Vt-747sp during recording. TheVt-747sp works wonderfully with keyboards,drum machines, synthesizers and other linelevel inputs enabling you to completelybypass the mixing console and go directly toyour DAW or tape machine.

Figure 5.1.2 - Mixdown Stereo Buss - Mainright/left Insert or across the entire stereo mix.

Figure 5.1.3 - Mixdown and/or Masteringon DAW - Across a stereo submix or theentire mixed stereo signal

Figure 5.1.4 - Mastering Tape Based - MainRight and Left Outputs

Figure 5.1.1 - Recording

Figure 5.1.2 - Stereo Mixdown (Buss)

Figure 5.1.3 - Mixdown or Mastering UsingDAW

Figure 5.1.4 - Mastering Tape Based


Applications AVALON DESIGN

Keyboard, synth,drum machine, etc.OR

Stereo Mics

Vt-747sp

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Tape Machineor

DAW

Tape Machineor

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Mixing Consolefor Monitoring

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Mixing Consolefor Monitoring

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Mixing Console

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DATor

CD Burner

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Inputs - Record Two New Tracks

Inputs Outputs

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Main Outputsor Tape Output

5.2.0 Application Settings

The following are a few example settings forthe Vt-747sp to be used as starting points forspecific applications. You will most likely needto adjust the settings given here for yourrecordings because of the many variableswhich depend on a recorded sound. Variablessuch as microphone choice, microphoneplacement, recording room, recording media,mixing console, the musician, etc., cangreatly alter and change the sound of arecording. Simply stated, trust your ears.

Note : The output controls the signal level tothe next piece of equipment in the audiochain. The output control is designed to besonically invisible. This means that you canset the output level based on what signallevel you want coming out of the Vt-747spand you will not color the signal by turning thiscontrol up or down. Therefore, the outputlevel is not included in the examplesettings.

5.2.1 Stereo Buss for Mixdown

Input : +3Gain : OutTSP: OutCompressor : InEQ->Comp : OutCompression Ratio : 5:1Compression Threshold : -15Attack : 11 o’clockRelease : FastMake-up : +1 (10 o’clock)Side-Chain : OutSide-Chain LF Threshold : bypassedSide-Chain LF Frequency : bypassedSide-Chain HF Threshold : bypassedSide-Chain HF Frequency : bypassedEqualizer : InEQ Faders from left (1) to right (6):1. +22. +13. +14. +15. +16. +2



5.2.2 Stereo Buss & Vocal De-ess

Input : +3Gain : OutTSP: InCompressor : InEQ->Comp : InCompression Ratio : 5:1Compression Threshold : -12Attack : FastRelease : FastMake-up : +1 (10 o’clock)Side-Chain : InSide-Chain LF Threshold : +15Side-Chain LF Frequency : 200HzSide-Chain HF Threshold : -15Side-Chain HF Frequency : 7kHzEqualizer : InEQ Faders from left (1) to right (6):1. +12. +13. +0.54. +0.55. +16. +1

5.2.3 De-ess on Vocals

Input : +2High Gain : OutTSP: InCompressor : InEQ->Comp : InCompression Ratio : 20:1Compression Threshold : -20Attack : FastRelease : FastMake-up : +2Side-Chain : InSide-Chain LF Threshold : +15Side-Chain LF Frequency : 200HzSide-Chain HF Threshold : -15Side-Chain HF Frequency : 7kHzEqualizer : InEQ Faders from left (1) to right (6):1. +12. 03. 04. +0.55. +0.56. +0.5



5.2.4 Stereo Keyboards

Input : +3High Gain : OutTSP: InCompressor : InEQ->Comp : OutCompression Ratio : 6:1Compression Threshold : -17Attack : 11 O’clockRelease : FastMake-up : +2Side-Chain : OutSide-Chain LF Threshold : bypassedSide-Chain LF Frequency : bypassedSide-Chain HF Threshold : bypassedSide-Chain HF Frequency : bypassedEqualizer : InEQ Faders from left (1) to right (6):1. 02. +13. +14. +25. +26. +1

