Shure Musical Instrument FP24 User Manual

Model FP24 User Guide  
Microphone Mixer  
Headphone Monitoring  
General Description  
Switchable between program audio or external (stereo) tape  
The Shure FP24 is a studio-quality two-channel, portable, stereo  
microphone mixer. With assignable L-C-R inputs, built-in slate mi-  
crophone, 1 kHz tone oscillator, and headphone monitor, the FP24  
is extremely flexible. Its impressive audio performance and com-  
prehensive features make it suitable for the front end of any studio  
or field production system. Radio, television, and film production  
engineers will especially value its compact size, sunlight-readable  
LEDs, and rugged mechanical and electrical construction that  
make it able to withstand extremes in the field.  
returns.  
High current headphone output has level control and peak  
indicator.  
Level Metering  
Dual-color LEDs indicate clipping and limiter activity for  
each channel.  
Sunlight-readable, seven segment GaN LED output meters.  
3-position LED brightness switch (intensity selector).  
Features  
High Performance Microphone Inputs  
Maximum of 66 dB of gain (each input).  
Audio Limiters  
“Unclippable” input peak limiters with adjustable limiter  
threshold (each input).  
Premium Lundahl input transformers provide superior audio  
Dual mono or linked stereo limiter operation.  
quality and freedom from interference problems.  
Flexible Powering  
Sealed, conductive plastic potentiometers for long life and  
Internal power from two AA batteries with easy access  
reliable gain adjustment.  
battery compartment.  
Phantom power, selectable between 48 volts and 15 volts.  
Chassis-isolated 5 to 14 VDC input for easy external DC  
Switchable low-cut filters with 80 and 160 Hz corner  
frequencies, 6 dB per octave. Filters are inserted prior to  
any active circuitry to maximize headroom.  
powering.  
Power LED indicates low battery power.  
Inputs assignable to Left, Center (both left and right) or  
Trouble-Free Design  
Right  
High-strength, extruded aluminum chassis with protective  
metal end panels withstands punishing field conditions.  
Audio Performance  
Dynamic range exceeding 110 dB.  
10 Hz to 50 kHz audio bandwidth.  
Exceptionally low distortion characteristics.  
All-metal connectors mount directly to the chassis for  
durability and RF immunity.  
Free from “Pin 1” grounding problems.  
RF filtering on all inputs and outputs.  
Discrete, 6-transistor, balanced output drivers provide signal  
integrity over long cable runs.  
2005, Shure Incorporated  
27A8727 (Rev. 1)  
Printed in U.S.A.  
 
Front Panel Controls, Connectors, and Indicators  
1
2
6
9
10  
11  
L
R
13  
4
MIC  
+16  
0
+4 +8 +12  
–30  
–15  
POWER  
FP24  
METER  
1kHz  
12  
1
2
L C R  
L C R  
SLATE  
TAPE RTN  
PHONES  
INT EXT  
3
5
7
8
Figure 1. Front Panel  
1. Input Gain Controls  
8. Tape Return Switch  
Sealed, conductive plastic rotary potentiometers.  
Toggle switch allows external audio to be monitored in the  
headphones. The center position is FP24 program audio.  
The left and right positions monitor tape return audio; the left  
position is locking, and the right position is momentary.  
2. Input Peak/Limiter LEDs  
Dual-color LED illuminates red at 3 dB below clipping; illumi-  
nates amber to indicate limiter activity.  
9. Headphone Connector  
3. L-C-R Switches (Input Assignment)  
Three-position switch assigns inputs to Left, Center (both  
left and right) or Right outputs.  
For stereo and mono headphones with ¼” connectors.  
10. Headphone Volume Control  
4. Slate Microphone  
11. Headphone Peak LED  
Condenser microphone with AGC activated by momentary  
Slate Microphone Switches. Slate Microphone output ap-  
pears at all outputs.  
Illuminates 3 dB before clipping of either channel of the  
headphone circuit and either channel of Tape Return audio.  
