Avalon VT-747SP Operation Manual

DESIGNAVALON

URE

LASS

A M

USIC

ECORDING

YSTEMS

VT-747SP

Operation Manual

Pure Class A Stereo Spectral Opto-Compressor Equalizer

AVALON DESIGN

URE

LASS

A M

USIC

ECORDING

YSTEMS

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 DESIGN

URE

LASS

A M

USIC

ECORDING

YSTEMS

Table of Contents

1.0 Introduction . . . . . . . . . . . . . . . . . . .4

1.1 Overview . . . . . . . . . . . . . . . . . . .4

1.2 Features . . . . . . . . . . . . . . . . . . . .5

1.3 Unpacking and Inspection . . . . . . .6

2.0 Quick Start-up . . . . . . . . . . . . . . . . .7

2.1 Quick Set-up Guide . . . . . . . . . . .8

2.2 Tips . . . . . . . . . . . . . . . . . . . . . . .9

2.3 Tutorial-Using it all . . . . . . . . . . . .9

3.0 Safety and Grounding . . . . . . . . . .10

3.1 Safety Instructions . . . . . . . . . . .10

3.2 Grounding Instructions . . . . . . . .10

3.3 AC Voltage Selection . . . . . . . . . .11

3.4 Fuse Replacement . . . . . . . . . . .12

3.4 Rack Mounting and Cooling . . . .12

3.5 Turn-on Procedure . . . . . . . . . . .13

4.0 Operation and Controls . . . . . . . . .14

4.1 Rear Panel Description . . . . . . . .17

4.2 Connections . . . . . . . . . . . . . . . .17

4.3 Unbalanced Operation . . . . . . . .17

4.4 Using the Vt-747sp . . . . . . . . . . .18

4.5 Six Band Passive Equalizer . . . .18

4.6 Using the Equalizer . . . . . . . . . . .18

4.7 Using the Side-chain . . . . . . . . . .19

5.0 Applications . . . . . . . . . . . . . . . . . .19

5.1.0 Typical Set-ups . . . . . . . . . . . .19

5.1.1 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 . . . . . . . . .21

5.2.1 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 . . . . . . . . .33

10.1 Recall Sheet . . . . . . . . . . . . . . .34

10.2 Block Diagram . . . . . . . . . . . . .35

11.0 Warranty . . . . . . . . . . . . . . . . . . . .36

11.1 Returns . . . . . . . . . . . . . . . . . . .36

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

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

Page 4 Avalon Vt-747sp Operation Manual

AVALON DESIGN

Introduction

1.0 Introduction

Welcome to Avalon and the world of high performance Pure Class A music recording systems. The Vt-747sp is an extremely versatile, pure Class A, vacuum tube/discrete TSP (Tube Signal Path) stereo optocompressor and program equalizer.

The Vt-747sp is the most creative and flexible stereo compressor available. With TSP(Tube Signal Path), the Vt-747sp uses three hand selected vacuum tubes in the signal path for warm tube tone or bypasses the tubes for classic Class Adiscrete transistor sound. Also featured on the Vt-747sp is a passive sixband graphic equalizer for gentle toneshaping plus a two-band parametric EQ for complete spectral side-chain or musical control.

The Vt-747sp is hand built in the USA using only the finest active and passive electronic components available. Many of these parts have been custom-manufactured exclusively for Avalon. A "no compromise" approach in every stage of design and production ensures that the Vt-747sp will give many years of dependable high-quality service.

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

1.1 Overview

The Vt-747sp combines a stereo tube/ discrete Class A opto-compressor with a musical six-band program equalizer, as well as Left/Right output level, gain reduction metering and an internal regulated power supply in a 2U space. Ideal for high performance DAW (digital audio workstation) input signal conditioning, stereo buss compression/EQ, stereo keyboards and mastering applications.

The Vt-747sp features a minimum signal path design utilizing sealed silver relays for all signal routing and bypass functions.

Compression with the Vt-747sp is achieved with twin optical attenuators that act as passive level controllers together 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, compression ratio, attack and release controls. Gain reduction indication is a large analog VU meter. Low and High Frequency (LF and HF) contour parametric spectral controls can be routed into the on-board side-chain path for enhanced frequency dependent compression with variable frequency and threshold levels. An SC LISTEN switch provides side chain listen mode for easy monitoring.

