Shure SE30-2E User Manual

MODELS SE30 & SE30-2E

GATED COMPRESSOR/MIXER

OPERATING AND SERVICE MANUAL

Copyright 1981, Shure Brothers Inc.

27A8025 (AK) (90A8103)

Printed in U.S.A.

Table of Contents

List of Illustrations

WARNING

To reduce the risk of fire or electric shock, do not
expose this appliance to rain or extreme moisture.

DESCRIPTION

The Shure Model SE30* Gated Compressor/Mixer is a

high-quality gated memory compressor combined with a
self-contained, portable, three-input mixer and remote
amplifier designed specifically for professional appli­cations in AM, FM, and TV broadcasting, film, tape, and
disc recording, CATV, and sound reinforcement. An acces­sory cover is available (A100A) which covers the front
controls and provides a handle, as well as a support stand
for tilting the front panel upward for easier vision of con­trols during operation. An accessory rack-mount kit
(A100B) is available for permanently installed program
compressor applications.

Features include:

Three transformer coupled inputs, switchable, low im-

pedance microphone or line level.
Individual feedback-type level controls for each input
to provide maximum clipping and minimum noise levels

over a wide dynamic range.
Low-frequency roll-off switch for each input.
Input 1 switchable on front panel to low-distortion, 1 kHz

tone oscillator.
Mix bus jack for adding additional mixers for additional

input capability.

Feedback-type output control (located after compres­sion attenuator) to provide optimum output noise level

regardless of setting.
Binding posts for balanced 600-ohm line output plus

professional three-pin male audio connector switchable
from line to microphone level output.
Two-level headphone monitor jack for 600 to 2,000 ohm

headphones.

Compression range of 40 dB, with a slope or compres­sion ratio of approximately 10 to 1 in the normal oper­ating range.

Gated Memory with a meter indicator to minimize

“pumping.”

True average-responding compression to maximize
output level regardless of peak-to-average ratio of pro­gram material, either music or speech. (Peak responding

circuit to reduce gain rapidly for significant increases in

the input signal.)

Response rate (averaging time constant) adjustment on

front panel to compensate for various types of program

material.
Extremely low distortion, noise, and RF susceptibility,
with wide, flat frequency response at any level of com-

pression.

+18 dB output capability.

Dual-scale illuminated meter for output VU indication
or dB compression.

+4 or +6 dBm range switch for VU meter.
AC or battery operation with built-in battery supply using

readily available 9-volt batteries.

*Unless otherwise noted, information applies to both SE30 and SE30-2E models.

(Model SE30 shown)

Automatic, noiseless switch-over to batteries in the
event of ac line failure.
Battery-check switch to check battery condition with­out interrupting operation of unit.
Detachable ac line cord.
Auxiliary meter lamp operates independently from a “D”
type dry cell for meter illumination when ac power is
not available.
Auxiliary high level input and output on phone jacks for
special applications (approximately --20 dBV).
Microphone and line inputs and outputs phase indi­cated.
Stereo parallel jack for synchronizing the compression
circuits of two units.

Listed by Underwriters’ Laboratories and Canadian

Standards Association (SE30 only).

GUARANTEE

This Shure product is guaranteed in normal use to be
free from electrical and mechanical defects for a period
of one year from date of purchase. Please retain proof of
purchase date. This guarantee includes all parts and
labor. This guarantee is in lieu of any and all other guar­antees or warranties, express or implied, and there shall
be no recovery for any consequential or incidental
damages.

Carefully repack the unit and return it prepaid to:

If outside the United States, return the unit to your dealer
or Authorized Shure Service Center for repair. The unit
will be returned to you prepaid.

SHIPPING INSTRUCTIONS

Shure Brothers Incorporated
Attention:
1501 West Shure Drive
Arlington Heights, Illinois 60004

Service Department

SPECIFICATIONS

Frequency Response:

Flat ±2 dB, 30 to 20,000 Hz.

Gain:

(Below compression threshold, output terminated,
Line 600 ohms, Microphone 150 ohms, Aux. 47 K
ohms.)

Noise:

Equivalent input noise: -129.5 dBV maximum (Micro­phone input, 150 ohms, 20 kHz equivalent noise band­width with lower cutoff frequency of 300 Hz, at full
gain.)
Equivalent input hum and noise: -126 dBV maximum
(same as above, but lower cutoff frequency of 20 Hz.)
Output: (Input controls minimum):

3

SPECIFICATIONS (Cont’d)

Distortion:

Below compression threshold, under 0.5% THD at
+15 dBm output, 30-20 kHz.
At 10 dB compression, under 1% THD at +15 dBm
output, Response Rate set to 7, 50-20 kHz. With Re­sponse Rate set to 0 (fast), under 2% THD at 50 Hz.
At 1 kHz, under 0.8% THD at any level of compres-

sion from 0 to 40 dB.

Compression Ratio:

8:1 minimum from 10 to 20 db compression.
5:1 minimum from 10 to 30 dB compression.

Compression Threshold:

Microphone: -96 dBV at maximum input gain.
Line: -48 dBV at maximum input gain.

Recovery Time:

Time required for gain to reach 90% of its final value
when input is reduced by 10 dB from 20 dB com-

pression is adjustable from approximately 100 milli­seconds to 8 seconds by Response Rate control.

Attack Time:

Same as recovery time for increases up to 12 dB.

Maintains peak to average ratio at 12 dB (sine-wave
equivalent).

Gated Memory:

In “hold” condition, less than 20 dB gain recovery
after 1 minute.

Tone Oscillator:

1.0 kHz ± 10%, THD under 1%.

Input Control Interaction:

Under 0.1 dB with any combination, mix bus jack
open. Under 1.5 dB with mix bus terminated in 50 K
ohms or less.

Lo-cut Filters:

-6 dB per octave, 3 dB down at approximately 150
Hz.

4

Input/Output:

Mix bus:

Impedance 3.9 K ohms. Gain (through 3.9 K ohms)
from mix bus to line output, is 63 dB. Gain from micro­phone input to mix bus is 26 dB (terminated in 3.9 K
ohms). Overall gain drops by 10 dB with mix bus
terminated.

Circuit Protection:

Shorting the outputs, even for prolonged periods, will
not damage the unit.
Microphone inputs will not be damaged by signals
of up to 3 volts.

Temperature Range:

Operating:

-18°C (0°F) to 57°C (135°F).

Storage:

-29°C (-20°F) to 74°C (165°F).

Weight:

9 Ibs., 13½ oz. (4.5 kg) with batteries and line cord.

Operating Voltage:

AC Operation:

108-132 volts, 50/60 Hz (SE30 only).
108-132 or 216-264 volts, 50/60 Hz (SE30-2E
only).

DC Operation:

30 volts ± 20%.

SPECIFICATIONS (Cont’d)

Battery Operation:

27 volts nominal, 21.5 volts minimum. Current con­sumption at 27 volts, 10 ma. at no signal; 12 ma. at
20 dB compression and +8 dBm output.

Battery Life:

Estimated 80 hours at 4 hours use per day.

Battery Complement:

9 volt, 6 Eveready type 222 or 216 or equivalent.

One heavy-duty 1.5 volt “D” size cell, Eveready type
D99 or equivalent to power Aux. Light approximately
8 hours continuously.

CONTROL AND CONNECTOR

DESCRIPTIONS (See Figure 2)

Input Controls: Control gain of individual input stages

(1)

to adjust relative levels between inputs and to adjust

amount of compression. Input 1 (1A) also controls
Tone Oscillator level when used.
Lo-cut Filter Switches: Low frequency response is re-

(2)

duced by 6 dB per octave below approximately 150 Hz
with switch set to IN. Input 1 switch (2A) also activates
tone oscillator.
Output Control: Controls output level when unit is

(3)

used in compression or acts as a master gain control
when compression is disabled. May be used for over­all fading. Does not affect amount of compression.

VU Range Switch: Selects meter sensitivity so 0 VU

(4)

indicates results from either +4 dBm or +8 dBm line

output level.

Gated Memory Indicator: Will be red when Gated

(5)

Memory is “holding” prior amount of compression

during a low input signal. Will be white whenever in-

put signal is above compression threshold, or if either

Gated Memory or compression is disabled. Illumi­nated by ac operated lamps or independent battery
operated auxiliary light.
Response Rate Control: Adjusts time constant of

(6)

compression system to compensate for different types

of program material. Generally, a faster setting (lower

numbers) results in a more constant output level but
a more audible compression effect. Setting this con­trol is a subjective matter, but the following guide­lines may be used:

Meter: Indicates either VU output level (upper VU

(7)

scale) or compression due to input signal above thres-

hold by the amount indicated (lower DB Compression
scale). VU meter isolated from dc on line output. Il­luminated by ac operated lamps or independent bat­tery operated auxiliary light.

