Shure FP51 Schematic

222

HARTREY AVENUE

SHU-

THE SOUND OF THE PROFESSIONALS'

..+

GENERAL

The FP51 is a compact, portable, high-quality gated memory dian Standards Association as Certified
compressor combined with a four-input, one-output
microphone mixer. Designed for applications in broadcasting,
recording and sound reinforcement, the FP51 integrates all the
features of professional compressors and mixers in a single
unit-small and lightweight enough for location use, but with
the reliability of a studio console.

FEATURES

40 dB compression range, with compression ratio approx­imately 10:l in normal operating range

Gated memory minimizes "pumping," has LED indicator
True average-responding compression maximizes output

level regardless of peak-to-average ratio of program
material. Peak-responding circuit reduces gain rapidly for
significant increases in input signal

Front-panel response rate adjustment (averaging time con­stant) compensates for variations in program material

Extremely low distortion, noise and RF su'sceptibility, with
wide, flat frequency response at all compression levels

Reliable operation under wide temperature and humidity
conditions

Protected against damage from input overload and
shorted outputs

Four transformer-coupled XLR inputs, each micro­phonelline switchable with low-cut filter and cuing func­tions

Phantom power for condenser microphone operation
Built-in tone oscillator permits checking levels and testing

lines

Transformer-coupled XLR output with microphonelline
switch

Headphone jacks (114-inch and mini-3.5 mm) with level con-

trol
Active, feedback-type input gain controls allow high-level

input signals without input attenuators
Illuminated triple-function VU meter indicates output level,

dB compression and battery condition
Powered by ac (120V or 240V-internally selectable) or

built-in battery pack gain (line)
Low battery drain provides up to 10 hours operation under

normal conditions
Noiseless and automatic switchover to and from battery

power without affecting compressor
Rugged, durable construction than 15 dB
Compact and lightweight for field use and transporting
Rack-mountable with accessory rack mount kit

Copyright

27A2216

1989,

Shure Brothers Inc.

(IJ)

@EVANSTON, ILLINOIS

60202-3696

PROFESSIONAL

Listed by Underwriters Laboratories Inc.; listed by Cana-

SPEClFlCATlONS

Frequency

30 to 20,000 Hz,

Voltage Gain

Inputs

*Dependent on input control setting.

outputs

Headphones

Compressor

Response

INPUT

Line 55dB 5dB -25dB 65dB 45dB

Mix

Bus 70dB 20dB

INPUT

Line

Mix Bus >3.5k 3.5k +2 dBV

OUTPUT

Mic
Line

Mix

Bus

Threshold: -88

Ratio:

Attack Time: 3 msec for level increases greater than 15

Recovery Time: 120 msec to

2

2 dB

(at 1 kHz)

lMWX)ANCE

FOR USE

25-600Q mics

level sources

WJEDANCE

FOR USE WITH

25-600Q mic
circuits

600 ohms

3.5k

8-2000 ohms

dBV typical at maximum input gain

(mic); -38

8:l minimum from 10 to 20 dB comprssion
5:l minimum from 10 to 30 dB compression

dB; 120

USA.

PRODUCTS

OUTPUT

MIX BUS PHONES (CUE)

--

(at 1 kHz)

WITH ACTUAL LEVEL AT 1 kHz

(at 1 kHz)

ACTUAL

1 ohm or

less

185 ohms

3.5k

100 ohms

dBV typical at maximum input

msec to 6 sec for increases of less

6

sec

INPUT CLIPPING

OUTPUT CLIPPING

LEVEL AT 1 kHz,

-34 dBV min.

(150-ohm load)

+

(600-ohm load)

-7

(3.5k load)

+

(200-ohm load)

PHONES

80dB

5%

THD

18 dBm min.

dBV min.

7 dBV min.

Printed in

--

U.S.A.

