Rane MS1S Manuel utilisateur

Marque: Rane

Modèle: MS1S

Catégorie: Équipement musical supplémentaire

Taper: Manuel utilisateur

M S1S

M I C S TAG E

Contents

FCC Statement 2

Important Safety Instructions 3

Features 6

General Description 6

Application Information 7

Features and Specications 9

Block Diagram 10

Architectural Specications 10

Unit Dimensions 11

Sound System Interconnection 12

Schematic 28

Warranty 31

Declaration of Conformity 34

21591

ATTENTION: RISQUE DE CHOCS ELECTRIQUE - NE PAS OUVRIR

RISK OF ELECTRIC SHOCK

DO NOT OPEN

CAUTION

To reduce the risk of electrical shock, do not open the unit. No user

serviceable parts inside. Refer servicing to qualied service personnel.

e symbols shown below are internationally accepted symbols that warn of

potential hazards with electrical products.

is symbol indicates that a dangerous voltage constituting a

risk of electric shock is present within this unit.

is symbol indicates that there are important operating and

maintenance instructions in the literature accompanying this

unit.

WARNING

FCC Statement

NOTE: is equipment has been tested and found to comply with the limits

for a Class B digital device, pursuant to part 15 of the FCC Rules. ese lim-

its are designed to provide reasonable protection against harmful interference

in a residential installation. is equipment generates, uses and can radiate

radio frequency energy and, if not installed and used in accordance with

the instructions, may cause harmful interference to radio communications.

However, there is no guarantee that interference will not occur in a particular

installation. If this equipment does cause harmful interference to radio or tele-

vision reception, which can be determined by turning the equipment o and

on, the user is encouraged to try to correct the interference by one or more of

the following measures:

• Reorient or relocate the receiving antenna.

• Increase the separation between the equipment and receiver.

• Connect the equipment into an outlet on a circuit dierent from that to

which the receiver is connected.

• Consult the dealer or an experienced radio/TV technician for help.

CAUTION: Changes or modications not expressly approved by Rane Corporation

could void the user's authority to operate the equipment.

is Class B digital apparatus complies with Canadian ICES-003.

Cet appareil numérique de la classe B est conforme à la norme NMB-003 du Canada.

Important Safety Instructions

1. Read these instructions.

2. Keep these instructions.

3. Heed all warnings.

4. Follow all instructions.

5. Do not use this apparatus near water.

6. Clean only with a dry cloth.

7. Do not block any ventilation openings. Install in accordance with

manufacturer’s instructions.

8. Do not install near any heat sources such as radiators, registers, stoves, or

other apparatus (including ampliers) that produce heat.

9. Do not defeat the safety purpose of the polarized or grounding-type plug. A

polarized plug has two blades with one wider than the other. A grounding-

type plug has two blades and a third grounding prong. e wide blade or

third prong is provided for your safety. If the provided plug does not t into

your outlet, consult an electrician for replacement of the obsolete outlet.

10. Protect the power cord and plug from being walked on or pinched

particularly at plugs, convenience receptacles, and the point where it exits

from the apparatus.

11. Only use attachments and accessories specied by Rane.

12. Use only with the cart, stand, tripod, bracket, or table specied by the

manufacturer, or sold with the apparatus. When a cart is used, use caution

when moving the cart/apparatus combination to avoid injury from tip-over.

13. Unplug this apparatus during lightning storms or when unused for long

periods of time.

14. Refer all servicing to qualied service personnel. Servicing is required

when the apparatus has been damaged in any way, such as power supply

cord or plug is damaged, liquid has been spilled or objects have fallen into

the apparatus, the apparatus has been exposed to rain or moisture, does not

operate normally, or has been dropped.

15. e plug on the power cord is the AC mains disconnect device and must

remain readily operable. To completely disconnect this apparatus from the

AC mains, disconnect the power supply cord plug from the AC receptacle.

16. is apparatus shall be connected to a mains socket outlet with a protec-

tive earthing connection.

17. When permanently connected, an all-pole mains switch with a contact

separation of at least 3 mm in each pole shall be incorporated in the

electrical installation of the building.