Meter Switch: Selects function of meter for VU out-

(8)

put level or DB Compression.

Battery Check Switch: Spring-return switch overrides

(9)

Meter switch, allows checking battery condition with-

out affecting operation of unit. A reading of 0 VU indi-

cates end-of-life.

(10) Aux. Light Switch: Spring-return switch allows illu-

mination of meter and Gated Memory indicator from

internal battery.

*Designed to mate with Cannon XL series, Switchcraft A3 (Q. G.) series. or equivalent connector.

Power Switch: Controls ac, external dc and internal

(11)

battery power applied to the unit, but will not prevent
power from being drawn from the internal batteries by
a load connected to 30 Volts DC jacks (26) when
switched to OFF.

REAR PANEL

Mix Bus Jack: Phono pin jack allows adding inputs by

interconnecting to a similar jack on another SE30

or M67 Mixer.
Input Connectors: Female professional three-pin au-

(13)

dio connectors* accept balanced low-impedance mi­crophone or high-level line inputs. Wired with pins
2 and 3 “hot” and pin 1 ground.
Mic/Line Input Switches: Select either microphone

(14)

or line level input sensitivity for each input.
Aux. Line Input Jack: Three-conductor (tip, ring,

(15)

sleeve) phone jack provides a second balanced line
input for Input 1. May be used in conjunction with, or
instead of, three-pin input connector when input
switch (14A) is set to LINE. Inserting a two-conductor
phone plug will automatically unbalance the input
without otherwise affecting operation. Tip and ring
are “hot,” sleeve is ground, and tip is in phase with

pin 2 of input and output.
Output Connector: Male professional three-pin audio

(16)

connector* provides balanced output at either line
level or microphone level (50 dB below line level).
Wired with pins 2 and 3 “hot” and pin 1 ground, in

phase with input connectors.
Mic/Line Output Switch: Selects either microphone

(17)

or line level output at output connector.

Aux. Output: Two-conductor (tip-sleeve) phone jack

(18)

provides isolated unbalanced aux. level (20 dB below

line level) output, for use with tape and cassette re-

corders and power amplifiers with high level, high
impedance inputs. Tip of jack is in phase with tip of

Aux. Line Input jack (15).

Headphone Jack: Three-conductor (tip, ring, sleeve)

(19)

phone jack wired to provide two different output levels

for 600 to 2,000 ohm headphones. If a two-conductor

(tip, sleeve) phone jack is inserted partially (to the first

detent), output will be approximately .18 volts into

1,000 ohms at +4 dBm output. If the plug is inserted
fully, the voltage will be approximately .38 volts. If
stereo headphones are used, signal will appear in both

phones. The tip and ring are in phase with pin 3 of
the input and output.

Line Output Terminals: Thumbscrews for direct wire

(20)

connections to balanced line, wired in parallel with
three-pin Output connector (16) in LINE position of

switch only. Phase is indicated by pin number ref-

erences, and a ground thumbscrew is provided.

Gated Memory Switch: Will disable Gated Memory

(21)

function without affecting other operation.

Compression Switch: Will disable compression and

(22)

Gated Memory functions of the SE30, converting it to

a high-quality linear mixer and remote amplifier.

Stereo Parallel Jack: Phono pin jack allows two units

(23)

to be synchronized to compress equally the channel

sum (L + R) signal. See Service section.

Battery Compartment: Requires six readily available

(24)

O-volt batteries (Eveready type 222 or 216 or equiva-

lent) wired in series-parallel for 27 volts dc and one

heavy-duty D cell (Eveready type D99 or equivalent)

5

FIGURE 2

CONTROLS AND CONNECTORS

(25) AC Power Receptacle: Special internationally ac-

cepted connector for detachable ac line cord, three­wire with safety ground pin.

(26) 30 Volts DC Jacks:

unit from an external 30 ± 20% dc source, or for
powering external equipment (up to 5 ma) from the
batteries or ac operated power supply of the SE30.
Controlled by front-panel Power switch (11) except
that an external load will discharge the batteries with
the unit OFF. In this case, remove the Battery Com­partment (24) when unit is turned off.

(27) Voltage Selector Switch: Selects operating voltage

range of 108-132 V or 216-264 V (SE30-2E only).

May be used for powering the

GENERAL OPERATION

POWER CONNECTIONS:
AC Line Operation: Insert female end of ac line cord into

chassis power receptacle (25) and connect male plug to a
three-wire grounding ac power receptacle providing 108
to 132 V, 50/60 Hz (SE30 only). Model SE30-2E: Obtain
a suitable three-pin male plug and attach it to the line
cord. Plug should be installed by qualified service per­sonnel. (Brown lead goes to “hot” or “live” terminal, blue
lead to neutral terminal, and green/yellow lead to ground

or earth terminal.) Select the proper operating voltage

(108-132 V or 216-264 V) using the voltage selector switch
(27). Insert female end of line cord into chassis power re-

ceptacle (25) and connect male plug to a three-wire

grounding ac power receptacle providing the proper ope-

rating voltage (108-132 V or 216-264 V, 50/60 Hz).

Battery Operation: Unit will automatically operate on bat-

teries installed in Battery Compartment (24) if unit is not
supplied with ac power. Condition of the 9-volt batteries
should be checked periodically with the Batt. Check Switch
(9) and batteries should be replaced as the meter indica­tion approaches 0 VU with the unit in operation. Standby
battery condition may be checked even during ac line
operation, but an indication of +½ VU should be con­sidered as the replacement point, since the battery voltage
will drop somewhat under load. The auxiliary light D cell
may be checked by operating the Aux. Light switch (10).
If the light becomes extremely dim, promptly replace or
remove the D cell to avoid damage due to leakage.

The unit will remain operative, except for the light, regard-

less of the condition of this cell.
Automatic Switchover: If batteries are installed in Battery
Compartment (24). operating power will be supplied by
these batteries in the event that the ac line voltage drops
too low or is removed. The switchover is automatic and

noiseless.
External DC Operation: An external source of dc may be
connected to the 30 Volts DC jacks (26) to operate the

unit if ac power is not used. The SE30 will draw approxi­mately 12 ma. at 30 volts and must be operated at 30 volts

± 20%.

INPUT CONNECTIONS:
Microphones: Inputs (13) with switches (14) set to MIC.

are designed to accept signals from low impedance (25 to
600 ohms) dynamic, ribbon, or condenser microphones,
or microphone level signals such as the low impedance
microphone level output of a mixer. Inputs are balanced
(transformer coupled, mumetal shielded) and connections

are pins 2 and 3 “hot,” pin 1 ground. For unbalanced
sources, connect either pin 2 or pin 3 to ground at the

input cable connector.

High Level Signals: With switches (14) set to LINE the

(See Figure 2)

inputs (13) will accept balanced 600-ohm line signals.
Inputs are bridging (with 66 K ohm impedance) so that

higher impedance sources such as Aux. signals (up to
33 K ohms) may also be used. For such unbalanced in­puts, the signal may be applied to pin 3, with pins 1 and
2 ground. Input 1 can accept two high-level signals simul­taneously through the three-pin Input connector (13a), and
through the Aux. Line Input jack (15), which are electrically
isolated but identical in gain and impedance.

OUTPUT CONNECTIONS:
Microphone: The microphone level output is available at

the Output connector (16) when the switch (17) set to MIC.
It is used for feeding a low-impedance microphone line
or the low impedance microphone input of an associated
piece of equipment. This is a balanced output with pin 1
ground and pins 2 and 3 “hot” and in phase with the cor­responding input pins. This output is isolated and may be
used simultaneously with all other outputs appearing on
other connectors.
Line: The line output is available at the Output connector
(16) when the switch (17) is set to LINE, and at all times

at the Line Output terminals (20). These two connectors
are then wired in parallel and are provided for intercon­nection convenience for either standard three-pin audio
connectors or for wires such as a telephone twisted pair.

This is a balanced output, transformer coupled with pin 1

ground and pins 2 and 3 “hot” and in phase with the cor­responding input pins. The Line Output terminals (20) are

similarly numbered for phase indication. This output may

be used to drive impedances above 150 ohms but the VU
meter is properly calibrated for use with a 600-ohm termi-

nated line. The line output transformer will operate prop­erly with up to 100 ma. flowing through the line, permitting
the use of ordinary “dialed-up” telephone lines with dc
across them. Operation at +4 dBm output is recommended
for this use to avoid any significant increase in distortion
due to overdriving the phone line. This output is isolated
and may be used simultaneously with all other outputs ex­cept that the Output connector (16) and Line Output termi­nals (20) are wired in parallel when the switch (17) is set to
LINE.

