Shure VA302 Schematic

VA302 SERIES

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OPERATING AND SERVICE MANUAL

Manufactured by

SHURE BROTHERS

Evanston, Illinois 60204 U.S.A.

Copyright 1978, Shure Brothers Inc.

AL406

(RE)

27A818

INC.

222 Hartrey Avenue

Printed in

U.S.A.

VA302

VA302 Series Vocal Master

SPECIFICATIONS

Series Console
Amplifier Type
Power Output

Voltage Gain

Frequency Response
Input Impedance

Distortion
Hum and Noise

Speaker Load lmpedance

Input Clipping Level

Bass Control Action ............................

Treble Control Action

"Aux. Hi-Level" Output Jack

...................................

...........

.....................................

.I00

watts continuous '(RMs); (to 8 ohm load, see Figure

.....................................

.........

...........................................

..................................................

Nominal

.............................

........................

............... .Impedance

output (to 8 ohm load); nominal

i10

-

.All silicon transistor mixer/power amplifier

3,

Page

.80

db Input Attenuator "Out"

65

.5%

8

ohms; operational

.Greater than

Greater than

t13

db at

db at

10,000

5,000

2

V at

50

watts to speakers, Clipping Level 4 V.

db lnput Attenuator "In" (8 ohm load)

k2

db

40

Hz.

to

.320

ohms lnput Attenuator "Out"

500

ohms lnput Attenuator "In"

maximum at rated output at

.60

db below rated output

(See Figure

25

Mv. Input Attenuator "Out"

150

Mv. lnput Attenuator "In"

100

Hz.

with respect to "flat" setting

Hz.

with respect to "flat" setting

ohms; Output

19

(8

ohm load)

20,000

5.3

Hz.

(typical)

ohms minimum

3,

Page 7)

db below speaker

1

7)

KHz.

"Mic. Level" Output ............. Hi-Z: impedance

Lo-Z: impedance

Echo-"To Input" Jack (Output To External Echo Unit)

Output

Echo-"To Output" Jack (Input From External Echo Unit)

"Reverb Switch" Jack

Center Notch Frequencies of "Anti-Feedback" Filters

20

db above microphone inputs with individual volumes at

200

Sensitivity

"Master Volume" Control at maximum settings; Clipping Level

setting of "Echo Gain" control. Clipping level increases with reduced

....................

Mv. for rated amplifier output with "Echo Gain" Control and

1,000

D.C. switching (no audio), parallels the Master Reverb

In-Out Switch. Any cable with a resistance of less

ohms; Output

36

..................

.................

nominal

ohms; Output

30

60

52

nominal

5

setting of "Echo Gain" control.

than

......

db below auxiliary output;

Mv. Clipping Level

db below auxiliary output;

Mv. Clipping Level

.Impedance

"10";

Clipping Level 3 V.

Impedance

2

V. with maximum

5,000

ohms may be used.

.

Filter "A"

Filter

"B"

Filter "C"

Filter "D"

120

10

10,000

ohms;

40,000

ohms;

5,000
2,200
1,000

155

Mv.
Mv.

Hz.

Hz.
Hz.

Hz.

Console (Continued)
power Supply: VA302-C

VA302E-C
VA302E6-C

Power Consumption

Ambient Temperature Range

Dimensions

Weight: VA302-C

VA300-S Speaker Column
Power Rating
Impedance
Frequency Response
Horizontal Distribution

.................................

........................................................

VA302E-C and VA302E6-C

.................................................................

.....................................................................

..................................................

...........................................

....................................

..................................................

..............................................................

.........................

.................

,100, 120,140, 200, 220, 240 volts, 50160 Hz.

180 watts with

-7°C. to 43°C. (20" F. to 11O0F.) without derating
213 mm height x 635 mm width x 375 mm depth

.........................................

,120 volts, 60 HZ.

Factory wired for 240 volt operation.

.80 watts maximum with no signal in.

1

KHz.

120/240 volts, 50160 HZ.

Switch selectable.

signal and 100 watts output,

400 watts maximum operating

(8% in.

x

25

in. x 14% in.)

18.6 kg (41 Ib)
.19.05

50 Hz. to 10,000 Hz.

kg

(42

Ib)

.I00 watts

16 ohms

140'
Vertical Distribution
Dimensions

Weight..

The Shure Model
consists of one Control Console (VA302-C) and two
Speaker Columns (VA300-S).

The Shure Model
consists of one Control Console
Speaker Columns (VA300-S).

The Shure Model
consists of one Control Console
Speaker Columns (VA300-S).

Designed specifically for the performing vocalist, the
Vocal Master Sound System provides the required porta­bility, flexibility, and dependability demanded by profes­sional entertainers.

mixerlpower amplifier Control Console permits the

The

user to mix up to six microphones with individual control

over volume, tone and reverberation. A solid-state 100 watt

R.M.S. power amplifier is incorporated in the Console.
Unique circuitry design protects the solid-state compo­nents against damage as a possible result of open-circuit

...............................

.................................................

VA302 Vocal Master Sound System

VA302E Vocal Master Sound System

VA302E6 Vocal Master Sound System

.................................................................

(VA302E-C) and two

(VA302E6-C) and two

65'

1594 mm height x 400 mm width x 222

(62% in. x

31.78 kg (70 Ib) including cable

or short-circuit conditions of the amplifier outputs. The
output transistors are also protected against overheating
by the use of automatic thermal sensors. All components
of the Vocal Master Sound System are conservatively rated
and are operated well within their respective tolerances to
assure long life and trouble-free performance.

The VA302-C is Underwriters' Laboratories, Inc. listed,

and is listed by the CSA Testing Laboratories as certified.

The VA300-S Speaker Columns are highly directional,

wide range, line-radiators. A rear-ported enclosure is uti-

lized which contributes to the directional characteristics of

the Speaker Column and is crucial in reduction of feed-

back.

VA300-S employs four special 8-inch loudspeakers

The
and two special 10-inch loudspeakers providing a total
cone area of 2,310 cm2 (358 in2).

Each Speaker Column is furnished with a

gauge, 2-conductor rubber jacketed cable with locking

phone plugs attached.

15% in.

mm depth

x

8%

in.)

15m (50 ft), #I8

\

FIGURE

Front Panel Controls (Refer to Figure 1)

1. "Anti Feedback" Switches (Four).

2.

"Reverb Intensity" Control.

&

3. "Reverb Treble

4.

"Master Reverb" Switch. 10. V.U. Meter "Hi/Lo" Sensitivity Switch.

5.

Individual Channel "Volume" Controls (Six). 11. V.U. Meter.

Bass" Controls (Dual Concentric).

1.

6,

Individual Channel "Treble & Bass" Controls
(Six, Dual Concentric).

7.

Individual Channel "Reverb" Switches (Six).

8.

"Master Volume" Control.

9.

"On-Off-On" Power Switch.

I

Rear Panel Controls and Connections (Refer to Figure 2)

11. Line Cord Storage Spindles.

12. A.C. Line Cord.

13. D.C. Fuse

(3AG/5A).

14. A.C. Fuse (3AG/3A/SB).

15. "Thermal Overload" lndicator Lamp.

16. "Reverb Switch" Remote Control Jack
(Phone Type).

17. "Speaker" Output Jacks (Two, Phone Type).

18. "Aux. Hi-Level" Output.

19. "Low-Hi" Impedance Switch for Microphone Output

FIGURE

2.

20. "Microphone" Level Output Connector
(Male Cannon Type).

21. Echo-"To Input" Jack (Switching Phone Type).

22. Echo-"To Output" Jack (Switching Phone Type).

23. Echo "Gain" Control.
"ln/Out" lnput Attenuator Switches (Six).

24.

25. "lnput" Connectors (Six, Female Cannon Type).

26. "Voltage Selector" Switch.

27. "Thermal Overload" lndicator Lamp.

28. A.C. Fuse (1.6 AT or 3.0 AT).

29. A.C. Power (Mains) Connector.

30. D.C. Fuse (5.0 A).

1

General Operating Instructions:

1. Set all front panel controls in the following manner: All
switches
Intensity" Control
and
and (6), set in the "flat response" position (indicator
ribs at
the "Off" position; "Hi-Lo" Sensitivity Switch (10) in
the "Hi" position.

2. Unwrap the A.C. line cord (12) from the storage spin­dles (11); plug line cord into an outlet. The VA302-C is
designed to operate from outlets supplying 110 to 130
volts, 60 Hz. The
operate from outlets supplying 220 to 260 volts, 50 to
60
operate on 110 to 130 volts, 50 to 60 Hz. See page 8
for instructions. The VA302E6-C is designed to oper­ate from outlets supplying 100, 120, 140, 200, 220, or
240 volts, 50 to 60 Hz. as selected by an integral volt­age-selector switch. See page 8 for instructions.