WARNING: To reduce the risk of re or electric shock, do not expose this

apparatus to rain or moisture. Apparatus shall not be exposed to dripping or

splashing and no objects lled with liquids, such as vases, shall be placed on

the apparatus.

WARNING: is product may contain chemicals known to the State of

California to cause cancer, or birth defects or other reproductive harm.

ATTENTION: RISQUE DE CHOCS ELECTRIQUE - NE PAS OUVRIR

RISK OF ELECTRIC SHOCK

DO NOT OPEN

CAUTION

An d’éviter tout risque de choc électrique, ne pas ouvrir l’appareil. Aucune pièce ne

peut être changée par l’utilisateur. Contactez un SAV qualié pour toute intervention.

Les symboles ci-dessous sont reconnus internationalement comme prévenant tout

risque électrique.

Ce symbole indique que cette unité utilise un voltage élevé constituant

un risque de choc électrique.

Ce symbole indique la présence d’instructions d’utilisation et de

maintenance importantes dans le document fourni.

ATTENTION

FCC

REMARQUE: Cet équipement a été testé et approuvé conforme aux limites pour

un appareil numérique de classe B, conformément au chapitre 15 des règles de la

FCC. Ces limites sont établis pour fournir une protection raisonnable contre tout

risque d’interférences et peuvent provoquer une énergie de radiofréquence s'il n'est

pas installé et utilisé conformément aux instructions, peut également provoquer

des interférences aux niveaux des équipements de communication. Cependant, il

n'existe aucune garantie que de telles interférences ne se produiront pas dans une

installation particulière. Si cet équipement provoque des interférences en réception

radio ou télévision, ceci peut être detecté en mettant l'équipement sous/hors tension,

l'utilisateur est encouragé à essayer de corriger cette interférence par une ou plusieurs

des mesures suivantes:

• Réorienter ou déplacer l'antenne de réception.

• Augmenter la distance entre l'équipement et le récepteur.

• Connecter l'équipement à une sortie sur un circuit diérent de celui sur lequel le

récepteur est branché.

• Consulter un revendeur ou un technicien radio / TV expérimenté.

ATTENTION: Les changements ou modications non expressément approuvés par

Rane Corporation peuvent annuler l'autorité de l'utilisateur à manipuler cet équipe-

ment et rendre ainsi nulles toutes les conditions de garantie.

Cet appareil numérique de classe B est conforme à la norme Canadienne ICES-003.

Cet appareil numérique de classe B est conforme à la norme Canadienne NMB-003.

INSTRUCTIONS DE SÉCURITÉ

1. Lisez ces instructions.

2. Gardez précieusement ces instructions.

3. Respectez les avertissements.

4. Suivez toutes les instructions.

5. Ne pas utiliser près d’une source d’eau.

6. Ne nettoyer qu’avec un chion doux.

7. N’obstruer aucune évacuation d’air. Eectuez l’installation en suivant les instruc-

tions du fabricant.

8. Ne pas disposer près d’une source de chaleur, c-à-d tout appareil produisant de la

chaleur sans exception.

9. Ne pas modier le cordon d’alimentation. Un cordon polarisé possède 2 lames,

l’une plus large que l’autre. Un cordon avec tresse de masse possède 2 lames plus

une 3è pour la terre. La lame large ou la tresse de masse assurent votre sécurité. Si le

cordon fourni ne correspond pas à votre prise, contactez votre électricien.

10. Faites en sorte que le cordon ne soit pas piétiné, ni au niveau du l, ni au niveau de

ses broches, ni au niveau des connecteurs de vos appareils.

11. N’utilisez que des accessoires recommandés par Rane.

12. N’utilisez que les éléments de transport, stands, pieds ou tables spéciés par le

fabricant ou vendu avec l’appareil. Quand vous utlisez une valise de transport,

prenez soin de vous déplacer avec cet équipement avec prudence an d’éviter tout

risque de blessure.

13. Débranchez cet appareil pendant un orage ou si vous ne l’utilisez pas pendant un

certain temps.

14. Adressez-vous à du personnel qualié pour tout service après vente. Celui-ci est

nécessaire dans n’importe quel cas où l’appareil est abimé : si le cordon ou les

ches sont endommagés, si du liquide a été renversé ou si des objets sont tombés

sur l’appareil, si celui-ci a été exposé à la pluie ou l’humidité, s’il ne fonctionne pas

correctement ou est tombé.

