Shure VA302 SERIES Service manual

VA302 SERIES
@hfd(>M&fih
OPERATING AND SERVICE MANUAL
Manufactured by
SHURE BROTHERS
INC.
222 HartreyAvenue
Evanston, Illinois60204 U.S.A.
Copyright 1978, Shure Brothers Inc.
AL406 (RE) 27A818 Printed in
U.S.A.

VA302 Series Vocal Master
SPECIFICATIONS
VA302 Series Console
Amplifier Type
................................... .All silicon transistor mixer/power amplifier
Power Output
........... .I00 watts continuous '(RMs); (to 8 ohm load, see Figure 3, Page 7)
Voltage Gain ..................................... .80 db Input Attenuator "Out" (8 ohm load)
65 db lnputAttenuator "In" (8 ohm load)
Frequency Response
..................................... k2 db 40 Hz. to 20,000 Hz. (typical)
Input Impedance
......... .320 ohms lnput Attenuator "Out"
500 ohms lnput Attenuator "In"
Distortion ........................................... .5% maximum at rated output at 1 KHz.
Hum and Noise .................................................. .60 db below rated output
Speaker Load lmpedance Nominal
8 ohms; operational 5.3 ohms minimum
(See Figure
3, Page 7)
Input Clipping Level ............................. .Greater than 25 Mv. Input Attenuator "Out"
Greater than
150 Mv. lnput Attenuator "In"
Bass Control Action ............................ t13 db at 100 Hz. with respect to "flat" setting
........................
Treble Control Action i10 db at 10,000 Hz. with respect to "flat" setting
"Aux. Hi-Level" Output Jack ................Impedance
5,000 ohms; Output 19 db below speaker
output (to8 ohm load); nominal - 2 V at 50 watts to speakers, Clipping Level 4 V.
"Mic. Level" Output .............Hi-Z: impedance 1,000 ohms; Output 30 db below auxiliary output;
nominal
60 Mv.Clipping Level 120 Mv.
Lo-Z: impedance
36 ohms; Output 52 dbbelowauxiliary output;
nominal
5 Mv. Clipping Level 10 Mv.
Echo-"To Input" Jack (Output To External Echo Unit)
.................. .Impedance 10,000 ohms;
Output 20 db abovemicrophone inputs with individualvolumes at "10"; Clipping Level 3 V.
Echo-"To Output" Jack (Input From External Echo Unit)
................. Impedance 40,000 ohms;
Sensitivity
200 Mv.for rated amplifier output with "Echo Gain" Control and
"Master Volume" Controlat maximumsettings; Clipping Level
2 V. with maximum
setting of "Echo Gain" control. Clipping level increases with reduced
setting of "Echo Gain" control.
"Reverb Switch" Jack
.................... D.C. switching (no audio), parallels the Master Reverb
In-Out Switch. Any cable with a resistance of less
than
5,000 ohms may be used.
......
Center Notch Frequenciesof "Anti-Feedback" Filters
. Filter "A" 5,000 Hz.
Filter "B" 2,200 Hz.
Filter "C" 1,000 Hz.
Filter "D" 155 Hz.

Console (Continued)
..................................................
power Supply: VA302-C ,120 volts, 60 HZ.
VA302E-C ........................................... 120/240 volts, 50160 HZ.
Factory wired for 240 volt operation.
VA302E6-C ......................... ,100, 120,140,200, 220, 240 volts, 50160 Hz.
Switch selectable.
....................................
Power Consumption .80watts maximum with no signal in.
180 watts with
1 KHz. signal and 100 watts output,
400 watts maximumoperating
Ambient Temperature Range
................. -7°C. to 43°C. (20" F. to 11O0F.)without derating
Dimensions
................................. 213 mm height x 635 mm width x 375 mm depth
(8% in.
x 25 in. x 14% in.)
........................................................
Weight: VA302-C 18.6 kg (41 Ib)
.........................................
VA302E-C and VA302E6-C .19.05
kg (42 Ib)
VA300-S Speaker Column
Power Rating
................................................................. .I00 watts
Impedance
..................................................................... 16 ohms
Frequency Response
.................................................. 50 Hz. to 10,000 Hz.
Horizontal Distribution
.............................................................. 140'
Vertical Distribution ................................................................. 65'
...............................
Dimensions 1594 mm height x 400 mm width x 222 mm depth
(62% in. x 15% in.
x 8% in.)
Weight..
................................................. 31.78 kg (70 Ib) including cable
The Shure Model VA302 Vocal Master Sound System
consists of one Control Console (VA302-C) and two
Speaker Columns (VA300-S).
The Shure Model VA302E Vocal Master Sound System
consists of one Control Console (VA302E-C) and two
Speaker Columns (VA300-S).
The Shure Model VA302E6 Vocal Master Sound System
consists of one Control Console (VA302E6-C) and two
Speaker Columns (VA300-S).
Designed specifically for the performing vocalist, the
Vocal Master Sound System provides the required porta-
bility, flexibility, and dependability demanded by profes-
sional entertainers.
The mixerlpower amplifier Control Console permits 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 compo-
nents against damage as a possible result of open-circuit
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.
The VA300-S employs four special 8-inch loudspeakers
and two special 10-inch loudspeakers providing a total
cone area of 2,310 cm2(358 in2).
EachSpeaker Column is furnishedwith a 15m (50ft), #I8
gauge, 2-conductor rubber jacketed cable with locking
phone plugs attached.
\