Aux. Output: An unbalanced output 20 dB below line level

is available at the Aux. Output jack (18) for a Separate,
isolated lower level feed. The impedance is 4.3 K ohms,

suitable for driving high impedance (10 K ohms or greater)

loads, such as reel to reel or cassette tape recorders or
power amplifiers. Tip of jack is in phase with tip of Aux.
Line Input jack (15).

Headphones: The headphone output appears on the rear
panel and is designated “Headphones.” A three-conductor
phone jack is used to provide a choice of level for different
sensitivity or impedance headphones. Normally, a two-con­ductor phone plug should be used. If inserted only par­tially (to the first detent), the available voltage is approxi­mately .18 volts into 1,000 ohms with +4 dBm out of the
Line Output. With the same output conditions (+4 dBm),
the second position will provide approximately .38 volts.
These voltages are selected for normal operation with
600-ohm to 2,000-ohm headphones. Other headphone im­pedances may be used, but with a variation in the head­phone monitor level. The headphone jack is isolated from
the line output and with the headphone output shorted the
maximum change in line level output is .5 dB. If stereo
phones are used, the three-conductor plug may be inserted
completely (to second position) and output will appear in
both phones.

7

GENERAL OPERATION (Cont’d)

The “Tip” connection of the headphone plug will be in

phase with Pin 3 of all Input (13) and Output (16) connec­tors, and with the tip of the Mix Bus jack (12).

TYPICAL SET-UP AND OPERATION

A typical set-up and operation procedure is described

for remote amplifier applications, with a single input source

(microphone).

1. Connect microphone to Input 1 connector (13a) and
set Input switches (14) to MIC. Set Output Switch (17)
to LINE and connect phone line either to Output jack
(16) or Line Output terminals (20). Insert ac line cord
into ac receptacle (25) and plug cord into ac source,
unless battery operation is desired. Monitor head­phones may be connected to Headphone jack (19).

2.

Set Compressor (22) and Gated Memory (21) switches
to ON, Meter switch (8) to DB COMP, Lo-Cut switches
(2) and VU Range switch (4) as appropriate.

3. Rotate Input Control (1) and Output Control (3) full
counterclockwise to 0, and set Response Rate Control
(6) to 3, assuming a typical speech input.

4. Turn Power switch (11) ON and wait approximately 1
minute for the circuitry to stabilize. DB Comp. meter (7)
should read full scale left (line below zero on lower
scale) and Gated Memory indicator (5) should be red.

5.

Set Input 1 switch (2a) to TONE OSC. and rotate Input
1 Control (la) clockwise for a DB Compression meter
(7) reading of 10 (lower scale). Gated Memory indi­cator (5) will change to white.

6. Set Meter switch (8) to VU and rotate Output Control
(3) for a VU meter (7) reading of 0 VU (upper scale).
Tone will be heard in headphones. The signal thus ap-

plied to the line may be used for calibration of the

equipment receiving the signal.

7. Reduce setting of the Output control (3) for a meter

reading of -2 VU, and return Input 1 switch (2a) to

IN. Note setting of Output Control (3) for future use.
(This reduction in sine-wave output is made to account
for the moderate short-term output dynamic range en­countered for speech with the suggested Response
Rate control setting. A faster setting would eliminate
the need for this, but the compression would then be­come more audible.)

8. Set Meter switch (8) to DB COMP.

9. Now, with the expected average sound level entering
the microphone, set the Input 1 control (la) for an
average DB Compression meter (7) reading of ap-

proximately 10 (lower scale). This is the recommended
operating level for the SE30, since the unit will now
be able to maintain a substantially constant output
level for input reductions of 10 dB and increases of
as much as 30 dB.

10. Observe the operation of the Gated Memory indicator
(5). It should be white during speech input and change
to red during pauses between sentences and words,

indicating that the DB compression level is being
“remembered” during program lapses.

If the indicator remains white or “jitters” with no
spoken input to the microphone, it is an indication
that the acoustic background noise level at the micro-

phone is near or above the Gated Memory threshold.

The solution to this is to reduce the setting of the

Input 1 Control (1a) until the Gated Memory Indicator
(5) is consistently red without speaking into the micro­phone. The DB Compression level will then be deter­mined by the loudness of the speaker and his proximity

to the microphone. This adjustment is very important
to insure proper operation in situations having very
high background noise levels, such as sporting events
or parades.

OPERATING CONSIDERATIONS

LARGE CHANGES IN INPUT LEVEL

If the overall sound and noise levels entering the micro­phone do not significantly change from those encountered
during set-up, as indicated by a DB Compression meter
(7) reading of 0 to 20 dB, and if proper operation of the
Gated Memory indicator (15) continues, it will not be neces­sary to adjust any controls further.

If, however, large changes in the signal going into the
microphone and/or in background noise do occur, some

Input 1 control (1A) readjustment may be advisable, as
indicated by the DB Compression meter and Gated Mem­ory indicator. For example, a significant increase in back­ground noise and signal may occur during an exciting por­tion of a sporting event, such that the Gated Memory no
longer “holds” during pauses and the DB Compression
reads higher than previously indicated. A gradual reduc­tion of the Input 1 control (1a) setting will not be noticeable
to the listener, due to the automatic effect of the compres­sor, but proper action will be restored.

During a later, more subdued portion of the program, it
may become apparent that the DB Compression meter (7)
is reading near zero, and the Gated Memory indicator does
not always change to white during speaking. A gradual
increase of the Input 1 control (la) setting will then allow
operation at the proper level. Thus, during operation, after
setting the proper output level with the master gain control,
it is generally necessary only to monitor compression level
on the DB Compression meter (7) and to observe proper
action of the Gated Memory indicator (5).

Control setting changes need only be made for long­term, large changes in signal or noise levels. It is not nec­essary to “ride gain” to maintain a constant line output
level as measured by the VU meter, since that is the com­pressor’s function.

RESPONSE RATE ADJUSTMENT

The proper setting of the Response Rate control (6)
is determined by subjective factors, according to the type
of program material. Generally, a slower setting will result

in less audible compression, but a wider short-term out-

put dynamic range, that is, a less consistent output level.
Faster settings will result in a more nearly constant output
level but will make the effect of compression more audible.
The Response Rate control (6) setting may be changed
during operation for more satisfactory results if desired. A
guideline for an initial setting according to program mate­rial is: Speech-3; Popular Music-5; Symphonic Music-

7. The output leveling effect may be observed for various
settings by observing the VU meter (Meter switch (8) set to
VU), while the subjective effect is best ascertained by

listening on monitor headphones.

MULTIPLE INPUTS

Up to three microphones or input sources may be used

simultaneously with the SE30. In this case, the overall

“mixed” signal and background noise levels determine

DB Compression and Gated Memory action. For the best

results when several inputs are to be used one at a time,

only the used Input controls should be turned up. For a

8

OPERATING CONSIDERATIONS (Cont’d)

conference or conversation situation, with several micro­phones “live” but only one speaker talking at a time, each
Input control should be set so that each speaker results in
approximately the same amount of compression, observing
that the overall level is correct for proper Gated Memory
action.

SIMULTANEOUS MIXED INPUTS

With simultaneous (mixed) inputs, the compressor will
automatically maintain a constant overall output level, so
that the balance among the sources may be adjusted easily
by monitoring with headphones. Simply observe that the
DB Compression meter (7) is reading in the normal oper­ating range and that Gated Memory action is proper.

AUTOMATIC “DUCKING”

The balance between two sources may be adjusted to
produce automatic “ducking,” for example, for an an­nouncer’s voice over musical programming. In this case,
set the Input control for the music source for a low amount
of compression, such as 5 dB. Then set the announcer’s
microphone Input control for 15 dB compression when he
is speaking. When the announcer talks during music, the
SE30’s gain will be reduced by 10 dB, “ducking” the music
level below the voice level by that amount. When he stops
speaking, the music will return to full output.

ADDITIONAL INPUTS

To accommodate more inputs than three, a Mix Bus
jack (12) is provided which may be connected to a similar
jack on another SE30 or M67 Mixer. When a Mixer
with a mix bus is used in conjunction with the SE30, a
compressed output may be obtained from the SE30, and
an uncompressed output of the same mixed material will

be available from the Mixer.

