Shure FP31 Schematic

222

SmUe@

THE

SOUND

GENERAL Power

The FP31
(ENG) electronic field production (EFP), or film produc­tion, mixer that provides the quality and features need­ed for remotes.

FEATURES
Inputs

w

.

Outputs

rn

rn

Copyr~ght
27A8080

OF

THE

PROFESSIONALS'~

is a portable electronic news gathering

Three transformer-coupled, 3-socket XLR-connector

inputs; each switchable to low-impedance
microphone or line level

Lo-Cut filters available at each input to reduce ex-

traneous low-frequency interference

(Phantom) simplex
microphones available at each microphone input

Built-in tone oscillator for level checks or line tests

Slate microphone with automatic gain control (AGC)
for take identification or for emergency use

Slate tone for identifying take locations during
editing

Two transformer-coupled, 3-pin XLR-connector out­puts, each switchable either to low-impedance
balanced microphone or to 600-ohm balanced line
level

Tape output to feed tape recorder input or other un­balanced Aux-level input

Front and side panel stereo headphone jacks (8 to
2,000 ohms, %-inch and 3.5 mm jacks) with separate

Phones level control. Either or both jacks can drive
Aux or unbalanced line-level inputs. Four separate
sources can be driven from these two headphone
outputs.

1991,

Shure Brothers

(KG)

Inc

Or

A-B

EVANSTON, ILLINOIS 60202-3696 V.S.A.

PROFESSIONAL PRODUCTS

for

'Ondenser

HARTREY AVENUE

Controls and Indicators

Active, feedback-type input gain controls permit
direct input of high-level sources without input
tenuators

Built-in Limiter with adjustable threshold - prevents
output clipping of mixer or input overload of
amplifier, telephone line or tape recorder

LED indicator flashes with Limiter operation or to
signal overload with Limiter defeated

Professional VU meter, factory set for 0 VU
dBm, internally adjustable for other VU levels

VU lamp, stays illuminated while pushbutton is
depressed, automatic 5-second turnoff after button
is released.

Battery check function with readout on VU meter
Master gain controls level at LinelMic and Tape out-

puts as well as tone oscillator level
Phones level control adjusts output at both head-

phone jacks

.

Mixer is powered by two standard 9V alkaline bat­teries that also supply simplex power for condenser
microphones

w

extreme!^

minimum battery life under normal conditions
Separate 9V alkaline battery supplies A-B power for

condenser microphones; third battery is not required

A-Q power is not used

if
Spring-loaded battery compartment prevents incor-

rect insertion of batteries; batteries available for
replacement instantly when compartment door is
opened

.

Mixer can be powered from any
such as: standard belt pack, automotive electrical
system, video tape recorder. or ac power converter

Mechanical

Extremely rugged and durable construction

Very small size and light weight

Carrying case and detachable shoulder strap sup-

plied

.

A~I

input and output connectors are professional

standard types

Performance

.

Reliable Operation under

temperature and humidity

.

Extremely low noise and low RF susceptibility per­mits use near microwave transmitters and in strong
hum fields

Wide, flat response, extremely low distortion, and up

+

18 dBm output level provide studio-quality per-

to
formance in a portable mixer

low battery drain provides 8-hour

11

to

18

Vdc source

characteristics

wide

extremes

Pr~nted n US

H

z

1

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=

+4

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1.

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SPECIFICATIONS
Frequency Response

30 Hz to 20 kHz

Distortion

Less than

dBm, 50 Hz to 20 kHz

Noise

Less than

Common Mode Rejection

65 dB minimum at 100 Hz, -30

Inputs

19

to

Line

'Including simplex or

Tone Oscillator

Slate Tone

Slate Microphone

Outputs

Mic

Line

Tape

Phone

Phase

Gain (at 1

INPUT OUTPUT

Line

Controls

Less than

1 kHz nominal at

400 Hz, 1

Electret condenser, omnidirectional, with AGC, ac­tivated while slate button is depressed

3-pin lnput
phase with tip of phone

CHANNEL GAIN: Active, feedback type, individual
for each input; Channel 1 control pulls out to activate
tone oscillator

