Shure FP31 Instruction manual

222 HARTREY AVENUE
SmUe@ EVANSTON,ILLINOIS60202-3696V.S.A.
THE SOUND OF THE PROFESSIONALS'~ PROFESSIONAL PRODUCTS
H
z
Controls and Indicators
Active, feedback-type input gain controls permit
direct input of high-level sources without input at-
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 = +4
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-
phonejacks
GENERAL Power
The FP31 is a portable electronic news gathering
. Mixer is powered by two standard 9V alkaline bat-
(ENG) electronic field production (EFP), or film produc- teries that also supply simplex power for condenser
tion, mixer that provides the quality and features need- microphones
ed for remotes.
w extreme!^ low battery drain provides 8-hour
FEATURES
minimum battery life under normal conditions
Separate 9V alkaline battery supplies A-B power for
Inputs
condenser microphones; third battery is not required
Three transformer-coupled, 3-socket XLR-connector if A-Qpower is not used
inputs; each switchable to low-impedance
microphone or line level Spring-loaded battery compartment prevents incor-
rect insertion of batteries; batteries available for
w Lo-Cut filters available at each input to reduce ex- replacement instantly when compartment door is
traneous low-frequency interference opened
. (Phantom) simplex Or A-B
for 'Ondenser
. Mixer can be powered from any 11 to 18 Vdc source
microphonesavailable at each microphone input such as: standard belt pack, automotive electrical
Built-intone oscillator for level checks or line tests system, video tape recorder. or ac power converter
Slate microphone with automatic gain control (AGC)
Mechanical characteristics
for take identification or for emergency use Extremely rugged and durable construction
Slate tone for identifying take locations during
editing Very small size and light weight
Carrying case and detachable shoulder strap sup-
Outputs plied
Two transformer-coupled, 3-pin XLR-connector out-
. A~I input and output connectors are professional
puts, each switchable either to low-impedance standard types
balanced microphone or to 600-ohm balanced line
level
Performance
rn Tape output to feed tape recorder input or other un- . Reliable Operation under wide extremes
balanced Aux-level input temperature and humidity
rn Front and side panel stereo headphone jacks (8 to
. Extremely low noise and low RF susceptibility per-
2,000 ohms, %-inchand 3.5 mmjacks) with separate mits use near microwave transmitters and in strong
hum fields
Phones level control. Either or both jacks can drive
Aux or unbalanced line-level inputs. Four separate Wide, flat response, extremely low distortion, and up
sources can be driven from these two headphone to
+ 18 dBm output level provide studio-quality per-
outputs. formance in a portable mixer
Copyr~ght 1991, Shure Brothers Inc
27A8080 (KG)
Pr~ntedn US A
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SPECIFICATIONS
Frequency Response
30 Hz to 20 kHz +2 dB
Distortion
Less than 0.25O/0 total harmonic distortion at +4
dBm, 50 Hz to 20 kHz
Noise
Less than
- 129 dBV equivalent input noise
Common Mode Rejection
65 dB minimum at 100 Hz, -30 dBV input
Inputs
Line
IMPEDANCE
19 to 6003*
Less than 10 k3 66 k3
lnput Clipping
Level
-47 to -17 dBV
(4.5 to 141 mV)
+3 to +33 dBV
(1.4 to 44V)
i
'Including simplex or A-B powered, and dynamic or ribbon microphones
Tone Oscillator
1 kHz nominal at +4 dBm, Master at approx. 7
Slate Tone
400 Hz, 1 sec, each time button is depressed
Slate Microphone
Electret condenser, omnidirectional, with AGC, ac-
tivated while slate button is depressed
Mic
Line
Tape
Phone
Outputs
Any low-Z mic
input
6003
IMPEDANCE
For Use With 1 Actual
18 k0 or greater
Output Clipping
Level
high level input
83 to 2 k3