3. Remove the speaker cables from the storage compart­ments in the
lock the right angle phone plug on the cable into either
of the two parallel-wired phone jacks; one on each
Speaker Column. Connect the other end of each cable
to the jacks on the rear panel of the Console marked
"Speakers" (17). These plugs are provided with lock­ing rings to lock the plug to the jack. Each speaker
cable is 15m (50 ft) in length and is made from heavy
duty 2-conductor,
each Speaker Column has a pair of parallel-wired input
jacks, an alternate speaker hook-up would be to con­nect a speaker cable from the Console to one Speaker
Column and then connect a second cable from this
Speaker
Either hook-up will provide an 8 ohm load. If longer
speaker cables are required, see page 6.

4. Connect one or more low impedance microphones to
the Console at the connectors marked "Inputs" (25).
The Console is designed to operate with any high
quality dynamic or ribbon-type low impedance micro­phone. For high impedance microphones see page 11.

5. Set all six Input Attenuator Switches (24) on the rear
panel of the Console to "Out." These switches should
generally be set in the "Out" position when using
low impedance dynamic or ribbon microphones. See
page 6 for a description of the switch function.

6. Turn on the Power Switch (9) located on the front panel
of the Console. Set the "Master Volume" Control (8) to

"5." While talking or singing into one of the micro­phones connected to the console, turn up the indi-

vidual volume control for that microphone to a normal

level. On Consoles with a three-position Power Switch
(9), use the "On" position which results in the least

amount of hum coming from the speakers.

(I), (4), (7), set to "Out" position; "Reverb

(2), and all "Volume" Controls (5)

(8), set at "0"; all "Treble" and "Bass" Controls (3)

12:OO o'clock); "On-Off-On" Switch (9) set in

VA302E-C is wired at the factory to

Hz.

A

simple wiring change allows the VA302E-C to

VA3OO-S Speaker Columns. Insert and

#18 gauge unshielded cable. Since

Column to the second Speaker Column.

7. Now turn up the other lndividual Channel Volume Con­trols (5) which are being used. By use of the individual
Channel Volume Controls
balanced for level so that the sound coming from the
speakers is in proper balance for each microphone.
Increasing or decreasing the Volume on one channel
will have no effect on the other channels of the Con­sole.

8. Note the action of the Individual Treble and Bass Con-

9. Turn the Reverb Intensity Control

10. Set all four Anti Feedback switches (1) to the "Out"

11. The Master Volume Control (8) will raise or lower the

12. For most applications set the V.U. Meter Sensitivity

(61;

trols
type, the large knob being the Bass control and the
smaller knob being the Treble control. Each of these
knobs incorporates an indicating rib. Under average
conditions, the controls should be set with indicating
ribs facing straight up
vide a normal "flat" frequency response. All Treble
and Bass Controls on the Console operate in the same
manner; turning the controls clockwise respectively
increases Bass or Treble, counterclockwise decreases
Bass or Treble. Note that changing the Bass or Treble
Controls on one channel has no effect on the other
channels of the unit.

"4." Set the Master Reverb switch (4) to the "In" posi­tion. Reverberation may now be selectively added to
any of the six channels by setting the Individual Chan­nel Reverb switches

different settings of the Reverb Intensity Control (2)

will not affect the overall system gain. Generally a set­ting of

adequate for vocals. The Reverb Treble and Bass Con­trols (3) operate in the same manner as those of the

individual channel Treble and Bass Controls but pro­vide independent tonal balance of the reverberant sig­nal only. These controls do not affect the tone of the
individual channels. For example, increasing Treble

and decreasing Bass will approximate the reverb

sound of a tape-type reverberation unit while decreas­ing Treble and increasing Bass will approximate the
sound of a plate-type reverberation device.

position. These switches can help eliminate feedback.

Each switch cuts out part of the critical
generating frequencies. See page 8 for a detailed de­scription on how to effectively use them.

volume of all channels simultaneously without affect-

ing the "balance," or "mix." NOTE: With the Console
driven at or near full power, pilot lamps will dim or vary
in brightness; this is a normal condition.

Switch (10) to the "Hi" position. With an 8-ohm speaker

load (two
watts output. With the Sensitivity Switch set to the

"Lo" position, a reading of
put. Adjust the volume controls for the desired sound

level. Note the meter reading and use it as a visual

reference for the desired sound level. For further in­formation on the V.U. Meter, see page 9.

these controls are of the dual concentric

"1" to

"4"

of the Reverb lntensity Control

VA3OO-S), a reading of 0 db indicates 50

(5), the microphones may be

(12:OO o'clock position) to pro-

(2)

to a setting of

(7)

to the "In" position. Note that

feedback-

0 db indicates 2 watts out-

(2)

is

lnput Connections:

Six individugl input connectors are provided on the rear

panel of the Console. These connectors are professional
3-pin female audio connectors (25). The Console is de­signed to operate with any high quality dynamic or
type low impedance microphone.

The main advantage of low impedance microphones

is that virtually unlimited cable lengths may be used,
whereas high impedance microphones require that cable
length not exceed 6m (20 ft).

Low impedance microphones should be wired using low
capacitance, two-conductor, shielded cable (such as
den #8412, #8422). When wiring professional 3-pin audio
connectors, the cable shield should be connected to Pin

1

and one of the two conductors to Pin No. 2, the other

No.
conductor. to Pin No. 3. When using several microphones,
consistency of cable wiring should be followed to insure
that all microphones are "in phase."

To test two microphones and their cables for proper
phasing, connect them to the Console. Talk or sing into
the two microphones while holding them three or four
inches apart. The amplified sound from the speaker col­umn will be the same when talking directly into either
microphone or directly between them if they are in phase
with each other. If the sound drops drastically, or a dead
spot is found when talking between the two microphones,
one of them, or their cables, is out of phase.

To change the phase of the one microphone, or cable,
interchange the conductors that are wired to Pins No. 2
and No. 3 of the 3-pin connector. Test all the microphones

and cables this way to insure that they are all "in phase"

with each other.

For high impedance microphones, see page 11.

For additional microphone inputs, connections from
electrified musical instruments, and connections to play
back a tape, see page 11.

ribbon-

Bel-

lnput Attenuator Switches:

Six individual input attenuator switches (24) are located
above the six input connectors. These screwdriver-slot
slide switches allow the microphone input signal to be
attenuated (reduced) before entering the preamplifier.

With the switch in the "Out" position, the signal from
the microphone is switched directly to the preamplifier of

the channel. With the switch in the

nal from the microphone is attenuated by 15 db before en-

tering the preamplifier.

This feature may be useful when working the micro­phones very close to the performer's lips as with "hard
rock" vocalists, who may produce signals in excess of

the clipping level of the preamplifiers; in such an instance,
the attenuator will generally eliminate the distortion which
would otherwise occur.

"In" position, the sig-

Output Connections:

Two parallel-wired "Speaker" output connectors are

provided on the rear panel of the Console. These connec-

tors are standard phone jacks (17).

Full rated output of the amplifier is obtained when the
speaker load is 8 ohms (two VA300-S Speakers). Speaker
loads of less than 5.3 ohms (more than three VA300-S
Speakers) should not be used with this amplifier. No dam­age to the speakers or amplifier will occur, but thermal
shutoff of the amplifier (overheating) may result.

It should be noted that various speaker loads will affect
the output power of the amplifier. See Figure 3, page 7 to
determine amplifier output power for the given speaker
load.

WARNING:

jacks or the speaker cables between two Vocal Master
Amplifiers or the Vocal Master and any other ampli­fier. This may result in damage to one or both ampli­fiers, and is not covered by the Guarantee.

The Vocal Master does not use speaker output matching
transformers and thus avoids the distortion, power loss
and added weight inherent in such transformers. The

speaker output voltage is 28.3 volts, to an 8-ohm load, for
100 watts. This allows long speaker lines with wiring prac­tices consistent with those used for 25-volt speaker lines.

Up to 30m (100 ft) of #18 gauge two-conductor cable
(such as Belden
connect from the Console to each 16-ohm

speaker. Greater cable lengths require heavier gauge wire
to avoid appreciable power loss in the speaker cable. For

30 to 51 m (100 to 170 ft), use

270 ft), use

#12 gauge wire. To maximize the power to each speaker, a

separate cable should be used to connect each speaker to
the Console.

Do not interconnect the speaker output

#8452,8478,8460, or 8461) may be used to

(VA3OO-S)

#16 gauge; 51 to 81 m (1 70 to

#f4 gauge; and 81 to 128m (270 to 425 ft), use

Speakers:

Selection of speakers for use in a vocal music system is
most critical. The factors which most significantly con­tribute to an outstanding vocal speaker system are correct
frequency range, distortion-free reproduction, and enough
sound power to fully penetrate the audience area.

The Shure VA300-S Speaker Column has been designed
to provide all of these features. It is recommended that
VA300-S Speaker Columns be used in pairs, each column
having a nominal impedance of 16 ohms, which provides
an impedance of 8 ohms when two are used. Each
utilizes two special 10-inch speakers and four special 8­inch speakers, and has a total speaker cone area of 2,310
cm2 (358 in2) per column. The VA300-S Speaker Column de­livers virtually uniform penetrating power over a
in the horizontal plane and a 65" angle in the vertical plane.

The rear-ported enclosure of the VA300-S contributes to

its highly directional pattern, which is critical in achieving
maximum audience penetration and reduction of feedback.