FIGURE 1.
6, Individual Channel "Treble & Bass" Controls
Front Panel Controls (Refer to Figure 1) (Six, Dual Concentric).
1. "Anti Feedback" Switches (Four).
7. Individual Channel "Reverb" Switches (Six).
2. "Reverb Intensity" Control. 8. "Master Volume" Control.
3. "Reverb Treble
& Bass" Controls (Dual Concentric). 9. "On-Off-On" Power Switch.
4. "Master Reverb" Switch. 10. V.U. Meter "Hi/Lo" Sensitivity Switch.
5. Individual Channel "Volume" Controls (Six). 11. V.U. Meter.
I 1
FIGURE 2.
Rear Panel Controls and Connections (Refer to Figure2)
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" ImpedanceSwitchfor Microphone Output
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.
24. "ln/Out" lnput Attenuator Switches (Six).
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).

GeneralOperating Instructions:
1. Set all front panel controls inthe following manner: All
switches (I), (4), (7), set to "Out" position; "Reverb
Intensity" Control (2), and all "Volume" Controls (5)
and (8),set at "0"; all "Treble" and "Bass" Controls (3)
and (6), set in the "flat response" position (indicator
ribs at 12:OO o'clock); "On-Off-On" Switch (9) set in
the "Off" position; "Hi-Lo" Sensitivity Switch (10) in
the "Hi" position.
2. Unwrap the A.C. line cord (12) from the storage spin-
dles (11); plug line cord into an outlet. The VA302-C is
designed to operate from outlets supplying 110 to 130
volts, 60 Hz. The VA302E-C is wired at the factory to
operate from outlets supplying 220 to 260 volts, 50 to
60
Hz. A simple wiring change allows the VA302E-C to
operate on 110 to 130 volts, 50 to 60 Hz. See page 8
for instructions. The VA302E6-C is designed to oper-
ate from outlets supplying 100, 120, 140, 200, 220, or
240 volts, 50 to 60 Hz. as selected by an integral volt-
age-selector switch. See page 8for instructions.
3. Removethe speaker cables from the storage compart-
ments in the VA3OO-S Speaker Columns. Insert and
lockthe rightangle phone plug onthe 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 lock-
ing 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, #18 gauge unshielded cable. Since
each Speaker Column hasa pairof parallel-wired input
jacks, an alternate speaker hook-up would be to con-
necta speaker cable from the Console to one Speaker
Column and then connect a second cable from this
Speaker Column to the second Speaker Column.
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 micro-
phone. For high impedance microphonessee 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. Turnon the Power Switch (9)locatedonthefront panel
of the Console. Set the "Master Volume" Control (8)to
"5." While talking or singing into one of the micro-
phones 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.
7. Nowturn upthe other lndividual Channel Volume Con-
trols (5) which are being used. By use of the individual
Channel Volume Controls (5), the microphonesmay be
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 Con-
sole.
8. Note the action of the IndividualTreble and Bass Con-
trols
(61; these controls are of the dual concentric
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 (12:OO o'clock position) to pro-
vide a normal "flat" frequency response. All Treble
and Bass Controls on the Console operate inthe 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.
9. Turn the Reverb Intensity Control
(2) to a setting of
"4." Set the Master Reverb switch (4) to the "In" posi-
tion. Reverberation may now be selectively added to
any of the six channels by setting the Individual Chan-
nel Reverb switches
(7) to the "In" position. Note that
different settings of the Reverb Intensity Control (2)
will not affect the overall system gain. Generally a set-
ting of "1" to
"4" of the Reverb lntensity Control (2) is
adequatefor vocals. The ReverbTreble and Bass Con-
trols (3) operate in the same manner as those of the
individual channel Treble and Bass Controls but pro-
vide independent tonal balance of the reverberant sig-
nal 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 decreas-
ing Treble and increasing Bass will approximate the
sound of a plate-type reverberation device.
10. Set all four Anti Feedback switches (1) to the "Out"
position.These switches can help eliminate feedback.
Each switch cuts out part of the critical feedback-
generating frequencies. See page 8 for a detailed de-
scription on how to effectively use them.
11. The Master Volume Control (8) will raise or lower the
volume of all channels simultaneously without affect-
ing the "balance," or "mix." NOTE: With the Console
driven at or near fullpower, pilot lamps will dim or vary
in brightness;this is a normal condition.
12. For most applications set the V.U. Meter Sensitivity
Switch (10)to the "Hi" position.With an 8-ohmspeaker
load (two VA3OO-S), a reading of 0 db indicates 50
watts output. With the Sensitivity Switch set to the
"Lo" position, a reading of 0 db indicates
2 watts out-
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 in-
formation on the V.U. Meter, see page 9.