Inputs may also be added by connecting the line level
or microphone level output of another mixer to one of the
SE30 inputs.

EXCESSIVE AMBIENT NOISE

Under certain conditions, such as high noise levels,
it may be impossible to adjust the Input control (1) so that
the Gated Memory can consistently discriminate between
background and program. In such a case, the Gated Mem­ory switch (21) should be set to Disable and the amount of
compression should be reduced to minimize the audible
effects of “pumping.”

In extremely severe cases, compression should not be

used at all, since the increase in background noise during

pauses will be quite unpleasant. The SE30 may then be
used as a high-quality linear mixer by setting the Comp.
switch (22) to DISABLE and setting the Meter switch (8)
to VU to monitor output level. As with any mixer it will then

be desirable to set the Input control (1) as high as pos­sible without clipping, and set the output VU level with
the Output control (7), to provide best signal-to-noise ratio.

FADING TECHNIQUE WITH COMPRESSION

Fading of inputs with a compressor must be accom­plished somewhat differently than with a linear mixer.
Since a slow reduction of input level within the compres­sion region will be compensated for by an increase in

gain, no audible fading will occur. Consequently, fading

an input down should be done rapidly, at least to the point
at which the Gated Memory changes to the “hold” state.

For overall program fades, it is desirable to use the
Output control (3), since it does not affect the amount of
compression but only the output level.

SPECIAL APPLICATION

CONSIDERATIONS

SOUND REINFORCEMENT

The SE30 may be used in sound reinforcement installa­tions, but some care must be exercised in such applica­tions. Since this compressor can only reduce its gain when
a signal exceeds its compression threshold, maximum gain
occurs with low signal levels, and the sound-reinforcement
system’s gain must be adjusted to be stable (no ringing or
howling) with no compressor gain reduction. This may be
accomplished by adjusting system gain with the SE30’s
Comp. switch (22) set to DISABLE. With proper system
adjustment, the SE30 may be used to level the sound of
a “wavering” speaker, or to prevent power amplifier over-

drive with extremely strong signals.

STEREO OPERATION

Two SE30’s may be synchronized to operate together for

stereo applications by interconnecting their Stereo Parallel

jacks (23) and performing the adjustment procedure out-

lined in the Service Section of the manual.

One unit will compress the left channel signal and the
other will compress the right channel signal, but both will
respond equally to the sum (left and right) signal to mini­mize apparent stereo image shift.

Because of the necessity of providing the two units
with a properly balanced stereo signal, it is recommended
that stereo applications be restricted to single inputs for
each channel, with mixing and balancing being accom­plished in another mixer prior to the SE30’s.

SINGLE INPUT PROGRAM COMPRESSOR

When the SE30 is used as a single line input, perma-

nently installed program compressor, it is possible to im­prove the signal-to-noise ratio by disabling two of the
inputs and thus reducing the electrical noise of the mixing
system. This modification is outlined in the Service Section.

RESPONSE RATE KNOB REMOVAL

To prevent inadvertent misadjustment of the Response

Rate control (6) the knob may be removed and the hole

filled with the plastic plug included with the SE30. This

procedure is described in the Service Section.

THEORY OF OPERATION

(See Figure 3)

Operation of the SE30 Gated Compressor/Mixer may be

explained by referring to the Functional Block Diagram,

Figure 3. The active devices in each stage, as well as other
important components, are identified by their reference
numbers, for ease of location on the Schematic Diagram
(Figure 4) and the Chassis Parts and Printed Circuit Board

Parts Placement diagrams (Figures 5 and 6). The first digit
of three-digit references indicates the printed circuit board

upon which the part is located.

INPUT-OUTPUT SIGNAL PATH

Balanced input signals entering through J1, J2, and J3
are amplified by the three transformer-coupled, variable­gain input preamplifiers. Low-level signals are applied di­rectly to the transformer primaries, and high-level (line)
signals are attenuated by balanced -48 dB resistive pads.

The Input controls are ganged, dual-section potentiometers

arranged such that a reduced control setting increases the
negative feedback around the stage, thus reducing gain
and increasing the input clipping level. Since the pream-

plifier stage gain cannot be reduced below 6 dB from its

9

FUNCTIONAL BLOCK DIAGRAM - FIGURE 3

THEORY OF OPERATION (Cont’d)

maximum of 30 dB, the second potentiometer section acts
as a conventional voltage divider output attenuator for low
control settings. The input transformers increase the signal

voltage by 21 dB.

Input 1 has a second line input, phone jack J12, which
operates only in the LINE position of S9. Additionally, this
stage (Q109, 110, 111) may be converted to a level-stabil-

ized, low distortion, 1 kHz Wien bridge tone oscillator.

A feedback-type, virtual-ground, low gain (3 dB) mixing
amplifier (Q112, 113, 114) assures nearly zero interaction
among input level control settings. Each input to the mixing
stage has a resistance-capacitance low frequency rolloff
filter providing a 6 dB per octave slope, 3 dB down at about
150 Hz. The mix bus jack (J5) contains a switch so that
when a phono plug is inserted, the mix bus impedance is

increased from near zero to 3.9 K ohms, for compatibility

with conventional mixing systems.

Automatic gain reduction is accomplished by the voltage
variable FET attenuator, R401 and Q401. With signal levels

below compression threshold, or when compression is dis­abled, the FET gate-to-source voltage is sufficiently neg­ative to prevent FET conduction. Increased signal levels,

however, are sensed and the dc control voltage is in­creased until the FET drain-to-source resistance is reduced
enough to maintain a nearly constant signal voltage across

Q401.

This compressed signal is applied to the Output Buffer

stage (Q402, 403, 404), which has variable feedback sim-

ilar to the input preamplifiers, via the dual-section Output

potentiometer. This assures optimum output-stage clipping
and noise characteristics, either with a constant, com­pressed signal to the Output Buffer stage, or with com­pression disabled. The output amplifier (Q508, 509, 510,

511) is a class -AB, fixed gain line driver stage transformer­coupled to the output load. A tertiary winding on T4 pro­vides a microphone level balanced output, and headphone
and unbalanced auxiliary outputs are also derived from
the output amplifier stage through appropriate pads.

A three-transistor circuit (Q504, 505, 506) provides
full-wave rectification and power amplification to drive the
meter (Ml) with proper damping characteristics for the
VU output level function. The gain of the VU driver circuit
is changed by S4 for the two VU ranges.

D.C. CONTROL GENERATION

The signal voltage appearing across the attenuator FET

(Q401) travels through a portion of the Output Buffer
(Q402, 403, 404) and a unity-gain Phase lnverter (Q405,

406, 407) to the Compression Buffer (Q408, 409), a 30-dB

gain stage. The output of this stage may be shorted to
ground by switch S14 to disable compression, or it may be
connected in parallel with a similar stage in a second SE30
via its Stereo Parallel jack (J8) so that stereo difference
signals will be canceled out and thus not compressed, and
the stereo sum will be the controlling signal.

The signal at this point enters a small class-B power

amplifier, the Rectifier Driver (Q501, 502, 503). A full-wave
diode bridge rectifier (D201, 202, 203, 204) is driven from
this amplifier through Driver Transformer T5, thus gen­erating full-wave rectified, unfiltered pulses whose am-

plitude is proportional to the absolute value of the signal
across the attenuator FET (Q401).

The Response Rate control (R5) and capacitor C203

form a resistance-capacitance integration or averaging

network with an adjustable time constant so that a smooth
dc voltage is generated, equal to the average value of the
full-wave rectified pulses. This dc voltage is amplified
(X2) by the AC/DC Amplifier (MC201, Q105) and applied
to the gate of the attenuator FET (Q401). The AC/DC Am­plifier has low input bias current to minimize its discharg­ing effect upon the integrating capacitor (C203). An adjust­ment associated with this amplifier applies an offset voltage
to the FET, setting the compression threshold.

The integrating R-C network assures an equal charge

and discharge time constant to provide a true average-

responding compression system. However, such a system

will exhibit a large overshoot in output when the input level

is suddenly increased. A Peak Detector (Q201, 203) is

therefore provided which monitors the instantaneous am-

plitude of the rectified pulses. If a pulse exceeds the av­erage value by a preset amount, this detector will very
rapidly charge C203 enough to maintain the peak signal

amplitude within a reasonable upper limit. The Peak De­tector threshold is set such that normal program material

at a constant level will not activate the circuit, but it will
reduce compressor gain rapidly for significant increases in
input level.