15. La che du cordon d’alimentation sert à brancher le courant alternatif AC et doit

absolument rester accessible. Pour déconnecter totalement l’appareil du secteur,

débranchez le câble d’alimentation de la prise secteur.

16. Cet appareil doit être branché à une prise terre avec protection.

17. Quand il est branché de manière permanente, un disjoncteur tripolaire normalisé

doit être incorporé dans l’installation électrique de l’immeuble.

18. En cas de montage en rack, laissez un espace susant pour la ventilation. Vous

pouvez disposer d’autres appareils au-dessus ou en-dessous de celui-ci, mais cer-

tains (tels que de gros amplicateurs) peuvent provoquer un buzz ou générer trop

de chaleur au risque d’endommager votre appareil et dégrader ses performances.

19. Cet appareil peut-être installé dans une baie standard ou un chassis normalisé

pour un montage en rack. Visser chaque trou de chaque oreille de rack pour une

meilleure xation et sécurité.

ATTENTION: an d’éviter tout risque de feu ou de choc électrique, gardez cet ap-

pareil éloigné de toute source d’humidité et d’éclaboussures quelles qu’elles soient.

L’appareil doit également être éloigné de tout objet possédant du liquide (boisson en

bouteilles, vases,…).

General Description

e Rane MS1S Mic Stage preamplier provides the answer when you need

just one microphone input in an otherwise line-level world. Give us a call to

go from either a dynamic, condenser or electret microphone to a line-level

input with a minimum of noise, distortion, cost and hassle.

e MS1S provides 48 V switchable Phantom Power with an indicator

LED, continuous rotary Gain trim between 15 dB and 60 dB, Signal/Over-

load LED, and XLR balanced Input & Output connectors. A Polarity switch

and high-current cross-coupled output line driver round out the features.

e MS1S utilizes one of the nest ultra low noise amplier designs

available. Featuring a true dierential input with high common-mode rejec-

tion, use of the MS1S guarantees performance usually found only in mixing

consoles costing thousands of times as much. Of course, for all of that extra

money you receive a proportional increase in KPSI (knobs per square inch).

e MS1S replaced the MS 1B Mic Stage with a new internal universal

power supply. e width increases by one inch, all other features are the same.

Features

• -127 dB Equivalent Input Noise

• Gain Control

• Signal / Overload Indicator

• Polarity Switch

M S1S

M I C S TAG E

• Switchable 48 V Phantom Power

• True Dierential Input

• Cross-coupled Line Driver

• Internal 100-240 VAC Power Supply

Application Information

Uses and applications for the MS1S should be obvious. But then again, it’s ob-

vious to us our taxes are too high and nothing is being done about that. With

this in mind, perhaps a few words on using the MS1S might not be wasted.

BALANCED USE

e MS1S provides a true cross-coupled balanced output. is is equivalent

to an electronic simulation of a transformer output. Rane follows the AES

standard of pin 2 = hot.

When running a long cable back to the mixer, run a line-level balanced

line rather than a mic-level line. e compact MS1S can mount closer to the

microphone, provide a local volume control (or not, just pull the knob o),

while the stronger signal minimizes RF and hum irritations.

UNBALANCED USE

Balanced use is recommended to minimize noise. Unbalanced lines are usu-

ally quiet under 10 feet (3 meters), but longer runs will introduce the hum

and interference you are trying to avoid. When you must drive an unbalanced

device with the MS1S's balanced output, keep the cable short, and connect

pin 2 to the “+” or “hot” lead, and tie pin 3 and ground together at the shield.

MIXING

e MS1S is designed to ll the need for adding a microphone channel to

line-level mixers, such as the Rane SM 26S or SM82S. Many installations

using either of these products invariably wind up with one unused input that

would do the job perfectly if only it could operate at mic-level. In rides the

MS1S to the rescue.

DIGITAL RECORDING AND SAMPLING

Another handy use for the MS1S is in recording applications. Many popular

products do not have a high enough quality mic preamp to suit the resolution

of the digital processing electronics. Such irony. Using the ultra low noise

MS1S to bring the mic inputs up to extremely high quality line-level is an

easy and aordable solution for this dilemma. No garbage in; no garbage out.