12. Power Switch  
5. Tone Oscillator/Slate Microphone Switch  
Toggle switch activates 1 kHz tone oscillator when switched  
to the left position and activates the slate microphone when  
momentarily moved to the right position. Microphone inputs  
are muted when Tone Oscillator or Slate Microphone are  
activated.  
Three-position switch selects the power source. The unit is  
powered from internal batteries when in the left position;  
powered from external DC source when in the right position.  
Center position is off.  
13. Power LED  
Two-color LED illuminates green when the unit is powered  
and changes to red when batteries require changing. For  
external DC, the power LED is always green.  
6. Output Meters  
Indicates peak output level in dBu.  
7. Meter Brightness Control  
Three-position switch adjusts the intensity of illumination of  
the output meter; low illumination, normal illumination, or  
super-bright illumination.  
Input Panel Connectors and Controls  
3. High Pass Filter Switch  
4
Three-position switch selects 80 Hz or 160 Hz corner fre-  
quency filters, 6 dB per octave. Filters affect both inputs.  
Center position of switch removes filters from the signal  
path.  
5
TAPE OUT  
TAPE RTN  
LEVEL  
L
R
4. Tape Output  
48V  
80  
LINK  
ON  
L
R
1
3.5 mm ( / in.) TRS stereo output (unbalanced) can be  
8
used to feed consumer level DAT, MiniDisc, and CD record-  
ers. Tip = Left, Ring = Right, Sleeve = Ground.  
15V  
160  
THRESHOLD  
LIMITER  
1
2
7
PHANTOM  
MIC INPUTS  
5. Tape Return Level Control  
Recessed potentiometers adjust Tape Return level feeding  
the Headphone Monitor.  
1
2
3
6
Figure 2. Side Input Panel  
6. Limiter Switch  
1. Mic Inputs  
Activates input peak limiter. ON position functions as a dual  
mono limiter, with each input signal controlling its own limit-  
er. LINK functions as a stereo limiter, with both left and right  
inputs controlled simultaneously. Center position of switch  
turns limiters off.  
Transformer-balanced XLR inputs accept microphone level  
signals. Pin 2 = hot, Pin 3 = cold, Pin 1 = ground.  
NOTE: You can use Shure A15LA line adapters to con-  
nect balanced, line-level sources to these inputs.  
2. Phantom Power  
7. Limiter Threshold Level Control  
Three-position switch selects either 48-Volt or 15-Volt phan-  
tom power for both inputs. Center position turns phantom  
power off.  
Recessed potentiometers adjust peak level of limiter activa-  
tion. Can be independently controlled for each input.  
3
 
Output Panel Connectors  
1. Strap Slot  
Attachment point for camera straps.  
2. Tape Return Input Connector  
3
2
1
3.5 mm ( / in.) TRS stereo (unbalanced) input for head-  
8
phone monitoring of external audio sources.  
Tip = left, ring = right, sleeve = ground.  
1
4
3. Left and Right Line Level Outputs  
Active-balanced XLR line-level outputs. +22 dBu peak out-  
put level. Pin 2 = hot, pin 3 = cold, pin 1 = ground. Pin 3  
can be grounded or ungrounded to drive unbalanced inputs.  
TAPE RTN  
5
1(L)  
2(R)  
4. Battery Compartment  
5–14 VDC  
LINE OUTPUTS  
+
Houses two AA batteries. Insert positive (+) end of batteries  
first.  
Figure 3. Side Output Panel  
5. External DC Power Input  
Accepts 5–14 VDC from an AC to DC transformer or a bat-  
tery supply. Locking, threaded coaxial connector.  
Center pin = positive, sleeve = negative. Use the supplied  
threaded connector for power supplies with plug-type con-  
nectors (such as the Shure PS20). See Figure 5 for wiring  
diagram.  