(0

3

0

0

rn

I-

ll

v

2

D

--I

rn

0

0

0

=

v

rn

m

V)
V)

0

P

g

2

rn

3

II

0

I

2

-

0

D

I

0

D

111

D

;

63

INPUT LEVEL

IMIC

I1

IN

dBV

COMPRESSION SYSTEM

INPUT-OUTPUT CHARACTERISTICS

FIGURE

1

Gated Memory

Threshold: -90.5 dBV typical at maximum input

gain (mic); -40.5

dBV typical at max-

imum input gain (line)

Recovery: In "hold" position, less than 20 dB gain

recovery after 1 minute

VU Meter

Dual-range, 3-function (output level in dB, gain reduction in
dB, battery check), illuminated (ac operation only)

Gated MemorylPeak Indicator

With meter switch in VU position, lights 6 dB below clipping;
with meter switch in

Comp position, lights when gated

memory is "holding"

Noise

Equivalent lnput Noise: - 129 dBV (low-impedance
microphone, 150 ohms, 300 to 20,000 Hz) into 600-ohm load
at full gain

Equivalent lnput Hum and Noise: -127

dBV (low­impedance microphone, 150 ohms, 20 to 20,000 Hz) into
600-ohm load at full gain

Output Noise: -77
counterclockwise [off]), -40

dBV maximum (output control full

dBV maximum (output control

full clockwise [on]) (input control down, 300 to 20,000 Hz)

dBV maximum (output con-

Output Hum and Noise:
trol down), -38

dBV maximum (output control up, input con-

-75

trol down, 20 to 20,000 Hz)

Distortion

0.4% THD, 30 to 20,000 Hz at + 15 dBm output; 0.5% or less

IM distortion at + 15 dBm output into 600 ohms

Common Mode Rejection

65 dB minimum with input of -20 dBV at 100 Hz

Control Interaction

Less than 1 dB with any control combination

Overload and Shorting Protection

Shorting outputs, even for prolonged periods, will cause no
damage; microphone input will not be damaged by signals

up to 3V

Low-Cut Filters

6 dB per octave rolloff at 150 Hz

Phase

All outputs in phase with respect to all inputs. Pin 2 is "high"
with respect to pin 3; pin 1 is ground. Tip of mix bus jack in
phase with pin 3. Tip and ring of headphone jacks in phase
with pin 2

Tone Oscillator

1 kHz; + 15 dBm minimum at line output with output level

full up

Phantom Power

30 Vdc nominal, 3.3k series resistance, automatically dis­abled with input switch in Line position

Operating Voltage

Ac Operation: 120 or 240 Vac -r-10% (internally
selectable), 50160 Hz,

5.5W

27

Dc Operation:
30

mA typical at 0 VU (+4 dBm) output; 21.5 Vdc minimum;

Vdc nominal at 27 mA typical no-signal,

battery life approximately 10 hours with alkaline batteries

+

4 dBm output in continuous use; three 9-volt bat-

at
teries, type NEDA

1604A (Duracell MN1604 or Eveready 522

recommended)

Temperature Range

Operating: -18O to 57OC (0° to 135OF)
Storage: -2g0 to 71°C (-20° to 160°F)

Dimensions

79.5 mm H x 310 mm W x 230 mm D (3-118 in. x 12-7132 in. x
9-1132 in.)

Weight

Net:
Packaged:

2.75 kg

(6

Ib

1

3.25 kg (7

02)

Ib 3 oz)

Certifications

Listed by Underwriters Laboratories Inc.; listed by Cana­dian Standards Association as Certified

CONTROLS AND CONNECTORS
Power Off-On
Channel Levellcue

Switch: applies power to the FP51 circuitry.

Rotary Controls: adjust individual input
channel signal levels. Each channel can be cued by pulling the
control knob outward to the detent position, rotating the knob
to the desired level, and pushing the knob inward to activate

'the channel.

Lo Cut Filter

Slide Switches: reduce unwanted low-frequency

signals such as wind noise by 6 dB per octave at 150 Hz.

Master

Rotary Control: determines mixed output level at out­put connector. The control also sets the tone oscillator level
when the

Gated MemorylPeak

Tone Osc

switch is turned on.

indicates, in gated memory mode,

LED:
that gated memory is "holding" prior amount of compression
during a low input signal, and turns off when input signal is
above compression threshold. In peak mode, the LED indi­cates approaching program overload. It is activated by the
shortest transient peak, but remains on long enough to pro­vide easy recognition. The chart below shows the effect of

Compressor

and

Gated Memory

switches on indicator opera-

tion.