5.2.5 Extreme Compression

Input : 0 - UnityGain : OutTSP: InCompressor : InEQ->Comp : InCompression Ratio : 20:1Compression Threshold : -20Attack : FastRelease : 12 O’clockMake-up : +10Side-Chain : OutSide-Chain LF Threshold : bypassedSide-Chain LF Frequency : bypassedSide-Chain HF Threshold : bypassedSide-Chain HF Frequency :bypassedEqualizer : InEQ Faders from left (1) to right (6):1. +32. +23. +14. +15. +26. +2



5.2.6 Acoustic Piano

Input : +2Gain : OutTSP: InCompressor : InEQ->Comp : OutCompression Ratio : 6:1Compression Threshold : -12Attack : FastRelease : FastMake-up : 0Side-Chain : InSide-Chain LF Threshold : +15Side-Chain LF Frequency : 70 HzSide-Chain HF Threshold : -15Side-Chain HF Frequency : 3kHzEqualizer : InEQ Faders from left (1) to right (6):1. +12. +23. +14. +25. +16. +1.5

5.2.7 Acoustic Guitar

Input : +3Gain : OutTSP: OutCompressor : InEQ->Comp : OutCompression Ratio : 9:1Compression Threshold : -15Attack : 10 O’clockRelease : FastMake-up : 0Side-Chain : InSide-Chain LF Threshold : 10 O’clockSide-Chain LF Frequency : 250 HzSide-Chain HF Threshold : 3 O’clockSide-Chain HF Frequency : 7 kHzEqualizer : InEQ Faders from left (1) to right (6):1. 02. -0.53. -14. 05. +0.56. +0.5




Compression andEQ PrimersAVALON DESIGN

5.2.8 Drum Overheads

Input : +4Gain : OutTSP: InCompressor : InEQ->Comp : OutCompression Ratio : 4:1Compression Threshold :-17Attack : FastRelease : FastMake-up : +5Side-Chain : OutSide-Chain LF Threshold : bypassedSide-Chain LF Frequency : bypassedSide-Chain HF Threshold : bypassedSide-Chain HF Frequency : bypassedEqualizer : InEQ Faders from left (1) to right (6):1. 02. +23. +14. +0.55. +16. +2

6.0 Compression Primer

A compressor is one of the most widely usedsignal processors in the recording studio.Compressors are used during the recordingprocess as well as during mixdown andmastering. During the recording processcompressors are used to control the dynamicrange or volume of a signal. For example,a singer may vary his volume level from awhisper to a scream during a particular song.A compressor will control the volume of thevocal so that the volume is consistent whetherthe singer is whispering or screaming. Duringmixdown compressors are used to "tightenup" the tracks so that nothing pops out of themix uncontrollably. During the masteringprocess compressors are used very slightly totighten up the entire mix and can give the mixa bigger sound.

The way a compressor works is like anautomatic fader. When the input signalexceeds a predetermined level called thethreshold , the gain is reduced by thecompressor and the signal is attenuated. Byattenuating the louder signal levels, you are infact, reducing the program’s overall dynamicrange. Because the range between theloudest and softest signal is "compressed" byincreasing the signal’s overall gain, theaverage level will be greater. Thus the signalwill be perceived as being louder than itotherwise would be.

Compression is measured by the ratio of thechange in output level (in dB) to the change ininput level, called the compression ratio . If acompressor is set to 8:1 compression then an8 dB increase in the input level will result in a1dB increase in the output level.

Compression V ariables Defined

Compressors are controlled by four mainfunctions: Threshold , Ratio , Attack andRelease .

Threshold : Defines the level wherecompression begins. If the sound level cominginto the input is below the threshold, thecompressor passes the signal with no change.When a louder signal rises above thethreshold, the compressor starts working,automatically reducing the output gain by theamount set with the ratio control.

Ratio : The ratio control is the amount ofvolume reduction relative to the original signallevel. A 1:1 (one to one) ratio is the lowestcompression ratio. This means that the volumethat goes into the compressor is exactly thesame as the volume that comes out. A 2:1 ratiomeans that the compressor will only allow theoutput level to rise 1dB for every 2dB that theinput is over the threshold. This way thecompressor allows the signal to be louder thanthe threshold, but only by half as much. This istypical moderate compression. A 4:1 ratio

means that if the input signal is 4dB over thethreshold, the compressor only allows anoutput 1dB over the threshold.

