Wohler LM25 Analog Series User manual

Title and Contents ...........................................................
Introduction.............................................................................................
Section 1: General Features and Specifications........
Description and Features ......................................................................
Applications and Specifications ............................................................
Rear and Front Panel Configurations .....................................................
Section 2: Operation .......................................................
Installation ............................................................................................
Front Panel Features .............................................................................
Rear Panel Features ...............................................................................
Section 3: Technical Information .................................
Level Meter Internal 10-Position DIP Switch Settings ..........................
Level Meter DIP Switch Locations ........................................................
Level Meter Alternate Scales .................................................................
LM25 Analog Interconnect Block Diagram ...........................................
LM25 Analog Series
1U Level Meter Units
Four, Six, or Eight Channels with
"Mini" Phoenix Input Connectors, and
25-Segment LED Bargraph Level Meters
Document P/N 821612 Rev-A
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CONTENTS
User Manual
© 2004 Wohler Technologies Inc. ALL rights reserved
ECO-2668 (10/13/04)

2© 2007 Wohler Technologies, Inc. ALL rights reserved
Introduction
Congratulations on your selection of a Wohler Technologies product. We are confident it represents the best performance and value
available, and we guarantee your satisfaction with it.
If you have questions or comments you may contact us at:
Wohler Technologies, Inc.
31055 Huntwood Avenue
Hayward, CA 94544
Phone: [phone] Fax: [phone]
US Toll-Free: 1-888-596-4537
www.wohler.com [e-mail]
1) Read these instructions.
2) Keep these instructions.
3) Heed all warnings.
4) Follow all instructions.
5) Do not use this apparatus near water.
6) Clean only with dry cloth.
7) Do not block any ventilation openings. Install in accordance with the manufacturer's instructions.
8) Do not install near any heat source such as radiators, heat registers, stoves, or other apparatus (including
amplifiers) that produce heat.
9) Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades
with one wider than the other. A grounding type plug has two blades and a third grounding prong. The
wide blade or the third prong are provided for your safety. If the provided plug does not fit into your outlet,
consult an electrician for replacement of the obsolete outlet.
10) Protect the power cord from being walked on or pinched, particularly at plugs convenience receptacles
and the point where they exit from the apparatus.
11) Only use attachments/accessories specified by the manufacturer.
12) Use only with the cart stand, tripod, bracket, or table specified by the manufacturer, or sold with the
apparatus. When a cart is used, use caution when moving the cart/apparatus combination to avoid injury
from tip-over.
13) Unplug this apparatus during lightning storms or when unused for long periods of time.
14) Refer all servicing to qualified service personnel. Servicing is required when the apparatus has been
damaged in any way, such as when power-supply cord or plug is damaged, liquid has been spilled or
objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not
operate normally, or has been dropped.
15) Do not expose this apparatus to rain or moisture.
16) The apparatus shall be connected to a mains socket outlet with a protective earthing connection.
Important Safety Instructions
CAUTION!
In products featuring an audio amplifier and speakers, the surface at the side of the
unit, where the audio amplifier heat sink is internally attached, may get very hot after
extended operation. When operating the unit excercise caution when touching this
surface and ensure that external materials which may be adversely affected by heat
are not in contact with it. There is a Hot Surface label (see diagram) attached to the
aforementioned surface of the product.

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© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
General Features
and Specifications
Description
Features
Applications
Specifications
Rear and Front Panel Configurations
Section 1

4© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
Features
The LM25 Analog Series audio level metering units offer high-resolution level metering with four, six, or eight channels in a space-
saving 1U rack-mountable enclosure.
Standard input connectors for the LM26 Analog Series are "mini" Phoenix type terminal block connectors. Analog input connec-
tor impedances are 27K Ω(ohm), balanced, and may be adjusted for Reference Level gain via rear panel DIP switch(es). A
recessed trim pot on the front panel adjusts level meter brightness. A green LED on the front panel offers power indication.
The level meters are horizontally mounted 25-segment tri-color LED bargraphs. The standard display mode is set as a single
segment PPM ‘dot’ above a VU bar; each segment’s color is fixed according to its position on the scale. Each bargraph meter four
channel section may be individually adjusted for a number of parameters, including Display Mode,Peak Hold,PPM Ballistics,
and Alternate Scales via rear panel and internal DIP switches. An Auto Line Level Calibrate feature is also available.
• 25-segment tri-color bargraph level meters provide wide dynamic range
•Monitors industry standard Analog audio signals
•Front panel power indication LED
•Standard input connectors are "mini"Phoenix
•Selectable input Referrence Level (0, +4, +6, or +8 dBfs)
•Selectable Display Mode (VU Only, VU/PPM, or PPM Only)
•Selectable Peak Hold (Manual, 3-Second, 10-Second, or Off)
•Selectable PPM Ballistics (Type I, Type II, DIN 45406, or SSRT)
•Selectable alternate Bargraph Scales (Extended VU, VU, BBC, NORDIC, and DIN)
•Front panel bargraph brightness control
• AES and SDI models also available
LM25 Analog Series
Level Metering Units
Description
Section 1: General Features and Specifications
LM25-4 Front Panel
LM25-8 Front Panel
713 Grandview Drive,
South San Francisco, CA 94080
650 589-5676 Fax: [phone]
LM25-6 Front Panel