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 de-
signed to operate with any highquality dynamic or ribbon-
type low impedancemicrophone.
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 Bel-
den #8412, #8422). When wiring professional 3-pin audio
connectors, the cable shield should be connected to Pin
No.
1 andone of the two conductors to Pin No. 2, the other
conductor. to Pin No. 3. When using several microphones,
consistency of cable wiring should be followed to insure
that all microphonesare "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 col-
umn 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"
witheach other.
For highimpedance microphones, see page 11.
For additional microphone inputs, connections from
electrified musical instruments, and connections to play
back a tape, see page 11.
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 "In" position, the sig-
nal from the microphone is attenuated by 15db before en-
tering the preamplifier.
This feature may be useful when working the micro-
phones very close to the performer's lips as with "hard
rock" vocalists, who may produce signals in excess of
the clipping levelof the preamplifiers; in such an instance,
the attenuator will generally eliminate the distortion which
would otherwise occur.
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 dam-
age to the speakers or amplifier will occur, but thermal
shutoff of theamplifier (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: Do not interconnect the speaker output
jacks or the speaker cables betweentwo Vocal Master
Amplifiers or the Vocal Master and any other ampli-
fier. This may result in damage to one or both ampli-
fiers, 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 prac-
tices consistent with those used for 25-volt speaker lines.
Up to 30m (100 ft) of #18 gauge two-conductor cable
(suchas Belden #8452,8478,8460, or 8461) may be used to
connect from the Console to each 16-ohm (VA3OO-S)
speaker. Greater cable lengths require heavier gauge wire
to avoid appreciable power loss in the speaker cable. For
30 to 51m (100to 170 ft), use #16 gauge; 51 to 81m (170 to
270 ft), use #f4 gauge; and 81 to 128m (270 to 425 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.
Speakers:
Selection of speakers for use in a vocal music system is
most critical. The factors which most significantly con-
tribute 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
COIU~~
utilizes two special 10-inch speakers and four special 8-
inch speakers, and has a total speaker cone area of 2,310
cm2(358in2)per column. The VA300-S Speaker Column de-
liversvirtually uniform penetratingpower over a 140" angle
inthe horizontal plane and a 65" angle inthe 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 primar-
ily 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
of the VA3OO-S. The nominal impedance of the VA3Ol-S is
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.