Attack : The very beginning of a sound isusually the loudest and most difficult to recordsmoothly (for example, vocals, slap bass,guitar, etc.). In many cases you want to letthese initial transients pass through beforepulling down the gain, other times you want thecompression to start right away. To help makeadjustments to this specific event, the attackcontrol adjusts the length of time it takes for thecompression to begin.

Release : Once the signal falls below thethreshold, the Release control determines howquickly the compressor "lets go" of the volumecontrol and lets the level rise back to unitygain. Just as the Attack control sets the volumeof the start of a sound, the Release control setsthe volume of the end of a sound. The releasecan be used creatively to make sounds cut-offsharply or sustain longer.

Compressors usually have built-in metering toallow monitoring of the amount of gainreduction taking place. The meter usually sitsat 0 VU when the input signal is below thethreshold and falls to the left to indicate thenumber of decibels of gain reduction. Also theactual speed of the moving needle indicatesthe attack and release speeds.


Compression andEQ Primers AVALON DESIGN

Time

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dB

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Graphic description of compression

6.1 Equalization Primer

An equalizer is a group of tone controls thatallow adjustment to the frequency range of anincoming signal using a number of separatefrequency bands. A graphic equalizerconsists of a number of pre-selectedfrequency bands, boost/cut control, and apre-set bandwidth or “Q” control for eachfrequency band. Each fader on a graphicequalizer corresponds to a specific frequencyrange to either cut or boost. The bandwidthof the frequency range is preselected. Themid bands are typically peak/dip while theend bands are typically shelving filters.

A six-band graphic (program) equalizer asfound in the Vt-747sp consists of sixfrequency selection controls: Low-bass, Mid-bass, Low-mid, Mid, High-mid, and High.Each frequency band has carefully selectedcut/boost, frequency range, and Qparameters that are useful and effective toshape and sweeten the signal. The LowBass, High Mid and High bands are shelvingfilters while the Mid-bass, Low-Mid, and Midbands are peak/dip filters. For details on theVt-747sp graphic EQ parameters seeChapter 3, Operation and Controls.

7.0 FAQs

The following are answers to F requentlyAsked Q uestions about the Vt-747sp :

Q: Can I use the Vt-747sp as an insert forcompression and EQ? A: Yes. the Vt-747sp is perfect as an insert fora recorded stereo signal such as keyboards,acoustic piano, drum overheads, acousticguitar, etc.

Q: What’s the main difference between the Vt-747sp’s compressor and Avalon’sAD2044 compressor?A: The Vt-747sp is a dedicated stereocompressor that is loaded with many differenttones and color. The Vt-747sp has vacuumtubes, six-band program equalizer and built inspectral control. The AD2044 is an ultra-highperformance pure Class A 100% discretetraditional compressor. It features extremedynamic range, ultimate low noise andcompletely transparent compression, greatfor mastering, tracking and mixing.

Q: How often will I need to change thetubes?A: The vacuum tubes on the Vt-747sp aremilitary spec tubes rated for over 5,000 hours.Avalon recommends changing the tubesapproximately every 2 years or so on a unitthat is used regularly. Avalon recommendsthat you replace tubes with exact make andmodel of the tubes that Avalon specifies. Youmay purchase a spare set of tubes for yourVt-747sp directly from Avalon.

Q: Can I damage the Vt-747sp by turningthe preamp gain up too high?A: No. The Vt-747sp has enormousheadroom. Crank it up and check it out.


FAQsAVALON DESIGN

Q: Why does Avalon use opto cells?A: Avalon uses opto-cell compressionbecause they are the most musical of allccntrol elements.

Q: Can I do mastering with a Vt-747sp ?A: Yes. Since the Vt-747sp is a dedicatedstereo unit it is a great tool for mastering. Thenoise floor is low enough for mastering andthe built-in EQ and side chain are perfect forgentle shaping and sweetening.

Q: Is the Vt-747sp durable enough for theroad?A: Yes. the Vt-747sp as well as all Avalonequipment is literally built like a tank. Steelchassis, metal faceplate, metal knobs, allcircuit boards are fixed with stainless steelhardware and more.