Clippity-clop; clippity-clop.

MICROPHONE TYPES

e available gain and large input range of the MS1S allows the use of

virtually any type of microphone. True 48V phantom power guarantees the

MS1S works with every microphone. e better the mic, the better the MS1S

sounds.

Ah, the sound of the thundering hoofs is deafening.

Features and Specications

Parameter Specication Limit Units Conditions/Comments

Input Impedance 2k 1%  Balanced

Gain Range 15 to 60 typ. dB

Phantom Power +48 4% V 10 mA max.

..........Impedance 6.81k 1%  Each leg

Max. Input Level +9 / -35 min. dBu Gain 15 / 60, balanced output

Equivalent Input Noise -127 typ. dBu 20 kHz BW, Rs=150 , Gain = 60 dB

Signal to Noise Ratio 94 typ. dB 20 kHz BW, Rs=150 , Gain = 15 dB, re 4 dBu

Dynamic Range 114 / 91 typ. dB Gain 15 / 60, 20 Hz to 20 kHz

CMRR 80 typ. dB R s=150 , 120 Hz, Gain = 60 dB

Frequency Response 3 to 200k typ. Hz +0, -3dB

THD+Noise (gain 60 dB) .004 (Output=+20 dBu) typ. % 55 Hz to 20 kHz, 20 kHz BW, Rl=10 k

THD+Noise (gain 15 dB) .0006 (Output=+20 dBu) typ. % 50 Hz to 20 kHz, 20 kHz BW, Rl=10 k

Line Driver Active Cross-coupled

Max. Output Level +18 / +24

min. dBu Balanced, 2 k load

Output Impedance 94 1%  Each Leg

Signal Indicator -11 typ. dBu Balanced output, Green LED

Overload Indicator +20 typ. dBu Balanced output, Amber LED

Output Cable Length 1000 feet / 300 meters typ. Belden 8451 or equivalent

Unit: Conformity FCC, CSA

Maximum Power 3

Universal Line Voltage 100-240 VAC 50/60 Hz

Power Cord C5 cord to C6 inlet IEC 60320-1

Unit: Size 1.64"H x 6.8"W x 4.26"D (4.2 cm x 17.3 cm x 10.8 cm)

..........Weight 1 lb 1 oz (0.5 kg)

Shipping Size 3.6"H x 11.75"W x 7.2"D (9.5 cm x 30 cm x 18 cm)

..........Weight 4 lb (1.8 kg)

©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 USA TEL 425-355-6000 FAX 425-347-7757 WEB rane.com

Features and Specications

Parameter Specication Limit Units Conditions/Comments

Input Impedance 2k 1%  Balanced

Gain Range 15 to 60 typ. dB

Phantom Power +48 4% V 10 mA max.

..........Impedance 6.81k 1%  Each leg

Max. Input Level +9 / -35 min. dBu Gain 15 / 60, balanced output

Equivalent Input Noise -127 typ. dBu 20 kHz BW, Rs=150 , Gain = 60 dB

Signal to Noise Ratio 94 typ. dB 20 kHz BW, Rs=150 , Gain = 15 dB, re 4 dBu

Dynamic Range 114 / 91 typ. dB Gain 15 / 60, 20 Hz to 20 kHz

CMRR 80 typ. dB R s=150 , 120 Hz, Gain = 60 dB

Frequency Response 3 to 200k typ. Hz +0, -3dB

THD+Noise (gain 60 dB) .004 (Output=+20 dBu) typ. % 55 Hz to 20 kHz, 20 kHz BW, Rl=10 k

THD+Noise (gain 15 dB) .0006 (Output=+20 dBu) typ. % 50 Hz to 20 kHz, 20 kHz BW, Rl=10 k

Line Driver Active Cross-coupled

Max. Output Level +18 / +24

min. dBu Balanced, 2 k load

Output Impedance 94 1%  Each Leg

Signal Indicator -11 typ. dBu Balanced output, Green LED

Overload Indicator +20 typ. dBu Balanced output, Amber LED

Output Cable Length 1000 feet / 300 meters typ. Belden 8451 or equivalent

Unit: Conformity FCC, CSA

Maximum Power 3

Universal Line Voltage 100-240 VAC 50/60 Hz

Power Cord C5 cord to C6 inlet IEC 60320-1

Unit: Size 1.64"H x 6.8"W x 4.26"D (4.2 cm x 17.3 cm x 10.8 cm)

