Studiomaster Auto 4 Owner's Manual

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Page 1

POWER

LEVEL

OUTPUT

LEVEL

-3

-6

-10

-20

SIGNAL

CLIP

SIGNAL

CLIP

SIGNAL

CLIP

SIGNAL

CLIP

LEVEL LEVEL LEVEL LEVEL

ACTIVE ACTIVE ACTIVE ACTIVE LOCKOUT

FIXED

PRIORITY

MASTER

OFF

LOUD LOUD LOUD LOUD

NORM. NORM. NORM. NORM.

SOFT SOFT SOFT SOFT

VOX

BYPASS

VOX

BYPASS

VOX

BYPASS

VOX

BYPASS

THRESHOLD

SELECTED CHANNEL

Auto 4

Owner’s Manual

MIXER

AUTOMATIC MICROPHONE

Page 2

CONTENTS

Introduction

Format

Unpacking

Important Information

Input Connectors

Front Panel Controls and Indicators

Rear Panel Controls

Set Up Procedure

Application Note

Operation of Single Auto 4 Mixer

Fixed Priority Mode

Auto Mode - All Low-Priority Channels

Auto Mode - Only one High-Priority Channel

Auto Mode - All High-Priority Channels

Cascaded Operation of Multiple Auto 4 Mixers

Control of External Lamps or Cameras

Control of Overhead Speakers

Technical Specifications

Page 3

INTRODUCTION

Auto 4 is a four channel automatic mixer, designed primarily for use in debating/discussion application.

Microphones can be connected to the Auto 4 with previously set priority for each microphone. Normally, only one low-priority microphone will be active at any time and connected to the output. Every other lowpriority microphone will be partly muted as long as another microphone is active.

Any microphone can be set to high-priority. In this case, the high-priority microphone can override other low-priority microphones.

A unique feature of the Auto 4 mixer is the threshold setting for each microphone. If the signal exceeds the threshold, then that channel can be made active depending on priority settings.

Each channel of the Auto 4 mixer has three threshold settings: Loud, Normal and Soft. These should be selected according to the actual speaker.

Several Auto 4 mixers can be interlinked to enable more than four microphones to be connected to the overall system. This is done using the Link In/Link Out connectors on the rear panel. Interconnection is by CAT5 cable and RJ45 connectors.

FORMAT

The Auto 4 Mixer operates with an external SMPS. Both the Auto 4 and the SMPS are packed together for convenience.

UNPACKING

Remove the Auto 4 Mixer from the packing and make sure that you have a SMPS with mains cord and a connector for connection to the mixer. Also, make sure that you have a warranty card. Keep the packing in the eventuality that your Auto 4 Mixer needs to be moved or returned for service or repair. Please complete and return your warranty card. Returning the completed warranty card does no diminish your statutory rights in any way.

IMPORTANT INFORMATION

Do not use your Auto 4 Mixer in environments having a very high humidity or where liquids may accidentally enter the mixer.

When powering up the system, switch on the power amplifiers after the Auto 4 Mixer has been turned on. This will avoid unexpected loudspeaker thumps.

In the event that a fault occurs, return the Auto 4 Mixer to your dealer or to an authorized service agency. Do not attempt to repair it yourself as this could be dangerous and will void the warranty.

Page 4

INPUT CONNECTORS

Each channel is provided with one XLR mic input and one ¼” TRS jack line input. Both mic and line sockets should not be used simultaneously.

MIC 3 pin XLR input

For balanced, low impedance microphones, wire pin 1 to screen/ground/earth, pin 2 to positive/hot/+ve phase, and pin 3 to negative/cold/-ve phase.

For unbalanced microphones, wire pin 1 to ground, pin 2 to signal, and pin 3 to pin 1.

48V phantom power may be applied to the microphone by selecting the appropriate switch on the rear panel.

Do not connect 48V phantom power to unbalanced microphones.

LINE ¼” TRS Jack for use with balanced, line level input signals

Wire Tip to positive/hot/+ve phase, Ring to negative/cold/-ve phase and Sleeve to ground. For unbalanced microphones, use a TS jack and wire Tip to signal and Sleeve to ground

The line input is electronically balanced but may also be used with unbalanced signals simply by plugging in an unbalanced TS jack.