GATED MEMORYIPEAK LED FUNCTIONS

Gated

Memory

off

I

Gated

Memory

on

Compressor
Compressor

VU Meter:

out No operation

in Gated memory

indicates

0 VU with a +4 dBm output (recom­mended for normal use to provide approximately 14 dB
headroom from operating level to clipping level) with

switch in VU position. Rear-panel
switch permits changing to

0 VU = +8 dBm. With

VU Range +41+8

VUlComp

slide

VUlComp

switch in Comp position, indicates compression due to input
signal above threshold (lower meter scale). The VU meter is lit
during ac operation only; therefore, the illumination serves as
a visual alarm if the ac is interrupted and the unit has
automatically switched to battery operation.

Batt Check

junction with the
the
batteries will give about a

Momentary Push-button Switch:

VU meter to indicate battery condition. With

Power

switch on and the switch depressed, a new set of

+

2

is good if the reading is above

VU indication. Battery condition

0 VU; a lower reading means

operates in con-

that new batteries are required for proper operation.

Gated Memory

Slide Switch: disables the gated memory

function without affecting other operations.

Response Rate

Rotary Control: adjusts the compression
system time constant to compensate for different types of pro­gram material. In general, a faster setting (toward the
counterclockwise position) results in a more constant output

level, but a more audible compression effect. Although the
control setting is subjective, the following knob positions offer
guidelines: speech -2; pop music -4; symphonic music- 7.

Compressor Off-On

and gated memory functions, converting the FP51 to a stan­dard microphone mixer.

Tone Osc Off-On

distortion 1 kHz tone for line tests and level checks. The tone
signal level is controlled by the
signal appears on both the
well as the
oscillator should be switched off when not in use.

Headphones

Headphones

Jack: permit monitoring mixer output through most stereo
headphones. The
put level of both jacks. Note that the headphones output level
is high enough for use as an auxiliary unbalanced line feed to
drive a tape deck or a power amplifier.

lnput

1-4

sional three-pin audio inputs. Pins 2 and
"neutral," and pin 1 is ground. For microphone operation, the

XLR Connectors: are transformer-balanced, profes-

lnput MiclLine

level inputs, the switches must be in the Line position.

Phantom Off-On

phantom power for condenser microphones to all inputs. With
the switch on and

+30 Vdc is applied to pins 2 and 3 of each input connector
(power is automatically removed in the Line position). Series
current-limiting resistance is 3.3 kilohms for each input. When
using other than Shure microphones, verify that the voltage
and resistance requirements are compatible.

Output

XLR Connector: is a professional three-pin audio con­nector for connection to either low-impedance microphone or
line-level inputs of power amplifiers, mixers, or other signal­processing equipment. The
either microphone- or line-level output signals.

Line Out

balanced 600-ohm line. Terminals are in parallel with the 3-pin

Output

Line position only. The red terminal is in parallel with pin 2 of
the
pin 3. Note that the line-level output signal is always present
on these terminals.

Mix Bus

put channel mixing bus. This facilitates stacking or "multing"
FP5ls to achieve additional input capacity without losing any
inputs. With two
example, the mix buses of each unit are directly connected,
providing two independent
isolated line amplifiers with eight individually
puts. Since the buses are directly connected, a 6 dB drop in the
gain of each output channel will occur, and the

put

specifications are not adversely affected by this connection.

Push Terminals: provide direct wire connection to a

connector when the

Output

connector, and the black terminal is in parallel with

Phono Pin Jack: provides direct access to the out-

controls must be increased to compensate. Noise

Slide Switch: disables the compressor

Slide Switch: provides a highly stable, low-

Master Level

lipe and microphone outputs, as

and

Mix Bus

1M-inch Phone Jack and Miniature 3.5 mm Phone

Headphones

switches must be in the Mic position; for line

Slide Switch: controls the application of

lnput MiclLine

rotary control adjusts the out-

switches in the Mic position,

Output MiclLine

Output MiclLine

FP5ls connected at their

Master

control. The tone

connectors. The tone

3

are "hot" and

switch selects

switch is in the

Mix Bus

gain controls and two

jacks, for

control\ed in-

Master

or

In-

INSTALLATION AND OPERATION
Battery Operation

In addition to 120- or 240-volt ac operation, the FP51 can be
operated from an internal battery pack. Current drain is
typically 30
recommended for remote, on-location operation, and as an
emergency backup source in case of ac power failure.

Access to the battery compartment is through the bottom of
the chassis. Three 9-volt transistor radio batteries power the
FP51 at full rated
batteries are recommended. Battery life is
hours at
loading will increase battery drain.