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 -S
6 VA301-S
1 VA300-S and 1 VA301-S
1 VA300-S and 2 VA301-S
1 VA3OO-S and 3 VA301 -S
1 VA300-S and 4 VA301-S
2 VA3OO-S and 1VA301-S
2 VA3OO-S and 2 VA301-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
4 5678910 15 20 30 40
IMPEDANCE (OHMS)
FIGURE 3. Typical output power vs. speaker load impedance for
the Vocal Master Console.
ColumnSpeaker 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 micro-
phone 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 de-
cided upon in order to reduce lowfrequency acoustic feed-
back and provide a relatively "dead" area at the sides of
the columnwith 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 mindthat 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 generaliza-
tions 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 necessi-
tate 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 bal-
cony, use the Shure Model A3S-S or A3S-T Speaker Stand.
The A3S-S stand will provide added stability and approxi-
mately 15O of tilt. The A3S-T stand provides adjustable tilt
of up to 30'. In an emergency, a spare microphone 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 micro-
phone 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 ~~302-6Vocal Master isfurnished 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 mini-
mum 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 three-
conductor power cable without a plug. To connect a plug
to the power cable, attach the brown lead to the live
(f)
terminal of the plug, attach the blue lead to the neutral (-)
terminal of the plug, and attach the green-yellow lead to
the earth-ground terminal of the plug.
The VA302E-C is factory wired for operation from a nom-
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 linepolarityfor minimum hum. If extension cords
are required to supply power to the VA302E, a high quality
cable with conductors of 0.75 square millimeters cross-
section or larger should be used.
An internal modification performed by competent per-
sonnel will allow the VA302E to be used with 120 volt, 50
to
60 Hz power.To change the power supply wiring for 120
volt operation, do the following:
1. UNPLUG THE AMPLIFIER POWER (MAINS) CABLE.
2. Remove the amplifier from its carrying case as de-
scribed 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.
6. Resolder the red-black lead wire to the solder-lug to
which the green-black transformer lead wire is al-
ready 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 re-
install. The nameplate nomenclature will now be suit-
able 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 detach-
able three-conductor A.C. power (mains) cable without a
connector on the "mains" end. To attach a connector, con-
nectthe brown conductor of the cable to the "live" terminal
of the connector, the blue conductor to the "neutral" ter-
minal, and the green-yellow conductor to the "earth"
(+)
terminal.
The VA302E6-C is designed to operate from 100, 120,
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 slow-
blow type (3.0 AT). The fuseholder located farthest from
the voltage-selector switch containsa 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 returnAC
power when the heat-sink temperature reduces to 73°C.
(164OF.). A thermal overload light (15), located on the rear
panel,will indicate ifthermal 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 short-
circuit 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 connec-
tions.
Anti Feedback Switches:
Acoustic feedback (a howl or squeal in the speakers)
may occur, depending on room acoustics and the physical
placement of microphones inrelationtothe speakers, when
volume is increased or when Bass or Treble controls are
boosted. To minimize feedback, four Anti Feedback
switches
(1) are incorporated in the Console. These
switches operate four "notch filters" which modify the fre-
quency response of the unit. Each switch controls part of
the audio spectrum. The top switch (A-yellow colored) fil-
ters 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
exception
of 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 simultane-
ously; 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 electro-
mechanical spring-type reverberation device utilizing a
total of four coil springs in two transmission paths. Re-
verberation is accomplished by driving the input ends of
the springs in a torsional mode and transferring the tor-
sional 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 electro-
mechanical device, it is sensitive to mechanical shock. It
is recommended that if the console is moved while operat-
ing,the Master Reverb In-Outswitch (4) be set to the "Out"
position. Thiswill avoid the possibilityof 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 importanceto 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 artifi-
cial reverberation, as the intensity of the reverberant signal
is increased,thetotal gain also increases;this usually leads
to acousticfeedback. The reverb mixingsystem used inthe
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
and Treble controls
(3) 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
modifythe non-reverb, or "dry" tones.The reverb tone con-
trols allow the user to change the reverberant sound to
compensate for the reverberation of each room in which
the system is used. Ina "boomy" sounding room,decrease
the Reverb Bass control or increase the Reverb Treble con-
trol, or do both to equalize the reverb signals for the de-
sired sound.
The individual channel reverb In-Out switches
(7) 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 phonejack 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 re-
motely turned on and off when the Master Reverb switch is
in the "In" position. The Master Reverb switch will always
override the remoteswitch and turn off the reverb, so care
should be taken to insure that the Master Reverb switch is
in the "In" position if an external remote switch is desired
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.
Sincethe remoteswitching 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, indicatesthe 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-
tion "0" VU on the meter corresponds to 4 volts on the
"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
vu
Power to 8-ohm load
+;
100 watts
50 watts
-3 25 watts
- 7 10watts
-10 5 watts
SENSITIVITY SWITCH IN "LO" POSITION
vu Power to 8-ohm load
4 watts
2 watts
1 watt
0.4 watts
0.2 watts

It should be noted that operation of the Console with
the meter reading into the red portion of the scale doesnot
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 disre-
gard 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 in-
structions 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. Notethat 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 isdesigned to work intoan
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
coverageareasof irregularlyshaped rooms.
With the "Lo Z-Hi Z" switch in the "Lo
Z" position the
microphone output connector is switched to a balanced
low impedance transformer; connector Pins
2 and 3 are
"hot" and Pin
1 is "ground." With the switch in the "Hi Z''
position the connector is sditched to provide a high impe-
dance output; connector Pin
3 is "hot" and Pin 1 is
"ground." See figure
4.
. - SHIELD- ,-
_-__--L
MIC. OUTPUT MIC. OUTPUT
HIGH IMPEDANCE LOW IMPEDANCE
(BALANCED LINE)
MICROPHONE OUTPUT PLUG CONNECTIONS
FIGURE 4. Microphone Output Plug Connections.
If the low impedance output is to be used with an un-
balanced 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 to-
gether. 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 Vocal Master
Echo:
Echo may be introduced into the Console by using an
accessory echo device (such as an Echoletteor 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 Con-
sole 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 de-
vice 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
balancedwith thegain of theConsole sothere is nochange
in level when the individual Reverb In-Out switches are
operated.
When connected inthe manner described, the individual
channel Reverb In-Out switches will offer selective echo in
addition to selective internal reverb. With the Master Re-
verb In-Out switch in the "Out" position, the individual
TO CONSOLE
ECHQ "TO IN- TO ECHO DEVICE
PUT' JACK HIGH IMPEDANCE
MICROPHONE
INPUT JACK
-
RESISTORS ARE 112 WATT 10% CARBON
FIGURE 5.
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 "In"
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 loadsof 10 kilohmsor greater. Thejack 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