Mono Jack

6.3 1/4’’mm

XLR CONNECTOR

Tip (+)

Sleeve

(GND)

Stereo Jack

6.3 mm 1/4’’

XLR CONNECTOR

Sleeve

(GND)

RING (-)TIP (+)

RING (-)

TIP (+)

Page 5

POWER

LEVEL

OUTPUT

LEVEL

-3

-6

-10

-20

SIGNAL

CLIP

SIGNAL

CLIP

SIGNAL

CLIP

SIGNAL

CLIP

LEVEL LEVEL LEVEL LEVEL

ACTIVE ACTIVE ACTIVE ACTIVE LOCKOUT

FIXED

PRIORITY

MASTER

OFF

LOUD LOUD LOUD LOUD

NORM. NORM. NORM. NORM.

SOFT SOFT SOFT SOFT

VOX

BYPASS

VOX

BYPASS

VOX

BYPASS

VOX

BYPASS

THRESHOLD

SELECTED CHANNEL

14 2 5

3 9

6 7 8

10 11

Auto 4

FRONT PANEL CONTROLS AND INDICATORS

1) LEVEL

2) LOUD/NORMAL/SOFT Channel threshold selection

3) VOX/BYPASS Threshold bypass for background music, VOX for voice operation

4) SIGNAL/CLIP Bicolor LED lights green at -20dBu, and red for clip at 0dBu

5) ACTIVE Green LED indicates that the channel is active

6) FIXED PRIORITY When selected, channel priority is in the following fixed order:

Channel 1 has priority over channels 2, 3 and 4 Channel 2 has priority over channels 3 and 4 Channel 3 has priority over channel 4

7) MASTER THRESHOLD

Threshold control is the level which activates the channel. If the channel signal exceeds the threshold, the channel is activated depending on the priority settings.

8) LOCKOUT

9) MASTER LEVEL

10) OUTPUT LEVEL

11) POWER Power on/off switch with LED indication

Channel level control

Common threshold control for all four channels

LED indicated that a high priority channel is active

Recessed control to adjust output level

LED bar graph indicates output level

Page 6

LINK OUT

INSERT

LINK IN

OUTPUT

MIC

PHANTOM

PRIORITY

ATTEN.

20dB

INPUT 4 INPUT 3 INPUT 2 INPUT 1

CONTROLVOLTAGE OUT

EXT. DC

24V

USE ONLY

RECOMMENDED PSU

12 13

1517 16

1819

OFF

LIMITER

LAST MIC

ATTEN.

12dB

LINE

12dB

LINE

12dB

LINE

12dB

LINE

REAR PANEL CHANNEL CONTROLS

A 4-position DIP switch is provided on the rear panel for each input channel. These switches are:

12) PRIORITY Set high priority (up) or low priority (down)

13) MIC/LINE Set Mic input (up) or Line input (down)

14) PHANTOM Set Phantom supply (48V) for Mic input (up). It is internally disabled for Line

15) ATTEN. 12dB/20dB Set attenuation of inactive channel : 20dB (up) or 12dB (down)

REAR PANEL COMMON CONTROLS

A 2-position DIP switch controls the output. These switches are:

16) LIMITER Set Limiter On (up) or Off (down).

17) LAST MIC Set Last Mic On (up) or Off (down)

The internal limiter restricts the output if it exceeds a threshold which is set to about 0dBu. This is designed to minimize signal clipping if the output signal is too large.

Normally, when a microphone is inactive, it is mu

ted. During a live discussion, every inactive microphone

is followed by another microphone which is active. At the end of the discussion, when all microphones are inactive, there is no output from the Auto 4 mixer, as if the entire system has “gone dead”.

To prevent this, the Last Mic option can be enabled. In that case, the last microphone is not muted, giving the effect that the microphone is not being used but “not gone dead”. Output from the amplifier would then be the ambient background sound.

18) CONTROL VOLTAGE OUT CMOS compatible logic signals, active high (5V)

Whenever any microphone is active, a corresponding control output is available on the rear panel. This can be used for a variety of applications such as activating a camera, disabling overhead speaker, etc.

