Shure VA 300 - Manual (Page 6)

Input Connections:
Six individual input connectors are provided on the rear
panel of the Console. These connectors are standard 1/4 inch
phone jacks (22). The Console is designed to operate with any
high quality dynamic or ribbon-type high impedance micro-
phone. High impedance microphone cables should be limited
to a maximum length of 6m (20 ft) to avoid high frequency’
signal loss and to reduce the possibility of hum and noise
pickup in the cables. Standard 1/4 inch phone plugs should be
attached to the “Console end” of the microphone cables; the
center conductor of the cable should be attached to the “tip”
terminal of the phone plug and the shield of the cable should
be connected to the “sleeve” terminal. For low impedance
microphones, see page 10.
For additional microphone inputs, see page 10. For connec-
tions from electrified musical instruments, see page 10. For
connections to play back a tape, see page 9. For connections
to a phonograph, see page 10.
Six individual input level adjustment switches (21) are lo-
cated above the six input jacks. These screwdriver-slot slide
switches allow the microphone input signal to be attenuated
(reduced) before entering the preamplifier.
With the switch in the “Mic.” position, the signal from the
microphone is switched directly to the preamplifier of the
channel. With the switch in the “Inst.” position, the signal
from the microphone is attenuated by 11 db before entering
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.
Output Connections:
Two parallel-wired “Speaker” output connectors are pro-
vided on the rear panel of the VA300. These connectors are
standard phone jacks (15).
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 may result.
It should be noted that various speaker loads will affect the
o u t p u t p o w e r o f t h e a m p l i f i e r . S e e F i g u r e 3 , P a g e 7 t o
determine amplifier output power for the given speaker load.
WARNING: Do not interconnect the speaker output jacks
or the speaker cables between two VA300 Amplifiers
or the VA300 and any other amplifier. This may result
in damage to one or both amplifiers, and is not covered
by the Guarantee.
The VA300 does not use speaker output matching trans-
formers and thus avoids the distortion, power loss and added
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-volt speaker lines.
Up to 30m (100 ft) of #18 gauge two-conductor cable
(such as Belden #8452, 8478, 8460, or 8461) may be used to
c o n n e c t f r o m t h e V A 3 0 0 - C t o e a c h 1 6 - o h m ( V A 3 0 0 - S )
speaker. Greater cable lengths require heavier gauge wire to
avoid appreciable power loss in the speaker cable. For 30 to
51m (100 to 170 ft), use #16 gauge; 51 to 81m (170 to 270
ft), use #14 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 VA300.
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 column utilizes two
special IO-inch speakers and four special 8-inch speakers, and
has a total speaker cone area of 2,310cm² (358 in²) per
c o l u m n . T h e V A 3 0 0 - S S p e a k e r C o l u m n d e l i v e r s v i r t u a l l y
uniform penetrating power over a 140° angle 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 VA301-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 of the VA300-S. The
nominal impedance of the VA301-S is 32 ohms, so that when
used in conjunction with two VA300-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 VA300 Vocal Master:
QUANTITY and SPEAKER MODEL
1 VA300-S
2 VA300-S
3 VA300-S
1 VA301-S
2 VA301-S
3 VA301-S
4 VA301-S
5 VA301-S
6 VA301-S
1 VA300-S and 1 VA301-S
1 VA300-S and 2 VA301-S
1 VA300-S and 3 VA301-S
1 VA300-S and 4 VA301-S
2 VA300-S and 1 VA301-S
2 VA300-S and 2 VA301-S
IMPEDANCE
O H M S ( N O M I N A L )
1 6
8
5.3
3 2
16
10.6
8
6.4
5.3
10.6
8
6 . 4
5.3
6.4
5.3
If additional speakers (more than in the table above) are
required, use a Shure PM300 Power Master Amplifier to drive
the extra speakers. See page 11 for instructions.
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