- 34 dBV (20 mV)
minimum into 1503
+ 18 dBm minimum
into
6003
-6 dBV (0.5V
RMS)
into
47 k3
+4 dBV (1.6V
RMS
Max)
into
2003
Phase
3-pin lnput
& Output connectors in phase; pin 3 in
phase with tip of phone
& mini jacks
Gain (at 1 kHz)
INPUT OUTPUT
Line
Line
-10 dB 40 dB
Controls
CHANNEL GAIN: Active, feedback type, individual
for each input; Channel 1controlpullsout toactivate
tone oscillator
MASTER GAIN: Controls LinelMic and Tape out-
puts, and tone oscillator and slate levels
LOW-CUT FILTERS: 7 dB rolloff at 100 Hz, -6
dBloctave slope
PHONES LEVEL: Controls bothheadphone outputs
LIMITER: Controls LinelMicandTape outputs;
+ 14
dBm factory-set threshold, internally screwdriver ad-
justable down to
+ 3 dBm; 3 msec attack, 500 msec
recovery time typical
SIMPLEXIDYNAMICIA-B SELECTORS: Individual
for each input, supplies 11to 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 inLINE
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-secondrepetition rate as long as power switch is
on
PEAKIOVERLOAD: Limiter IN
- Red LED flashes to
indicateonset of limiting; Limiter OUT-flashes 6 dB
below output clipping level
BATTERY CHECK: Converts VU Meter to battery
condition or circuit voltage indicator; 0 VU or higher
indicates good batteries or adequate (11 to 18 Vdc)
external power source
VU METER: Factory-set at 0 VU
= +4 dBm; 0 VU
level internally screwdriver adjustable
VU LAMP: Illuminates meter while button is
depressed; automatic shufoff 5 seconds after
release
Power
MIXER AND SIMPLEX (PHANTOM) POWER: SUP-
plied by two internal 9V standard alkaline batteries
(Duracell MN1604 or equivalent) or external 11 to 18
Vdc supply; &hour battery life under normal opera-
tion
SIMPLEX POWER: 11 to 18 Vdc nominal through
6200
A-B POWER: Supplied by additional 9V standard
alkaline battery
Connectors
LlNElMlC INPUTSAND OUTPUTS: 3-pinXLR type
TAPE OUT: 3.5 mm mini jack
PHONES: Stereo jacks; one standard %-inch
phone and one 3.5 mm mini
12 VDC EXTERNAL POWER: Single-pin dc power
jack
Temperature Range
OPERATING:
- 18 to + 57OC (0 to 135OF)
STORAGE: -29 to +7I0C (-20 to + 160°F)
Dimensions
48.3 mm
H x 160 mmW x 135 mm D (1-718x 6-5116 x
5-5116 in.)
Net Weight (less batteries)
1 kg (2.2 Ib)
Supplied Accessories
Removable shoulder strap, carrying case

OPERATION
LineIMic Inputs and Outputs
XLR-type 3-pin connectors, transformer-coupledba-
lanced-linecircuits;pins
2 and 3 aresignalconductors;
pin 1 is ground.All XLR connectorsare in phasewith
one another.
Lo-Cut Filters
Activatedby Inlout switchabove each Channel Gain
Control to provide low-frequency rolloff as shown in
Figure 1. Reduce undesirable low-frequencysignals
such as wind noise.
FREQUENCY IN Hz
LO-CUTFILTER ACTION
FIGURE 1
Channel Gain Controls
Determinepreamplifiergain and provide preamplifier
output attenuation.As gain is reduced, input clipping
level increasesfor channel. Optimum signal-to-noise
ratiooccurswithChannelcontrolsset ashighaspossi-
ble (consistent with maintaining adequate control
range and input clipping level).
Tone Oscillator
Activatedby pullingoutChannel1controlknob;stable
1kHz oscillator;leveldeterminedby Mastergaincon-
trol.Oscillatorsignal appearsat alloutputs.When not
in use, Channel
1 control knob should be pushedin.
Slate
Depressing Slate button activates 1 -second 400 Hz
tone andturns on Slate Microphone.Omnidirectional
electret Slate Microphoneremainson while button is
depressed,canbeusedtoidentifyrecordedsegments
or as emergency field microphone. Slate Tone and
AGC'dmicrophoneaudiolevelsarecontrolledbyMas-
ter Gain Control.
Master Gain Control
Determines output levels at LineJMic and Tape out-
puts. Also sets Tone Oscillator levelwhen Channel
1
knob is pulled out, and Slate-tone and -microphone
levelwhen Slate button is pushed.