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 with lowest phase change while offering simple and effective tone control. The EQ can be placed pre or post compressor for enhanced effects.

The Vt-747sp features TSP (Tube Signal Path) which gives you the choice of either tube tone (utilizing three high-voltage dual triode tubes), or the classic, Class A discrete transistor sound (utilizing discrete transistor amplifiers) in the primary opto buffers and output stages.

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 LED meters provide a 60dB range with fast L-R output status 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

Page 5

Avalon Vt-747sp Operation Manual

AVALON DESIGN

Introduction

Inside view of Vt-747SP

1.3 Unpacking and Inspection

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

1. Vt-747sp

2. Power cable

3. Warranty card

4. Operation Manual

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

Note: You must fill out and send in your warranty card in order to receive warranty and technical support. If you have not already filled out your warranty card please take the time to do so now.

Page 6 Avalon Vt-747sp Operation Manual

AVALON DESIGN

Introduction

Vt-747sp contents and packaging

2.0 Quick Start-up

The following chapter is designed to help you get started using your Vt-747sp right away without having to read the entire manual. Make sure however to take time to read the manual at a later date as there are many safety aspects and features of the Vt-747sp that will not be discussed here.

If you are familiar with this type of equipment you can also familiarize yourself with your Vt-747sp and the functions with the Quick Set-up Guide on page 8.

Note: The Vt-747sp is an extremely high performance piece of musical equipment. Every setting has great potential for musicality. Do not be afraid of turning the

knobs or faders to their full extreme positions.

Hook it up, turn it on and play:

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

2. Plug in the AC power cable and connect your Vt-747sp to your stereo source. (XLR type connectors pin 2 is hot.) You can use the Vt-747sp in mono, however, the Left and Right will always work together as one dedicated stereo pair.

3. Turn on the power and allow 60 seconds while the soft-start procedure commences. You may hear a relay click at about 45 seconds. During the soft-start procedure, the Vt-747sp is in hard-wire bypass mode and will pass signal, but the controls will not work. For optimum performance,

allow 30 minutes for the Vt-747sp to fully warm up.

4. With all switches in the disengaged or nonilluminated position, run a signal through the Vt-747sp. Use the output control on the right hand side of the unit to check basic operation.(see figure 2.0 below)

5. Now you are ready to start pressing switches, turning knobs and pushing EQ faders!

The Quick Set-Up Guide on the following page gives a brief description of the switches and controls on the Vt-747sp.

Page 7

Avalon Vt-747sp Operation Manual

AVALON DESIGN

Quick Start-up

figure 2.0 Quick Start up

Keyboard or Stereo Source

Right and Left Outputs

Outputs

Right and Left Inputs

Vt-747sp

Inputs

Mixing Console

Monitoring System

Page 8 Avalon Vt-747sp Operation Manual

AVALON DESIGN

Quick Start-up

TSP

Twin Signal Path

Switch (in) swaps

three (3) tubes

into the audio

path from discrete

Class A amps.