Q: Should I power down the Vt-747sp ?A: The Vt-747sp is equipped with a “soft-start”procedure that slowly brings the unit to lifewithout damaging the tubes. Avalonrecommends that you turn the unit off if notbeing used for more than 4 hours. Thisprocedure will also save on your electric bills.

Q: Will the Vt-747sp continue to workwhen I travel to different countries?A: Yes. The power supply on the Vt-747sphas selectable voltages: 100V, 120V, 220V,and 240V. It is very easy to change thevoltage. See chapter 3.

Q: Why is the High-Mid Band on the Vt-747sp shelving and not peak/dip like theother Mid Bands?A: Having two shelving bands on the high endof the equalizer gives more flexibility andmusicality. If you want to utilize the High-MidBand as a peak/dip then simply cut (turn

down) the High Frequency band to bringdown the ultra high end, giving you morecreative possibilities.

Q: Why does the needle in the VU metersometimes drift to the left of 0dB after theVt-747sp warms up?A: As the unit warms up, after approximately30 minutes, the resistance of the meter coil isincreased with heat and the needle thensettles into its operating 0dB position. Ifinadequate cooling is provided, the operatingemperature will be too high. (just like the oldLA2A’s). To calibrate the VU meter to 0dB seepage 32.

Q: Will the Vt-747sp work with unbalancedinputs on my recording device?A: Yes. You need to make sure that thecables you are using are wired the same (pin2 hot). You can get a cable that has XLR onone side and RCA or 1/4” on the other. Thiswill work fine for unbalanced systems. Keepthe cables 20 ft in length or less for best sonicperformance.

Q: Can I use the Vt-747sp with a recordingdevice that is designed for -10dB operation?A: Yes. The Vt-747sp will work however theoutput signal from the Vt-747sp may be toohot. Adjust the output control on the Vt-747spto match the input to the -10dB device. If youhave a choice, always run at +4dB.

Q: Can I use different types of tubes in theVt-747sp to get different or better sounds?A: Avalon has selected the tubes in your Vt-747sp for optimal sonic performance. Avalondoes not recommend experimenting withdifferent types of tubes because they maycause extreme damage to the Vt-747sp.


FAQs AVALON DESIGN

Q: Why does the Vt-747sp have a six-bandgraphic EQ?A: The Vt-747sp’s graphic EQ is designed tobe very simple to operate and musical. It isintended to enhance the program material forsonic retouching and eliminates the need topatch and addtional EQ if only minoradjustments are required.

Q: What are the advantages of using theVt-747sp with my digital recording sys-tem?A. The Vt-747sp breaths life into digitalrecordings. It will add air to the top, enhancethe space in the lower mid range and solidifythe bottom end. This process is very effectiveif used with high quality A-D and D-A convert-ers. Even if your converters are not of thehighest quality it will still enhance your record-ings.

Q: Will the Vt-747sp help to warm up thesignal going to a digital recorder?A: Yes. The Vt-747sp will give the signal aricher warmer sound. The bottom end will openup and your recorded music will sound bigger.It works wonderfully for synths, drummachines, and keyboards that wouldotherwise sound thin and lifeless.

Q: Can I use the SIDE CHAIN LISTEN func-tion as a parametric EQ?A: Yes. Press in the SIDE CHAIN LISTENbutton and use the Threshold controls ascut/boost and the two frequency selectors toselect the frequencies of interest. Note thatthe Threshold controls will act in the oppositedirection. (ie. clockwise will cut and counterclockwise will boost selected frequency.)

Q: What is the difference between theVt-737sp and the Vt-747sp?A: The Vt-737sp is a mono Mic, Line, andInstrument level preamplifier with compressorand parametric equalizer. It is great forrecording one channel at a time and formixdown on the most important channel.

The Vt-747sp is a dedicated stereo line levelcompressor and graphic equalizer. It has nomicrophone preamplifier . The Vt-747sp isgreat for stereo keyboards, synthesizers, drummachines, stereo submix or mix bussapplications and mastering.