The Shure VA3Ol-S Speaker Column is intended primar­ily for use as an "on-stage monitor." While this speaker
meets all of the criteria for an excellent vocal system

speaker, its area of coverage is more localized than that

VA3OO-S. The nominal impedance of the VA3Ol-S is

of the

32 ohms, so that when used in conjunction with two

VA3OO-S Speaker Columns, the total system impedance
becomes 6.4 ohms. An integral volume control on the
VA301-S permits its use on-stage as a monitor at the
highest possible sound level without feedback.

COIU~~

140" angle

The following list shows various speaker combinations
and the resultant impedance loads which are suitable for
use with the Vocal Master Console:

QUANTITY and IMPEDANCE

SPEAKER MODEL OHMS (NOMINAL)

5

~~301

6

1

VA300-S and 1 VA301-S

1 VA300-S and 2 VA301-S
1 VA3OO-S and 3 VA301
1 VA300-S and 4 VA301 -S
2

VA3OO-S and 1 VA301-S

2

VA3OO-S and 2 VA301-S

-S

VA301 -S

-S

If additional speakers (more than in the table above) are
required, use a Shure Power Master Amplifier to drive the
extra speakers. See page 12 for instructions.

LV

FIGURE

4

5678910

IMPEDANCE

3.

Typical output power vs. speaker load impedance for

the Vocal Master Console.

15

20

(OHMS)

30

40

Column Speaker Placement:

It must always be kept in mind that every room or space
is acoustically unique and there are no set "rules" for
speaker placement. A number of generalizations however
may be made which will at least provide a good starting
point under various conditions.

Always consider speaker placement in relation to micro­phone placement. It is desirable for the loudspeakers and
microphones to be in close proximity in order to provide

the illusion of source-oriented sound. Source-oriented
sound, ideally, should provide the listener with the illusion
that all of the sound is coming directly from the sound
source, the stage or performance area. It is also desirable
to keep loudspeakers and microphones separated in order
to achieve a high threshold of acoustic feedback. While
these statements are contradictory, a good solution to
both can generally be accomplished.

When the VA300-S Speaker Columns are used on stage,
as they most often are with a portable system, the
speakers should be placed at the sides of the stage and
as far forward as possible. With this setup, the entire stage
area will be relatively free from acoustic feedback; also
the illusion of sound coming from the center of the stage
will be quite good except for the first few forward rows of
seats.

The Shure VA300-S Speaker Column has been designed
with rear ports to give the column a bidirectional horizontal
polar pattern below 200 Hz. This design feature was de­cided upon in order to reduce low frequency acoustic feed­back and provide a relatively "dead" area at the sides of
the column with the result that microphones may be placed

there with minimal feedback problems at low frequencies.

Try to keep the speaker columns above the heads of the
audience. The easiest way to do this is put the speaker
columns on the stage. If the stage is only a foot or two
high, raise the speaker columns up by placing them on a

solid platform or box.

Keeping in mind that the speaker columns have a narrow
coverage angle in the vertical plane and a broad coverage

angle in the horizontal plane, here are a few generaliza­tions on speaker requirements for various room shapes.

A deep, narrow auditorium would generally require only

two speakers if the seating is all on one level. If balconies
were added to this same room, additional speaker columns
would be required to aim sound up into them.

A shallow, broad room might require four speakers to

be utilized in order to cover the extreme horizontal ex-

panse. Again if balconies were added, four more speakers
might be required to expand the vertical coverage.

The "Theatre-in-the-Round" will almost always necessi­tate the use of at least four columns. More speakers might
be required to provide adequate horizontal coverage if the
theatre is very deep.

To "aim" speakers up for effective coverage of a bal­cony, use the Shure Model

A3S-S stand will provide added stability and approxi-

The

mately

of up to

15O of tilt. The A3S-T stand provides adjustable tilt

30'. In an emergency, a spare microphone stand

A3S-S or A3S-T Speaker Stand.

can be used to hold up a tilted speaker column. Adjust the
height of the microphone stand to one or two inches less

than the height of the top edge of the upper rear port on
the back of the speaker. Tilt the speaker back until the top
edge of the upper rear port rests on the top of the micro­phone stand. Changing the height of the microphone stand
adjusts the amount of tilt on the speaker.

The VA300-S Speaker Column may be used on its side,

though this reduces the horizontal coverage and the pene-

trating power. In a low ceiling, small intimate room such

as a night club, horizontal mounting, at or near the ceiling
level may be very successful. An alternate solution for this

type of small room is to use

VA3Ol-S Monitor Speakers. It
is not recommended that the VA300-S Speaker Column be
used on its side in larger rooms.

It is not possible to adequately cover all

phases of
speaker placement in all types of rooms in this manual.
Just remember that every room is acoustically different
from any other and therefore speaker placement will vary
from room to room.

Good speaker placement will provide the audience with
even distribution of sound intensity, sound which is free
from excessive reverberation and echoes, and the illusion
of sound emanating from the real source.

VA302 Power Requirements:

The ~~302-6 Vocal Master is furnished with a three con-

ductor power cable and three-prong plug. Connect the

power cable to an outlet which supplies 120 10% volts
A.C., 60 Hz power. The three-position toggle switch
on the front panel controls power to the amplifier. This
switch (9) is also used to reverse line polarity for mini­mum hum. If extension cords are required to supply power
to the

VA302, a high quality #18 gauge or larger cord

should be used.

VA302E Power Requirements:

The VA302E-C Vocal Master is furnished with a three­conductor power cable without a plug. To connect a plug
to the power cable, attach the brown lead to the live
terminal of the plug, attach the blue lead to the neutral

(f)

(-)

terminal of the plug, and attach the green-yellow lead to
the earth-ground terminal of the plug.

VA302E-C is factory wired for operation from a nom-

The

inal 240 volt power supply. Connect the power cable to an

&

outlet which supplies 240

10% volts A.C., 50 to 60 Hz
power. The three-position toggle switch on the front panel
controls power to the amplifier. This switch (9) is also used
to reverse line polarity for minimum hum. If extension cords
are required to supply power to the
cable with conductors of 0.75 square millimeters

VA302E, a high quality

cross-

section or larger should be used.

An internal modification performed by competent per-

sonnel will allow the

60

Hz power. To change the power supply wiring for 120

to

VA302E to be used with 120 volt, 50

volt operation, do the following:

1. UNPLUG THE AMPLIFIER POWER (MAINS) CABLE.

2. Remove the amplifier from its carrying case as de­scribed on page 14.

3. With the amplifier upside-down, note the six wires
from the power transformer

TI.

4. Unsolder the yellow-black transformer lead wire and
the red-black transformer lead wire from their

solder-

lug.

5.

Resolder the yellow-black lead wire to the solder-lug
to which the all-black transformer lead wire is already
attached.

Resolder the red-black lead wire to the solder-lug to

6.
which the green-black transformer lead wire is al­ready attached.

7. Reinstall the amplifier in its carrying case.

8.

Remove the four screws from the nameplate on the
back of the amplifier. Turn the nameplate over and re­install. The nameplate nomenclature will now be suit­able for 120 volt use.

To change the

VA302E back for use with 240 volt power,
reverse the above steps. Be careful to reconnect the
yellow-black and red-black transformer lead wires to an
UNUSED-UNGROUNDED solder-lug. A pictorial diagram
of the transformer lead wire connections is located on the
inside of the chassis. The circuit diagram for both 120 volt
and 240 volt operation is shown on page 22 of this manual.

VA302E6 Power Requirements:

The VA302E6-C Vocal Master is supplied with a detach­able three-conductor A.C. power (mains) cable without a
connector on the "mains" end. To attach a connector, con-

nect the brown conductor of the cable to the "live" terminal
of the connector, the blue conductor to the "neutral" ter­minal, and the green-yellow conductor to the "earth"

(+)

terminal.

VA302E6-C is designed to operate from 100, 120,

The

140, 200, 220, or 240 volts, 50 to 60 Hertz power (mains).

An integral voltage-selector switch, located on the rear

panel, allows selection of the proper voltage.

As shipped from the factory, the

VA302E6-C is set to op-

erate from 240 volts.

The A.C. fuseholder, located nearest the voltage-selector

switch, contains a 1.6 ampere slow-blow fuse (1.6 AT)
which should be used when the unit is operated from 200
through 240 volts. When operated from 100 through 140
volts, this fuse should be changed to a 3 ampere

slow­blow type (3.0 AT). The fuseholder located farthest from
the voltage-selector switch contains a 5 ampere (5.0 A) fuse
which should not be replaced by other values under any
circumstances. Each of the three fuses mentioned is a
5mm x 20mm type, and two of each value are supplied with

the unit.

CAUTION - DO NOT CHANGE VOLTAGE-SELECTOR

SWITCH SETTING OR ATTEMPT TO REPLACE FUSES
WITHOUT FIRST DISCONNECTING THE A.C. POWER
(MAINS) CABLE.

Thermal Overload/Ventilation:

The Console is equipped with thermal sensing switches
on the heat-sinks of the output transistors. The thermal
switches are set to shut off AC power to the amplifier when
a temperature of 90°C. (194°F.) is attained on the

heat-

sinks; the switches will automatically recycle and return AC

power when the heat-sink temperature reduces to

73°C.