F4 

Boost-cut

sets amplitude

of mid-range

-4dB to +4dB

detent at 0dB

2kHz

peak-dip

FI 

Boost-cut

sets amplitude

of low-bass

-24dB to +24dB

detent at 0dB

15Hz

shelf

F2 

Boost-cut

sets amplitude

of mid-bass

-8dB to +8dB

detent at 0dB

125Hz

peak-dip

F3 

Boost-cut

sets amplitude

of low-mid

-4dB to +4dB

detent at 0dB

500Hz

peak-dip

F5 

Boost-cut

sets amplitude

of presence

-10dB to +10dB

detent at 0dB

5kHz

shelf

F6 

Boost-cut

sets amplitude

of treble

-20dB to +20dB

detent at 0dB

32kHz

shelf

AVALON

VACUUM TUBE

0 1

IN IN IN IN INININ

747

dB+

-15 +15 -15 +15

0dB

+2 +6

+10

SIDE-CHAIN THRESHOLD

CONTOUR

SC LISTENSIDE-CHAIN

CAL

GAIN

+10dB

100

160 250

300

400

70 600

200

600

800

1k6 2k5

10k

700 6k

TSP

EQ COMP

INPUT

20 8

610

FAST SLOW

ATTACK

TUBE

SIGNAL

PATH

FAST SLOW

RELEASE

GAIN

MAKE-UP

COMPRESSOR

METER

RATIO

COMPRESSION

120

102

dB+

THRESHOLD

20 20

1615

3+2

DESIGN

AVALO N

123

321

CLASS A PROGRAM EQUALIZER LEVEL

SIGNAL

dB+

OUTPUT

20 6

EQUALIZER

182430

VT-747SP QUICK SET-UP OPERATING GUIDE

+10dB switch

Boosts input

amplifier by

+10dB for extra

tube over-drive

INPUT GAIN

Trims input level

-20dB to +8dB

detent at 0dB

(+18dB with +10dB IN)

LF and HF THRE

LD

Range -15dB to +15dB, detent at 0dB,

clockwise rotation raises the threshold

(less compression) and counter clockwise

rotation lowers the threshold (more compression)

at the frequencies set by the LF (low frequency)

and HF (high-frequency) spectral frequency

controls located directly below

THRESHOLD

Sets compressor

input threshold

from -30dB to

+20dB

COMPRESSION

Sets ratio of

compressor

from 1:1 to 20:1

COMPRESSOR

Switch (in) engages

compressor into

signal path

(hard-wire bypass)

SIX (6) BAND PASSIVE CLASS A, PROGRAM EQUALIZER

EQ to COMP

Inserts the

six (6) band

EQ pre the

compressor

Blue LED

Indicates

compressor

speed and

activation

SC Listen

Switch (in)

for Spectral EQ

into audio path

to monitor SC

ATTACK

Variable attack

time for the

compressor

2mS to 200mS

RELEASE

Variable release

time for the

compressor

100mS to 5S

SPECTRAL

Sweep frequency

for LF and HF

bands, used with

above threshold

controls

SIDE-CHAIN

Inserts spectral

EQ into side-

chain

METER

Recessed

screwdriver

adjust for 0dB

gain-reduction

meter trim.

AC POWER

Note: Check 

rear power input

connector for

correct local

ac voltage. Allow

forty seconds for

the soft-start

procedure to

activate the

the audio

signal path.

AVALON

Class A Vacuum Tube

STEREO SPECTRAL OPTO-COMPRESSOR WITH TSP

POWER LED

Indicates ac

power is on

MAKE-UP

0dB to +10dB

variable gain on

opto-compressor

METER

High quality

VU meter

indicates

gain reduction

0dB to -20dB

VT-747SP

Avalon Design is a division of Avalon Industries, Inc. 2001

OUTPUT METER

Fast LED meter

indicates both L-R

spectral content

and output level

-30dB to +30dB

OUTPUT LEVEL

Stereo output

level control

-20dB to +6dB

detent at 0dB

EQ

Switch (in)

activates 6 band

passive EQ into

audio path

(hard-wire bypass)

Note:

For the best sonic performance, 

allow thirty minutes for warm-up.



When not in use, turn the ac off. This will

extend the life of the electronics . . Enjoy!

Note:

Knob settings shown represent

starting positions only.

TSP

TWIN SIGNAL PATH

All units in dBu.

Figure 2.1 Quick Set-up Guide

2.2 Tips

Unity Level - The Vt-747sp is calibrated so

that unity level is +4dBu.

INPUT - Use the input control as a gain control, not a level control. This will drive the tubes and/or transistors harder for different tone.

OUTPUT - Use the output control as the overall level control.

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

EQ > COMP - Inserts the six-band graphic EQ before (pre) the compressor in the signal path.

SIDE-CHAIN - Engages the built-in sidechain. Use the SIDE CHAIN THRESHOLD and the corresponding frequency bands to compress specific frequencies.

SC LISTEN - To monitor the signal through the side chain.

GR (Blue LED) - Fast-acting LED illuminates when 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 get you familiar with all of the functions of the Vt-747sp.

Start by plugging a stereo source (CD player, stereo keyboard, Submix output, etc.) into your Vt-747sp. If possible, run directly out of the Vt-747sp to powered monitors bypassing the console or mixing board. Choose a musical selection, loop, patch, sample or instrument with wide dynamic range so you can experiment with the compressor.