With batteries in the battery compartment, the FP51 will
automatically and silently switch to battery operation should
the ac voltage fall below a suitable level.

Battery condition can be determined using the
switch on the front panel. With the FP51
tivate the
set of batteries will give about a
condition is good if the reading is above
means that new batteries are required for proper operation.

mA at +4 dBm output level. Battery operation is

out~ut. Duracell MN1604 or Evereadv 522

+4 dBm continuous use. Note that ~hantom Dower

approximat~ly 10

Batt Check

Power

Batt Check

switch and observe the VU meter. A new

+2 VU indication. Battery

switch on, ac-

0 VU; a lower reading

Connections

Connect the signal sources to the three-pin XLR

nectors. Connect the three-pin XLR

Line Out

telephone line, etc. Set the

appropriate signal level.

puts, for information on increasing the number of available
microphone- or line-level inputs.

phone jack, if desired, for monitoring the FP51 output.

the FP51
desired, refer to the Service section.

terminals to the input of a power amplifier, mixer,

to the Operating Hints section titled, Additional In-

Refer

Connect headphones to the phone jack or 3.5 mm mini
Connect the line cord to a 120

is to be ac-operated. If 240-volt ac operation is

Output

Output MiclLine

Vac 2 lo%, 50160

lnput

Hz

source if

con-

connector andlor

switch for the

Adjustments

Turn the
the
or

+8

trols fully counterclockwise to 0, and set the
control for the program material to be used.

If desired, turn on the

nel Level

and undesirable low-frequency signals (see Figure

Note that each input
capability. To cue a channel while the other channels are
carrying program material, pull the desired
trol outward to the cue position. This removes that channel
from the mixing circuitry and routes it only to the
jacks. Adjust the

listening level, and adjust the cued
proper mixing level. Restore the cued signal to the program
mix by pushing the

Turn on the

warmup time. The VU meter will light in ac operation. Turn the

Phantom

microphones are to be used with the
turn the
pedance microphones.) Note that phantom power cannot be
applied to the inputs with the
position; if line-level condenser microphones (such as Shure's
SM82) are to be operated on phantom power, contact Shure's
Service department for modification instructions.

Turn on the

approximately 10 on the VU meter lower scale will result, and

the

Set the
for a
heard in headphones connected to either phone jack. The tone
signal can be used to calibrate equipment following the

Reduce the
reading, and turn off the

MemorylPeak

memory is "holding" the prior amount of compression. Note
the

reduction is made to compensate for the moderate short-term

output dynamic range encountered for speech using the

Compressor

VUlComp

switch to Comp, and the

dBm. Rotate the

and

Gated Memory

Channel Level

slide switches on,

VU Range

and

switch to + 4

Master Level

Response Rate

controls. The filter action will help reduce wind noise

Lo Cut Filter

FREQUENCY

LO CUT FILTER ACTION

FIGURE

Channel Level

switches above the

IN

HERTZ

2

control has a cuing

Chan-

2).

Channel Level

Headphones

Headphones

Channel Level

Power

switch and allow approximately 1 minute

switch on if non-battery-operated condenser

Phantom

switch on when using

Tone Osc

Gated MemorylPeak

VUlComp

0 VU meter reading (upper scale). The tone signal can be

Master

control setting for future use. (Note: This output

switch to VU and rotate the

Master

LED will turn on, indicating that the gated

control setting for a -2 VU meter

level control to a comfortable

Channel Level

control inward.

FP51.

MiclLine

switch. A dB compression reading of

LED will turn off.

Tone Osc

switches in the Line

switch. The

control for a

(Caution:

unbalanced

Master

Do

low im-

control

FP51.

Gated

con-

con-

not

suggested response rate setting. A faster setting would
eliminate the need, but compression would become more audi­ble.)

Operation

Set the
sound level entering the Channel 1 microphone, set the Chan­nel 1
approximately 10 dB. This is the
operating level, because with this setting the unit can main­tain a substantially constant output level for input reductions
of 10 dB and increases of as much as 30 dB.

With the

Gated MemorylPeak

input, and turn on during pauses between sentences and
words (indicating that the compression level is being
"remembered" during program lapses).