19) EXT. DC 24V The Auto 4 Mixer can be operated on external 24V dc supply.

Please note that the negative terminal of this 24V supply should not be connected to signal ground.

20) INSERT ¼” TRS insert jack for connection to external signal processing units.

Wire Tip to Send, Ring to Return and Sleeve to Ground.

Page 7

21) LINK IN & LINK OUT RJ45 connectors for linking several Auto 4 mixers.

Use a CAT 5 cable to connect Link Out of one Auto 4 mixer to Link In of the next mixer. When several Auto 4 mixers are linked in this way, output of the last mixer should be connected to the amplifier.

22) DC Input Connector

Connector to power supply unit. Use the power supply which has been supplied with the mixer.

Page 8

SET UP PROCEDURE

= Connect Microphone to input 1 XLR

= Select rear panel switches to set Low Priority, Mic mode, Phantom off, Attenuation 20dB

= Set VOX/ Bypass switch to Bypass

= Connect output XLR to input of amplifier

= the power to the Auto 4Switch on

= Switch on the amplifier

= Speak normally into the microphone

= Set Channel Level until the Signal/Clip Led lights occasionally

= Set Master level (screw-driver adjustment) as required

= Set VOX/Bypass switch to VOX

Set channel threshold to normal

= If required, set to Loud or Soft, depending on the speaker

= Set Master Threshold to minimum

= Increase Master Threshold so that background sound does not turn on the channel

= Speak normally into the microphone

= If required decrease Master Threshold so that sound does not break at the beginning of a word

= Repeat above procedure for all other channels

Page 9

APPLICATION NOTE

OPERATION OF SINGLE AUTO 4 MIXER

Fixed Priority Mode

Front Panel Settings

Common Settings: Master Threshold: 9 o’clock position

Fixed Priority: on (pressed)

Master Level: Maximum

Settings for each channel: Level: (or, according to microphone requirement)9 o’clock position Threshold: Normal

Rear Panel Settings

Common Settings: Last Mic: Off Limiter: Off

Settings for each channel: Priority Switch: Low Mic/Line Switch: Mic Phantom Switch: Low Atten. Switch: 20dB

Channel 1 Channel 2 Channel 3 Channel 4 Output

On On or Off On or Off On or Off Output from Ch. 1

– other channels attenuated by 20dB and mixed with Ch.1

Off On On or Off On or Off

– other channels attenuated by 20dB and mixed with Ch.2

Off Off On On or Off

– channel 4 attenuated by 20dB and mixed with Ch.3

In this mode:

Channel 1 has priority over channels 2, 3, and 4 Channel 2 has priority over channels 3 and 4 Channel 3 has priority over channel 4

All non-priority channels are attenuated and mixed with the priority channel.

Off Off Off On Output from Ch. 4

FIXED PRIORITYMASTER

THRESHOLD

OFF

LIMITER

LAST MIC

MASTER

LEVEL

MIC

PHANTOM

PRIORITY

ATTEN.

20dB

12dB

LINE

LEVEL

THRESHOLD

LOUD

NORM.

SOFT

Output from Ch. 2

Output from Ch. 3

Page 10

THRESHOLD

LOUD

NORM.

SOFT

Auto Mode - All Low-Priority Channels

Front Panel Settings

Common Settings: Master Threshold: 9 o’clock position Master Level: Maximum Fixed Priority: Off (released)

Settings for each channel: Level: (or, according to microphone requirement)9 o’clock position Threshold: Normal

Rear Panel Settings

Common Settings: Last Mic: Off Limiter: Off

Settings for each channel: Priority Switch: Low Mic/Line Switch: Mic Phantom Switch: Low Atten. Switch: 20dB

On Off Off Off On Becomes On but

inactive while

Channel 1 is

active

Off Off Channel 1 added

with 20dB attenuated Channel 2

while Channel 1 is

active

Off On

inactive while

Channel 2 is

active

with 20dB attenuated Channel 3

In this mode:

Only one channel is active at any time. All other channels are inactive. Inactive channels are attenuated by 20dB and mixed with the active channel.