MASTER GAIN: Controls LinelMic and Tape out­puts, and tone oscillator and slate levels

LOW-CUT FILTERS: 7 dB
dBloctave slope

PHONES LEVEL: Controls both headphone outputs
LIMITER: Controls LinelMic and Tape outputs;

dBm factory-set threshold, internally screwdriver ad-

justable down to

recovery time typical

sec, each time button is depressed

For

Any low-Z mic

input

6003

18

k0

or greater

high level input

83

to

kHz)

-10 dB 40 dB

+2 dB

0.25O/0 total harmonic distortion at +4

-

129 dBV equivalent input noise

dBV input

IMPEDANCE

6003*

10 k3 66 k3

A-B

powered, and dynamic or ribbon microphones

+4 dBm, Master at approx. 7

IMPEDANCE

Use With 1 Actual

2 k3

&

Output connectors in phase; pin 3 in

&

mini jacks

Line

+

3 dBm; 3 msec attack, 500 msec

lnput Clipping

Level

-47

to

-17 dBV

(4.5

to

141 mV)

+3

to

+33

dBV

(1.4

to

i

Output Clipping

-

34 dBV (20 mV)

minimum into

+

18 dBm

-6

+4 dBV (1.6V

rolloff at 100 Hz, -6

44V)

Level

minimum

into

6003

dBV (0.5V

47 k3

into

Max)

into

2003

1503

RMS)

RMS

+

14

SIMPLEXIDYNAMICIA-B SELECTORS: Individual

for each input, supplies 11 to 18 Vdc Simplex (phan-

tom) or 9 Vdc A-B power with lnput in MIC position;

supplies no power with Selector in DYN position (for

dynamic or ribbon microphones) or with lnput in

position

Control Interaction

Less than 1 dB with any control combination

Output Isolation

Shorting one output shall cause no more than 8 dB

level drop at 1 kHz at other output

Overload and Shorting Protection

Shorting outputs, even for prolonged periods, shall

cause no damage. Microphone inputs will not be

damaged by signals up to 3 volts.

Indicators

POWER ON: Green LED flashes at approximately
I-second repetition rate as long as power switch is

on

-

PEAKIOVERLOAD: Limiter IN
indicate onset of limiting; Limiter OUT-flashes 6 dB
below output clipping level

BATTERY CHECK: Converts VU Meter to battery

condition or circuit voltage indicator;

indicates good batteries or adequate (11 to 18 Vdc)

external power source
VU METER: Factory-set at

level internally screwdriver adjustable

VU LAMP: Illuminates meter while button is

Red LED flashes to

0 VU or higher

0 VU = +4 dBm; 0 VU

depressed; automatic shufoff 5 seconds after

release

Power

MIXER AND SIMPLEX (PHANTOM) POWER:

plied by two internal 9V standard alkaline batteries
(Duracell
Vdc supply;
tion

SIMPLEX POWER:
6200

A-B POWER: Supplied by additional 9V standard
alkaline battery

Connectors

LlNElMlC INPUTS AND OUTPUTS: 3-pin XLR type
TAPE OUT: 3.5 mm mini jack

PHONES: Stereo jacks; one standard

phone and one

12 VDC EXTERNAL POWER: Single-pin dc power
jack

Temperature Range

OPERATING:
STORAGE: -29 to +7I0C (-20 to + 160°F)

Dimensions

48.3 mm
5-5116 in.)

Net Weight (less batteries)

1 kg (2.2 Ib)

Supplied Accessories

Removable shoulder strap, carrying case

MN1604 or equivalent) or external 11 to 18

&hour battery life under normal opera-

11 to 18 Vdc nominal through

%-inch

3.5

mm mini

-

18 to + 57OC (0 to 135OF)

H

x 160 mm W x 135 mm D (1-718 x 6-5116 x

LINE

SUP-

OPERATION

LineIMic Inputs and Outputs

XLR-type 3-pin connectors, transformer-coupled ba-

2

lanced-line circuits; pins

and 3 are signal conductors;
pin 1 is ground. All XLR connectors are in phase with
one another.

Lo-Cut Filters

Activated by Inlout switch above each Channel Gain
Control to provide low-frequency

rolloff as shown in
Figure 1. Reduce undesirable low-frequency signals
such as wind noise.