If the LED remains off or flickers with no spoken microphone
input, the acoustic background noise level at the microphone
is near or above the gated memory threshold. This can be cor­rected by reducing the Channel 1

Gated MemorylPeak

microphone. The compression level is then determined by the
loudness of the talker and the talker's proximity to the
microphones. This adjustment is very important for proper
operation in installations with high background noise levels,
such as sporting events or parades.

Program levels can be monitored by moving the
switch to VU. The meter then indicates program output level (0

VU = +4 or +8 dBm). The VU meter is factory-calibrated for

use with a 600-ohm terminated line. The
the rear panel selects either a
meter indication. (This switch changes the meter indication
but does not change the actual output level.) Microphone out­put levels are 50 dB below line output. The
mended for normal use to provide approximately 14 dB of
headroom from operating level to clipping level.

The VU meter is illuminated by a single cartridge-type,
incandescent lamp. The lamp is only lit for ac operation. Con­sequently, the illumination serves as a visual alarm if the ac is
interrupted and the unit has automatically switched to battery
operat ion.

The VU meter is connected on the primary side of the output
transformer to assure protection from any dc level on a
telephone line.

VUlComp

LevellCue

VUlComp

switch to Comp, and with an average

control for an average compression reading of

switch in the Comp position, observe the
LED. It should remain off during speech

LED stays on without speaking into the

FP5l's recommended

LevellCue

setting until the

VUlComp

+

VU Range

4

or a + 8 dBm output at 0 VU

+4 range is recom-

switch on

6.3V

OPERATING HINTS
Large Input Level Changes

If the overall sound and noise levels at the microphone do
not significantly change from those encountered during setup
(as indicated by a compression meter reading of
and if proper operation of the
further control adjustment is not necessary. However, if large
changes in the signal
microphone do occur, some
ment may be advisable, based on changes in the compression
meter reading and action of the
ple, a significant increase in background noise and signal may
occur during an exciting part of a sporting event, so that the
gated memory no longer "holds" during pauses and the com­pression reads higher than previously. A gradual reduction of
the

Channel Level

due to the automatic effect of the compressor, but proper ac­tion will be restored.

During a later, more subdued part of the program, it may
become apparent that the compression meter is reading near
0, and the
speech. A gradual increase in
operation at the proper level. Thus, during operation, after set­ting the proper output level with the
generally only necessary to monitor compression level on the
compression meter and to observe proper action of the

Memory

Control setting changes need only be made for long-term,
large signal or noise level changes. It is not necessary to "ride
gain" to maintain a constant line level output as measured on
the VU meter, since that is the compressor's function.

Gated Memory

LED.

setting will not be noticeable to the listener,

Gated Memory

andlor background noise at the

Channel Level

Gated Memory

LED does not always turn off during

Channel Level

Master

0 to 20 dB),

LED continues,

control readjust-

LED. For exam-

setting will allow

control, it is

Gated

Response Rate Adjustment

Proper setting of the
types of program material is determined by subjective factors,
that is, by the operator's individual perception of what con­stitutes "good sound." Generally,

less audible compression, but a wider, short-term output
dynamic range,
ting means a more constant output level, but the compression
effect becomes more audible.

The

Response Rate

operation if desired. An initial setting guideline based on pro­gram material is: Speech-2; Popular Music-4; Symphonic

Music-7. The output leveling effect can be observed for
various settings by observing the VU meter
set to VU), while the subjective effect is monitored by listening
on headphones.

i.e., a less consistent output level. A faster set-

Response Rate

a

control setting can be changed during

control for different

slower setting will result in

(VUlComp

switch

Multiple Inputs

Up to four microphones or other input sources can be used
with the
signal and background noise levels determine compression
and gated memory action. For optimum results when several

inputs are used, only the

nels in use should be turned up.
microphones but only one person talking at any time, each

Channel Level

in approximately the same amount of compression. At the
same time, the overall level should be monitored for proper
gated memory action.

FP51. With multiple sources, the overall "mixed"

Channel Level

For a conference or conversation setup, with several "live"

control should be set so that each talker results

controls for the chan-

Simultaneous Mixed Inputs

With simultaneous mixed inputs (up to four signal sources
operating at the same time), the compressor automatically
maintains a constant overall output level. Therefore, the
balance of signal sources is easily adjusted using head­phones. Simply observe the compression meter for normal
operating range, and check the
action.