..........Weight 1 lb 1 oz (0.5 kg)

Shipping Size 3.6"H x 11.75"W x 7.2"D (9.5 cm x 30 cm x 18 cm)

..........Weight 4 lb (1.8 kg)

©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 USA TEL 425-355-6000 FAX 425-347-7757 WEB rane.com

All features & specications subject to change without notice.

Architectural Specications

e microphone preamplier shall be a single channel stand-alone unit with

a removable IEC power cord. e unit shall accept voltages from 100 to 240

VAC. e input and output shall be tted with XLR connectors. A polarity

inverting switch shall be included. Phantom power of no less than 48 volts

shall be provided in compliance with IEC 60268-15 and be controlled by a

slide switch with an LED indicator. A gain control shall be provided with 18-

66 dB adjustment range. Power, system signal and overload indicators shall

be provided. High current cross-coupled active output line driver shall be

standard, as well as input RFI lter protection.

e unit shall be a Rane MS1S Microphone Stage.

Block Diagram

SIGNAL / OVERLOAD

MIC

INPUT

PHANTOM

POWER

+48V

12-60 dB

GAIN

LEVEL

LINE

FILTER

RFI

OUT

INVERT

+6 dB

4.26"

0.15"

2.5"

6.8"

6.1"

.7"

0.775"

0.35"

4.225"

1.636"

MAX

MIN

MS1S

MIC STAG E

GAIN

SIG

48V PHANTOM

POWER

MIC IN

LINE OUT

NORMAL

POLARITY

POWER

INVERT

RANE CORP.

MS1S

50/60 Hz 3 WATTS

100-240 V

PIN 2: (+)

PIN 3: (

–

)

PIN 1:

Unit Dimensions

Rane Technical Sta

RaneNote 110

Sound System Interconnection

• Cause & prevention of ground loops

• Interfacing balanced & unbalanced

• Proper pin connections and wiring

• Chassis ground vs. signal ground

• Ground lift switches

RaneNote

Introduction

is note, originally written in 1985, continues to be one of our most useful

references. It’s popularity stems from the continual and perpetual diculty

of hooking up audio equipment without suering through all sorts of bizarre

noises, hums, buzzes, whistles, etc.— not to mention the extreme nancial,

physical and psychological price. As technology progresses it is inevitable that

electronic equipment and its wiring should be subject to constant improve-

ment. Many things have improved in the audio industry since 1985, but

unfortunately wiring isn’t one of them. However, nally the Audio Engineer-

ing Society (AES) has issued a standards document for interconnection of pro

audio equipment. It is AES48, titled “AES48-2005: AES standard on inter-

connections —Grounding and EMC practices — Shields of connectors in audio

equipment containing active circuitry.”

Rane’s policy is to accommodate rather than dictate. However, this docu-

ment contains suggestions for external wiring changes that should ideally only

be implemented by trained technical personnel. Safety regulations require

that all original grounding means provided from the factory be left intact for

safe operation. No guarantee of responsibility for incidental or consequential

damages can be provided. (In other words, don’t modify cables, or try your own

version of grounding unless you really understand exactly what type of output and

input you have to connect.)

Ground Loops

Almost all cases of noise can be traced directly to ground loops, grounding or

lack thereof. It is important to understand the mechanism that causes ground-

ing noise in order to eectively eliminate it. Each component of a sound

system produces its own ground internally. is ground is usually called the

audio signal ground. Connecting devices together with the interconnect-

ing cables can tie the signal grounds of the two units together in one place

through the conductors in the cable. Ground loops occur when the grounds of

the two units are also tied together in another place: via the third wire in the

line cord, by tying the metal chassis together through the rack rails, etc. ese

situations create a circuit through which current may ow in a closed “loop”

from one unit’s ground out to a second unit and back to the rst. It is not sim-

ply the presence of this current that creates the hum—it is when this current

ows through a unit’s audio signal ground that creates the hum. In fact, even

without a ground loop, a little noise current always ows through every inter-

connecting cable (i.e., it is impossible to eliminate these currents entirely). e