FREQUENCY

IN

Hz

LO-CUT FILTER ACTION

FIGURE

1

Channel Gain Controls

Determine preamplifier gain and provide preamplifier
output attenuation. As gain is reduced, input clipping
level increases for channel. Optimum signal-to-noise
ratio occurs with Channel controlsset as high as possi­ble (consistent with maintaining adequate control
range and input clipping level).

Tone Oscillator

Activated by pulling out Channel 1 control knob; stable

1 kHz oscillator; level determined by Master gain con­trol. Oscillator signal appears at all outputs. When not
in use, Channel

1

control knob should be pushed in.

Slate

Depressing Slate button activates 1 -second 400
tone and turns on Slate Microphone. Omnidirectional
electret Slate Microphone remains on while button is
depressed, can be used to identify recorded segments
or as emergency field microphone. Slate Tone and
AGC'd microphone audio levels are controlled by Mas­ter Gain Control.

Master Gain Control

Determines output levels at LineJMic and Tape out­puts. Also sets Tone Oscillator level when Channel
knob is pulled out, and Slate-tone and -microphone
level when Slate button is pushed.

Headphone Jacks

Two stereo phone jacks: one mini 3.5 mm (front panel)
and one 114-inch phone (side panel). Combined out­put, including Tone Oscillator, Slate Tone and Slate Mi­crophone, appears at headphone jacks. Can be used
to drive up to four headphones or Aux-level recorder
or amplifier inputs. To wire either connector for two out­puts, connect one conductor to tip; connect other con­ductor to ring; and connect

shield(s) to sleeve of appro-

priate mating stereo plug. Tip and ring of headphone

jacks in-phase with pin 3 of XLR

put connectors.

Phones Control

Sets output level at headphone jacks.

Limiter

Limiter Inlout switch turns on fast-acting, peak-res­ponding limiter circuit to cut overload distortion during
loud program intervals without affecting normal pro­gram levels. Limiter switch In (operating) restricts
maximum mixer output to approximately +14
creasing individual Channel or Master gain controls in­creases both average output and amount of limiting. To
change Limiter threshold, see section on Limiter
Threshold Adjustment.

Peak

LED

Indicates Limiter operation with Limiter switch In. With
switch Out, flashes at 6dB below output clipping. Peak
indicator responds much faster than meter, activated
by even shortest transient peak, yet remains lit long
enough to provide easy recognition.

VU Meter

Factory calibrated for
load at Line output. (Microphone output levels are 50

dB below Line output.) Supplied

mended for normal use to provide approximately
headroom between operating level and clipping level.

To change

0 VU level, see section on VU Meter Adjust-

ment.

VU Lamp

Illuminates meter while button is depressed; automati­cally turns off 5 seconds after release to prevent bat-

tery drain.

Tape Outputs

3.5 mm jack to feed unbalanced Aux-level input of tape
recorder or amplifier. Tip of connector in phase with pin

3

of XLR connectors.

Telephone Lines

Hz

In Line position, output transformer will operate with
dc-biased "dialed up" telephone lines although there
may be slight increase in distortion. When connecting
FP31 to telephone line, use FCC-Registered* inter­face adapter between mixer and telephone line.

'DOC-Certified

in

Canada

Condenser Microphone Power

Condenser microphones, either

1

(simplex) powered or 9 Vdc
supplied from any Mic input of
inside battery compartment, are three 3-position
switches. Center position is for dynamic microphones
(no dc power supplied to Mic input); left position is for
9-Vdc A-B power, right position is for 11
phantom power.

NOTE: No power is supplied to any input with
switch in Line position. No
less right-side battery is present.

Mixer Powering

In ordinary portable use, the FP31 is powered by two
standard 9-Vdc alkaline batteries installed in

LineJMicinput andout-

dBm. In-

+4

dBm = 0 VU with 600-ohm

0 VU level is recom-

12

to 18 Vdc phantom

A-B(T) powered, can be

FP31. Below batteries,

-

to 18-Vdc

LineJMic

A-B

power is supplied un-

leftmost

14dB