The AC/DC *Amplifier also has an input terminal for
signal voltage, fed via the Output Buffer and Phase In­verter. This serves to apply one-half of the signal voltage
across FET Q401 to its gate, along with the dc control
voltage, thus reducing distortion due to the FET’s non-

linear resistance characteristic.

The dc control voltage applied to the gate of Q401 is

used to drive meter Ml through the dB Compression Meter
Amplifier (MC201, Q206). This amplifier has gain, offset, and
gain reduction adjustments to allow calibration of the

meter reading to correspond at three points to actual levels
of compression, despite the nonlinear relationship between

compression and dc control voltage.

GATED MEMORY

The Gated Memory Switch FET Q204 allows the in­tegrating capacitor (C203) to be charged and discharged
as described under normal signal conditions. However,
when the input signal drops below compression threshold,
Q204 becomes an open circuit, preventing discharge of

C203 and maintaining the amount of gain reduction just
prior to the opening of the FET switch.

The Gated Memory Amplifier (MC301, Q306) receives
the uncompressed signal, proportional to input level, from
the Mixing Amplifier. A fast-acting voltage doubler rec­tifier (D303, 304) converts this signal to a dc level which is
applied to the Comparator (MC301, Q304) after being

clamped by Q305 to assure fast recovery. The Comparator
output is a two-level dc signal applied to the gate of FET
Q204, and to the Gated Memory Indicator Driver (Q302,

303) to indicate the state of the Gated Memory circuit. The
gain of the Gated Memory Amplifier is adjustable to allow
setting the comparison threshold, and the switching FET

may be prevented from opening by switches S13 or S14.

When power is first applied to the SE30, approximately
30 seconds is required for the dc power supply voltages
to become properly established. During this interval, Timer
Q301 and Discharge Switch Q202 partially discharge inte­grating capacitor C203, preventing a possible “latch-up”
condition due to a turn-on transient combined with Gated

Memory Switch Q204 being open.

11

SCHEMATIC DIAGRAM - FIGURE 4A

SCHEMATIC DIAGRAM - FIGURE 4B

SCHEMATIC DIAGRAM - FIGURE 4C

SCHEMATIC DIAGRAM - FIGURE 4D

SCHEMATIC DIAGRAM

PIN CONNECTIONS-

TOP VIEW

INTEGRATED CIRCUIT MC201 AND MC301

FIGURE 4E

REPLACEMENT PARTS FOR SE30-TABLE 1

16

NOTE:

THE COMMECIAL ALTERNATES SHOWN ABOVE ARE NOT NECESSARILY EQUIVALENTS, BUT MAY BE USED IN THE EVENT THAT DIRECT FACTORY REPLACEMENTS ARE NOT

IMMEDIATELY AVAILABLE. TO MAINTAIN SPECIFICATIONS AND RELIABILITY, SHURE FACTORY REPLACEMENT PARTS SHOULD BE USED.
FOR REPLACEMENT, PURCHASE Q502-Q503 AND Q510-Q511 AS MATCHED PAIRS TIS92M-TIS93M.
ORDER REPLACEMENT PARTS UNDER THlS NUMBER WHEN APPLICABLE. IF NO NUMBER IS SHOWN IN THlS COLUMN, ORDER UNDER SHURE PART NUMBER.
REPLACEMENT OF THESE PARTS NECESSITATES RECALIBRATION OF UNIT. SEE SERVICE SECTION.

(TABLE 1 cont’d on next page)

TABLE 1 (Cont’d)

THE COMMERCIAL ALTERNATES SHOWN ABOVE ARE NOT NECESSARILY EQUIVALENTS BUT MAY BE USED IN THE EVENT THAT DIRECT FACTORY REPLACEMENTS ARE NOT

NOTE:

IMMEDIATELY AVAILABLE. TO MAINTAIN SPECIFICATIONS AND RELIABILITY, SHURE FACTORY REPLACMENT PARTS SHOULD BE USED.
FOR REPLACEMENT, PURCHASE Q502-Q503 AND Q510-Q511 AS MATCHED PAIRS TIS92M-TIS93M.
ORDER REPLACEMENT PARTS UNDER THIS NUMBER WHEN APPLICABLE. IF NO NUMBER IS SHOWN IN THlS COLUMN, ORDER UNDER SHURE PART NUMBER.
REPLACEMENT OF THESE PARTS NECESSITATES RECALIBRATION OF UNIT. SEE SERVICE SECTION.

17

TEST VOLTAGES, P. C. BOARD TERMINALS

TABLE 2A

18

TEST VOLTAGES, TRANSISTORS - TABLE 2B

19

TEST VOLTAGES, INTEGRATED CIRCUITS

TABLE 1C

NOTES TO SCHEMATIC DIAGRAM AND

TEST VOLTAGES (Figure 4, Table 2)

1. All capacitors shown in microfarads and 50 volts or
more unless otherwise indicated. Electrolytic capac­itors shown in mF X volts. pF = picofarad.

2. All fixed resistors ±10%, ¼ watt unless otherwise

shown. K = 1,000

M = 1,OOO,OOO

3. Components and wiring enclosed within dashed lines
are parts of printed circuit board assemblies.

4. The following symbols denote:

Direct chassis ground
Wired circuit ground
Printed circuit board ground

5. Arrows on potentiometers denote clockwise rotation.

6. Wire color designations with asterisks refer to
stranded No. 20 AWG wiring, and those in parentheses
refer to integral component leads. All other wires are
stranded No. 24 AWG.

20

7.

P. C. board terminals and wire destinations are shown

as board number-pin letter.

8. First digit of three-digit component references (for
example, R101) denotes number of printed circuit
board upon which part is mounted. One and two-digit
component references denote chassis-mounted parts.

9. AC and DC voltages given in Tables 2A, 2B and 2C
are measured with a 2.2 megohm or greater AC volt­meter and a 10 megohm or greater DC voltmeter. All
switches set as shown in schematic diagram. AC line
= 120 V, 60 Hz. Input 3 control set to 5, Input 1 and 2
controls set to zero, and Response Rate control set
to 3. Input signal 1 kHz applied to Input 3, level ad-

justed for 10 dB compression (signal at Pin A, board

3 equal to -30 dBV or 32 mV). Output control ad­justed for + 4 dBm (+ 1.8 dBV or 1.23 V) line output
into a 600-ohm load.

CHASSIS PARTS PLACEMENT

FIGURE 5

21

PRINTED CIRCUIT BOARD 1

22

PRINTED CIRCUIT BOARD 2

PARTS PLACEMENT

FIGURE 6A

PRINTED CIRCUIT BOARD 3

PRINTED CIRCUIT BOARD 4

PARTS PLACEMENT

FIGURE 6B

23

PRINTED CIRCUIT BOARD 5

PARTS PLACEMENT

FIGURE 6C

24

SERVICE INSTRUCTIONS

The SE30 Gated Compressor/Mixer uses components

of the highest quality, operating well within their ratings
to assure long life and excellent stability. No routine main­tenance is necessary with the exception of battery re-

placement.

CAUTION:

BATTERY REPLACEMENT:

No special tools are required.

1.

Turn knob on back of Battery Compartment (24) ¼
turn counterclockwise to OPEN position.

2.

Slide compartment rearward out of chassis.

3.

Release cover by unscrewing thumbscrew on top of
cover.

4.

Tilt cover upwards, pivoting at connector end of com­partment, thus exposing batteries.

5.

Unsnap the six 9-volt batteries and replace. Remove
the 1.5-volt D cell and replace.
Note: The SE30 may be operated in an emergency

6.

Pivot cover down, align thumbscrew with speednut,
and tighten fully. Batteries are now held firmly by pads
in cover.

7.

Align metal bottom plate of compartment with plastic
guides in SE30 chassis and gently slide compartment
fully into chassis.

8.

Rotate knob clockwise to LOCK position.

COVER REMOVAL AND REPLACEMENT

Most servicing and calibration can be performed with

only the top cover removed. The only tool required is a

No. 1 or No. 2 Phillips screwdriver.

1.

Turn Power switch (11) OFF and remove ac line cord
from AC Power Receptacle (25).

2.

Remove the upper of the two Phillips screws on each
side of the SE30.

3.

Remove the top cover by grasping the upper half of
each side and pulling straight up. This exposes the
components shown in the top view of Figure 5.

4.

End plates may be removed for easier access to side­mounted components by removing the remaining Phil­lips screws on each side of the SE30. The end plates
may then be removed by pulling straight up.

5.