Gated Memory

LED for proper

Automatic "Ducking"

The balance between two sound sources can be adjusted to

produce automatic "ducking," that is, the lowering of one
signal as another signal commences. A prime example of this
technique is the lowering of the music level when an an-

nouncer's voice begins. This is accomplished by setting the

Channel Level

say 5 dB (with the
the announcer's
dB. When the announcer speaks during musical numbers, the

FP51 gain is reduced by 10 dB, "ducking" the music level 10 dB
below the voice level. When the announcer stops speaking, the

music returns to full output.

for the music source to a low compression level,

VUlComp

Channel Level

switch in the Comp position). Then

is set for a higher level, say 15

Additional Outputs

If more inputs than the four available on the FP51 are need-

ed for the installation, another FP51 or any Shure mixer with a

mix bus jack can be connected. Note that when the FP51 is us­ed with a different mixer, a compressed output is available
from the FP51 and an uncompressed output is obtained from
the other mixer.

lnputs can also be added to the FP51 by connecting the

or microphone-level output of another mixer to one of the FP51

inputs. The added mixed input signals will be processed by the
compressor and gated memory if they are in use.

line-

Excessive Ambient Noise

Under certain conditions, such as high noise levels, it may

be impossible to adjust the
gated memory can consistently discriminate between

background and program. If this happens, the
switch should be turned off and the amount of dB compres­sion reduced to minimize the audible effects of "pumping."

In extremely severe cases, compression should not be used

at all, because the increase in background noise during

pauses will be quite unpleasant. The FP51 can then be used as
a high-quality linear mixer by turning the
off and setting the

level. As with any mixer, set the
as possible without clipping, and set the output VU level with

Master

the

control for optimum signal-to-noise ratio.

VUlComp

Channel Level

control so that the

Gated Memory

switch to VU to monitor output

Compressor

Channel Level

control as high

swritch

Fading with Compression

lnput fading with a compressor is accomplished somewhat
differently than with a linear mixer. Since a
input level within the compression region is compensated by
an automatic increase in gain, no audible fading will occur.
Consequently, fading an input down should be done rapidly, at
least to the point where the gated memory changes to the

"hold" state.

For overall fades, use the

only the output level, not the amount of compression.

Master

slow

reduction of

control, since it affects

Sound Reinforcement

Some care must be exercised when using the FP51 in sound
reinforcement installations. Since the compressor can only
reduce its gain when a signal exceeds its compression

threshold, maximum gain occurs with low-level signals, and
the sound reinforcement system's gain must be adjusted for
stability (no ringing or howling) with no compressor gain
reduction. This can be accomplished by adjusting system gain
with the
system adjustment, the FP51 can be used to level the sound of
a "wavering" talker, or to prevent power amplifier overdrive
with extremely strong signals.

FP5l's

Compressor

switch turned off. With proper

Single lnput Program Compressor

If the FP51 is to be used as a single-input, permanently in­stalled program compressor, the signal-to-noise ratio can be
improved by disabling the remaining inputs, thus reducing the
electrical noise of the mixing system. This modification is
described in the Service section.

Telephone Interconnection

When using the FP51 connected directly to a telephone line,
check to see whether the telephone company requires an inter­face coupler between the FP51 and the telephone line. If a
coupler is required, make certain the coupler selected and the
wiring arrangement are in compliance with local telephone
company regulations. Connect the telephone line to the FP51

Output

connector.

When direct connection to a telephone line is not possible,
acoustic coupling to a telephone handset may be used. A

Shure Model 50AC Telephone Acoustic Coupler can be con-

nected to the 600-ohm
tached to most telephone handsets.

Line Out

terminals of the FP51 and at-

Telephone Line Surge Protection

When using the FP51 connected directly to a telephone line

subject to lightning-induced voltage surges, the following part

(commercially available) can be installed across the
connector to provide additional protection for output circuit
components: Metal Oxide Varistor, General Electric Co.,
Type No.

V22ZA1.

Output

ACCESSORY

The Model A16R Rack Panel Kit consists of a 19 in. x 3-112 in.
(483 mm x 89 mm) precut rack panel and necessary hardware
for rack-mounting the FP51 with its cover in place and end
caps removed in a standard 19 in. (483 mm) audio rack panel.

SERVICE

WARNING

Voltages in this equipment are hazardous to life. Refer
servicing to qualified service personnel.