Operational Notes  
Input Transformers  
Phantom Power  
The FP24 uses premium Lundahl input transformers with pre-  
mium magnetic core material to achieve high signal-handling capa-  
bility, flat frequency response and minimum distortion. Because  
these transformers provide galvanic isolation from the driving  
source, they offer superior isolation from the adverse and uncon-  
trolled environments of field-production. Their high common-mode  
impedance also provides exceptional common-mode rejection.  
Use one of the two phantom power settings on the FP24 for mi-  
crophones that require it. Some microphones need the 48-Volt set-  
ting to avoid a loss of headroom and increased distortion. The  
15-Volt setting, however, lengthens battery life, and electret-con-  
denser microphones rated for operation at 15 V or less generally  
receive no performance benefit from the 48-Volt setting. Consult  
your microphone documentation for phantom power requirements.  
Dynamic microphones do not require phantom power. A properly  
connected balanced, dynamic microphone is not affected by the  
presence of phantom power and does not draw any current. How-  
ever, poorly or incorrectly wired microphone cable can cause audi-  
ble artifacts in the microphone signal (phantom power can be an  
excellent cable tester). It is good practice to turn phantom power off  
when not needed.  
Output Circuitry and Tape Output  
Each line level XLR output of the FP24 uses a discrete, six-tran-  
sistor, “impedance balanced” output stage. The circuit uses over-  
sized, high speed transistors to achieve low distortion, robust line  
driving capability. Pin 2 is driven with signal, and pin 3 is not. (A  
common misunderstanding is that a “balanced” output refers to  
equal and opposite signals on pins 2 and 3. Correctly, “ impedance  
balanced” refers to equal impedances from pins 2 and 3 to ground,  
not equal signal voltages.) To drive unbalanced inputs, pin 3 can be  
grounded or left unconnected. There is no change in signal level  
driving balanced or unbalanced inputs.  
High Pass Filter  
To remove excess low-frequency energy in the audio signal, use  
either of the two high pass (low cut) filter settings on the FP24. Use  
the 80 Hz position for most applications, such as recording speech,  
music, and ambient sound. The 160 Hz position is useful for en-  
hancing speech clarity and reducing wind-noise. The high pass fil-  
ter is a single pole design, 6 dB per octave.  
The FP24’s tape output feeds consumer-level devices, such as  
computer sound cards, DAT or MiniDisc recorders, and cassette  
1
1
recorders. A cable wired with 3.5 mm ( / in.) TRS to 3.5 mm ( /  
8
8
1
in.) TRS or 3.5 mm ( / in.) TRS to Left/Right phono (RCA) connec-  
8
When possible, equalize at the sound source by microphone  
selection, placement, use of a windscreen, and onboard micro-  
phone filtering. Using both the high pass filter on the FP24 and the  
one on a microphone has an additive effect, increasing the overall  
slope of the roll-off.  
tors will connect the FP24 to such devices.  
Using the FP24 as a Mixer  
The FP24 can be used as a simple two-channel mixer. Possible  
applications include:  
Headphone Monitoring and Tape Return  
The three position Tape Return switch on the front panel selects  
the audio source being monitored:  
Quickly reversing the stereo image of a recording without  
reconnecting inputs or outputs.  
During set up, checking for mono compatibility by assigning  
Center Position—Program audio (normal operation). Monitors  
both inputs to the same output.  
the Left and Right outputs of the FP24.  
Recording dialog in mono.  
Left and Right Positions—Secondary audio source. Monitors  
audio from the Tape Return input of the FP24. Can be used to verify  
that signal is reaching cameras and tape machines. Left is locking;  
right is momentary.  
Performing “mix minus” by routing Input 1 to Center and  
Input 2 to Right. A summed mono signal of both inputs  
appears at the Right output while only Input 1 appears at  
the Left output. This is useful for post production processing  
of Input 1 audio.  
Important: The FP24 can drive headphones to very high levels.  
Exercise care when monitoring. Reduce the level when the Head-  
phone Peak LED illuminates.  