The bottom cover may be removed either with or with­out removing the end plates as above. Invert the SE30
and unscrew the four bumpers (feet). The bottom cover

may then be pulled straight up from the central
chassis. The SE30 will operate properly, except for
possible increased hum pickup, with both the top and
bottom covers removed.

6.

Replace the bottom cover by placing the chassis up­side-down and sliding the cover over the chassis,
securing it in place with the four bumpers and screws.

If the end plates are attached to the cover, position it
so that the large holes in the end plates are near the
front of the chassis.

7.

Replace each end plate, if necessary, by sliding it
between the end of the chassis and the inside of the
bottom cover, securing it with a Phillips screw. Posi-

There are no user serviceable parts within the
case of the SE30. Refer servicing to qualified
service personnel.

with only three 9-volt batteries, installed in
either the right or left row of battery connectors.
The 1.5-volt D cell operates only the auxiliary
light, and may be omitted if this feature is not
required.

tion the large hole near the front of the chassis. The

right and left end plates are interchangeable.

8. Replace the top cover by sliding the ends downward,
guided by the recesses in the end plates. Secure with
the two remaining Phillips screws.

CHASSIS PARTS

Figure 5 illustrates the location of each chassis-mounted
component by reference number, corresponding with those
in the Schematic Diagrams (Figure 4) and Replacement
Parts List (Table 1). Note that all one and two-digit refer­ence numbers denote ‘chassis-mounted components.

The five printed circuit boards are numbered 1 through
5 from left to right, and are easily removable as outlined
below. Trimmer potentiometers used during calibration
are located on P.C. Boards 2 and 3 and are shown in Figure

5. Complete replacement P.C. Board Assemblies are avail­able. See Replacement Parts List (Table 1), and note that
the replacement of certain components and P.C. Boards
will necessitate recalibration of the unit.

The color-coded chassis wiring is indicated both in the

Schematic Diagrams (Figure 4) and in the P.C. Board Parts
Placement Diagrams (Figure 6). Connections associated
with each printed circuit board are shown in the Schematic
Diagram as follows:
PC. Board 1, Figure 4A; P.C. Board 2 and P.C. Board 3,
Figure 4B; P.C. Board 4, Figure 4C; and P.C. Board 5,
Figures 4C and 4D. Power supply wiring is shown in
Figure 4D.

LAMP REPLACEMENT

The tools required are a No. 1 or No. 2 Phillips screw-

driver, and ¼" and 5/16" open-end wrenches.

1.

Remove the topcover as described above.

To replace the ac operated pilot lamps (PL1 and

2.
PL2), remove the hexagonal-head screws mounting
the lampholders to their vertical brackets, using the

¼" open-end wrench.

The sockets may now be pulled rearward and rotated

3.
up so that the #47 bulbs may be replaced. It is advis­able to replace both of these lamps when one burns
out.
Replace the sockets in position and secure with the

4.
hexagonal head screws. Note that there are two holes
in each bracket, the rear hole for the socket tab and
the front hole for the screw.
To replace the battery operated Aux. Light (PL3), note

5.
the position of the socket between the Gated Memory
indicator (M2) and the meter (M1). Remove the hex
nut and lockwasher holding the socket to the left
meter stud, using the 5/16" open-end wrench.

6.

Unscrew the bulb and replace with a #223 lamp,
tightening it firmly in the socket.

7.

Position the socket bracket over the meter stud, fol-

lowed by the lockwasher and the nut, and tighten

while holding the socket in proper position.

8.

Replace the top cover.

PRINTED CIRCUIT BOARD REMOVAL AND SERVICE

A standard blade screwdriver or similar prying tool and
long-nose pliers are the only tools needed, unless sol­dered components are to be replaced. To avoid component
and printed circuit board damage, a soldering iron of 40
watts or less is recommended

1. Remove AC line cord and remove top cover as de­scribed above.

2. Each printed circuit board is mounted by four plastic

25

SERVICE INSTRUCTIONS (Cont’d)

push-on retainers so that it may be raised above the
chassis for service without complete removal. With all
power turned off, depress retainer locking tab, if any,
and pry each corner of the board from its retainers. Lift

the board straight up assuring that all wires clear any
obstructions, and position the two lower board mount­ing holes over the two upper plastic retainers. Snap the
board over the retainers, thus exposing the component

side and most of the conductor side of the board.

After positioning one or more boards in this manner,
the SE30 may be operated and measurements made.

3.

All connections to printed circuit boards are made by
push-on terminals crimped to color-coded wires. To
remove a printed circuit board, first turn off all power
and remove ac line cord, then grasp each brass ter­minal with long-nose pliers and pull away from board.
The board may then be pried from its retainers and
lifted out of the chassis.

4.

Figure 6 illustrates the location and position of each

printed circuit board component. Note that all such
components have three-digit reference numbers, the
first digit of which denotes the printed circuit board

number. The colors of wires connected to each ter-

minal are also shown to aid in reconnecting boards.
Color abbreviations with asterisks refer to stranded

No. 20 AWG wiring, and those in parenthesis refer to
integral component leads. All other wires are smaller,
stranded No. 24 AWG.

5.

Printed Circuit Board 4 requires special handling, as

noted in Figure 6B. To avoid possible erratic operation
under high humidity conditions, the area of the board
which includes Q401, R401-404, and C401-403 must
be kept free of contamination from perspiration, skin
oils, and the like on both sides. This area should not
be touched with the fingers, and if any of these com­ponents must be replaced, soldering flux must be re­moved by brushing with a solvent such as clean wood
alcohol (methanol) or denatured alcohol. (Do not use
rubbing alcohol.) After flux removal, rinse with dis­tilled water to remove electrolyte contaminants.
CAUTION: Alcohol is flammable. Do not use near fire.

Note that FET Q401 is mounted inverted to the board
with a direct soldered connection between R402 and
the gate lead.

6.

Integrated circuits MC201 and MC301 are mounted in
14-pin sockets to facilitate removal and replacement.
The notch on one end and a dot or mark identify pin 1,
which must be positioned as shown in Figures 6A and
6B and as indicated on the printed circuit board.
Typical voltage measurements are given for Various

7.
points in the circuitry in Tables 2A, 2B, and 2C. The
notes to Schematic Diagram and Test Voltages Outline
the test conditions for these measurements. Voltages at
all printed circuit board terminals are given in Table
2A, and board-mounted transistor and integrated cir­cuit terminals voltages are given in Tables 2B and 2C.
All voltages are measured with respect to chassis
ground.

8.

Replacement of Printed Circuit Boards 2, 4, or 5, or
of MC201 will necessitate recalibration of the com­pression system as outlined below. In addition, Printed
Circuit Board 3 replacement requires Gated Memory
recalibration, and Printed Circuit Board 5, or meter
Ml replacement require VU Meter calibration. Com­pression system calibration should also be checked
if meter M1 is replaced.

26

CALIBRATION

Each SE30 Gated Compressor/Mixer is individually cali-

brated at the factory with six internal trimming potentiom-

eters and a selected fixed resistor, to compensate for

individual component variations and to assure uniform and
accurate performance. The complete calibration procedure
is given here for qualified service personnel with access
to laboratory quality instruments, in the event that com­ponent replacement or changes in internal control settings
necessitate recalibration.

For those without adequate facilities, the complete unit
may be returned to the factory for calibration. Carefully
repack the unit and return it to the factory Service Depart­ment. The unit will be returned to you prepaid.

EQUIPMENT NEEDED:

A high-impedance (2 megohm or greater), high-sensi­tivity (10 mV full scale or better) ac voltmeter, such as a
Hewlett-Packard 400 GL or Ballantine 861, is necessary for

accurate results. The meter should be equipped with a

clip-on shielded test cable.

In addition, a sine-wave audio generator, capable of

producing 1 volt at 1 kHz with less than 1% total harmonic

distortion, is desirable. A generator with an accurate 10
dB stepped output attenuator, such as the Hewlett-Packard

204D, will greatly simplify changes in input level necessary

during the procedure. A shielded cable to connect the out-

put of the generator to the professional three-pin female
Input 1 receptacle will be needed. Unbalance the generator

output (low side connected to chassis), if generator output

is balanced, and wire the cable so that input connector
pins 1 and 3 are to the low side of the generator and pin 2
is to the high side.

There are three different portions of circuitry which re-

quire calibration: the Gated Memory, the compression sys­tem, and the VU meter. A standard blade screwdriver may

be used to adjust the trimmer potentiometers during the

Gated Memory and compression system calibration. VU
meter calibration requires the selection of a fixed resistor
and soldering it in place on P.C. Board 5.