HeadphoneJacks
Two stereophonejacks: one mini3.5mm(frontpanel)
and one 114-inchphone (side panel). Combined out-
put,includingTone Oscillator,SlateToneandSlateMi-
crophone,appearsat headphonejacks. Can be used
to drive up to four headphonesor Aux-level recorder
or amplifierinputs.To wireeitherconnectorfortwoout-
puts,connect oneconductortotip;connectothercon-
ductorto ring;andconnectshield(s)tosleeveof appro-
priate mating stereo plug. Tip and ring of headphone
jacks in-phasewithpin3of XLR LineJMicinputandout-
putconnectors.
Phones Control
Sets output level at headphonejacks.
Limiter
Limiter Inlout switch turns on fast-acting, peak-res-
pondinglimitercircuitto cut overloaddistortionduring
loud program intervals without affecting normal pro-
gram levels. Limiter switch In (operating) restricts
maximummixer outputto approximately+14dBm. In-
creasingindividualChannelor Mastergaincontrolsin-
creasesbothaverageoutputandamountof limiting.To
change Limiter threshold, see section on Limiter
ThresholdAdjustment.
Peak LED
IndicatesLimiteroperationwith Limiterswitch In.With
switchOut,flashesat6dBbelowoutputclipping.Peak
indicator respondsmuch faster than meter, activated
by even shortest transient peak, yet remains lit long
enoughto provideeasy recognition.
VU Meter
Factory calibrated for +4 dBm = 0 VU with 600-ohm
loadat Lineoutput. (Microphoneoutput levelsare 50
dB below Line output.) Supplied0 VU level is recom-
mendedfor normalusetoprovideapproximately14dB
headroombetweenoperating leveland clipping level.
To change0VU level,seesectiononVU MeterAdjust-
ment.
VU Lamp
Illuminatesmeterwhilebuttonisdepressed; automati-
cally turns off 5 secondsafter releaseto prevent bat-
tery drain.
Tape Outputs
3.5 mmjack tofeedunbalancedAux-levelinputof tape
recorderor amplifier.Tipof connectorinphasewith pin
3 of XLR connectors.
Telephone Lines
In Line position, output transformer will operate with
dc-biased "dialed up" telephone lines although there
maybeslight increasein distortion.When connecting
FP31 to telephone line, use FCC-Registered* inter-
face adapter between mixer andtelephone line.
'DOC-Certified in Canada
Condenser MicrophonePower
Condensermicrophones,either 12 to 18Vdc phantom
(simplex)powered or 9 Vdc A-B(T) powered, can be
suppliedfrom any Mic input of FP31.Below batteries,
inside battery compartment, are three 3-position
switches.Center position isfor dynamic microphones
(nodc powersuppliedto Mic input); left position is for
9-Vdc A-B power, right position is for 11
- to 18-Vdc
phantompower.
NOTE:Nopowerissuppliedto anyinputwith LineJMic
switch in Line position. No A-B power issupplied un-
less right-sidebattery is present.
Mixer Powering
Inordinary portable use, the FP31 is powered by two
standard9-Vdc alkaline batteries installed in leftmost

batterycompartmentpositions.Phantompowerisalso
suppliedby these batteries.
The FP31canalsobepoweredby an 11to 18Vdc ex-
ternal source, such as an automotive battery, battery
beltpack,Shure PS20AC Adapter or other low-ripple
ac power converter (see Figure 2), using the12 Vdc
single-pincoaxial inputconnectorinthe left-sidepan-
el. To filter possible power-supply hum and noise, in-
stall a 100
C2 resistoronthe "+" sideof the dc output.
The outsidebarrelof the matingconnectoris positive.
u
- J
*Wire with white stripe is 12 V+ Coaxial Plug
Cutoff molded dcpower plug of PS20 and wire new
connector
as shown
POWERINGFP31 FROM EXTERNALAC ADAPTER
FIGURE 2
Parts Required:
1 Shure PS20AC Adapter or equivalent (dc output
= 12Vdc, 100mA minimum)
1 100
L2 1 W resistor
1
Coaxialdcpowerplugtofit FP31 external dc pow-
er jack (2.1 or 2.5 rnm I.D.) Radio Shack
#274-1567A
Batteriescan beleft inplaceas backupincaseoffail-
ureof externalsource.Switchovertointernalbatteries
is performedby disconnectingexternal plug.