mere presence of this ground loop current is no cause for alarm if your system

uses properly implemented and completely balanced interconnects, which are

excellent at rejecting ground loop and other noise currents. Balanced intercon-

nect was developed to be immune to these noise currents, which can never be

entirely eliminated. What makes a ground loop current annoying is when the

audio signal is aected. Unfortunately, many manufacturers of balanced au-

dio equipment design the internal grounding system improperly, thus creating

balanced equipment that is not immune to the cabling’s noise currents. is is

one reason for the bad reputation sometimes given to balanced interconnect.

A second reason for balanced interconnect’s bad reputation comes from

those who think connecting unbalanced equipment into “superior” balanced

equipment should improve things. Sorry. Balanced interconnect is not compat-

ible with unbalanced. e small physical nature and short cable runs of com-

pletely unbalanced systems (home audio) also contain these ground loop noise

currents. However, the currents in unbalanced systems never get large enough to

aect the audio to the point where it is a nuisance. Mixing balanced and unbal-

anced equipment, however, is an entirely dierent story, since balanced and

unbalanced interconnect are truly not compatible. e rest of this note shows

several recommended implementations for all of these interconnection schemes.

e potential or voltage which pushes these noise currents through the

circuit is developed between the independent grounds of the two or more units

in the system. e impedance of this circuit is low, and even though the voltage

is low, the current is high, thanks to Mr. Ohm, without whose help we wouldn’t

have these problems. It would take a very high resolution ohm meter to measure

the impedance of the steel chassis or the rack rails. We’re talking thousandths

of an ohm. So trying to measure this stu won’t necessarily help you. We just

thought we’d warn you.

The Absolute Best Right Way To Do It

e method specied by AES48 is to use balanced lines and tie the cable shield

to the metal chassis (right where it enters the chassis) at both ends of the cable.

A balanced line requires three separate conductors, two of which are signal

(+ and –) and one shield (see Figure 1a). e shield serves to guard the sensitive

audio lines from interference. Only by using balanced line interconnects can you

guarantee (yes, guarantee) hum-free results. Always use twisted pair cable. Chassis

tying the shield at each end also guarantees the best possible protection from RFI

[radio frequency interference] and other noises [neon signs, lighting dimmers].

Neil Muncy

, an electroacoustic consultant and seasoned veteran of years

of successful system design, chairs the AES Standards Committee (SC-05-05)

working on this subject. He tirelessly tours the world giving seminars and dis-

pensing information on how to successfully hook-up pro audio equipment

He makes the simple point that it is absurd that you cannot go out and buy

pro audio equipment from several dierent manufacturers, buy standard o-

the-shelf cable assemblies, come home, hook it all up and have it work hum

and noise free. Plug and play. Sadly, almost never is this the case, despite the

science and rules of noise-free interconnect known and documented for over

60 years (see References for complete information).

It all boils down to using balanced lines, only balanced lines, and nothing

but balanced lines. is is why they were developed. Further, that you tie the

shield to the chassis, at the point it enters the chassis, and at both ends of the cable

(more on ‘both ends’ later).

Since standard XLR cables come with their shields tied to pin 1 at each

end (the shells are not tied, nor need be), this means equipment using 3-pin,

XLR-type connectors must tie pin 1 to the chassis (usually called chassis

ground) — not the audio signal ground as is most common.

Not using signal ground is the most radical departure from common pro-

audio practice. Not that there is any argument about its validity. ere isn’t.

is is the right way to do it. So why doesn’t audio equipment come wired

this way? Well, some does, and since 1993, more of it does. at’s when Rane

started manufacturing some of its products with balanced inputs and outputs

tying pin 1 to chassis. So why doesn’t everyone do it this way? Because life is

messy, some things are hard to change, and there will always be equipment in

use that was made before proper grounding practices were in eect.

Unbalanced equipment is another problem: it is everwhere, easily available

and inexpensive. All those RCA and ¼" TS connectors found on consumer

equipment; eect-loops and insert-points on consoles; signal processing boxes;

digital and analog tape recorders; computer cards; mixing consoles; et cetera.

e next several pages give tips on how to successfully address hooking

up unbalanced equipment. Unbalanced equipment when “blindly” connected

with fully balanced units starts a pattern of hum and undesirable operation,

requiring extra measures to correct the situation.