4
 
Limiters  
Power Sources and Battery-Life  
The FP24 has two built-in peak-responding limiters, one for each  
input channel. Each limiter has a two-stage circuit: the first stage  
keeps the input gain stage from clipping; the second stage limits the  
variable gain stage according to the Limiter Threshold control set-  
ting. This unique, two-stage topology limits the gain stage directly  
after the mic input transformer without changing the input imped-  
ance as other “at the mic” limiters do. The circuit enables the FP24  
to limit in excess of 50 dB, making it very difficult to clip the unit re-  
gardless of the gain setting.  
The FP24 operates from either two internal AA alkaline cells or  
an external 5–14 VDC battery supply or AC to DC transformer  
(such as the Shure PS20). The power connector is a locking,  
threaded coaxial connector. Center pin = positive, sleeve = nega-  
tive. Use the supplied threaded power connector if necessary (see  
Figure 5).  
The external DC input supply is galvanically isolated (floating)  
from the chassis and the rest of the circuitry. The isolation provides  
trouble-free interconnection to other pieces of equipment sharing  
the same DC power source. The center pin of the locking DC con-  
nector is positive, and the sleeve is negative. Since the external DC  
supply is floating, the positive or the negative can be connected to  
the chassis with no adverse effects.  
The FP24’s limiters can operate in either either dual-mono or ste-  
reo. Use the three-position switch on the input panel to set the limit-  
ing mode:  
In the middle position, the limiters are turned off.  
Two AA, 1.5 Volt lithium cells can power the FP24 for up to  
approximately 11 hours. However, several factors affect how long  
a given pair of batteries will last. These factors include battery  
chemistry, ambient temperature, use of phantom power, output  
meter brightness, and the output drive level of the FP24. The chart  
below provides estimates of battery life in different kinds of circum-  
stances. Experimentation can determine expected battery life for  
specific setups and environments.  
In dual mono operation (ON switch position), the limiters  
work independently, responding only to their input signals.  
In stereo-linked operation (LINK switch position), the  
limiters control both channels identically. This maintains a  
stable stereo image.  
When the limiters activate, the Peak/Limiter LED on the front  
panel illuminates amber in proportion to the amount of limiting for  
each channel.  
NOTE: AA carbon cells and AA nickel-cadmium cells are not rec-  
ommended for use in the FP24 since they have lower power capac-  
ity than other types and will result in very short service life.  
Tone Oscillator and Slate Microphone  
The switch labeled 1 kHz/SLATE on the front panel controls two  
functions. The 1 kHz position (left) mutes all inputs and sends a 1  
kHz sine wave calibration tone at +4 dBu to all outputs. The tone  
oscillator can be used to verify connections and set nominal levels  
on recording and transmission equipment.  
Battery  
Type  
Microphone Type and  
FP24 Settings  
Battery  
Life  
Eveready AA  
2 dynamic handheld microphones, low  
11 hrs.  
6 hrs.  
No. L91 (lithium) meter brightness, no headphones  
2 dynamic handheld microphones, low  
meter, low headphone level  
The SLATE position (right) is a momentary switch position that  
activates the built-in slate microphone located behind the front pan-  
el. When the switch is held to the right, all inputs are muted and  
slate mic signal is sent to all outputs. The slate mic circuit contains  
an AGC (automatic gain control) to keep the slate level relatively  
constant regardless of the acoustic level. Use the slate microphone  
to document takes right at the mixer location when microphones  
are on talent or away from the production mixer.  
2 condenser, 15-Volt phantom pow-  
ered microphones, normal meter in-  
tensity, normal headphone level  
Duracell AA MN  
1500 (alkaline)  
4 hrs.  
2 hrs.  
2 studio condenser, 48-Volt phantom  
powered microphones, super bright  
meter intensity, high headphone level  
Test conditions: 70 degrees F, 42 dB of gain with an acoustic music  
source, 600 ohm load, +4 dBu output  
Metering and Clip-Indicators  
Three two-color clip-indicators monitor signal levels throughout  
the FP24:  
Interconnecting the FP24 and FP33  
1. Above each input gain control, a two-color LED glows red 3  
dB below clipping. This clip circuit monitors both the front end  
gain stage and the variable gain stage.  