CAUTION
12Vdc inputcircuitisnotfused.Any externalsource
should be providedwith in-linefuse, 0.25 A, 250 V,
as safety wecaution.
Battery Check
DepressingBATTbuttonconvertsVU Metertoreadout
of batterycondition (two mixer-poweringbatteries)or
of supplyvoltage. Readingsof 0VU or higher indicate
good batteriesor adequateexternal supply.
VU METER ADJUSTMENT
To set the VU Meter for a value different from the
supplied0 VU
= +4 dBm, proceed as follows.
1. Connecta 600-ohmloadto one of the Lineoutputs.
2. Connectanacvoltmeter (e.g.,
HP 400GL)inparallel
with the load.
3. Pulloutthe Channel 1knobto activatetheTone Os-
cillator.
4. Adjustthe Tone Oscillatorlevelwith the Mastergain
control untilthe ac voltmeter reading is at the level
desired.
5. With a screwdriver, adjustthe VU Leveltrimpot (left
of the A-BIDYNISPLX Selector switches) until the
VU Meter reads0.
LIMITER THRESHOLD ADJUSTMENT
To adjustthe Limiterthresholdfor a value differentfrom
the supplied
+I 4 dBm, proceed as follows.
1. Connect a 600-ohm load and an ac voltmeter to a
Line output as described insteps 1 and 2 above.
2. Pulloutthe Channel1knobto activatetheTone Os-
cillator.
3. With Limiter switch Out, adjust Master gain control
untilthe ac voltmeter readingisat the leveldesired.
4. Move the Limiter switch In, and adjust Limiter
Thresholdtrimpot (left of the VU Leveltrimpot) until
the level drops 0.5 dB.
FURNISHED ACCESSORIES
CarryingCase ....................... 9588066
.....................
Shoulder Strap 90BX2600

REPLACEMENT PARTS LIST
Reference
Designation
C102, C104, C106 C107, C109,
C115, C119, C126, C130, C205, C302, C303,C305 C112, (2120, C153 C114, C154, C122, C150,
C211, C154,
C212 C128 C129, C131, C206
C133
C144 C145, C146, C147 C148
(2149, C157, C158, C159
C152
D101-D112, D115, D117, D120, D201,
D202, D203
D306
D113, D114, D302, D303, D304, D305 D118, 0119, D205
Replace. ment Kit Commercial Alternate
I
Replacement Kit Consists
Of:
CIty.l Part No.
I
Description
86V628 Capacitor, Electrolytic,
I
--
1-1
I I
Panasonic ECEBOJK220
22 pF, 6.3V
Commercial Alternate
L1-L10
-
-
-
80A250 Ferrite Bead Ring
L201, L202
-
- -
80A365 Ferrite Bead Ring
L301
Panasonic ECEBI
EK4R7
Stackpole 57-0181 Stackpole 57-3425
VU Meter (Special VU Range) Cartridge, Electret
Knob, MIC 1-3
Knob, MASTER Knob, PHONES
Battery Cover Lamp, TI, IOV, .027A
Transistor, NPN Transistor. NPN
None Radio Shack 270-090
None None None None Precision Lamp PL7218 Motorola 2N5210
Farranti FST185L
86AC629 Capacitor, Electrolytic,
4.7 pF, 25V
86AD629 Capacitor, Electrolytic,
470 pF, 16V
Marcon CESSMIE4R7
Marcon CESSMlC471 MP6
-
-
PLI
-
-
Q101 RKC89 Q102, Q103,
-
-
(2104, Q301 Q302 RKC66
R110
&
S108
-
-
868629 Capacitor, Electrolytic,
1-1
I
470 pF, 16V Marcon CESSMlC471A Capacitor, Electrolytic, 33 pF, 1ov Capacitor, Electrolytic,