Figure 1a. The right way to do it.

–

RED

BLACK 2-CONDUCTOR SHIELDED CABLE

2-CONDUCTOR SHIELDED CABLE

SHIELD

RED

BLACK

SHIELD

RED

BLACK

SHIELD

RED

BLACK

SHIELD

RED

BLACK

SHIELD

RED

BLACK

SHIELD

CHASSIS

GROUND

CHASSIS

GROUND

SIGNAL

GROUND

–

BALANCED OUTPUTS BALANCED INPUTS

MALE FEMALEMALE

FEMALE

The Next Best Right Way To Do It

e quickest, quietest and most foolproof method to connect balanced and

unbalanced is to transformer isolate all unbalanced connections. See

Figure 2.

Many manufacturers provide several tools for this task, including Rane.

Consult your audio dealer to explore the options available.

e goal of these adaptors is to allow the use of standard cables. With these

transformer isolation boxes, modication of cable assemblies is unnecessary.

Virtually any two pieces of audio equipment can be successfully interfaced

without risk of unwanted hum and noise.

Another way to create the necessary isolation is to use a direct box. Origi-

nally named for its use to convert the high impedance, high level output of an

electric guitar to the low impedance, low level input of a recording console, it

allowed the player to plug “directly” into the console. Now this term is com-

monly used to describe any box used to convert unbalanced lines to balanced

lines.

T CONNECTED

CHASSIS

(PLASTIC JA

CK)

EARTH GROUNDED

METAL ENCLOSURE

CHASSIS IS

GROUNDED TO PIN 1

1/4”

TIP-SLEEVE

CASE LUG MAY

CONNECT TO

CHASSIS

(NOT REQUIRED)

TRANSFORMER

UNBALANCED BALANCED

CASE

(+)

(–)

COMMON (WRONG) PRACTICE RECOMMENDED PRACTICE

(–)

(+)

OPTIONAL

CASE

CHASSIS

GROUND

SIGNAL

GROUND

CHASSIS

GROUND

CHASSIS

GROUND

Figure 2. Transformer Isolation

Figure 1b. Recommmended practice.

The Last Best Right Way To Do It

If transformer isolation is not an option, special cable assemblies are a

last resort. e key here is to prevent the shield currents from owing into a

unit whose grounding scheme creates ground loops (hum) in the audio path

(i.e., most audio equipment).

It is true that connecting both ends of the shield is theoretically the best

way to interconnect equipment –though this assumes the interconnected

equipment is internally grounded properly. Since most equipment is not

internally grounded properly, connecting both ends of the shield is not often

practiced, since doing so usually creates noisy interconnections.

A common solution to these noisy hum and buzz problems involves dis-

connecting one end of the shield, even though one can not buy o-the-shelf

cables with the shield disconnected at one end. e best end to disconnect

is the receiving end. If one end of the shield is disconnected, the noisy hum

current stops owing and away goes the hum — but only at low frequencies.

A ground-sending-end-only shield connection minimizes the possibility of

high frequency (radio) interference since it prevents the shield from acting as

an antenna to the next input. Many reduce this potential RF interference by

providing an RF path through a small capacitor (0.1 or 0.01 microfarad ce-

ramic disc) connected from the lifted end of the shield to the chassis. (is is

referred to as the “hybrid shield termination” where the sending end is bonded

to the chassis and the receiving end is capacitively coupled. See Neutrik’s

EMC-XLR for example.) e fact that many modern day installers still follow

this one-end-only rule with consistent success indicates this and other ac-

ceptable solutions to RF issues exist, though the increasing use of digital and

wireless technology greatly increases the possibility of future RF problems.

If you’ve truly isolated your hum problem to a specic unit, chances are,

even though the documentation indicates proper chassis grounded shields,

the suspect unit is not internally grounded properly. Here is where special test

cable assemblies, shown in Figure 3, really come in handy. ese assemblies

allow you to connect the shield to chassis ground at the point of entry, or to pin

1, or to lift one end of the shield. e task becomes more dicult when the

unit you’ve isolated has multiple inputs and outputs. On a suspect unit with

multiple cables, try various congurations on each connection to nd out if

special cable assemblies are needed at more than one point.