(164OF.). A thermal overload light (15), located on the rear

panel, will indicate if thermal cycling has occurred. Thermal
cycling may occur if air is not allowed to circulate through
the grilles of the amplifier, if there is a prolonged short­circuit on the speaker output, or if the ambient temperature
exceeds

43°C. (110°F.) while the console is operating at or
near full power. Thermal cycling may also occur if the
speaker load impedance is less than 5.3 ohms. See page 6,
Output Connections, for instructions on speaker connec­tions.

Anti Feedback Switches:

Acoustic feedback (a howl or squeal in the speakers)
may occur, depending on room acoustics and the physical
placement of microphones in relation to the speakers, when
volume is increased or when Bass or Treble controls are
boosted. To minimize feedback, four Anti Feedback

(1)

switches

are incorporated in the Console. These
switches operate four "notch filters" which modify the fre­quency response of the unit. Each switch controls part of
the audio spectrum. The top switch (A-yellow colored) fil­ters the highest feedback pitch (squeal), while the bottom
switch (D-deep orange colored) filters the lowest feedback
pitch (howl). The middle switches (B and

C) filter the mid-

dle feedback pitches. The action of each filter, with the

of

exception

the (D) filter, has very little effect on the tonal

quality of the voice. When using the (D) filter, a decrease

in Bass tones may be noticed. To compensate for this
simply increase all the individual Channel Bass controls
slightly for the desired sound. This feedback switch (D)
may be used in a very

"boomy" environment to eliminate

some of the low frequency room reverberation.

If feedback occurs, locate the one Anti Feedback switch

(1)

which eliminates the feedback. Gain may then be in-

creased or tone control increased until another feedback

pitch is apparent. One of the other filters may then be

introduced which will eliminate that feedback. IMPOR-

TANT: no more than two filters should be used simultane­ously; the effect of more than two filters is one of reduc-

ing overall gain and the overall tonal quality of the system
may be significantly affected.

Mixing:

Each of the six channels employ an individual Volume
control, Bass control, Treble control, and reverberation
selector switch.

Individual Volume controls permit proper mixing of the

various inputs.

The Bass control allows 13 db of boost or attenuation
at 100 Hz. It permits enhancement of a thin voice and is
often useful as a low frequency attenuator in

"boomy"

rooms.

The Treble control permits 10 db of boost or attenuation

at 10 KHz, and is useful to "brighten" an otherwise

flat-

sounding voice. It is often used to great advantage to re-

duce high frequency acoustic reverberation in reflective

rooms.

The Master Volume control (8) adjusts the output level

of the total mixed output, allowing simultaneous increase

or decrease of all channels without affecting the mix of the
inputs.

Reverb:

The Vocal Master Console includes a built-in electro­mechanical spring-type reverberation device utilizing a
total of four coil springs in two transmission paths. Re­verberation is accomplished by driving the input ends of
the springs in a torsional mode and transferring the tor­sional movement at the other end of the springs back into
an electrical signal which exhibits time delay with a long
decay time. Since the reverberation device is an electro­mechanical device, it is sensitive to mechanical shock. It
is recommended that if the console is moved while operat­ing, the Master Reverb In-Out switch (4) be set to the "Out"
position. This will avoid the possibility of jarring the springs
and producing unwanted sounds.

Unique to the Vocal Master is the fact that no matter how
much reverberation is used, there is always a backbone of
"dry" signal on the total output. Of great importance to the
user, and also unique to the Vocal Master, is the system
which permits the reverb intensity to be increased without
increasing overall gain. In most units which employ artifi­cial reverberation, as the intensity of the reverberant signal
is increased, the total gain also increases; this usually leads
to acoustic feedback. The reverb mixing system used in the
Vocal Master reduces the "dry" signal as the reverberant
signal is increased; this accounts for an almost constant
gain and reduces the possibility of feedback as reverb is
added.

Three controls are pertinent to the Vocal Master Reverb

operation. The amount of reverb is selected by the Reverb

Intensity control (2). Generally, this control is not used

above a setting of

"5" for vocalists, though higher settings

may be required for instruments. Separate Reverb Bass

(3)

and Treble controls

are provided for the reverb signal
only and are independent of the other tone controls on the
unit. These controls modify the reverberant signals in es-

sentially the same way the individual channel tone controls

modify the non-reverb, or "dry" tones. The reverb tone con­trols allow the user to change the reverberant sound to
compensate for the reverberation of each room in which
the system is used. In a

"boomy" sounding room, decrease
the Reverb Bass control or increase the Reverb Treble con­trol, or do both to equalize the reverb signals for the de-

sired sound.

(7)

The individual channel reverb In-Out switches

are
basically intended to allow the user the option of having
reverb on one or more channels while retaining a "dry"
(non-reverb) signal on the other channels. These switches

can also be used to perform a variety of other functions
which are described under Special Operating Instructions.

The Master Reverb In-Out switch allows instantaneous

reverb turn-on or shut-off, no matter how the individual

channel reverb selector switches are set. This feature al-

lows the user to "pre-program" the console for reverbera-

tion.

A phone jack marked "Reverb Switch" (16) is located on

the rear panel of the console. This jack parallels the Master

Reverb "In-Out" switch (4) and allows the reverb to be re­motely turned on and off when the Master Reverb switch is

"In" position. The Master Reverb switch will always

in the

override the remote switch and turn off the reverb, so care
should be taken to insure that the Master Reverb switch is

"In" position if an external remote switch is desired

in the

to control the reverb switching. If an external remote switch

is used, and is in the "Off" position, the Master Reverb

"ln-

Out" switch cannot override it and activate the reverb.

Since the remote switching is D.C., and no audio appears

on this jack, any length of unshielded cable can be used

between the Console and the remote switch without hum
or noise. The remote switch can be any single pole, single

throw switch.

VU

Meter:

The VU Meter measures the voltage on the "Speaker"

jacks and, with a given speaker load, indicates the Console

output power to that load. A 3 db increase indicates a

doubling of output power, while a 3 db decrease halves
output power. The VU Meter Sensitivity Switch increases

the sensitivity of the VU Meter by 14 db when set to the
"Lo" position. With the Sensitivity Switch in the "Lo" posi-

"0" VU on the meter corresponds to 4 volts on the

tion

"Speaker" jack, which is 2 watts with an 8-ohm load (two
VABOO-S Speakers). In the "Hi" position "0" VU corre-

sponds to 20 volts on the "Speaker" jack, which is 50 watts
with an 8-ohm load.

With an 8-ohm speaker load (two VA300-S) zero VU is
50 watts. Output power for other VU readings is shown in
the table below.

SENSITIVITY SWITCH IN "HI" POSITION

v u

+;

-3

-

7

-10 5 watts

SENSITIVITY SWITCH IN "LO" POSITION

vu

Power to 8-ohm

100 watts

50 watts
25 watts
10 watts

Power to 8-ohm load

4

2

1

0.4 watts

0.2 watts

watts
watts
watt

load

It should be noted that operation of the Console with
the meter reading into the red portion of the scale does not
indicate any type of overload. "Pinning" the meter, while
not a good practice, will not damage it. If the Console is
operated without a speaker load (nothing plugged into the
"Speaker" jacks) the VU meter readings are meaningless
because the Console is delivering zero power. Just disre­gard the meter readings if the Console is operated in this
manner.

Auxiliary Hi-Level Output:

A phone jack on the rear panel marked "Aux. Hi-Level
Output" is provided for connections to tape recorders for
making recordings, or to additional power amplifiers, such
as the Shure Power Master

PM300 Series. For specific in­structions for such connections, see the section marked
Special Operating Instructions.

The signal at this jack is the same signal that drives the

console power amplifier and is considered to be an auxil-

iary, high impedance output for driving high-level,

high-

impedance inputs. Note that all the Console controls, Mas-

ter Volume, Anti Feedback, Reverb, etc., affect this signal.

The interconnecting cable used with this jack should be
a low capacitance, single conductor, shielded cable (such
as Belden

#8401, #8410, #a41 1).

Limit the cable length to 15m (50 ft) to avoid loss of high

frequency signal and to reduce the possibility of hum

pickup.
Microphone Level Output:

A microphone level output connector is provided on the

rear panel of the Console. This connector is a professional

three-pin male audio connector (20). A "Lo Z-Hi Z" im-

pedance selector switch (19) is located above the output

connector. This screwdriver-slot, slide switch selects the

impedance of the microphone output. The signal at this
connector is the same signal (but at

mic, level) that drives
the Console power amplifier and is designed to work into an
amplifier or tape recorder microphone input. This output
is useful for providing a signal feed to a house P.A. system
for coverage in other rooms, or for low level fill in difficult
coverage areas of irregularly shaped rooms.