FAQsAVALON DESIGN

8.0 Trouble Shooting

If you experience any problems with yourVt-747sp, please make sure to first isolate theproblem to your Vt-747sp. In many cases theproblem can be a bad cable or another pieceof equipment in the signal path.

It is easiest to isolate the problem by removingas many pieces of extraneous gear in thesignal path as possible. If you believe thatyour Vt-747sp has a problem, please set upthe following test system:

1. Plug your input source (keyboard, synthesizeror line input) into Vt-747sp; make sure to checkyour cables.

2. Connect the output of Vt-747sp directly to yourpowered speakers or monitor system. Use theOUTPUT control on the Vt-747sp to adjust thevolume.

Once you have isolated the problem to theVt-747sp please check the following list forsuggested solutions.


Trouble Shooting AVALON DESIGN

Problem

No Power

No Power

Lights dim /no sound

No sound

Hum or buzzingnoise

Distorted sound

Distorted sound

Cause

Power cable on back of chassis notsecurely plugged in

Fuse blown due to power surge orimproper AC voltage setting

Improper AC voltage setting

Bad cable

ground loop

Vt-747sp is overheating

Input source overloading

Solution

Plug in power cable

Replace fuse (page 12) and check ACvoltage setting (page 11)

Check AC voltage setting (page 11)

Check cables

Check cable wiring and grounding, liftground on Vt-747sp (page 10)

Make sure Vt-747sp has adequatecooling and ventilation (page 12)

Try a different input source, reduceinput level control

Vt-747sp Trouble Shooting Table

Tube Related Symptoms

The following list are symptoms of a failingvacuum tube. If you are experiencing thesesymptoms please call your local dealer orthe Avalon factory at 949-492-2000.

1. Background noise (a crackling or sizzlingsound)

2. Ringing noise

3. Low output volume

4. Distorted sound

Other problems

Please call your nearest dealer or the Avalonfactory at 949-492-2000 if you have anytechnical questions or are experiencingproblems not listed in our Trouble ShootingTable.


Trouble ShootingAVALON DESIGN

9.0 Service and Contact Information

Maintenance and Tube LifeBecause of the exceptional build quality of theVt-747sp, the unit will perform for many yearsto come. Like any musical instrument, itneeds care and maintenance to keep it in topshape.

Vacuum Tube ReplacementFor peak performance, Avalon Designrecommends changing these tubes every5000 hours of run time. Changing the tubesevery two years is recommended assuminguse of 8 hours per day, 7 days per week. Amatched set of replacement tubes can bepurchased directly from your local dealer orAvalon. Avalon only recommends Sovtek6922 vacuum tubes for your Vt-747sp.Replacement of tubes should be performedby an authorized Avalon technician.

Meter Calibration and AlignmentThe VU meter can be easily adjusted to 0 VUwhen no signal is present. To adjust the VUmeter to zero:1. Turn the unit on2. Let unit warm up for at least 30 minutes3. Unplug all inputs4. From the front of the unit use a small flathead screwdriver to turn the recessed trim potso that the needle reads zero.

External CleaningThe Vt-747sp can be cleaned using anordinary mild house cleaner such as 409 orWindex. Do not use abrasive cleaners orpetroleum-based solvents. Doing so couldcause damage to the finish.

Contact InformationAvalon DesignPO Box 5976San Clemente, CA 92673

Tel: 949-492-2000Fax: 949-492-4284

Email: [email protected]: www.avalondesign.com


Service Information AVALON DESIGN

10.0 Technical Information

Your Vt-747sp is built to withstand manyyears of high performance music making. Ifyou experience any malfunctions orproblems, please contact the dealer whereyour unit was purchased. If your Vt-747sphas outlasted your dealer, please contactAvalon directly.

Specifications

Circuit Topology : Three dual triode vacuumtubes, plus high-voltage discrete Class A

Input Gain Range : Balanced, Class A, 20kohms, +6dB with high gain switch in

Maximum input leve l: +36 dB balanced XLR

Maximum output level : +30dB balancedXLR 600 ohms, DC coupled, Pin 2 hot

Output gain range : Output trim gain -45dB to +10dB

Noise 20-20kHz unweighted : -92dBu

Distortion (THD, IMD) @ 1kHz : 0.5%

Bandwidth (-3dB) : 1 to 200kHz

Frequency Response : 10 to 40kHz +/-0.2dB

VU meter and gain reduction : 0VU=+4dBuand gain reduction to -20dB.