Channel 1 Channel 2 Channel 3 Channel 4 Output

Off Becomes On Off Off Channel 2

Becomes On but Off Channel 2 added

Channel 1

MASTER

THRESHOLD

MASTER

LEVEL

OFF

FIXED PRIORITY

LEVEL

OFF

LIMITER

LAST MIC

MIC

PHANTOM

PRIORITY

ATTEN.

20dB

12dB

LINE

Page 11

MIC

PHANTOM

PRIORITY

ATTEN.

20dB

12dB

LINE

MIC

PHANTOM

PRIORITY

ATTEN.

20dB

12dB

LINE

MIC

PHANTOM

PRIORITY

ATTEN.

20dB

12dB

LINE

MIC

PHANTOM

PRIORITY

ATTEN.

20dB

12dB

LINE

THRESHOLD

LOUD

NORM.

SOFT

Auto Mode - Only one High-Priority Channel

Front Panel Settings

Common Settings: Master Threshold: 9 o’clock position Master Level: Maximum Fixed Priority: Off (released)

Settings for each channel: Level: (or, according to microphone requirement)9 o’clock position Threshold: Normal

Rear Panel Settings

Common Settings: Last Mic: Off Limiter: Off

Settings for each channel: Priority Switch: Low (Channels 2, 3 and 4) Priority Switch: High (Channel 1) Mic/Line Switch: Mic Phantom Switch: Low Atten. Switch: 20dB

Off On Off Off

Becomes On

while Channel 2 is

active

On Off Off

becomes active immediately and mutes channel 2 (20dB attenuation)

while Channel 1 is

active

active and remains active – channel 2 is attenuated by

20dB Off Off On Off Off Off On Becomes on but

inactive while

Channel 3 is

active

Channel 3 added

with 20dB

attenuated

Channel 4 Off Off Off

while Channel 3 is

active

Channel 4

In this mode:

High-priority channel can interrupt any low-priority channel. A low-priority channel can become active only when the high-priority channel becomes inactive. Inactive channels are attenuated by 20dB and mixed with the active channel.

Channel 1 Channel 2 Channel 3 Channel 4 Output

Channel 2

Channel 1

Channel 3

Becomes On Off Off Channel 1 is

Becomes On

MASTER

THRESHOLD

MASTER

LEVEL

OFF

FIXED PRIORITY

LEVEL

OFF

LIMITER

LAST MIC

Channel 4

Channel 3

Channel 2 Channel 1

Page 12

MIC

PHANTOM

PRIORITY

ATTEN.

20dB

12dB

LINE

THRESHOLD

LOUD

NORM.

SOFT

Auto Mode - All High-Priority Channels

Front Panel Settings

Threshold: Normal

Rear Panel Settings

Common Settings: Last Mic: Off Limiter: Off

Settings for each channel: Priority Switch: High Mic/Line Switch: Mic Phantom Switch: Low Atten. Switch: 20dB

On Off Off Off On On Off Off

mixed, gain

reduced by 3dB On On On Off 2

3 mixed, gain

reduced by 3dB On On On On

mixed, gain

reduced by 6dB

In this mode:

All high-priority channels can be active at the same time. If two or three channels are active, the output is reduced by 3dB. If all four channels are active, the output is reduced by 6dB.

Fixed Priority: Off (released)

Common Settings: Master Threshold: 9 o’clock position Master Level: Maximum

Settings for each channel: Level: (or, according to microphone requirement)9 o’clock position

Channel 1 Channel 2 Channel 3 Channel 4 Output

Channel 1

Channel 1 and 2

Channel 1, 2 and

All Channels

MASTER

THRESHOLD

MASTER

LEVEL

OFF

FIXED PRIORITY

LEVEL

OFF

LIMITER

LAST MIC

Page 13

CASCADED OPERATION OF MULTIPLE AUTO 4 MIXERS

Auto 4 Mixer 1 Auto 4 Mixer 2 Auto 4 Mixer 3 System operates as Active channels

Auto mode

Low priority on all channels

Auto mode

Low priority on all channels

Auto mode

Low priority on all channels

12-channel Auto 4 Mixer

Only one channel at any time

Auto mode

Low priority on all channels

Auto mode

High priority channels 5 & 8 Low priority channels 6 & 7

Auto mode

Low priority on all channels

12-channel Auto 4 Mixer

Channels 5 & 8 can interrupt

any other channels.