resistance pad (attenuator) will be required inthe line from
the Console to the echo device input. If the echo device in-
put 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 "Auxil-
iary Hi-Level Output" on the Console. To use the "Micro-
phone Level Output" connect a cable from the Console to
the Microphone lnput on the tape recorder. Set the Con-
sole "Lo 2-Hi
Z" impedance selector switch to match the
impedance of microphones normally used with the tape
recorder. Use the "Lo 2" position for microphones up to
1000 ohms, and the "Hi 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 record-
ings see page 13, Stereo Operation.
PlayingTapes:
To play back tape recorded material through the Con-
sole, connect a cable from the tape recorder's High Level
Output to the Echo "To Output" jack on the Console. Ad-
just the Echo "Gain" control, the "Master Volume" control,
and thetape recorder playback levelcontrol for the desired
volume. Notethat those lnputChannels 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
connectedto a Console microphone input, 50 dB of attenu-
ation 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 micro-
phone 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
a
microphone in front of acoustical, nonelectrified instru-
ments, or infront of the instrument loudspeakers to "mike"
an instrument. As an alternate direct connections may be
usedfor instruments with a "pickup" or preamplifier output
(suchas a guitar or keyboard instrument). Connections are
the same asfor high impedance microphones, see page 11.
When the instruments play very loud, signals in excess
of the Console preamplifier clipping level may be encoun-
tered, 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 lnputAttenuator Switches, page6.
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 A95UTrans-
former is supplied with an adapter to accept phone plugs.
Limit the high impedance cable length to 6m (20ft) 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 micro-
phone 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
Figure
6.
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
I J
FIGURE 7.
'Current A95 Line Matching Transformers have a smaller diameter low
impedance end for direct plug-ln connections to the "Inputs." When
using older A95A Line Matching Transformers connect a cable between
the transformer and the Console "lnput."

Adjust the Echo Gain control and the mixer volume con-
trols 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" posi-
tion, 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 InputsUsinga Second Console:
A second Console may be used as a mixer to provide
additional inputs.
Connect an accessory line matching transformer, Shure
Model A95U, to the Echo "To Input" jack on the second
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.
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
lnputAttenuator Switcheson 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 us-
ing 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.
Additional Power or Area Coverage:
Inthose applications which require more powerthanone
Vocal Master system is able to deliver, such as very large
auditoriums and stadiums, and inthose 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
use a PM300 Series Power Master amplifier and additional
Speaker Columns. Generally two Speaker Columns should
be connected to each amplifier. See Figure 9.
SPEAKERS
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 15m (50ft) of low capacitance, single conduc-
tor, shielded type (suchas Belden #8401, #8410, #8411).
Set the Volume Control on the Power Master to "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 Mas-
ter will "follow" all control settings of the Console. Addi-
tional Power Master Amplifiers may be added to the sys-
tem by connecting a cable from the unused input jack on
the last Power Master to one of the input jacks on the next
Power Master. See Figure
9. 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.
SPEAKERS
FIGURE 10.

Set the controls on the second Console as follows: Anti
Feedback'Switches to "Out," Master Reverb Switch "Out,"
IndividualVolume Controls to "0," and the Master Volume
to "5." Adjust the Echo "Gain" Control to approximately
113 rotation from the C.C.W. off position, and use this con-
trol 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
connectedto the "Aux. Hi-Level Output" jack onthe second
Console.
Microphone Cuing:
Microphone "cuing" may be preset by using the indi-
vidual 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. Inthe "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 nor-
mal 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 possi-
bility 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
systems, simply use a
"Y" connector on that microphone
and feed its signal to one Input on each Console. For mak-
ing 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 indi-
vidual 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
effect, like "throwing"
a 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 fedfrom the open inputjack of the Power Master.
NOTE: Reverberation can be added to only those chan-
nels 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 rightchannel of the tape recorder; see page
11 Tape Recording.
A 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.

FIGURE 11.
INDIVIDUAL JACK SWITCH
REVERB SWITCH OPERATES WHEN
PLUG IS INSERTED
IN
,
1508 ATTEN
WPUT BASS& IND
-:-I OUT
-TREBLECONT'L - VOLUMEcoNTL
ATTENLATOR
CJ'yLITCH
r
I , MASTER
REVERB REVERB REVERB
BASS a -
SPRING
- . INTENSITY
-
TREBLE
CONTROLS
0 i~'.
CONTROL
I
VA302 Series Vocal Master
v U
METER
Amplifier Service (See Guarantee):
from the back to permit access to the front panel. (Note:
' TO SPEAKERS
Uncoil the cable before pushingthe chassis. Push against
The VocalMasterConsole uses
the high- amplifier chassis not against the grille on the back,) The
est quality, operating well within their respective ratings to
entire amplifier may be pulled forward at this point and
assure long life. CAUTION: There are no user serviceable separated
from the case.
parts inside. Refer servicing to qualified service personnel.
AUX MIC LEVEL
HIGH LEVEL OUTPUT
OUTPUT (HIGH/ LOW 2)
VA302-C SERIES FUNCTIONAL DIAGRAM
Front Panel Removal:
Amplifier Removal:
To ease servicing of components on the front panel, re-
To remove the amplifier from its carrying case, remove move the four screws on the bottom rim of the front panel.
the three screws located at the top front edge of the case (Note: Stand amplifier on end with transformer side down.)
and the six screws, four within the plastic feet, on the Figure
12, Page 15, shows the amplifier with the front panel
bottom of the case. Push the amplifier slightly forward removed and tilted to a convenient servicing position.