Output meter : Twin 20 segment LED VUmeters with -27dB to +30dB range

Compressor type : optical passive attenuator

Make-up gain : Variable 0dB to +10dB stereotracking

Compression ratio : Variable 1:1 to 20:1

Threshold : Variable -30dB to +20dB

Attack : Variable 2mS to 200mS

Release : Variable 100mS to 5 seconds

Side-chain spectral contour : Variablethreshold -15dB to +15dB, frequency 70Hz to9kHz

Equalizer type : Discrete Class A, passivedesign optimized for full-range programmaterial

Frequency bands (6) :1. LF +/-24dB 15Hz shelf response2. MF1 +/-8dB 125Hz selected Q response3. MF2 +/-4dB 500Hz selected Q response4. MF3 +/-4dB 2kHz selected Q response5. MF4 +/-10dB 5kHz selected shelf6. MF5 +/-20dB 32kHz shelf response

AC power : Internal toroidal 100v to 240v, 50-60Hz selectable, 60 watts maximum,enclosed in separate steel chassis

Dimensions : 19 x 12 x 3.5 inches 482 x 305 x 89 mm

Weight : 22 lbs. (10 kg)

Dimensions - shipping carton : 21 x 18 x 8 inches533 x 457 x 203 mm

Weight packed : 26 lbs. ( 11.8 kg)


Technical InformationAVALON DESIGN


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10.1 Vt-747sp Recall Sheet


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10.2 Vt-747sp Block Diagram

11.0 Warranty

Avalon Industries, Inc. warrants this productagainst defects in material or workmanship asfollows:1. For a period of one (1) year from the dateof purchase Avalon will pay the labor chargesto repair the defective product. After this one(1) year period, all labor charges will be paidby the customer.2. Avalon will supply at no charge, new orrebuilt replacements for any defectivemechanical switches, potentiometers ormoving parts for a period of one (1) year fromoriginal date of purchase.3. Avalon will supply at no charge, newreplacement for any defective vacuum tubesfor a period of ninety days (90) from theoriginal date of purchase.4. This warranty is void if the product hasbeen found to be subjected to misuse, abuseor unauthorized service.5. This warranty does not cover cosmeticdamage, and damage due to acts of God,accident or transit damage.6. Proof of purchase in the form of a bill ofsale or invoice to provide evidence that theunit is within the warranty period must bepresented to obtain warranty service.7. This warranty is only valid if the serialnumber appears on the product.

Outside of the USA

Please check www.avalondesign.com foryour nearest authorized service center.

11.1 Returns

If your Vt-747sp has become defective withinthe one (1) year period as specified above,please contact the place of purchase toarrange for warranty repair. If you wouldrather work directly with Avalon, please callthe factory at (949) 492-2000.

To return a unit to Avalon for repair orexchange, you will need to obtain a ReturnAuthorization Number (RA) from Avalon. Donot send your unit to Avalon without anRA number .

12.0 Safety Standards

Avalon Industries, Inc. declares that theVt-747sp conforms to standards EN55013(Emissions), EN55020 (Immunity), andEN60065 (Product Safety).


Warranty and Safety Standards AVALON DESIGN

Appendix A - Glossary

amplification – The process by which asignal level is increased.

amplitude – The distance above or below thecenterline of a signal’s waveform. The greaterthe distance from the centerline, the largerthe pressure variation or electrical signal.

attack – The initial transient or first part of theenvelope of a signal. The beginning of a note.

attenuate – To reduce the signal level

balanced – In a classic balanced audiocircuit, the two legs of the circuit (+ and -) areisolated from the circuit ground by exactly thesame impedance. Additionally, each legcarries the signal at exactly the same levelbut with opposite polarity. Balanced inputcircuits can offer excellent rejection of noiseand grounding loops.

balanced line – A cable having twoconductors and a ground connection andoften surrounded by a shield. With respect toground, the conductors are at equal potentialbut opposite polarity. These lines are oftenused in professional setting to reduce oreliminate induced noise and interference fromexternal electromagnetic sources.