Z"

With the "Lo Z-Hi Z" switch in the "Lo

position the

microphone output connector is switched to a balanced

2

low impedance transformer; connector Pins
"hot" and Pin

1

is "ground." With the switch in the "Hi Z''

and 3 are

position the connector is sditched to provide a high impe-

3

dance output; connector Pin
"ground." See figure

MIC. OUTPUT MIC. OUTPUT

HIGH IMPEDANCE

MICROPHONE OUTPUT

FIGURE

4.

4.

Microphone

is "hot" and Pin 1 is

.

-

_-__--L

LOW

(BALANCED LINE)

PLUG

CONNECTIONS

Output Plug

Connections.

SHIELD-

,-

IMPEDANCE

If the low impedance output is to be used with an un­balanced input, such as an input that uses a phone plug
or other connector with only two connections, connect Pins
1 and 2 of the Console microphone output connector to­gether. Use this as the "ground" and connect Pin 3 as the

"hot."

It should be noted that the signal at this connector is

"out-of-phase" with the Microphone Inputs. See page

6,

lnput Connections, for information on phasing.

VA302

Series

Echo:

Echo may be introduced into the Console by using an

accessory echo device (such as an Echolette or Dynacord).

To use an external echo device in conjunction with the
Console, interconnect the two units as follows: attach low
capacitance, single conductor, shielded cable to the Con­sole jack marked Echo "To Input." Connect the opposite
end of this cable to the echo device jack marked "Input"
(Aux. High Level). Connect a similar cable to the echo de­vice jack marked "Output" (Aux. High Level) and connect
the opposite end of this cable to the Console jack marked

Echo "To Output."

Using the "Echo Gain" Control in conjunction with the

level controls on the echo

u.nit, the echo signal may be
balanced with the gain of the Console so there is no change
in level when the individual Reverb In-Out switches are

operated.

When connected in the manner described, the individual
channel Reverb In-Out switches will offer selective echo in
addition to selective internal reverb. With the Master Re­verb In-Out switch in the "Out" position, the individual

Vocal

TO CONSOLE
ECHQ "TO

PUT' JACK HIGH IMPEDANCE

Master

IN-

RESISTORS ARE 112 WATT

FIGURE

TO ECHO DEVICE

MICROPHONE
INPUT JACK

-

5.

10%

CARBON

channel Reverb switches will select "dry" (no echo) in the
"In" position and "Echo" in the "Out" position.

Changing the Master Reverb In-Out switch to the
position will permit selection of echo (individual channel
Reverb switch "Out") or reverb (individual channel Reverb
switch

"In").

The output signal of the Console at the jack marked
Echo "To Output" is considered high level and is suitable
for use with loads of 10 kilohms or greater. The jack marked
Echo "To Input" presents a 40 kilohm load to the source
and will accept high level signals. Some echo units employ

inputs suitable only for very low level; in such cases, a

"In"

resistance pad (attenuator) will be required in the line from
the Console to the echo device input. If the echo device in­put is suitable for only high impedance microphones a re-

sistive pad consisting of a 100 kilohm and a 3.3 kilohm re-

sistor is required. (See figure 5.) Almost all makes of echo
units use different output levels; these may generally be
compensated for by use of the gain controls on the echo
unit and the "Echo Gain" control on the Console.

Tape Recording:

Tape recordings of the Vocal Master output can be made
from either the "Microphone Level Output" or the "Auxil­iary Hi-Level Output" on the Console. To use the "Micro­phone Level Output" connect a cable from the Console to
the Microphone lnput on the tape recorder. Set the Con­sole "Lo 2-Hi

Z"

impedance selector switch to match the
impedance of microphones normally used with the tape
recorder. Use the "Lo
1000 ohms, and the "Hi

2" position for microphones up to

Z"

position for microphones 1000

ohms or greater impedance.

See the section on Microphone Level Output for wiring

instructions.

To use the "Auxiliary Hi-Level Output" on the Console,
connect a cable to the Auxiliary Hi-Level lnput on the tape
recorder. See the section on Auxiliary Hi-Level Output,
page 10, for cable length and type. For stereo tape record­ings see page 13, Stereo Operation.

Playing Tapes:

To play back tape recorded material through the Con­sole, connect a cable from the tape recorder's High Level
Output to the Echo "To Output" jack on the Console. Ad­just the Echo "Gain" control, the "Master Volume" control,
and the tape recorder playback level control for the desired
volume. Note that those lnput Channels on the Console that
are switched to Individual Reverb "Out" are now turned
off. See the section on Microphone Cuing on page 13.

Limit the cable length connected to this jack to 50 feet
of low capacitance, single conductor, shielded cable (such
as Belden

#8401, #8410, #8411)

to

avoid loss of high fre-

quency signal and to reduce the hum pickup.

An alternate method is to connect the high-level output

of the tape recorder to a three-pin professional plug ("hot"

lead to pin 3, shield to pin

I), and connect the plug to a
Shure Model A15LA Line lnput Attenuator. With the A15LA
connected to a Console microphone input, 50 dB of attenu­ation is provided at that input.

Still another method is to use a Shure A95 Series Line
Matching Transformer, with the auxiliary high-level tape
recorder output attached to the high-impedance end and
the low-impedance end attached to the Console micro­phone input. The Console Attenuator switch should be in
the

"In" position. NOTE: It may be necessary to add a
Shure A15A Attenuator to provide an additional 15 dB of
attenuation.

Musical Instruments:

Most electrified musical instruments may be amplified

through the Vocal Master with great effectiveness. Place

microphone in front of acoustical, nonelectrified instru-

ments, or in front of the instrument loudspeakers to "mike"
an instrument. As an alternate direct connections may be
used for instruments with a "pickup" or preamplifier output

(such as a guitar or keyboard instrument). Connections are

the same as for high impedance microphones, see page 11.

When the instruments play very loud, signals in excess
of the Console preamplifier clipping level may be encoun­tered, and produce distortion. Should this occur, switch
the input attenuator on that channel to the

"In" position

and adjust the channel volume control for the desired level.
See lnput Attenuator Switches, page 6.

High lmpedance Microphones:

High impedance microphones may be used with the
Console by adding accessory matching transformers
(Shure A95 Series) to the Inputs.

The Shure Model

A95U Line Matching Transformer is
terminated at the low impedance end with a professional
three-pin male audio connector for direct connection' to
the Console Inputs. The high impedance end of
former is supplied with an adapter to accept phone plugs.

Limit the high impedance cable length to 6m (20 ft) to avoid
loss of high frequency signal. If a longer cable is required
use approximately

3m (10 ft) of high impedance cable be-

tween the microphone and the matching transformer, and

add as much cable as is required between the transformer

and the Console Input.

Additional Inputs Using A Mixer:

If additional microphone inputs are required, a micro­phone mixer (such as a Shure M68 type) or a second Vocal
Master Console may be used.

When using a microphone mixer for the additional in-

puts, connect the mixer Lo lmpedance Mic. Output to one

of the lnput connectors on the Console. The individual in-

put control on the channel, bass, treble, volume, and re-

verb, provide master control over the mixer inputs. See

6.

Figure

FIGURE

6.

When reverb and external echo are not required, the

mixer may be connected to the Echo "To Output" jack.

With this arrangement the mixer Aux. High Level Output is

connected to the Console Echo "To Output" jack. See
Figure

7.

A

VA302 CONSOLE

a

I

'Current A95 Line Matching Transformers have a smaller diameter low

impedance end for direct
using older
the transformer and the Console "lnput."

A95A Line Matching Transformers connect a cable between

FIGURE

plug-ln connections to the "Inputs." When

7.

A95U Trans-

J

Adjust the Echo Gain control and the mixer volume con­trols to matcti the gain of the Console inputs. With the
mixer connected in this configuration the individual Reverb
In-Out switches on the Console should be set to the

"In"
position. When these switches are set to the "Out" posi­tion, that individual channel will be muted, or "cued." See
the description on "cuing." Still more inputs may be added
by stacking additional mixers onto the first mixer. See the
Mixer Operation Instructions.

Additional Inputs Using a Second Console:

A second Console may be used as a mixer to provide

additional inputs.

Connect an accessory line matching transformer, Shure

A95U, to the Echo "To Input" jack on the second

Model

Console. Connect a cable from the low impedance end of

the transformer to an lnput on the original Console and

set the lnput Attenuator on that input to the

"In" position.

See Figure 8.

PM300 Series Power Master amplifier and additional

use a
Speaker Columns. Generally two Speaker Columns should
be connected to each amplifier. See Figure 9.

SPEAKERS

SPEAKERS

FIGURE

8.

At this point it should be noted that the microphones on
the original Console are out of phase with those on the
second Console. If the microphone pickups for the two
Consoles are different sources, for instance the original
Console is a vocal pickup and the second an instrumental
pickup, this is not a problem.

For further information on Phasing see the section on

lnput Attenuator Switches on page

6.

With this arrangement, the power amplifier section on
the second Console is not being used. If additional power
and coverage are required, this power amplifier section
may also be used. See the section on additional power us­ing a second Console, Figure 10.

If it is necessary to use two Consoles on a permanent

basis a factory authorized COMMON MIX. BUS MODIFI-

CATION is available. Contact your Shure Dealer or the
Shure Factory for further information on this.

FIGURE

9.