Set push button switches to their off or nonilluminated position.

1. INPUT - Set to 5. (Adjust OUTPUT so that

overall signal level is at a comfortable monitoring level.

2. GAIN +10dB - Press in and out to get a feel

for the sound of the high gain switch. Leave it non-illuminated.

3. EQUALIZER - (Located on right side of

panel) press in equalizer switch and familiarize yourself with the six band equalizer. Adjust the two outside bands half way between unity and maximum, and the four mid-bands to half way between unity and minimum. Toggle the EQUALIZER switch in and out.

4. COMPRESSOR - Press in COMPRESSOR

switchand turn the main compression controls to the following: COMPRESSION - fully clockwise THRESHOLD - fully counter clockwise ATTACK - fully counter clockwise (Fast) RELEASE - fully clockwise (Slow)

Page 9

Avalon Vt-747sp Operation Manual

AVALON DESIGN

Quick Start-up

5. EQ->COMP - Press in to insert the EQ before (pre) the compressor in the signal path.

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

7. Press in SIDE CHAIN and SC LISTEN. You are now monitoring the signal going through the side chain. You can use the side chain listen function as a parametric EQ on the primary audio path.

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

9. Press out the SCLISTEN switch (disengaged).

Now you have full compression, with fast attack and slow release, and two different frequencies going into the side chain that are being compressed more than the overall stereo signal.

Make yourself familiar with all of the functions in the Vt-747sp. The combinations, colors, and tones are endless. For more details on each specific control or switch, please refer to Chapter 4 - Operations and Controls.

3.0 Safety and Grounding

The following chapter describes how to safely install your Vt-747sp for optimal sonic performance.

3.1 Safety Instructions

This unit contains voltages that can cause serious injury or death. Do not operate with the covers removed.

Improper connection of the equipmentgrounding cable can result in a risk of electric shock.

Check with a qualified electrician or serviceman if you are in doubt about your electrical power or ground connection. The Vt-747sp is for use with an AC supply as selected by the AC voltage selector (located within 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 grounded AC power circuit.

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

Page 10 Avalon Vt-747sp Operation Manual

AVALON DESIGN

Safety and Grounding

This product is equipped with an AC power inlet and must be connected to a three-wire grounded plug.

The AC power cable must be plugged into an appropriate outlet that is correctly installed and grounded in accordance with all local electrical safety codes and ordinances.

If hum or ground-buzz is induced into the system, remove the rear-mounted GROUND LINK. This ground-link isolates the AC chassis ground from the audio ground. When the LINK is removed, the AC ground remains connected to the chassis via the AC inlet connector and provides a direct path for any electrical fault or dangerous condition.

Warning! No ground adapter should ever be used with this unit.

3.3 AC Voltage Selection

Before connecting the Vt-747sp to the AC supply, check the OPERATING VOLTAGE located on the rear of the chassis in the AC 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 cable

connected to the AC inlet.

2. Insert a small flat-head screwdriver tip into

the voltage selector cavity. Carefully lift-open the hinged cover from left to right.

3. Rotate the selector wheel to show the

correct voltage for your location, then push the 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.

Page 11

Avalon Vt-747sp Operation Manual

AVALON DESIGN

Safety and

Grounding

AVALON DESIGN

3.4 Fuse Replacement

The fuse on the Vt-747sp is located within the AC plug assembly on the back of the unit. A fuse can blow if the AC selection is not selected properly or if there is a sudden surge of AC to your Vt-747sp.

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

To change the fuse:

1. Make sure there is no AC cable connected to the AC inlet.

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

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

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

3.5 Rack Mounting and Cooling

The Vt-747sp is designed to be mounted in a standard 19" equipment rack. As vacuum tubes and Class Acircuitry can generate heat, it is highly recommended that an additional rack space above and below the unit be kept empty to allow for adequate cooling. Avalon Design has developed 1U ventilation panels (VP-1) specifically to keep your rack-mounted gear cool.

Page 12 Avalon Vt-747sp Operation Manual

AVALON DESIGN

Safety and Grounding

Avalon units with VP-1 vent panels

+ 28 hidden pages

Avalon VT-747SP Operation Manual

Specifications and Main Features

Frequently Asked Questions

User Manual