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A phone jack marked “Reverb Switch” (17) is located on

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

R e v e r b   I n - O u t   s w i t c h   ( 4 )   a n d   a l l o w s   t h e   r e v e r b   t o   b e

remotely turned on and off when the Master Reverb switch is
in the “In” position. The Master Reverb switch will always

override the remote switch 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.

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.

To Tape Recorder:

A phone jack on the rear panel marked “To Tape Recorder”

is provided for connections to tape recorders for making

recordings, or to additional power amplifiers, such as the

PM300. 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 auxiliary,

high impedance output for driving high-level, high impedance
inputs. Note that all the Console controls, Master Volume,
Antifeedback, Reverb, etc., affect this signal.

VA300 Vocal Master

SPECIAL OPERATING INSTRUCTIONS

Echo:

Echo may be introduced into the VA300-C by using an

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

To use an external echo device in conjunction with the

VA300, 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

l e v e l   c o n t r o l s   o n   t h e   e c h o   u n i t ,   t h e   e c h o   s i g n a l   m a y   b e

balanced with the gain of the VA300 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 channel

Reverb switches will select “dry” (no echo) in the “In” posi-

tion and “Echo” in the “Out” position.

Changing the Master Reverb In-Out switch to the “In” po-

sition will permit selection of echo (individual channel Reverb

switch “Out”) or reverb (individual channel Reverb switch
“ I n ” ) .

The output signal of the VA300-C at the jack marked Echo

“ T o   O u t p u t ” 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 Kohm 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 in the line from the VA300-C to

the echo device input. If the echo device input is suitable for

only high impedance microphones a resistive pad consisting of

a 100 kilohm and a 3.3 kilohm resistor is required. (See figure

4). Almost all makes of echo units use different output levels;
these may generally be compensated for by use of the gain

Figure 4

controls on the echo unit and the “Echo Gain” control on the
Console.

Tape Recording:

T o   t a p e   r e c o r d   t h e   V A 3 0 0   o u t p u t ,   c o n n e c t   a   l o w

capacitance, single conductor, shielded cable (such as Belden

# 8 4 0 1 ,   # 8 4 1 0 ,   # 8 4 1 1 )   f r o m   t h e   j a c k   m a r k e d   “ T o   T a p e

Recorder” to the Auxiliary High Level Input of the tape re-

corder.

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

frequency signal and to reduce the possibility of hum pickup.

Use the tape recorder controls to set recording levels. Note

that the VA300 Master Volume control affects the signal level

a t   t h e   “ T o   T a p e   R e c o r d e r ”   j a c k .   T o   m a k e   s t e r e o   t a p e

recordings see the section on stereo operation, on page 12.

Playing Tapes:

To play back tape recorded material through the VA300,

connect a cable from the tape recorder’s High Level Output to

one of the six Input jacks on the Console. Set that channel’s

Input Attenuator Switch to “Inst.” Individual channel Treble
and Bass controls should be set to 12:00 o’clock.

The individual channel Volume Control may be used, in

conjunction with the tape recorder playback level control, to

adjust volume.

9

Summary of Contents for Vocal Master VA 300

Page 1: ...VA 300 OPERATING AND SERVICE MANUAL Manufactured by SHURE BROTHERS INC 222 Hartrey Avenue Evanston Illinois 60204 U S A Copyright 1978 Shure Brothers Inc AL404 RE 27A819 Printed in U S A...

Page 2: ...eble Control Action 10 db at 10 000 Hz with respect to flat setting To Tape Recorder Jack Impedance 5 000 ohms Output 19 db below speaker output nominal 2 V at 50 watts to speakers Clipping Level 4 V...

Page 3: ...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 cir cuitry design protects th...

Page 4: ...olume Control 9 Thermal Overload Indicator Lamp 10 On Off On Power Switch Figure 2 Rear Panel Controls and Connections Refer to Figure 2 11 Line Cord Storage Spindles 12 A C Line Cord 13 D C Fuse 3AG...

Page 5: ...O to whichever 7 8 9 10 11 On position results in the least amount of hum coming from the speakers Now turn up the other Individual Channel Volume Controls 5 which are being used By use of the Indivi...

Page 6: ...weight inherent in such transformers The speaker output vol tage 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 vol...

Page 7: ...o them A shallow broad room might require four speakers to be utilized in order to cover the extreme horizontal expanse Again if balconies were added four more speakers might be required to expand the...

Page 8: ...flat sounding voice It is often used to great advantage to reduce high frequency acoustic reverberation in reflective rooms The Master Volume control 8 adjusts the output level of the total mixed outp...

Page 9: ...perated 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...

Page 10: ...put jack the low impedance end is terminated with a Cannon type 3 pin female connector The main advantage of low impedance microphones is that virtually unlimited cable lengths may be used whereas hig...

Page 11: ...TION is available Contact your Shure Dealer or the Shure Factory for further information on this Additional Power or Area Coverage In those applications which require more power than one VA300 Vocal M...

Page 12: ...tems simply use a Y connector on that microphone and feed its signal to one Input on each Console For making stereo tapes the To Tape Recorder jacks one on each console may now be connected to the lef...

Page 13: ...dge of the case and the six screws four within the plastic feet on the bottom of the case Push the amplifier slightly forward from the back to permit access to the front panel Note Uncoil the cable be...

Page 14: ...he following modifica tion if not already performed place insulated tubing over the leads of a 3 3k 1 2W resistor and solder it across the terminals to which the white and black leads of transformer T...

Page 15: ...ctive 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 resist ance in...

Page 16: ...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 norma...

Page 17: ...hms Read ings outside of these limits indicate possible failure 6 Reconnect lead disconnected in Step 3 Install back of cabinet tightly REPLACEMENT PARTS LIST FOR VA300 S SPEAKER COLUMN REP REPLACEMEN...

Page 18: ...A018 Potentiometer 50K R15 RKC60 1 46A020 Potentiometer 2 5K R17 R18 45EC439B Resistor 43 ohms 5 W R19 R21 R20 45EC209B Resistor 20 ohms 5 W R22 45EC129B Resistor 12 ohms 5 W R23 RKC47 1 45A38 Resisto...

Page 19: ...ALTERNATE POWER SUPPLY INCORPORATED IN EARLY PRODUCTION UNITS Figure 17 19...

Page 20: ...ume controls set to maximum 11 Master reverb switch set to OUT position except as noted Chassis Ground Preamplifier Ground 12 Individual channel reverb switches set to OUT pos Reverb ition except wher...

Page 21: ...VA300 C CIRCUIT DIAGRAM ISSUE 6 21 Figure 18...

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