1 pF, 25V
Capacitor, Electrolytic,
220 pF, 16V
Capacitor, Electrolytic, 220 pF, 25V
Capacitor, Electrolytic,
47 pF, 1ov
Capacitor, Electrolytic,
100 pF, 16V
Capacitor, Electrolytic,
22 IF, 16V
Capacitor, Electrolytic,
1000pF, 25V
Diode, Silicon, Computer,
75v
I.C.C. 336RSS010M
Panasonic ECEBIHKO10
Marcon CESSMIC221
I.C.C. 227RMR025M
Marcon CESSMlA470
I.C.C. 107RMR016M I.C.C. 226RSS016M
I.C.C. 108RMR025M
TI IN4148
1
86A335
I
Transistor, PNP TI TI593
None
Potentiometer, look, with
SPDT Switch
Potentiometer, lOOk
Potentiometer, 50k
I
Potentiometer, lOOk
I
Potentiometer, 50k Potentiometer, 50k
Switch, Slide, 4PDT
None None
Piher PTlOLh(2.5)lOOk None Piher PTIOLh(2.5)50k
Alcoswitch MSS4200RG
SI04. S105,
I
--
I
-
1
55A8022
I
Switch, Slide, DPTT
I
Alcoswitch SLS-230PC
1
Sl06
I
51D243 Transformer, Input
I
Sw~tch,Slide, DPDT Swttch, Pushbutton, SPDT
None None
Raytheon RC4156N
National Semiconductor LM386N-4 None Raytheon RC4156N Motorola LM393N
TI UA78LIOACLP
Raytheon LM339DB
ved for piece partswhere
Rlc
None None
51
A8015
1
Transformer, Output
Diode, Germanium, 30V RCA 1N48, 1N60 868808 lntegrated Circuit, Quad Op
I
Ampl (Selectedfor NF)
U301
Parts listedas RKC Kits Kit number is shown wi
RKC21
I
4
1
86A404
1
Silicon Rectifier. 100V. '%A Motorola IN4002
I
lntegrated Circuit, Audio
Power Amplifier
ihould be order1
be shipped in
I
Diode, Light Emitting, Green Diode, Light Emitting, Red
Connector, Three Socket Connector, Three-Pin
Phone Jack, Miniature, 3.5mm
Phone Jack,
'h
in.
Power Jack, Coaxial
d
bythat kitnumber. Orders recc
IKC quantities.
Rohm SLR34MG3
Rohm SLR340R3 ITT Cannon XLR-3-31-F77
ITT Cannon XLR-3-32-F77
None None None
redfor piece parts where RK(
Opto-Isolator
lntegrated Circuit, Quad Op
lntegrated Circuit, Dual
comparator
lntegrated Circuit, 10V Regulator lntegrated Circuit, Quad
Comparator
'arts listedas RKC Kits <it number is shown wi
1
be ordered bythat kit number. Orders re(
lipped in RKC quantities.

PC BOARDS
BOTTOM BOARD - COMPONENT SIDE BOTTOM BOARD-SOLDER SIDE
TOP BOARD - COMPONENT SIDE TOP BOARD
- SOLDER SIDE
METER BOARD - COMPONENT SlDE
. -
METER BOARD - SOLDER SlDE

CIRCUIT DIAGRAM
TAPE OUT I
MINI JACK I
r----------7
I
I
I
I
I
I
I
PUONE JACK
I #HE TONE OSC
TONE 09C.
RME TMR
NOTES BT I 9V 8T2
1.
ALL CAPACITORS INp.F bND 50V OR MDRE WLESS OTHERWISE SHIWN. 7.
AC VOLTAGES SHOW FOR VL02B OBTAINED WITH LIMITER "IN"
ELECTROLYTIC CAPACITORS SWIN
pF X VOLTS. (THRESHOLD AT
+Ik ISM) bND WILL VARY DEPENDING UWN CIRCUIT
2. ALL RESISTORS L/WI 5% LNLESS OTHERWISE SPECIFIED. PARAMETERS AND SETTING
OF LIM ADJ CWTROL (W31.
3. FOLLOWlffi SYP(BOLS DEMTE:
8.
AC VOLTAGES SHIWN FOR 930% OBTAINED WITH VU ADJ CONTROL
(~~5.3) SET m IN~ICATE o w AT +4 rn~ LINE PUT.