To use the Power Master Amplifier, connect a cable from

the Console jack marked "Aux. Hi-Level Output" to an in-

put on the Power Master Amplifier. The cable used should
be limited to

tor, shielded type (such as Belden

Set the Volume Control on the Power Master to

15m (50 ft) of low capacitance, single conduc-

#8401, #8410, #8411).

"7"

to
obtain the same amplification level from both the Console
and the Power Master when identical speaker loads are
employed on each amplifier. The output of the Power Mas­ter will "follow" all control settings of the Console. Addi­tional Power Master Amplifiers may be added to the sys­tem by connecting a cable from the unused input jack on
the last Power Master to one of the input jacks on the next

9.

Power Master. See Figure

NOTE: The unused input jack
on the last Power Master in the "chain" can then be used
for tape recording. See the Special Operating Instructions
on Tape Recording.

To use a second Console in place of a Power Master to
obtain additional power, connect a cable from the original
Console jack marked

"Aux. Hi-Level Output" to the jack
marked Echo "To Output" on the second Console. See
Figure 10.

Additional Power or Area Coverage:

In those applications which require more power than one
Vocal Master system is able to deliver, such as very large
auditoriums and stadiums, and in those installations where
the audience is so widespread, such as

Theatre-in-the-

Round and for coverage in adjoining rooms or when more

than three speaker columns are required, it is advisable to

SPEAKERS

FIGURE

10.

Set the controls on the second Console as follows: Anti

Feedback'Switches to "Out," Master Reverb Switch "Out,"

Individual Volume Controls to

to

"5."

Adjust the Echo "Gain" Control to approximately

113 rotation from the

C.C.W.

"0," and the Master Volume

off position, and use this con­trol as a volume control to obtain the same amplification
level from both of the Consoles. Once the Echo "Gain"
Control is preset, the output of the second Console will

"follow" all control settings of the original Console. Small
changes in amplification level on the second Console can
be made by adjusting its Master Volume Control.

An additional Console,

PM300 or tape recorder can be

connected to the "Aux. Hi-Level Output" jack on the second

Console.
Microphone Cuing:

Microphone "cuing" may be preset by using the indi­vidual Reverb "In-Out" switches to reduce the volume of,
or turn off an unused individual microphone channel. This

is useful when it is desired to preset the individual volume

controls but only have one or two microphones "live" at a
time. This allows tighter control of feedback, or additional
control to avoid pickup from off-stage microphones.

Insert an unwired phone plug into the Echo "To Output"

Jack. With the individual Reverb switch in the

"In" position,
the channel will operate normally. In the "Out" position, the
channel level is reduced or turned off. The level of the
"Out" or "Cued" channel is controlled by the "Echo Gain"

control; turning this control fully counterclockwise turns
off the "Cued" channel. Returning the individual Reverb

"In-Out" switches to "In" restores the channel to the nor­mal level.

For remote "Cuing" on and off, plug a foot switch into

the Echo "To Output" Jack on the Console. Turn the "Echo

Gain" control fully clockwise. With the foot switch in the

"On" position, the channels will operate normally. With the

foot switch "Off" those channels switched to individual

Reverb "Out" are turned completely off. This is useful for
remotely turning on and off preselected channels (Micro-

phones). The cable used with the foot switch should be
limited to 15m (50

ft) of low capacitance, single conductor,

shielded type (such as

Belden #8401, #8410, #8411) to
avoid high frequency signal loss and to reduce the possi­bility of hum pickup in the cables.

Stereo Operation:*

Stereo operation may obviously be obtained by using two
Vocal Master systems without any interconnections. If it is
desired to have one of the microphones connected to both

"Y"

systems, simply use a
and feed its signal to one

connector on that microphone

Input on each Console. For mak­ing stereo tapes, the "Aux. Hi-Level Output" jacks, one on
each Console, may now be connected to the left and right

Auxiliary Inputs, respectively, on a stereo tape recorder.

Alternatively, stereo may be accomplished by using one

system and one Power Master with additional speakers.

A

connection is made from the Console jack marked Echo
"To Input" to an input of the Power Master. Those input
channels of the Console which are to be reproduced
through the Console speakers will require that the indi­vidual channel Reverb "In-Out" switches be in the

"In"
position. The channels on which the switches are in the
"Out" position will be heard at the speakers connected
to the Power Master. This may be used for a special echo

a

effect, like "throwing"

voice from the rear of the room.

Stereo recordings may also be made using one Vocal

Master Console and one Power Master. One channel of

the stereo tape recorder would be fed from the Console
jack marked "Aux. Hi-Level Output," the other channel
would be fed from the open input jack of the Power Master.

NOTE: Reverberation can be added to only those chan­nels that are being reproduced by the speakers connected

to the Vocal Master Console.

A very convenient way of recording with a stereo tape

recorder is to record the vocals on one tape channel and

the instruments on the other tape channel. Connect the

Console "Microphone Level Output" or the

"Aux. Hi-Level

Output" to the right channel of the tape recorder; see page

A

11 Tape Recording.

separate microphone is connected
to the left channel microphone input of the tape recorder;
an omni-directional microphone suspended from the ceil-

ing is recommended.

'As

a general rule stereo sound reinforcement of this type is quite dis-

tracting to listen to and is recommended only for special effects.

WPUT BASS& IND

-:-I

IN

-TREBLE CONT'L - VOLUME coNTL

OUT

ATTENLATOR

CJ'yLITCH

1508 ATTEN

,

INDIVIDUAL JACK SWITCH

REVERB SWITCH OPERATES WHEN

PLUG IS INSERTED

a

MIC

I

-

LEVEL

r

REVERB

BASS

TREBLE
CONTROLS

AUX

HIGH LEVEL OUTPUT

OUTPUT (HIGH/ LOW

,

MASTER

REVERB

SPRING

0

-

.

i~'.

REVERB

INTENSITY

CONTROL

-

I

v

U

METER

2)

VA302-C SERIES FUNCTIONAL DIAGRAM

'

TO SPEAKERS

FIGURE

VA302

Amplifier Service (See Guarantee):

The Vocal Master Console
est quality, operating well within their respective ratings to
assure long life.
parts inside. Refer servicing to qualified service personnel.

Amplifier Removal:

To remove the amplifier from its carrying case, remove
the three screws located at the top front

and the six screws, four within the plastic feet, on the Figure
bottom of the case. Push the amplifier slightly forward

CAUTION:

uses

There are no user serviceable

Series Vocal Master

the

high-

edge of the case

11.

from the back to permit access to the front panel. (Note:

Uncoil the cable before pushing the chassis. Push against
amplifier chassis not against the grille on the back,) The

entire
separated

Front Panel Removal:

To ease servicing of components on the front panel, re­move the four screws on the bottom rim of the front panel.
(Note: Stand amplifier on end with transformer side down.)

removed and tilted to a convenient servicing position.

amplifier

from

12,

Page

may

be

pulled

forward

the

case.

15,

shows the amplifier with the front panel

at

this

point

and

FIGURE 12.

Driver Transistors:

The driver transistors

Q33

and

Q34,

Figure

12,

Page

15,

are located on the amplifier chassis. Before removing these
transistors, write down the lead color and location at each
transistor solder junction. If replacing transistors, apply

120

type

Wakefield thermal joint compound to each side of
the insulation wafer to provide good thermal transfer from
transistor to chassis. After replacement and before con­necting transistor leads, check transistors with an ohm­meter between case and chassis; there should be no con­tinuity. Be sure that these transistors are not inverted in

Q33

17,

Page

is an NPN

21

for

the circuit; they are not identical devices.

Q34

transistor, while

is PNP transistor. Refer to the lower

right corner of the circuit diagram, Figure

terminal code. NOTE: when replacing driver transistors,
perform the following modification (if not already per-

a

3.3k,

Y2W

formed): solder

resistor across the terminals
to which the white and black leads of transformer T2 are
connected. Add a second ground wire from the terminal

nearest the front of the unit to which resistor R21 is con­nected, through the chassis grommet, to the ground on
the Speaker Output jacks (same path as existing wire).

Output Transistors:

The output transistors

15,

are located on the black finned heat sinks. Replace­ment procedure is the same for the driver transistors,
and

Q34.

NOTE: The output transistors,

matched for

current gain

Q35

through

Q38,

Figure

12,

Page

Q33

Q35

through

Q38,

must be

and part number. When replac­ing output transistors be sure to replace with devices which
have the same gain code as the original transistors. Shure
transistors are coded either by the last letter in the part
number or a color-dot on the top of the transistor.

Blue

Dot

=

Red

Orange

Yellow

Green

Dot

=

Dot

=

Dot

=

Dot = E

A

B

C

D

Brown

Pink

Violet

Black

White

Dot

=

Dot = G
Dot

=

Dot

=

Dot

=

F

H

J

K

FIGURE

13.