bandwidth – The band of frequencies thatpass through a device with a loss of less than3dB, expressed in hertz or in musicaloctaves.

channel – A single functional path in an audiocircuit.

clipping – A cause of audio distortion that isthe result of excessive gain requiring thepeaks of the audio signal to rise above thecapabilities of the circuit.

compressor – In effect, an automatic fader.When the input signal exceeds apredetermined level, called the threshold, thegain is reduced by the compressor and thesignal is attenuated.

compression ratio – The ratio of signaldynamic range between the compressor inputand the output above the device’s setthreshold point (such as 2:1, 4:1, 20:1).

console – A term for a sound mixer, usually alarge desk-type mixing board used to mixtogether multiple track musical material.

crosstalk – The unwanted leakage of asignal from one channel or track onto another.

decibel (dB) – A unit of audio measurementof sound pressure level (SPL), signal level,and changes of difference in signal level. Thedecibel is a logarithmic (log) mathematicalfunction that reduces large numeric valuesinto smaller, more manageable numbers.Decibel is calculated as 10 times the log ofthe ratio of two powers, and 20 times the logof the ratio of two voltages.

dBm : Decibels referenced to 1 milliwatt.

dBu or dBv : Decibels referenced to 0.775volt.

dBV : Decibels referenced to 1 volt.


GlossaryAVALON DESIGNAVALON DESIGN

de-ess – Using a frequency-dependentfunction in a compressor to reduce excessivesibilance ("sss”, "sh," and "ch") sounds.

detent – A point of slight physical resistance(a click stop) in the travel of a knob or slidecontrol.

dynamic range – The range between themaximum and minimum sound levels of anaudio system. It is usually expressed indecibels as the difference between the levelat peak clipping and the level of the noisefloor.

equalizer – A frequency-dependent amplifierthat controls the relative amplitude of variousfrequencies in the audible bandwidth. Theequalizer lets you exercise tonal control overthe harmonic content or timbre of a sound.

EQ curve – A graph of the response of anequalizer, with frequency on the x (horizontal)axis and amplitude (level) on the y (vertical)axis. Equalizer types and effects are oftennamed after the shape of the graphedresponse curve, such as peak, dip, shelf,notch, knee and so on.

fade – A slow change in volume.

fader – A linear attenuation device or linearvolume control.

feedback – The returning of a loudspeakersignal back into a microphone feeding theloudspeaker. Excessive feedback results inunpleasant, screaming sounds usually atparticular, high frequencies.

filter – A simple equalizer designed toremove certain ranges of frequencies. A high-pass filter (also called a low-cut filter) reducesor eliminates frequencies below the cutofffrequency. There are also high-cut (low-pass)filters, bandpass filters, which cut both highand low frequencies but leave a band offrequencies in the middle untouched, andnotch filters, which remove a narrow band butleave the high and low frequencies alone.

flanging – A process whereby a delayedsignal is combined with itself undelayed. Thedelay is varied to create continual changes insound.

frequency – The rate at which a sound waverepeats a cycle. The number of cycles thatoccurs over the period of one second is calledhertz (Hz). Often , the perceived range ofhearing is from 20Hz to 18,000Hz.

gain – The measure of how much a circuitamplifies a signal. Gain may be stated as aratio of input to output values, such asdecibels from line amplifier.

gain stage – An amplification point in a signalpath, either within a system or a singledevice. Overall system gain is distributedbetween the various gain stages.

graphic EQ – A type of equalizer where thefrequency bands for cut/boost andbandwidths are fixed. Graphic EQs areusually controlled by faders instead of knobs.

ground – The point of zero voltage in a circuitor electrical system.