You can connect the balanced, line level XLR outputs of the  
FP24 to the mix bus of the FP33 using the Shure A33LK accessory  
kit (or construct a cable assembly as shown in Figure 4 on the fol-  
lowing page).  
2. A headphone-clip LED, located above the headphone level  
control, indicates when either channel of the headphone cir-  
cuit approaches clipping.  
Combining an FP24 and a Shure FP33 (or FP32A) mixer yields  
a flexible, cost-effective, 5 X 2 field mixing setup with the following  
features:  
3. The headphone-clip LED also indicates when either channel  
of the tape return audio is near clipping.  
Simultaneously accepts a stereo microphone, hard-wired  
shotgun, and two RF lavalier microphones.  
When the limiter is activated, these input LEDs glow amber in  
proportion to the amount of limiting.  
48-volt phantom power for all five microphone inputs  
The FP24 has a seven segment LED output meter that shows  
peak output level in dBu. From left to right, the first three LEDs are  
separated by 15 dB and the remaining LEDs are separated by 4 dB.  
This calibration provides a 46 dB-dynamic range with good resolu-  
tion in the critical signal level range.  
Limiters on the FP24 inputs  
Input assignment switches on the FP24 and pan pots on the  
FP33 inputs  
Two output buses—assignable to mic or line level output.  
Master volume and headphone monitoring for all five inputs  
The meter uses premium Gallium Nitride (GaN) LEDs which are  
visible even in direct sunlight. A three-position switch on the front  
panel controls the brightness of the output meter. Choose low, nor-  
mal, or super-bright.  
controlled from the FP33.  
Compact—FP24 adds little bulk to an existing FP33  
package.  
CAUTION – When set to super-bright intensity, the LEDs in the  
output meter can irritate or damage eyes with prolonged direct ex-  
posure.  
The FP24’s isolated external DC input jack eliminates  
ground related interference problems.  
5
 
This class B digital apparatus complies with Canadian ICES–003.  
Eligible to bear CE marking.  
NOTE: When interconnecting the FP24 and FP33, inputs from  
the FP24 appear at the FP33 mixbus with their polarity reversed.  
(This is unavoidable due to the nature of the interconnection.) To  
avoid cancellation or interference effects (e.g., comb filtering) be-  
tween the signals from the FP24 and FP33 inputs, use Shure  
A15PRS polarity inverters on the FP24 inputs, or do one of the fol-  
lowing:  
Conforms to European EMC directive 89/336/EEC: Professional Audio Products  
Standard EN 55103 (1996); Part 1 (emissions) and Part 2 (immunity). The FP24 is  
intended for use in environments E1 (residential) and E2 (light industrial) as defined in  
European EMC standard EN 55103. It meets the applicable tests and performance  
criteria found in the standard for these environments. EMC conformance is based on  
the use of shielded interconnecting cables.  
N 108  
Keep microphones connected to the FP24 as far away as  
possible from those connected to the FP33.  
For microphones that must be close together (such as those  
Limited Two-year Warranty  
in a stereo pair), connect them to the same mixer.  
Shure Incorporated (“Shure”) hereby warrants that this product will be free from de-  
fects in materials and workmanship for a period of two years from date of purchase.  
At its option Shure will repair or replace the defective product and promptly return it to  
you, or refund the purchase price. You should retain proof of purchase to validate the  
purchase date and return it with any warranty claim.  
NOTE: If constructing your own FP24/FP33 interconnect cable:  
Keep cable length to a minimum, since the interconnection  
is unbalanced.  
Be sure to drive the FP33 mix bus off of pin 2 of the FP24  
since the FP24 inputs are reverse polarity with respect to  
FP33 inputs.  