FIGURE 12.
Driver Transistors:
The driver transistors Q33 and Q34, Figure 12, Page 15,
are locatedonthe amplifier chassis. Before removing these
transistors, write down the lead color and location at each
transistor solder junction. If replacing transistors, apply
type
120 Wakefield thermal joint compound to each side of
the insulation wafer to provide good thermal transfer from
transistor to chassis. After replacement and before con-
necting transistor leads, check transistors with an ohm-
meter between case and chassis; there should be no con-
tinuity. Be sure that these transistors are not inverted in
the circuit; they are not identical devices.
Q33 is an NPN
transistor, while
Q34 is PNP transistor. Refer to the lower
right corner of the circuit diagram, Figure
17, Page 21 for
terminal code. NOTE: when replacing driver transistors,
perform the following modification (if not already per-
formed): solder
a 3.3k, Y2W 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 con-
nected, through the chassis grommet, to the ground on
the Speaker Output jacks (same path as existing wire).
Output Transistors:
The output transistors Q35 through Q38, Figure 12, Page
15, are located on the black finned heat sinks. Replace-
ment procedure is the same for the driver transistors,
Q33
and Q34.
NOTE: The output transistors, Q35 through Q38, must be
matched for
current gain and part number. When replac-
ingoutput transistors be sure to replacewith 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 = A
Red Dot = B
Orange Dot = C
Yellow
Dot = D
Green Dot = E
Brown Dot = F
Pink Dot = G
Violet Dot = H
Black Dot = J
White Dot = K

FIGURE 13.
Small Signal and Predriver Transistors:
FIGURE 14.
Check Transistors and Diodes:
Transistors Q1 through Q30, Figure 14,Page 16, and Q31
and (232, Figure 12, Page 15, are mechanically supported
by their leads. When replacing these transistors, it is im-
perative that proper lead configuration be followed.
A min-
imum of soldering heat should be used to avoid damage to
the transistor. Refer to the lower right corner of the circuit
diagram, Figure
17, Page 21, for lead code.
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
.. .
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 re-
sistance 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 (Q1
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.

If all conditions in the following table are met, the tran- Lamp Replacement:
sistor may,be considered free of any gross defect; if any of
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 Lead
Collector Emitter
Emitter Collector
Collector Base
Emitter Base
Base Collector
Base Emitter
OHMMETER READING
N.P.N. P.N.P.
Transistor Transistor
High High
High High
High Low
- Low
Low High
Low
-
With the ohmmeter "plus" probe on the anode end of a
diode, and the "minus" probeonthe cathode end,the ohm-
meter should read approximately 2000 ohms or less. With
the meter probes reversed, a reading of about 10,000ohms
or more should occur. If either of these conditions is not
met, the diode should be replaced.
Power DrainResistor (R,,,):
The following condition may occur after replacement
of driver transistors Q33 and Q34, output transistors Q35
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 meas-
ured figure exceeds 75 watts, insert a resistor (R,,,,) in
parallel with the 56-ohm resistor between the base of
transistor Q33 and the junction of diodes D6 and D8
(figure 17, page 21). RsEL(1/2W, 10%) should be either
180 ohms to decrease the power consumption by 20
watts, or 82 ohms to decrease the power consumption
by30 watts.
The two lamps I2and
13, Figure 12, Page 15, which pro-
vide illumination of the front panel controls are 115 to 125
volt, 15watt incandescent bulbs. These bulbs are soldered
and epoxied into the molded plastic sockets in order to
meet Underwriters' Laboratoriesrequirements. The assem-
bly may be removed by unsoldering the lamp leads at the
terminal strips and removing the screw that holds the
socket to the chassis.
ReverberationAssembly:
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 am-
plifier 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 nor-
mally used to mount this sub-assembly. If extensive dam-
age has occurred, a replacement Reverberation Assembly
may be ordered through the dealer or from the factory
Service Department.
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 avail-
able. 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.
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 (50ft) Speaker Extension Cable
A95 Series LineMatchingTransformers
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. Removebackof cabinet.
4. Disconnect one end of the lead connected between
the two 10 inch loudspeakers.
5. Using an ohmmeter, measure resistance of the voice-
coil of each loudspeaker individually. Each 10 inch
speaker should measure between 12 and 16 ohms.
Each
8 inch speaker should measure between 5 and
8 ohms. Readings outside of these limits indicate
possible failure.
6. Apply 60
Hz, 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 inch
and 10 inch loudspeakers.
7. Reconnect lead disconnected in Step 4. Install back
of cabinet tightly.
REPLACEMENT PARTS LIST FOR
VASOO-S SPEAKER COLUMN
'Recommended replacement cable connectors (not available from factory.
Switchcraft part numbers given:) Straight Locking Plug:
$282 Right ~n~l;
Lockin Plug: #228; Locking Extension Jack (for Extension cable Assern-
bly): $123.
REPLACEMENT KIT CONSISTS OF
m
COLOR CODED TERMINAL
QTY. PART NO.
1 80A207
1 80A208
1 90A1375
1 946462
1 90A1373
1 95A436
4 65A1001A
- 39A279
- 48A20
FIGURE 15.
DESCRIPTION
8 Inch Loudspeaker
10Inch Loudspeaker
Rear Panel Assembly
Column Cabinet
Cable and Plug Assembly
Handle Assembly
Bumper (Plastic Foot)
Name Plate
Side Rail
FIGURE 16.