During the Gated Memory and compression system Cali-

bration, the internal signal level at terminal A of P.C. Board

3 is monitored and adjusted. The signal voltage at this

point will be referred to as E3A. The test signal is provided

by an external sine-wave generator, or the internal Tone
Oscillator may be used. If an external generator is used,
connect its mating cable to the Input 1 connector (13A) with
the Input switch (14A) set to LINE, and the Input 1 Filter
switch (2A) set to IN. Adjust the generator for 1 volt output
at 1 kHz. If the Tone Oscillator is used, set the front-panel

Input 1 Filter switch (2A) to TONE OSC.

If the Tone Oscillator or an external generator without a

stepped attenuator is used, the voltage at terminal A of

P.C. Board 3 (E3A) should be adjusted to the required

values by the Input 1 control (1A). If the external generator
does have a stepped attenuator, the Input 1 control (1A)
should be adjusted so that a l-volt generator output results

in 1 volt at terminal A of P.C. Board 3. Lower levels are then
obtained by using the generator’s attenuator.

Calibration must be performed with the top cover re­moved to permit access to the trimmer potentiometers and

test points, and during compression system calibration,

removal of the bottom cover is also suggested. For com­plete safety from hazardous powerline voltages, the SE30

should be battery-operated during calibration, using fresh

batteries which indicate +1½ VU or better on the meter,
with the Batt. Check switch (9) actuated and the Power
switch (11) ON.

SERVICE INSTRUCTIONS (Cont’d)

PROCEDURE:

First, the meter (7) must be mechanically set to zero.
Turn the Power switch (11) OFF and wait one minute. The
meter pointer should rest over the mark at the left-hand
end of the scale, left of the -20 VU and 0 dB Compression
line. Using a small blade screwdriver, rotate the black
plastic screw below the meter face to set the pointer, if
necessary. The electrical calibrations may now be per­formed as outlined below.

Unless otherwise specified, set all Lo-cut Filter switches
(2) to IN, the Meter switch (8) to DB COMP., the Power (11),
Gated Memory (21), and Comp. (22) switches to ON, the
Input (14) and Output (17) switches to LINE, and the VU
Range switch (4) to +4. Set Output (3) and Input (1) con-

trols to 0, except for Input 1 (1A), adjusted as above. Set

Response Rate control (6) to 3. Measure all voltages with
respect to chassis ground.

GATED MEMORY CALIBRATION:

The Gated Memory calibration should be checked and

adjusted before proceeding to the compression system

calibration.

Connect meter probe to P.C. Board 3, terminal A,
leaving existing gray wire connected, to measure E3A.

Adjust input such that E3A is -43.5 dBV (6.6 mV).

Red portion of Gated Memory indicator (5) should be
exposed.
Adjust input such that E3A is -41.5 dBV (8.4 mV).
Red portion of Gated Memory indicator (5) should be
covered by white vane.
If steps 2 and 3 are not correct, adjust input such that
E3A is -42.5 dBV (7.5 mV) and rotate R318 fully
counterclockwise. Gated Memory indicator (5) will be
white. Slowly rotate R318 clockwise just until red
portion of Gated Memory indicator is exposed. Re­check steps 2 and 3.

COMPRESSION SYSTEM CALIBRATION:

Because of the interdependence of trimmer settings, the

following procedure must be followed in the order listed.

The Gated Memory must first be properly calibrated as

outlined above.

The voltage at terminal L, P.C. Board 4, referred to as
E4L, must also be measured. This terminal is a test point
with no wire connected to it, and access may most easily
be obtained by setting the chassis on its right or left end
and inserting the meter probe from the chassis bottom
through the rectangular hole near transformers T4 and T5.

The temporary wiring change in step 2 may also most

easily be done from the bottom of the unit.

Average Level Adjustment (R212).
Set input such that E3A is -30 dBV (31.6 mV). Voltage
E4L must be -40 ± 0.2 dBV (10± 0.2 mV). If neces­sary, adjust R212 for the proper E4L reading, but allow
15 seconds of settling time after moving R212 setting

to read E4L. If this setting is changed, all subsequent

calibration steps must be checked.
Peak Level Adjustment (R211).
Move blue wire from terminal C of P.C. Board 2 to

terminal D. Set input such that E3A is -20 dBV (100

mV). Voltage E4L must be -27.5 ± 0.3 dbV (44 ± 3
mV). If necessary, adjust R211 for proper E4L reading.
Return blue wire from terminal D of P.C. Board 2 to
terminal C.
DB Compression Meter Calibration Check.
A. Set input such that E3A is -40 dBV (10 mV).

Meter pointer should lie over 0 on the DB Com­pression scale.

B.

Set input such that E3A is -20 dBV (100 mV).

Meter pointer should lie in region occupied by
20 on the DB Compression scale. If either of these
checks is not correct, proceed to step 4.

C.

Set input such that E3A is 0 dBV (1.0 V). Meter
pointer should lie in region occupied by 40 on the
DB Compression scale. If checks A and B are
correct, but if this check is not, proceed to step 5.

4. DB Compression Meter Calibration, 0 and 20 Points
(R213, R214).

The settings of R213 and R214 interact to calibrate the
meter to read 0 when E3A is -40 dBV (10 mV) and to

read 20 when E3A is -20 dBV (100 mV).

A. Rotate R215 fully clockwise.
B. Set input such that E3A is -40 dBV (10 mV). Ro-

tate R213 for a meter reading of 0.

C. Set input such that E3A is -20 dBV (100 mV). If

meter reading is less than 20, rotate R214 slightly
clockwise. If meter reading is more than 20, rotate
R214 slightly counterclockwise. The effect upon
the meter reading at this point is unimportant.

D. Set input such that E3A is -40 dBV (10 mV) and

again rotate R213 for a meter reading of 0.

E. Again set input such that E3A is -20 dBV (100 mV)

and observe meter for a reading of 20.

F. Repeat steps B through E until meter reads 0 when

E3A is -40 dBV (10 mV) and 20 when E3A is -20
dBV (100 mV).

G. Proceed to step 5.

5. DB Compression Meter Calibration, 40 Point (R215).
Set input such that E3A is 0 dBV (1.0 V). Rotate R215
until meter reads 40 on the DB Compression scale.

VU METER CALIBRATION:

Proper VU meter calibration is determined by a VU
CAL trimmer potentiometer (R529) on P.C. Board 5. The
check outlined in step 1 may be performed if P.C. Board 5
has not been replaced, but the procedure of step 2 must
be followed if it has been changed.

First, connect a 600-ohm ± 5%, ½ watt resistor (two
1200-ohm, 5%, ¼ watt resistors in parallel may be used)
between terminals 3 and 2 of the Line Output connector

(20).

1. Calibration check.
A.

Set input so that meter reads approximately 20 on
the DB Compression scale, with the Meter switch

(8) set to DB COMP.

Set the Meter switch (8) to VU and rotate the Out-

B.

put control (3) until the meter reads 0 on the VU

scale.
The voltage measured across the 600 ohm resistor

C.

should be 1.8 ± 0.3 dBV (1.23 ± 0.04 V). This is

4.0 ± 0.3 dBm.

2. Calibration procedure.
If meter Ml has been replaced, first check calibration

in step 1. If check fails, follow procedure below.
A. Set input such that meter reads approximately 20

on the DB Compression scale, with the Meter
switch (8) set to DB COMP.

B. Set the Output control (3) such that the voltage

measured across the 600-ohm resistor connected

to the Output terminals (20) is 1.8 dBV (1.23 V or

4.0 dBm).

27

SERVICE INSTRUCTIONS (Cont’d)

C. Set the Meter switch (8) to VU and the VU Range

switch (4) to +4. Adjust VU CAL trimmer poten­tiometer (R529) for a 0 VU meter reading. Cali-

bration is complete.

STEREO SYNCHRONIZATION

Two SE30’s may be synchronized to operate together
for two-channel stereo applications. With the Stereo Par­allel jacks (23) connected together and the adjustment
below performed, the two units will respond equally to the
sum (left and right) signal to minimize apparent stereo
image shift. After synchronization, the two units will track
together over at least a 20 dB compression range. It is in­tended that the two units be supplied with a properly bal­anced and mixed stereo signal from a separate mixer or
other source.

The synchronizing adjustment procedure may be per-

formed upon two properly calibrated SE30’s as outlined

below. The same equipment needed for calibration is
used for this procedure, except that an external audio
generator is a necessity. A second cable for connecting

the generator to the input connector also is required.

ADJUSTMENT:

1.