The FP51 can be disassembled as follows. Remove four
screws securing the cover assembly to the chassis. Carefully
lift the cover assembly up and away from the chassis, taking
care not to snag any wire leads or components. (It is not
necessary to remove the end caps from the cover for access to
the chassis.)

240

Vac Operation

To change the FP51 operating voltage from 120 Vac to 240
Vac, follow these steps.

1. Locate the Power board.

2. Remove the jumper plug from connector J205 (marked
120V), and carefully insert it in connector J206 (marked

240V), making sure all six pins are properly engaged.

3. Insert the

the fuseholder marked

4. Replace the ac line cord (if necessary) with one designed

for
U.S. and Canada, local regulations may require replacing
the line cord with one having wire

follows:

US., Canada Black White Green
Europe Brown Blue

5. Mark the FP51 rear panel with the new operating voltage.

T50mA1250V fuse (packaged with the FP51) in

the240-volt source. If the FP51 is to be used outside the

F202.

insu(ation colors as

"Live" or Earth

"Hot" Neutral Ground

Green/Yellow

or

Single lnput Compressor

To disable Inputs 2, 3 and 4 so that the FP51 can operate as

a single-input program compressor with an improved signal-to-

noise ratio, follow these steps.

1. On the main board, locate interboard connector

2.

Lift the connector locking latch upward approximately 3

mm (118 in.) and carefully withdraw the
ribbon cable from the connector.

3. Carefully bend leads 2, 3 and 4 approximately

vent their reentering the connector. Note that the board is
marked with a

4.

Carefully reinsert the ribbon cable (leads 1 and 5-8) in the
connector housing and depress the locking latch.

5. Mark the FP51 rear panel indicating that inputs 2, 3 and 4
are disabled. This modification will provide an improve­ment in signal-to-noise of approximately 2.5 dB.

"1" for the channel 1 lead.

J302.

45O to pre-

Lamp Replacement

To replace the VU meter lamp (PL501), locate the lamp
directly behind the front panel and above the meter housing.
Using a small screwdriver or fuse puller, carefully remove the
cartridge-type lamp. Replace only with an identical lamp.

NUMBER OR

PART

SHURE

COMMERCIAL ALTERNATE

Shure 4021 OFT

Shure 30206FT

86A8302; TI TIP30A

Shure

Shure Motorola 86A350; 2N5210

Shure 86A329; Motorola 2N5458

National LM386N-4

FT,

Shure 86A334; Rohm TIS92

50303FT

Shure 50402FT; Alco TPB21 RG-PC6

Shure

Shure 50304FT

Shure 50305FT

Shure 50306FT

Shure 5031 1 FT

- -

Shure 50301 FT

Shure 50401FT

Shure 50403FT; Alco MSS4200

Shure 60402FT; Alco MSS4200RG

86A335; Rohm ns93

Shure 50601 FT

Shure

Shure 60403FT: Alco MSS4200R

Shure 50501 FT

50502FT

Shure

Shure 60502FT

Shure 86A808A; Raytheon RC4156DB

Shure 50601 FT; National LM78L12C

Shure 50602FT; TI TL062D

Shure 60604FT; Motorola LM393M

Shure 50603FT; TI no71

Shure 30601

Shure 95A8015

Headphones)

8

DESCRlFllON

Knob (Response Rate

REFERENCE DESIGNATION

MP3

ALTERNATE

NUMBER OR

PART

SHURE

COMMERCIAL

Duracell MN1604

6.3V. 150 mA
NPN

Lamp. Meter.

Transistor,

Transistor, NPN

PL501

Q202-Q203, Q306.0308, Q310

Q201

503D337F063CK;

Shure 601 11 FT;

Shure 40101FT;

Sprague 503D107F050PD

Sprague

Field Effect Transistor

Field Effect Transistor

0301 -Q305, Q311-0312

Q307. Q309

Shure 601 12FT:

Sprague 503D107F050W

Shure 40102FT;

Nichicon 1V330MAA

Transistor. PNP

Potentiometer, Dual

Transistor, NPN

R317-R320

P313. Q315

Q314

Sprague 503D226M050LA

Shure 60105FT;

Panasonic ECE-A35ZR7

Shure 40103FT;

50k150k (Channel LevellCue)

Potentiometer, Trimmer, 50k

R340.R.383, R420

Shure 60107FT;

Nichicon IVlOlMPA

200k

Potentiometer. CW Audio Taper.