REPLACEMENT PARTS LIST FOR VA302-C SERIES CONSOLES
Capacitor, 2500 x 100
Capacitor, 4000
x 60
Silicon Rectifier,3A., 200 V.
Zener Diode, 22V,, 1W.,
5%
Silicon Rectifier,100 V., %A.
Zener Diode,3.6 V., 1 W., 5%
Germanium Diode
Silicon Diode,50 V., '/PA.
A.C. Fuse (VA302 and VA302E)
A.C. Fuse (VA302E6 only)
for 200-240 volts
A.C. Fuse (VA302E6 only)
for 100-140volts
D.C. Fuse (VA302 and VA302E)
D.C. Fuse (VA302E6 only)
Wired inA.C. Fuse (VA302 only)
. .
I ITP. I
REPL.
KIT NO.
Pilot Lamp (VA302 only)
Pilot Lamp (VA302E andVA302E6)
Lamp Assembly
Connector, Mic. Input
Phone Jack
Phone Jack
PhoneJack
Connector Mic. Output
3 Wire A.C. Line Cord and Plug
(VA302 only)
Line Cord (VA302E only)
Line Cord and Connector
(VA302E6 only)
ReverberationAssembly
Anti Feedback Inductor Assembly
VU Meter
HandleAssembly
Console Cabinet
Volume Control KnobAssembly
TrebleControl Knob Assembly
Bass Control Knob
Knob and Screw (Line Cord
Storage Spindle)
Shield
Bumper (Plastic Foot)
Fuse Holder (VA302 only)
Fuse Holder (Screw Slot,
VA302E only)
Fuse Holder (5 x 20mm VA302E6 only)
A.C. Chassis Power Connector
(VA302E6 only)
Cabinet Upper Side Rail
Cabinet Lower Side Rail
Transistor (Replaces 86A327)
Transistor
Transistor 110 V. BVceo Min.
Transistor 110 V. BVCEOMin.
Transistor 105V. BVcxo Min.
(Mutually Interchangeable)
Transistor 110V. BVcco Min.,
REPLACEMENT KIT CONSISTS OF:
QTY.
1 PART NO. I DESCRIPTION
NONE
NONE
Motorola No. 1
N4721
Motorola No. 1N4748A
Motorola No. IN4002
Motorola No. 1N4729A
Sylvania No. 1N48, IN60
Motorola No. 1N4001
Littelfuse 3AG/3A/SB (Slo-Bio)
5
x 20mm, 1.6 AT, 250 V.
COMMERCIAL ALTERNATE
I
5 x 20mm, 3.0 AT, 250 V.
Littelfuse 3AGl5A
5 x 20mm,5.0 A, 250 V.
Bussmann MDVI5AISB (Slo-Blo)
Pig-tail
Leecraft No. 36N1311-6
Leecraft No. 36HN-1311-7W
NONE
Switchcraft No. C3F
Switchcraft No. 12-A
Switchcraft No. 14-8
Switchcraft No. 11
Switchcraft No. C3M
NONE
NONE
NONE
GibbsNo. 4L (Insulated Output)
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
Littelfuse No. 342014
Littelfuse No. 341001
SchurterType FEB
Switchcraft No. EAC-301
NONE
NONE
Motorola No. MPS-6521
Texas Inst. No. 2N3711
Motorola No. MPS-3392
RCA No. 40349
RCA No. 2N3441
Motorola No. 2N3741 Selected
RCA No. 2N3773
R1-R6, R14 RKC58 46A017 Potentiometer,Dual 50K/50K NONE
R7-R12, / RKC59 1 1 46A016 Potentiometer, 50K. 1 NONE
I Rl6 RKC57
RKC6O
---
--
---
RKC47
RKC61
---
RKC37
RKClO
RKC44t
RKC43
RKC42
RKC41
RKC40
---
---
Potentiometer,50K.
Potentiometer, 2.5K.
Resistor. .43 ohms, 5 W.
Resistor, .20 ohms, 5W.
Resistor, .l2ohms, 5
W.
Resistor
Toggle Switch (VA302 and VA302E)
Toggle Switch
(2 position VA302E6 only)
Thermostat
.
Slide Switch (Screw Slot)
Rocker Switch, Chrome
Rocker Switch, Redlorange
Rocker Switch, Orange
Rocker Switch, Orange/Yellow
Rocker Switch, Yellow
Slide Switch, Black
Voltage-Selector Switch
NONE
NONE
NONE
NONE
NONE
Workman No. FRT-2
Cutler-Hammer No. 7563K5
MarquardtType No. 0132
NONE
Continental-Wirt No. G-326
NONE
NONE
NONE
NONE
NONE
NONE
NONE
(VA302E6 only)
RKC35 51A215 Power Transformer (VA302 only)
1 1 RKCl47 1 1 51A241 1
NONE
Power Transformer (PMSOOE and
1 NONE
PM300E6)
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 Partsshould be used.
'When ordering 86A332 or 868332,specify current gain code. See Page 15.
"Parts listed as RKC Kit8 should be ordered by that kit number.
Any orden receivedfor plece parts where RKC Kit number is shown will be shlpped In RKC quantities.
+Forgray switch order Part No. 55A73F.
19
RKC28
RKC84 1
1 51A217
90H2150 Feedback Transformer
Mic.Transformer Assy. NONE
NONE