Connect the Input 1 connectors (13A) of both units
simultaneously to the audio generator, observing
proper phasing. Cables should be wired such that
input connector pins 1 and 3 are to the low side of
the generator and pin 2 is to the high side. Set the

Mic/Line input Switches (14A) appropriately.

2.

Set the output of the audio generator for the expected
signal level to be applied to the units. This will be ad-

justed as follows to correspond with 10 dB of com-

pression.

3.

Set Output (3) and Input (1) controls to zero, and Re-

sponse Rate controls (6) to the same setting on both

units, preferably between 2 and 5. Set VU Range

switches (4) and Input 1 Lo-Cut Filter switches (1A)

the same on both units, as required. Set Comp.
switches (22) to ON and Gated Memory switches (21)
to DISABLE. Set Meter switches (8) to VU.

4.

Remove the top covers of both units and apply power.

5.

Measure the signal voltage at terminal A of P.C. Board
3 (referred to as E3A) of one unit. Rotate the Input 1
control (1A) of this unit until E3A is -30 dBv (31.6 mv).
Measure E3A of the second unit and set its input 1
control (1A) for the same reading. Do not readjust
either input 1 control after this step.

6.

Set the Output control (3) of the first unit for a meter
reading of 0 VU. Repeat for the second unit.

7.

Connect the Stereo Parallel jacks (23) of the two units
together, using a phono pin plug shielded jumper
cable.

8.

After 30 seconds, observe the VU meter readings of
the two units and note which unit’s meter reading has

increased above 0 VU. Slowly rotate R212 of this unit

clockwise until its VU meter reads 0 VU. Allow 30

seconds for meter reading to stabilize.

9.

Reduce generator output until E3A of this unit is -40
dBv (10mv) and set Meter switch (8) to DB COMP.
Adjust R213 for a reading of 0 on the dB Compression
scale of the meter. Do not disturb any adjustments on

the other unit.

10.

Increase generator output until E3A of this unit is -20
dBv (100 mv). Set both Meter switches (8) to DB
COMP. and observe readings of both meters.

11.

Short circuit the output of the audio generator and
note the time required for the meter readings of each
unit to fall to 0 DB Compression. Remove the generator
short circuit and allow the meter readings to rise and
stabilize.

12.

Adjust the Response Rate control (6) of one of the

units in the appropriate direction to make the two
meter fall times equal and repeat Step 11 to check the
results.

13.

Repeat Steps 11 and 12 until meter fall times are equal.

The settings of the two Response Rate controls may be

somewhat different because of individual component
variations between units.

14.

Replace the top covers of both units.

OPERATION:

After performing the above adjustments, do not disturb
any of the Input, Output, or Response Rate control settings
thus established. If the Gated Memory feature is desired,

set the Gated Memory switches (21) on both units to ON.

The units may now be fed from a balanced, mixed, stereo

source whose level will determine the amount of compres-

sion as indicated on the DB Compression meters of the

SE30’s. Because of individual component variations be-

tween units, the two meters may indicate somewhat dif-

ferently, but both units will operate similarly if adjusted as
outlined above.

Since stereo operation is recommended for only a single

pair of inputs, it may be desirable to improve the operating
signal-to-noise ratio by disabling the two unused input
channels on each unit. This procedure is described in the
Modifications section below.

If it is necessary to change the Response Rate control
settings to compensate for different types of program
material, the timing of the two units should be adjusted to
be equal. This may be done without removing the covers
by applying a signal from an external audio generator to

the inputs of both units simultaneously. Set the Gated

Memory switches (21) of both units to DISABLE and ad-

just the generator output for a DB Compression reading of

approximately 20 on either unit’s meter. Set the Response

Rate control (6) of one unit to the number desired, then

adjust the Response Rate control of the other unit as de­scribed in Steps 11, 12, and 13 above.

28

MODIFICATIONS

Noise Improvement for Single Inputs:

The overall signal-to-noise ratio of the SE30 may be im­proved for single-input applications by disabling the two
unused input channels. This automatically reduces the
noise level of the mixing circuitry without changing the
gain or other characteristics of the remaining input. It is

recommended that Input 1 be used and Inputs 2 and 3 dis­abled to retain the Tone Oscillator and Aux. Line Input
features associated with Input 1. To disable Inputs 2 and 3,

follow the procedure below.

1. Remove AC line cord and turn off all power. Remove
the top cover.

2.

Locate resistors R12 and R13 (33K ohms), between In­put 2 and 3 controls and their associated Lo-cut Filter
switches. Disconnect resistors R12 and R13 from

switches S2 and S3. Bend removed lead of resistor

away from all terminals, wires, and chassis.

3. Replace top cover. During operation, set Input 2 and

Input 3 controls to zero.

Response Rate Knob Removal:

To prevent inadvertent misadjustment of the Response
Rate Control for applications in which a fixed setting may
be established, the knob may be removed.

1. Experimentally determine the proper Response Rate
Control setting for the intended application and rotate
the knob to this position.

2. Remove AC line cord and turn off all power. Remove
the top cover.

3.

Note that the plastic Response Rate knob (K5) extends

through the front panel, over the shaft of potentiom-

eter R5. Insert the blade of a standard screwdriver
between the rear of the knob and the shaft bushing of
R5, and twist the screwdriver ¼ turn. This will slide
the knob forward on the shaft partially out of the front
panel.

4.

Grasp the knob and pull it completely out of the front
panel.

5.

Push the black plastic plug supplied with the SE30 into
the hole thus exposed.

6. To permit subsequent control adjustment or replace­ment of the knob, the plug may be released by remov-

ing the top cover and using long-nose pliers to pinch

together the locking devices on either side of the plug

body.

Telephone Line Surge Protection:

When using the SE30 to feed a telephone line subject

to lightning induced voltage surges, the following part

(commercially available) can be installed across the Line
Output terminals to provide additional protection for out­put circuit components:

Metal Oxide Varistor
General Electric Co.

Type No. V22ZA1

29

MODEL A100A CARRYING HANDLE ASSEMBLY

The Shure Model A100A Carrying Handle Assembly
provides a means for conveniently carrying the Shure
Model SE30 Gated Compressor/Mixer. The Model

A100A serves as a handle for carrying the SE30, as a

cover for the front panel, and as a tilt stand for position-

ing the SE30 at an angle for easy reading of the con­trols and meters. The A100A is easily switched from
carrying handle use to tilt stand use simply by re­adjusting two knurled bolts which secure the Model
A100A to the SE30. When in the tilt stand position,
the SE30 rests on rubber feet mounted on the Model
A100A. When in a carrying position, the SE30 may be

rested on any flat surface and is then protected by the
die cast corners on the rear of the case.

to mount the Model A100A on the Model SE30,
proceed as follows:

1. Place the back (bottom) of the SE30 on a flat
surface with the front controls facing up.

2. Position the Model A100A over the front of the
SE30. The top of the screw slots on the sides

of the Model A100A should align with the two
tapped holes (C) on the sides of the SE30. See

Figure 1, Carrying Position.

3. Screw the two knurled bolts supplied with the

Model A100A fully clockwise into the two tapped
holes (C) on each side of the SE30.

To position the Model A100A in tilt stand position,

proceed as follows:

1.

Loosen the knurled bolts at sides of Model A100A
by turning them partially counterclockwise.

2. Lift the Model A100A away from the SE30 so
that the knurled bolts pass through the bottom

of screw slots.

3. Swing the Model A100A handle beneath the SE30
and tighten the knurled nuts (screw clockwise).

See Figure 1 Position in Use.

MODEL A100B RACK PANEL

The Model A100B Rack Panel provides the Model
SE30 with supports for rack mounting. To mount the
Model A100B to the Model SE30, proceed as follows:

1.

Unscrew the four rubber feet from the bottom

of the SE30 to eliminate the obstruction of the

rubber feet when sliding the SE30 into a rack

panel.

2.

Remove screws A and B (turn counterclockwise)

from each side of the SE30. See Figure 2, Rack

Panel.

3.

Position the Model A100B brackets on the sides
of the SE30; the three holes of the rack panels
are to be aligned with the three tapped holes
A, B and C on sides of SE30.

4.

Replace screws A and B (turn fully clockwise)
to fasten brackets to SE30.

5.

Screw the ¼ inch bolts supplied with the Model

A100B fully clockwise into the tapped holes at C.

OVERALL DIMENSIONS

RACK PANEL

FIGURE 2

CARRYING POSITION

CARRYING HANDLE ASSEMBLY

Copyright 1979, Shure Brothers Inc
27A865 (SK)

TILT STAND POSITION

FIGURE 1

Printed In U.S.A.