Glossary AVALON DESIGNAVALON DESIGN

ground loop – A condition that exists in animproper grounding situation, whereby a DCcurrent differential exists between one signalpath and another, resulting in a 50Hz or 60Hzhum.

headroom – The difference between nominaloperating level and peak clipping in an audiosystem.

hertz – The unit of measure for frequency ofoscillation, equal to 1 cycle per second.Abbreviated Hz. kHz is an abbreviation forkilohertz, or 1000 Hertz.

impedance – The opposition of current flowin a circuit.

knee – A sharp bend in an EQ responsecurve. Also used in describing dynamicprocessors.

line level – A signal level that is referenced toeither +4dB (professional) of –10dB (semi-pro/consumer). mastering – The processing and transfer of afinal, sequenced or mixed audio tape to amedium for duplication.

mixdown – The process in which theseparate audio tracks of a multiple trackrecording are combined, balanced, androuted through the recording console. Duringmixdown, volume, tone, special effects andspatial positioning can be artistically set bythe engineer to create a stereo or surroundsound mix that is then recorded to a masterrecording device, such as a DAT recorder.

monaural – Confined to a signal channel.One microphone is a mono pickup; manymicrophones mixed to one channel is a mono

mix. Several mono sources, however, can bepanned into a stereo (or at least two-channel)mix.

mono – short for monaural.

noise – Unwanted sounds. Hum, buzz orhiss; could be crosstalk or digital hiss.

noise floor – The residual level of noise inany system. The lower the noise floor and thehigher the headroom, the more usabledynamic range a system has.

overload – The distortion that occurs whenan applied signal exceeds a system’smaximum input level.

parametric EQ – A parametric EQ allowscontinuous control of each of the threeprimary EQ parameters (frequency, gain andbandwidth) independently.

passive EQ - A filter topology similar to earlyequalizer designs (such as pultec) wherepassive components (capacitors) are only usedto filter the signal. In a passive EQ, amplifiers areonly used as make-up gain devices. Thecapacitors used to filter the signal are notincorporated in the active feedback stage of thecircuit. Passive EQ’s have a distinctively smoothand musical sound.

peak amplitude – The maximum instantaneousamplitude of a signal.


GlossaryAVALON DESIGN

phase – The degree of progression in thecycle of a wave, where one complete cycle is360 degrees. Phase is measured in degreesof a cycle and will result in audible variationsof a combined signal’s amplitude and overallfrequency response.

phase shift – The difference in degrees ofphase angle between corresponding pointson two waves.

potentiometer (pot) – A rotary gain, pan, orother type of continuously variable signalcontrol.preamplifier - A piece of equipment thatboosts the signal level so that the signaloperates at a higher and more desired levelenabling greater frequency and dynamicrange.

release time – Once compression has begun,the time taken for the attenuated signal to returnto 63% of its original (unprocessed) level.

resistance – The opposition to the flow ofDC current in a wire or circuit.

ribbon microphone – A microphone thatuses a diaphragm of extremely thin,aluminum ribbon suspended in a strong fieldof magnetic flux. As sound-pressurevariations displace the metal diaphragm inaccordance with air-particle velocity, theribbon cuts across the magnetic lines of flux.This induces a current in the ribbon ofproportional amplitude and frequency to theacoustic waveform.

side chain - A function on a compressorwhere a specified frequency range iscompressed more than the overall musicalprogram. Many compressors have a jack for

an equalizer to be inserted into thecompressor drive electronics.

shelving filter – A rise or drop in frequencyresponse at a selected frequency that tapersoff to a preset level and continues at the levelto the end of the audio spectrum.

spectral control - The use of a side chain ina compressor to compress selectedfrequencies of a musical program. Oneexample of spectral control is removing the“sss” sounds of a vocal (de-essing).

sweep EQ – An equalizer that allows you to"sweep" or continuously vary the frequency ofone or more sections.

unbalanced – An electrical circuit in whichthe two legs of the circuit are not balancedwith respect to ground. Unbalanced circuitconnections require only two conductors(signal "hot" and ground). Unbalanced audiocircuitry is less expensive to build, but undercertain circumstances is more susceptible tonoise. An unbalanced audio cable has onlyone conductor plus a surrounding shield, inwhich the shield is at ground potential. Theconductor and the shield carry the signal.

volume – Electrical or sound level in an audiosystem.

waveform – A graph of a signal’s soundpressure or voltage level versus time.


Glossary AVALON DESIGN

Vt-747sp - Operation Manual (Version 1.0 - 2001)

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Transcript of Vt-747sp - Operation Manual (Version 1.0 - 2001)