;;K;S 6 EE~ "AD AC
0 PCMLTAGE I VOLTAGE
4. ALL VOLTAGES MEASURED WITH 32.5 MLTS DC APPLIED m lwv nett
POWER INPUT CWECTOR. ALL SWITCHES IN WSITIONS SWNI EXCEPT
AS NOTED. MIC
1 INPUT LEVEL -80 DBV (0.1 mV RMSI ACROSS PINS
2 AND
3 OF JLI SUPPLIED BY 150 MI L KHZ SOURCE. LINE OUTPUT
(J4 OR
J5) WADED WITH 600 OHMS. PHPlES OUTPUTS
LOADED WITH
200 OMS FROM TIP AND RING TO SLEEVE. TAPE
MIT WADED WITH 47K
OHMS. INPUT L PJvD WSTER CONTROLS CLOCKWISE. PH3NES KNTROL
SET FOR 0.W RHS ON WIPER (APPROXIMATELY MID POSITION). VOLTAGES
ARE MEASURED WITH RESPECT TO GROLND EXCEPT
WHERE
SHMN.
X bND
AC VOLTAGES MEASLRED WITH LO HEWM METERS. VALUES ARE TYPICAL
LAC VOLTAGES ARE RMS VALUES)
bND MAY VARY + 20%.
5. WLTAGES SHMN FOR ULOZC PND D OBTAINED WITH TONE OX: SWITCHED ON.
6.
MLTAGES SHlWN FOR Urn6 OBTAINED WITH SLATE SWITCH MPRESSED.
AC VOLTAGES SHOWN FOR SECTIOvS A AND B OF UL06 WILL VARY WITH
ACOUSTICAL
INPUT m WL. VAWES GIVEN PS(E TYPICAL MR AN AC
COUPLED ILpF) L KHz, 3 mV RMS SIGNAL APPLIED AT THE JLNCTIW OF
RL57 AND R158.
THIS MAY RE APPROXIMATED BY A STEADY WISTLE
WITHIN 6" OF THE FlMNT PANEL. VOLTAGES SMFOR SECTICNS C
bND D OF ULW ARE BEST READ WITH R209 SHORTED
CU TO PREVENT THE
SLATE TONE TIMER FROM TIMING OUT THE SLATE TONE OSCILLATOR.
I
e
3
4
5
5
T eot
BOTTOll VIEW
WlOl
A -WmA Vcc/,
WZG2 A - W3Ol A VUDFZ
0- 8 VE
0 0----9 6 Vcc
C (2-----o C PK IND. DRIVE
C - C PK IND OR
D - D MIX CHAN 3
0 - D
E - E UTE TONEPWR E 0------o E GND
F - F MIX UiAN I
F - F AUX
G- GMIXCIlAN2 G o-----O G IOV
H- HCaEIMP3OVT
J - J PREAMP &! WT
K cr-----O K PREAMP I OUT
L - L SLATE TMR OUT
M - M VU OR
N - N PROG
P- P A-0 BATT-
R - R A-8 BArr+
5- SGND

A single-pincoaxial 12 Vdc external power,jack.permits the mixer The mixer requires 11to 18Vdc for operating power. Inter-
to be powered froman-11 io 18 volt source such as a video tape nal power is supplied by two standard rectangular 9-volt
The three &socket professional audio input connec- recorder,
automotive electrical system or ac power converter. Such
P
alkaline-batteries(Duracell K~1604 ~r<~u~valent)w~ch-
tors are individually switchable to balanced 600-ohm an external source will also provide simplex power to the also provlde s~mplex(phantom) power to the microphone
line or low-impedance microphone level. In the MIC microphone inputs, but a battery is still required for A-B power. inputs. Battery life
IS approximately 8 hours.
position, either simplex (phantom) or A-B power
IS I IMPORTANT: Use only alkaline batteries.
available at each input for powering condenser
____I
microphones. Each input transformer is Mumetal t
shielded for maximum resistance to electrical hum. When powering the mixer from an external source, the batteries A thi~d-91volt-batte~:is used to supply
may be left in place as backup in case of failure of the source. ~3-~owerat each microphone input.