Figure 3. Test cable

TEST

WIRE

GROUND CLIP

FEMALE

MALE

RED

BLACK

SHIELD

RED

BLACK

SHIELD

2-CONDUCTOR SHIELDED CABLE

See Figure 4 for suggested cable assemblies for your particular intercon-

nection needs. Find the appropriate output conguration (down the left side)

and then match this with the correct input conguration (across the top of the

page.) en refer to the following pages for a recommended wiring diagram.

Ground Lifts

Many units come equipped with ground lift switches. In only a few cases can

it be shown that a ground lift switch improves ground related noise. (Has a

ground lift switch ever really worked for you?) In reality, the presence of a

ground lift switch greatly reduces a unit’s ability to be “properly” grounded

and therefore immune to ground loop hums and buzzes. Ground lifts are sim-

ply another Band-Aid

to try in case of grounding problems. It is true that an

entire system of properly grounded equipment, without ground lift switches,

is guaranteed (yes guaranteed) to be hum free. e problem is most equipment

is not (both internally and externally, AC system wise) grounded properly.

Most units with ground lifts are shipped so the unit is “grounded” —

meaning the chassis is connected to audio signal ground. (is should be the

best and is the “safest” position for a ground lift switch.) If after hooking up

your system it exhibits excessive hum or buzzing, there is an incompatibility

somewhere in the system’s grounding conguration. In addition to these spe-

cial cable assemblies that may help, here are some more things to try:

1. Try combinations of lifting grounds on units supplied with lift switches (or

links). It is wise to do this with the power o!

2. If you have an entirely balanced system, verify all chassis are tied to a good

earth ground, for safety’s sake and hum protection. Completely unbalanced

systems never earth ground anything (except cable TV, often a ground loop

source). If you have a mixed balanced and unbalanced system, do yourself

a favor and use isolation transformers or, if you can’t do that, try the special

cable assemblies described here and expect it to take many hours to get

things quiet. May the Force be with you.

3. Balanced units with outboard power supplies (wall warts or “bumps” in the

line cord) do not ground the chassis through the line cord. Make sure such

units are solidly grounded by tying the chassis to an earth ground using a

star washer for a reliable contact. (Rane always provides this chassis point

as an external screw with a toothed washer.) Any device with a 3-prong AC

plug, such as an amplier, may serve as an earth ground point. Rack rails

may or may not serve this purpose depending on screw locations and paint

jobs.

Floating, Pseudo, and Quasi-Balancing

During inspection, you may run across a ¼" output called oating unbal-

anced, sometimes also called psuedo-balanced or quasi-balanced. In this

conguration, the sleeve of the output stage is not connected inside the unit

and the ring is connected (usually through a small resistor) to the audio signal

ground. is allows the tip and ring to “appear” as an equal impedance, not-

quite balanced output stage, even though the output circuitry is unbalanced.

Floating unbalanced often works to drive either a balanced or unbalanced

input, depending if a TS or TRS standard cable is plugged into it. When it

hums, a special cable is required. See drawings #11 and #12, and do not make

the cross-coupled modication of tying the ring and sleeve together.

Winning the Wiring Wars

• Use balanced connections whenever possible, with the shield bonded to the

metal chassis at both ends.

• Transformer isolate all unbalanced connections from balanced connec-

tions.

• Use special cable assemblies when unbalanced lines cannot be transformer

isolated.

• Any unbalanced cable must be kept under 10 feet

(3 m) in length. Lengths longer than this will amplify all the nasty side

eects of unbalanced circuitry's ground loops.

Summary

If you are unable to do things correctly (i.e. use fully balanced wiring with

shields tied to the chassis at both ends, or transformer isolate all unbalanced

signals from balanced signals) then there is no guarantee that a hum-free

interconnect can be achieved, nor is there a denite scheme that will assure

noise-free operation in all congurations.

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Rane MS1S Manuel utilisateur

Marque: Rane

Modèle: MS1S

Catégorie: Équipement musical supplémentaire

Taper: Manuel utilisateur

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