If channels 5 & 8 are active

at the same time, output is

attenuated by 3dB

Auto mode

Low priority on all channels

Auto mode

High priority channel 5 Low priority channels 6, 7 & 8

Auto mode

High priority channel 10 Low priority channels 9, 11 &12

12-channel Auto 4 Mixer

Channels 5 & 10 can

interrupt any other channels.

If channels 5 & 10 are active

at the same time, both are

available at output without

attenuation

Auto mode

Low priority on all channels

Manual mode

Priority sequence: Channel 5 has priority over 6, 7 and 8; Channel 6 has priority over 7 & 8; Channel 7 has priority over 8

Auto mode

High priority channel 10 Low priority channels 9, 11 &12

8-channel Auto 4 Mixer with channels 1 to4and9to12.

Channel 10 can interrupt any

of the channels (1 to 4, 9, 11,

or 12).

Output of Auto 4 Mixer 2 is

mixed with the final output

Auto 4 Mixer 1

Channels 1 to 4

Auto 4 Mixer 2

Channels 5 to 8

Auto 4 Mixer 3

Channels 9 to 12

Link In Link InLink OutLink Out

To Amplifier

Page 14

Control of External Lamps or Cameras

Whenever a mic is active, a corresponding control voltage is available from the rear panel. This can be used to switch on overhead lamp or camera as shown below:

During a discussion, there could be frequent changes between different microphones. But, frequent changes of lamp / camera may not be desirable. The delay circuits should ignore short interruptions by any speaker and enable the lamp / camera of the main microphone.

Ch. 1 Ch. 2 Ch. 3

Ch. 4

Inputs from microphones

1234

Control Outputs

Delay circuit

Switch lamp / camera 1

Switch lamp / camera 2

Switch lamp / camera 3

Switch lamp / camera 4

Auto 4 Mixer

Amplifier

Control of Overhead Speakers

Whenever a microphone is active, a corresponding control voltage can be used to switch off overhead speaker. This prevents feedback from the microphone into its own speaker. This application is shown below:

During a discussion, there could be frequent changes between different microphones. In order to avoid feedback, the overhead speaker should be switched off as soon as any microphone becomes active.

Auto 4 Mixer

Ch. 1 Ch. 2 Ch. 3

Ch. 4

Inputs from microphones

1 2 3 4

Control Outputs

Switch off Speaker 1

Switch off Speaker 2

Switch off Speaker 3

Switch off Speaker 4

Auto 4 Mixer Amplifier

Page 15

Output Impedance 200 ohms≤

TECHNICAL SPECIFICATIONS

Input Impedance

Maximum Input Level

Maximum Output Level*

Mic 4,000 ohms

≥

Line 30,000 ohms≥

Mic - 30 dBu Line + 20 dBu

Line +14 dBu

Maximum Gain ≥ 70 dB

Inactive Channel Attenuation 12dB or 20dB switch-selectable

Frequency Response 60 Hz to 30 kHz at - 3dB points

Dynamic Range** 75 dB ± 10 dB, dependent upon gain control settings

Equivalent Input Noise –120 dBu (150 ohms) at maximum gain

Switch-selectable Options Limiter (above 0dBu), Last Mic On

Microphone Phantom +48V DC

Control Voltage Out +5V DC

Power Requirement 230V AC, 100 mA, max. for external SMPS

Operating Temperature 0° to 40° C

* Master Level control set at maximum (fully clockwise). ** Input terminated with 150 ohms, A-weighted using Audio Precision System.

+24V DC, 250mA max. for external DC supply

Dimensions 482.6 mm W x 135 mm x 44 mm H

Weight 2.2 Kg

Included Accessories SMPS with connectors, Link Cable

Page 16

LITMA5M8 REV.0

PRODUCT OF AUDIOPLUS

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