Switchover to battery power is performed by removing the plug When the ~nputselector switch is in the
from the 12Vdc jack. To prevent the possibility of damage caused Line
position, the power is automatically
by leaking batteries, remove the batteries during any prolonged off for that input.
period of storage or nonuse.
t
-- --
Using .the.-On10ff-switch to turn the power on
starts the green Power On indicator LED
- flashing . .. - -- . --- -
!
with a repetition rate of approxima~ly1 second.
I
The LEDcontinues to flash so long as the switch
1
The Slate-pushbutton inserts a 1-second low-frequency
tone (400 Hz) each time it is depressed, and it keeps the
slate microphone on as long as it is depressed. is on.
-..- . .. -..-.- -,
Individual Lo-Cutfilter switches for each inputreduce low- The VU-Meterissupplied set for 0
,
frequency interference from air-conditioner or fan noise, VU = + 4 dBm. This level can be -
wind, strong hum fields, or similar sources. The filters in- changed by an internal adjust-
,
sert a 7 dB rolloff at 100 Hz with a slope of -6 dB per oc- ment (see section on VU Meter
,
tave. Adjustment).
I
The Limiteflhreshold-and-VU-Meter_tfimpots are
locatedthrough screwdriver slots below the bat-
tery compartment and to the left of the Simplex or A-B power is selected by
- -- - --- -
means of switches directlybelow the battery
A-BISimplex switches.
The VU Lama bushbutton momentarilv il-
compartment, inside the battery door. Inthe
DYN position, no power is supplied to the
Mic inputs.
--- - -
luminates ;he Zier dlal:~; automatic timed
release shuts off the lamp after 5 seconds. The
lamp remains lit while the button is depressed.
7
A13 5 mm mini jack provides an Aux-level Tape
iiL-- - --
output with minimum clipping level of 0.5V RMS
(-6 dBV).
On Channel-1,-the. Gain-Control- knob-
pulls out to activate a 1 kHz tone
oscillator that serves as a level-setting
aid. The oscillator level is set with the
--
Master control and is indicated on the
VU Meter.
The-re<Peal&ED flashes to indicate the onset
of limiting.When the Limiter is Out, the red LED
acts as an overload indicator and begins
flashing at 6 dB below output clipping level.
The Battery check pushbutton converts the VU
L
~ecrto a7battery condition orcircuit voltage in-
dicator while the button is depressed.
s7
i
A built-in pushbutton-operated, electret condenser
slate microphone can be used either for identifying
- -
recorded segments or as an emergency field,
microphone.
The Master gain control sets the output level at the
;
LinelMic and~a~e~ut~u~s.Gain is 40 dB from Mic In to
Mic Out or from Line Into Line Out; 90 dB from Mic In to
r
Each input-channel-has-its own-gain-
control. The input clipping-level for Ab.5-mm-minijack and a quarjerjnchphonejack-
provide two stereo headphone outputs that can
microphones is from -47 to
- 17dBV
depending on the channel control set-
ting. For line inputs, the clipping level
ranges from +3 to +33 dBV, again
depending on the control setting.
Line Out, 68 dB from Mic In to Tape Out, and 18 dB from
J
Line Into Tape Out.
s
!
be used simultaneously. They are designed to
drive mono or stereo headsets with impedances
of 8to2,000 ohms. Theycanalsobeusedtodrive
up to four Aux-level tape recorder or amplifier in-
puts.
s
Abeparate Phones volume control sets the level
at the TCa~~eF~tpGt~;-maxii~moutput is
1.6V RMS ( + 4 dBV) to 200 ohms.
I
Two 3-pin professional audio output
- -- - - -- --- -- - -
,
connectors are individually switchable to
--
-
600-ohm Gne level or I&-impedance
microphone level. Minimum clipping levels
are
+ 18 dBm (Line)and -34 dBV (Mic).
The output Limiter has a threshold of
+ 14 dBm at the
- --
600-ohm Line output (4 dB below clipping), with com-
parable levels at the Mic and Tape outputs. The
threshold can be internally adjusted down to +3 dBm
(see section on Limiter Threshold Adjustment). The
Limiter attack time is
3 msec typical, with 500 msec
typical recovery time, for unobtrusive operation.