If you believe this product is defective within the warranty period, carefully repack  
the unit, insure it, and return it postage prepaid to:  
Shure Incorporated  
Attention: Service Department  
5800 W. Touhy Avenue  
FP24 XLR–L  
FP24 XLR–R  
FP33 mixbus  
820 ohm  
Evanston, Illinois 60714–4608 U.S.A.  
Outside the United States, return the product to your dealer or Authorized Service  
Center.  
This warranty does not apply in cases of abuse or misuse of the product, use con-  
trary to Shure’s instruction, or unauthorized repair. All implied WARRANTIES OF MER-  
CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE are hereby disclaimed  
and Shure hereby disclaims liability for incidental, special, or consequential damages  
resulting from the use or unavailability of this product.  
Some states do not allow limitations on how long an implied warranty lasts, or the  
exclusion or limitation of incidental or consequential damages, so the above limitation  
may not apply to you. This warranty gives you specific legal rights, and you may have  
other rights which vary from state to state.  
820 ohm  
Figure 4. FP24/FP33 Mix Bus Interconnect Cable  
FCC Declaration of Conformity  
We of  
Positive: Solder to center pin  
(marked with a white stripe on PS20 cable)  
Shure Incorporated  
5800 W. Touhy Avenue  
Evanston IL 607144608 U.S.A.  
847–600–2000  
declare under our sole responsibility that the following product,  
Model: FP24  
Name: FP24 Microphone mixer/preamplifier  
was tested and found to comply with Part 15 of the FCC rules.  
Negative: Solder to sleeve  
Operation is subject to the following two conditions: (1) this device may not cause  
harmful interference, and (2) this device must accept any interference received, includ-  
ing interference that may cause undesired operation.  
Figure 5. Attaching the Supplied Threaded Power  
Connector.  
Testing was completed by the following NVLAP or A2LA accredited laboratory:  
Certification  
L.S. Compliance, Inc.  
W66 N220 Commerce Court  
Cedarburg, Wisconsin 53012  
Telephone 262–375–4400  
Fax 262–375–4248  
Authorized under the DECLARATION OF CONFORMITY provision of FCC part 15  
as a Class B digital device. Tested to comply with FCC standards. FOR HOME OR  
OFFICE USE. This product complies with part 15 of the FCC rules. Operation is  
subject to the following two conditions: (1) this device may not cause harmful  
interference, and (2) this device must accept any interference received, including  
interference that may cause undesired operation. Changes or modifications not  
expressly approved by Shure Incorporated could void your authority to operate this  
equipment.  
Shure Incorporated, Manufacturer.  
This equipment has been tested and found to comply with the limits for a class B  
digital device, pursuant to Part 15 of the FCC rules. These limits are designed to  
provide reasonable protection against harmful interference in a residential installation.  
Signed:  
Date: Sept. 15, 2000  
This equipment generates, uses and can radiate radio frequency energy and, if not  
installed and used in accordance with the instructions, may cause harmful interference  
to radio communications. However, there is no guarantee that interference will not  
occur in a particular installation. If this equipment does cause harmful interference to  
radio or television reception, which can be determined by turning the equipment off and  
on, the user is encouraged to try to correct the interference by one or more of the  
following measures:  
Name, Title: Craig Kozokar, Project Engineer, EMC  
S
S
S
S
Reorient or relocate the receiving antenna  
Increase the separation between the equipment and the receiver  
5800 W. Touhy Avenue, Niles, IL 60714-4608, U.S.A.  
In U.S.A., Phone: 1-847-600-2000 Fax: 1-847-600-1212  
In Europe, Phone: 49-7131-72140 Fax: 49-7131-721414  
In Asia, Phone: 1-852-2893-4290 Fax: 1-852-2893-4055  
International Fax: 1-847-600-6446  
Connect the equipment into an outlet on a circuit different from that to  
which the receiver is connected  
Consult the dealer or an experienced radio/TV technician for help  
6
 

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