(Master)

R343

Shure 30107FT

Shure 101 l2FT;

2M

Potentiometer, Trimmer. 5k

Potentiometer, Linear Taper,

R363. R411. R430

R364

Nichicon lClO2MRA

Shure 60108FT;

Sprague 503D477F035QE

(Response Rate)

Shure 86A404;

10k

ol R317-R320

(Headphones)

Potentiometer, CW Autio Taper,

Part

R701

5301 -5304

Motorola 1 N4002

Shure 60202FT;

Motorola IN5239

Switch. Slide DWT (Lo Cut. Tone

OSC. Compressor, Gated Memory.

VUIComp)

S501-S508

Shure 86A415. TIIGE 1N4148

Shure 66A405;

Switch. Push-button (Batt Check)

S509

RCA SK3087 (I N48)

4PDT (MiclLine)

Switch, Slide. 4PDT (Power)

Switch. Slide,

S510

S601-S604, S606

Motorola 1N56232A

Shure 50201FT;

(Phantom, VU Range)

Switch, Slide, 4WT

S605, S607

Shure 60206FT; Rohm SLR340R3

Shure 80F159; Littelfuse 313.100

Transformer, Power

T201

60208FT; Littelfuse 218.050

Shure 50202FT

Shure

Input

Transformer,

Transformer, Output

Integrated Circuit, Op Amp

T301 -T304

T305

U301, U304-U306

Shure 60216FT: Cannon XLB-3-31WV

Shure 6021 7FT; Cannon XLB-3-32WV

Shure 10202FT

Integrated Circuit. Op Amp

Integrated Circuit. Op Amp

U302

U303, U309

Shure 60218FT

Integrated Circuit, Dual Comparator

U307-U308

Shure 20203FT

Circult. Audio Amp

Integrated Circuit. Op Amp

integrated

U310

U701

Shure 60219FT; Stackpoie 57-3425

Shure 50203FT

3-Conductor

ft)

Line Cord and Plug,

Grounded, 1 .Em (6

W25

Shure 50205FT

Shure 50204FT

REPLACEMENT PARTS LIST

DESCRlFllON

Battery, Alkaline, 9V

Capacitor, Electrolytic, 330 pF, 63V

REFERENCE DESIGNATION

BTI -BT3

C202

Capacitor, Electrolytic, 100 pF, 63V

C203

pF, 35V

Capacitor, Electrolytic, 10,

C204-C205. C323. C325. C335.

C379-C382

pF, 35V

Capacitor, Electrolytic, 33

C206, C702

pF, 35V

Capacitor, Electrolytic, 22

C301-C304, C316, C342. C350, C368,

C370, C375

pF, 35V

Capacitor, Electrolytic. 4.7

C317, C322. C327. C332.

C366, C703. C705-C706

pF. 16V

pF, 35V

Capacitor, Electrolytic. 220

Capacitor, Electrolytic, 100

C329. C601-C602

C369. C707

Capacitor, Electrolytic. 1000 ,IF, 16V

C372

Capacitor, Electrolytic, 470 pF, 35V

C374. C377

112A

Diode. Silicon, 1 OOV.

Zener Diode. 9V, 112W

D201 -D204. D206-D207

D205

German~um

Diode,

Diode, Computer, 75V

D301-0312. D314-D325,

0330-D333. D701

D313,0326-D329

Zener Diode. 5.6V

D336

Diode, Light-Emiiting. Red

D501

Slow-Blow, 3AG, 0.1A. 250V

Fuse,

F201

0.05A, 250V

Fuse, Time Delay,

F202

Phono Pin Jack (Mix Bus)

J1

%Socket XLR (Input)

Connector,

Connector, 3-Pin XLR (Output)

J101, J104

J105

Dual Push Terminal (Line Out)

J107

Phone Jack, 3-Circuit Switching

J701

3-Circuit

Switching (Headphones)

Ferrite Bead Ring

(Headphones)

Mini Phone Jack,

L1 01-L113, L301-L304. L701

J702

VU/Comp

Knob (Channel Levellcue)

Meter,

MI

MPI

Knob (Master Level)

MP2

PRINTED CIRCUIT BOARDS

Component Side

PRINTED CIRCUIT BOARDS

Solder Side