FIGURE

Small Signal and Predriver Transistors:

Transistors

(232, Figure 12, Page 15, are mechanically supported

and
by their leads. When replacing these transistors, it is im­perative that proper lead configuration be followed.
imum of soldering heat should be used to avoid damage to
the transistor. Refer to the lower right corner of the circuit
diagram, Figure

Diodes:

Diodes D6 and D7, see Figure 12, Page 15, are located
on the black finned heat sink with the output transistors.
Special care is required to insulate these diodes from the
heat sink while providing good thermal transfer from sink
to diode. Heat shrinkable tubing or "spaghetti" should be
placed over the diode and connecting leads; the diode
should be securely clamped to the heat sink with the clamp

..

Q1 through Q30, Figure 14, Page 16, and Q31

17,

Page 21, for lead code.

.

A

min-

14.

Check Transistors and Diodes:

Defective transistors and diodes may be located by use

of an ohmmeter. Polarity of the ohmmeter must be verified

before these checks are made.

With a known diode orientation, measure the diode re­sistance in the forward and reverse directions. The lowest
meter reading will establish the probe at the cathode end

(schematic symbol arrow points to cathode) as the "minus"
probe while the other probe will be "plus." Some ohm-

meters are not polarized in this manner with relation to

"volts plus probe" and "volts minus probe."

To check transistors, the ohmmeter should be set to the

100 ohm or 1,000 ohm scale. Small signal transistors
through Q32) must be removed from the circuit before
testing. Transistors mounted with screws (Q33 through

(238) may be tested in place; however, the leads to these

.

. .

rranslsrors rnusr De removea.

,

(Q1

If all conditions in the following table are met, the tran- Lamp Replacement:

may,be considered free of any gross defect; if any of

sistor
the following conditions are not met, the transistor should
be replaced. See lower right corner of circuit diagram,
Figure 17, Page 21, for transistor terminal code.

OHMMETER CONNECTIONS

"Plus" "Minus"

Lead

Collector Emitter
Emitter Collector
Collector Base
Emitter Base
Base Collector
Base Emitter

Lead

OHMMETER READING

N.P.N. P. N.P.

Transistor Transistor

High High
High High
High Low

-

Low High
Low

Low

-

With the ohmmeter "plus" probe on the anode end of a

diode, and the

"minus" probe on the cathode end, the ohm­meter should read approximately 2000 ohms or less. With
the meter probes reversed, a reading of about 10,000 ohms
or more should occur. If either of these conditions is not
met, the diode should be replaced.

Power Drain Resistor

(R,,,):

The two lamps I2 and
vide illumination of the front panel controls are 115 to 125
volt, 15 watt incandescent bulbs. These bulbs are soldered
and epoxied into the molded plastic sockets in order to
meet Underwriters' Laboratories requirements. The assem­bly may be removed by unsoldering the lamp leads at the

terminal strips and removing the screw that holds the
socket to the chassis.

Reverberation Assembly:

The Reverberation Assembly M2, Figure 13, Page 16,

may be removed and returned to the factory Service De-

partment for repair if a malfunction should occur. The am­plifier can be operated without this assembly. To eliminate
possible damage, or shock hazard, the plug-in cables

should be temporarily inserted in the nylon inserts nor­mally used to mount this sub-assembly. If extensive dam­age has occurred, a replacement Reverberation Assembly

may be ordered through the dealer or from the factory

Service Department.

The following condition may occur after replacement
of driver transistors
through Q38, or diodes D6 and D7. If the unit appears to
operate at an excessively high temperature or thermally
recycles after about 10 minutes with no signal input, the
"cold" standby power drain may be excessive (up to 20
watts higher than normal; a higher power drain indicates
further circuitry problems). The nominal power drain
under these conditions should be 60 watts; if the meas­ured figure exceeds 75 watts, insert a resistor
parallel with the 56-ohm resistor between the base of
transistor

Q33 and the junction of diodes D6 and D8
(figure 17, page 21).
180 ohms to decrease the power consumption by 20
watts, or 82 ohms to decrease the power consumption

by 30 watts.

Q33 and Q34, output transistors Q35

(R,,,,) in

RsEL (1/2W, 10%) should be either

Replacement Parts:

Parts that are readily available through local electronic
parts distributors are not shown on the accompanying
Parts List. Their values are shown on the circuit diagram.

The special custom made parts are shown on the Parts

List.

The commercial alternates shown on the Parts List are

not necessarily equivalents, but may be used in the event

that direct factory replacements are not immediately avail­able. To maintain the highest possible performance and
reliability, Shure factory replacement parts should be used.
When ordering replacement parts, specify the Shure Re-

placement Kit Number, description, product model number

and serial number.

13,

Figure 12, Page 15, which pro-

EQUIPMENT DESIGNED

FOR USE

WITH

THE VOCAL MASTER

VA302 CONSOLE SERIES

VA300-S Vocal Master Speaker Column
VA301-S Vocal Master Monitor Speaker
PM300 Power Master Booster Amplifier
PM3OOE Power Master Booster Amplifier

PM300E6 Power Master Booster Amplifier
A3PC Soft Cover Set
A3PC-C Console Soft Cover
A3PC-S Speaker Column Soft Cover

A31PC-S Monitor Speaker Soft Cover

ASS-C Fold-Up Console Stand
A3S-S Speaker Stand
A3S-T Speaker Stand
A50XC 15m (50 ft) Speaker Extension Cable
A95 Series Line Matching Transformers

GUARANTEE: This Shure product is guaranteed in normal use to
be free from electrical and mechanical defects for a period of one
year from the date of purchase. Please retain proof of purchase
date. This guarantee includes all parts and labor.

SHIPPING INSTRUCTIONS: Carefully repack the unit and return

it prepaid to the factory. If outside the United States, return the

unit to your authorized Shure Service Center for repair. The unit

will be returned to you prepaid.
SERVICE: If information or service should be required, contact

your local Shure Vocal Master dealer explaining your difficulty
in detail. In addition, the Shure factory service department will
be ready to assist you immediately upon request.

VA300-S Speaker Servicing:

1. Unplug cables from speaker jacks.

2. Using an ohmmeter, measure the resistance of the
speaker column. The resistance should be between

12

and 16 ohms. Readings outside of these limits

indicate possible failure.

3.

Remove back of cabinet.

4.

Disconnect one end of the lead connected

between

the two 10 inch loudspeakers.

5.

Using an ohmmeter, measure resistance of the voice­coil of each loudspeaker individually. Each 10 inch
speaker should measure between 12 and 16 ohms.

8

Each

8

inch speaker should measure between 5 and

ohms. Readings outside of these limits indicate

possible failure.

Hz,

6. Apply 60

1 to 10 volts, to each of the six speak-

ers individually. Any buzzes or rattles indicate pos-

sible failure. The speakers should all sound gener-

ally alike with a slight difference between the

8

and 10 inch loudspeakers.

7.

Reconnect lead disconnected in Step

of

cabinet tightly.

4.

Install back

inch

COLOR CODED TERMINAL

FIGURE

m

15.

REPLACEMENT PARTS LIST FOR

VASOO-S

QTY. PART NO.

'Recommended replacement cable connectors (not available from factory.

Switchcraft part numbers given:) Straight Locking Plug:
Lockin

Plug:

bly):

$123.

#228; Locking Extension Jack (for Extension cable Assern-

SPEAKER COLUMN

REPLACEMENT KIT CONSISTS OF

DESCRIPTION

1

80A207
1 80A208
1 90A1375
1 946462
1 90A1373
1 95A436

4

65A1001A

-

39A279

-

48A20

8

Inch Loudspeaker

Inch Loudspeaker

10
Rear Panel Assembly
Column Cabinet
Cable and Plug Assembly
Handle Assembly
Bumper (Plastic Foot)
Name Plate
Side Rail

$282

Right ~n~l;

FIGURE

16.

REPLACEMENT PARTS LIST FOR VA302-C SERIES CONSOLES

.

.

REPL.

I

ITP.

R1-R6, R14 RKC58 46A017 Potentiometer, Dual 50K/50K NONE

R7-R12,

I

Rl6

1

T2

T3-T9

NOTE:

The Commercial Alternates shown above are not necessarily equivalents but may be used in the event that direct factory replacements are not immediately
available. To maintain the highest possible performance and reliability, Shure Factory Replacement Parts should be used.

'When ordering

"Parts listed as RKC

+For gray switch order

KIT NO.

I

/

RKC59
RKC57

RKC6O

---

--

---

RKC47
RKC61

---

RKC37
RKClO
RKC44t
RKC43
RKC42
RKC41
RKC40

---

---

RKC35 51A215 Power Transformer (VA302 only)

1

RKCl47
RKC28

RKC84

86A332 or 868332, specify current gain code. See Page 15.

Kit8 should be ordered by that kit number.

Part

No. 55A73F.

QTY.

1

1

1

1

REPLACEMENT KIT CONSISTS OF:

1

PART NO.

1

46A016 Potentiometer, 50K.

1

51A241

51A217
90H2150

I

A.C. Chassis Power Connector
Cabinet Upper Side Rail

Cabinet Lower
Transistor (Replaces

Transistor

Toggle Switch
Thermostat

Slide Switch (Screw Slot)
Rocker Switch, Chrome

Rocker Switch, Orange
Rocker Switch, Yellow

Slide Switch, Black
Voltage-Selector Switch

Power Transformer

1

Any

orden received for plece parts where RKC Kit number is shown will be shlpped In RKC quantities.