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. Inthe power
amplifier, Q31 to Q38, the key DC voltages are 94(col-
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 pro-
ceed with the AC voltage measurements.
The numbers within the symbols
o on the circuit dia-
gram denote the D.C. voltage at that point with the follow-
ing test conditions:
1. Voltages measured at points indicated with respect to
chassis, unless otherwise indicated.
2. Line voltage
- VA302-C: 120v. 60 Hz.
VA302E-C: 120/240~.50/60 HZ.
VA302E6-C: 100, 120, 140, 200, 220, or
240v. 50/60 Hz.
3. No input signal applied.
4. D.C. voltage measurements may vary &20% from the
values shown.
5. Measured with a VTVM of 11-megohms input impe-
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 volt-
ages are: emitter 4.0, base 0.0, and collector 22.0.
A.C. Voltage Measurements:
The numbers within the symbols on the circuit dia-
gram denote the A.C. voltage at that point with the follow-
ing test conditions:
1. Voltages measured at points indicated with respect to
chassis, unless otherwise specified.
2. Linevoltage
- as specified above.
3. 1,000
Hz. signal applied to input, in "IN" position, at
0.8 millivolts.
4. Measured with an A.C. VTVM of 1.0 megohms or
greater input impedance.
5. Noninductive load of 8 ohms, 200 watts connected to
speaker output jack for Q31 through Q38.
6. Echo input and output jacks to be open; echo gain
control set to maximum.
7. All anti feedback switches set to "OUT" position.
8. Reverb intensity set to minimum.
9. All tone controls set to 12o'clock position.
10. All volume controls set to maximum.
11. Master reverb switch set to
"OUT" position except as
noted.
12. Individual channel reverb switches set to
"OUT" posi-
tion except where noted.
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
frequency may be varied t100
Hz. to obtain the A.C.
measurements shown.
16. For VU Meter specifications, see page 9.
Ohmmeter Measurements:
With the A.C. line cord unplugged and the power switch
in the "OFF" position, the following ohmmeter measure-
ments 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, R19,R20,
and R22, ohmmeter minus probe to ground: greater
than 100 ohms.
5. Ohmmeter plus probe to BI, ohmmeter minus probe
to the junction of R17, R19, R20,and R22: greater than
100 ohms.
6. To test transistors and diodes, see page 16.
Shure part numbers are not shown in the parts list ac-
companying the circuit diagram if parts are readily avail-
able 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 non-
electrolytic capacitors are to be 100 volts or more unless
otherwise specified in the circuit diagram. Electrolytic ca-
pacitors 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 cir-
cuit diagram.
Resistorsshown in the upper two lines of circuitry on the
diagram are '/4 watt unless otherwise specified. Resistors
shown inthe lower lineof circuitry are
l/2 watt unless other-
wise specified.
The following ground symbols denote:
Chassis
Ground
Preamplifier
1
Ground
-
-
Reverb
Driver Ground