DESCRIPTION

Capacitor, 2500 x 100
Capacitor, 4000
Silicon Rectifier,
Zener Diode,
Silicon Rectifier, 100 V., %A.
Zener Diode, 3.6 V., 1
Germanium Diode
Silicon Diode, 50 V.,
A.C. Fuse (VA302 and VA302E)
A.C. Fuse (VA302E6 only)

for 200-240 volts

A.C. Fuse
D.C. Fuse (VA302 and VA302E)

D.C. Fuse (VA302E6 only)
Wired in A.C. Fuse (VA302 only)

Pilot Lamp
Pilot Lamp
Lamp Assembly
Connector, Mic. Input
Phone Jack
Phone Jack
Phone Jack
Connector Mic. Output
3 Wire A.C. Line Cord and Plug

Line Cord

Line Cord and Connector
Reverberation Assembly

Anti Feedback Inductor Assembly
VU Meter
Handle Assembly
Console Cabinet
Volume Control Knob Assembly
Treble Control Knob Assembly
Bass Control Knob
Knob and Screw (Line Cord

Shield
Bumper (Plastic Foot)
Fuse Holder
Fuse Holder (Screw Slot,

Fuse Holder (5 x

Transistor 110 V.
Transistor 110 V.
Transistor 105 V.
(Mutually Interchangeable)
Transistor 110 V.

Potentiometer, 50K.
Potentiometer,
Resistor. .43 ohms, 5 W.

Resistor, .20 ohms, 5W.
Resistor,
Resistor
Toggle Switch

Rocker Switch,
Rocker Switch,

Feedback Transformer
Mic. Transformer Assy.

(VA302E6 only)

for 100-140

(VA302 only)

(VA302E only)

(VA302E6 only)

Storage Spindle)

VA302E only)

(VA302E6 only)

.l2 ohms, 5

(2 position

(VA302E6 only)

PM300E6)

x

60

3A., 200 V.

22V,, 1 W.,

volts

(VA302 only)
(VA302E and VA302E6)

(VA302 only)

VA302E6 only)

.

5%

W., 5%

'/PA.

20mm VA302E6 only)

Side Rail

86A327)

BVceo Min.
BVCEO Min.
BVcxo Min.

BVcco Min.,

2.5K.

W.

(VA302 and VA302E)

Redlorange

Orange/Yellow

(PMSOOE and

COMMERCIAL ALTERNATE

NONE
NONE

Motorola No. 1
Motorola No. 1N4748A
Motorola No. IN4002
Motorola No. 1 N4729A
Sylvania No. 1 N48, IN60
Motorola No. 1 N4001
Littelfuse 3AG/3A/SB (Slo-Bio)
5

x

20mm, 1.6 AT, 250 V.
5 x 20mm, 3.0 AT, 250 V.
Littelfuse 3AGl5A

5

x

20mm, 5.0 A, 250 V.
Bussmann

Pig-tail
Leecraft No. 36N1311-6
Leecraft No. 36HN-1311-7W
NONE
Switchcraft No. C3F
Switchcraft No. 12-A
Switchcraft No.
Switchcraft No. 11
Switchcraft No. C3M
NONE

NONE
NONE

Gibbs No. 4L (Insulated Output)
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE

NONE
Littelfuse No. 342014
Littelfuse No. 341001

SchurterType FEB
Switchcraft No.

NONE
NONE
Motorola No. MPS-6521

Texas

Motorola No. MPS-3392
RCA No. 40349
RCA No.
Motorola No. 2N3741 Selected

RCA No.

1

NONE
NONE

NONE
NONE

NONE
NONE
Workman No. FRT-2
Cutler-Hammer No.
Marquardt Type No. 0132

NONE
Continental-Wirt No. G-326
NONE
NONE
NONE
NONE
NONE
NONE

NONE

NONE

1

NONE
NONE

NONE

N4721

MDVI5AISB (Slo-Blo)

14-8

EAC-301

Inst. No. 2N3711

2N3441

2N3773

7563K5

I

19

Notes

to

Circuit Diagram

D.C. Voltage Measurements:

Check the DC voltages first, because any deviation from
the nominal voltages will affect the AC voltage. In the power
amplifier, Q31 to Q38, the key DC voltages are
lector of Q33, 035, and Q37), -22 (collector of Q31),
and the split voltage at the junction of R17, R19, R20, and
R22. If these three key DC voltages are correct, then pro­ceed with the AC voltage measurements.

The numbers within the symbols
gram denote the D.C. voltage at that point with the follow­ing test conditions:

1. Voltages measured at points indicated with respect to
chassis, unless otherwise indicated.

-

2. Line voltage

3. No input signal applied.

4. D.C. voltage measurements may vary
values shown.

5. Measured with a VTVM of

dance.

6. Q27 transistor voltages on the circuit diagram are with

the master reverb switch in the "IN" position. With the

master reverb switch in the "OUT" position, Q27 volt­ages are: emitter 4.0, base 0.0, and collector 22.0.

A.C.

Voltage Measurements:

The numbers within the symbols
gram denote the A.C. voltage at that point with the follow­ing test conditions:

1. Voltages measured at points indicated with respect to
chassis, unless otherwise specified.

2. Line voltage

3. 1,000

4.

5.

6. Echo input and output jacks to be open; echo gain

7. All anti feedback switches set to "OUT" position.

8. Reverb intensity set to minimum.

9.

10. All volume controls set to maximum.

11. Master reverb switch set to

12. Individual channel reverb switches set to

Hz.

0.8 millivolts.
Measured with an A.C. VTVM of 1.0 megohms or

greater input impedance.

Noninductive load of 8 ohms, 200 watts connected to

speaker output jack for Q31 through Q38.

control set to maximum.

All tone controls set to 12 o'clock position.

noted.
tion except where noted.

VA302-C: 120v. 60
VA302E-C: 120/240~. 50/60 HZ.
VA302E6-C: 100, 120, 140, 200, 220, or
240v. 50/60

-

as specified above.

signal applied to input,

o

on the circuit dia-

Hz.

Hz.

11-megohms input impe-

on the circuit dia-

in

"OUT"

position except as

94 (col-

&20% from the

"IN" position, at

"OUT"

posi-

13. Transistor voltage measurements for Q20 through Q27
must be made with master reverb switch and individual
channel reverb switches in the "IN" position.

14.

A.C. voltage measurements may vary ?:50°h from the
values shown.

15.

For A.C. measurements on Q25, Q26, and Q27, the

t100

Hz.

frequency may be varied
measurements shown.

16. For VU Meter specifications, see page

Ohmmeter Measurements:

With the A.C. line cord unplugged and the power switch
in the "OFF" position, the following ohmmeter measure­ments may be made:

1. Reverberation Assembly M2 input and output coils
approximately 180 ohms.

2. Anti feedback Inductors M3 approximately 300 ohms.

3.

B-

to ground approximately 50 ohms

4. Ohmmeter plus probe to the junction of R17,

and R22, ohmmeter minus probe to ground: greater
than 100 ohms.

5.

Ohmmeter plus probe to

to the junction of R17,

100 ohms.

6.

To test transistors and diodes, see page 16.

Shure part numbers are not shown in the parts list ac­companying the circuit diagram if parts are readily avail­able through local electronic parts supply distributors. In
these instances, the circuit diagram will show the value of
the standard parts.

All capacitor values are shown in microfarads. All
electrolytic capacitors are to be 100 volts or more unless
otherwise specified in the circuit diagram. Electrolytic ca­pacitors are shown in microfarads and volts.

All resistor values are shown in ohms. Resistors are all
to be 10% tolerance unless specifically noted on the cir­cuit diagram.

Resistors shown in the upper two lines of circuitry on the
diagram are
shown in the lower line of circuitry are
wise specified.

The following ground symbols denote:

Chassis
Ground

Preamplifier

Ground

Reverb
Driver Ground

'/4 watt unless otherwise specified. Resistors

1

-

-

BI,

R19, R20, and R22: greater than

to obtain the A.C.

9.

R19, R20,

ohmmeter minus probe

non-

l/2

watt unless other-

I

VA302-C CIRCUIT DIAGRAM

I

FIGURE

17.

VA302E-C POWER SUPPLY CIRCUIT DIAGRAM

Eil(-

THERMAL

VA302E6-C POWER SUPPLY CIRCUIT DIAGRAM

OVERLOAD

FIGURE

GRWBLK. RED

BLACK

600

RED/BLK.

I

I

YEL./BLK.

TI BLUE

ii

GRN./BLK. RED

S

I

18.

120 VOLT POWER

SUPPLY WIRING

240 VOLT POWER

SUPPLY WIRING

200- 240 VOLT

100-

140

VOL

CHASSIS

POWER

5

4 I

100

V. POSITION 120 V. POSITION

1.6

AT

240

V.

POSITION

S

I

7'

4

'2

I 4 I

140 V. POSITION

4

200 V. POSITION 220 V. POSITION

I

TI

4

I

VOLTAGE SWITCHING POSITIONS

I

FIGURE

19.

22