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© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
Applications
The LM25 Analog Series of level metering units are an adaptable and effective way to monitor any analog audio application. The
following are some of the applications where an LM25 unit would prove valuable.
· Radio Broadcast Station
· TV Control Room
· Mobile Broadcast unit
· Remote Radio Station
· Sound Staging development
· Recording Studio
· Cinema
· Theatrical Staging
· Music Design Application
· Broadcasting Schools
· Home Theater
· Any Aural Media applications
Units are certified to meet, at time of manufacture, all currently applicable product safety and EMC requirements, such as those of CE. 0 dbv ref.
0.775V RMS. Features and specifications subject to improvement without notice.
Specifications
Section 1: General Features and Specifications
Level Meter Type:
Segment Quantity:
Level Gain (DIP switch selectable):
Bargraph Length:
LED Segment Size:
LED Segment Pitch:
Segment Display Color:
Peak Emmision Wavelength:
Segment Brighness, (If = 20 mA):
Segment Brightness, Uniformity:
Adjacent Segment "Off" Brightness:
Dynamic Range,
Extended VU (Standard Analog) Scale:
Midscale Resolution,
Extended VU (Standard Analog) Scale:
Analog Full Scale Input:
Input Sampling Rate:
Analog Input Impedance:
Input Connectors:
AC Mains Power:
Power Consumption:
Dimensions:
Weight:
LED bargraph
25
0, +4, +6, +8 dB
2.5" (63.5 mm)
0.2" x 0.07" (5.16 x 1.78 mm)
0.10" (2.54 mm)
Tri-color (red, amber, green)
Green: 570 nm, Red: 630 nm
5.5 mcd
<8% difference between segments
<1% of brightness of active segment
62 dB
2 dB
+19 dBv
>=48 kHz
27k Ω(Ohm), balanced
"mini" Phoenix, female (Standard)
100-250 VAC, 50/60 Hz universal input, auto-switch
25 watts
3.5 x 19 x 8" (89 x 483 x 203 mm)
8 lbs (3.5 kg)

6© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-ASection 1: General Features and Specifications
The 1U rear panels are comprised of modular panel sections. One to Two of the modular panel sections have the audio input connectors,
with any remaining sections using a blank panel. This arrangement permits mixing of different types of input modules, although such mixes
are considered special order items.
The following illustration shows the standard input connectors available for use in the four, six, and eight channel models.
Rear Panel Configurations
Mini-Phoenix Input Modular Section
(standard)
Below are illustrations showing the two standard configurations of the LM25 Analog Series rear panels.
LM25-4 Rear Panel
LM25-8 Rear Panel
LM25-6 Rear Panel

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© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
Operation
Installation
Front Panel Features
Rear Panel Features
Section 2

8© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-ASection 2: Operation
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© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
Mounting
The unit should be mounted where convenient for operating persons, ideally at approximately eye level for best viewing.
Heat Dissipation
Heat produced by these units is negligible. No special considerations for cooling are necessary as long as the ambient temperature
inside the rack area does not exceed approximately 40°C (104°F).
Mechanical Bracing
The chassis is securely attached to the front panel at six points along its surface, not just at the four corners of the chassis ears. This
feature will reduce or eliminate rear bracing requirements in most mobile/portable applications. The weight of internal components is
distributed fairly evenly around the unit.
Audio Connections
Connection of the audio feeds is straightforward. The system interconnect block diagrams located on page 19 may be referred to
for clarification of the general signal paths into the LM25 Analog Series units.
Electrical Interference
As with any audio equipment, maximum immunity from electrical interference requires the use of shielded cable; however, satisfac-
tory results can sometimes be obtained without it. The internal circuitry common is connected to the chassis.
AC Power
The unit's AC mains connection is via a standard IEC inlet, with safety ground connected directly to the unit's chassis. The universal
AC input (100-240VAC, 50/60 Hz) switching power supply is a self-resetting sealed type, with automatic over-voltage and over-
current shutdown. There is no user-replaceable fuse in either the primary or secondary circuit.
Level Meter Parameter Settings
The Peak Hold,PPM Ballisatics, and Alternate Scale level meter settings are selected using a DIP switch accessable only by
removing the top cover of the unit. Should the user wish to change these settings, it should be done before installation into an
enclosed rack or difficult to access area. See page 16 for setting information.
The Reference Level Gain calibration and the bargraph Display Mode settings may be selected after installation via the DIP
switches on the rear panel as long as the rear panel is easily accessable. If installation makes the rear panel difficult to access, then
these adjustments should be made before installation. See page 12 for setting information.
Installation
Section 2: Operation

10 © 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
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Please refer to Figure-2a on the following page to familiarize yourself with the front panel features of the LM25 Analog Series units. The
following sections describe these functions and are referenced, by number, to Figure-2a.
Section 2: Operation
Front Panel Features
Bargraph Brightness Adjust
This control is recessed into the front panel and can be accessed using a small flathead screwdriver. Turning it clockwise
will increase the relative brightness of the bargraph LED segments. Adjusting this one control will simultaneously affect the
brightness of all bargraph displays.
Audio Level Meters
Audio levels for the analog input sources are displayed via these 25-segment tri-color (green, amber, red) LED bargraph
display level meters.
Each LED bargraph represents a single channel. To the left of each LED bargraph is a channel number which corresponds
to one of two numbers found next to the input connectors on the rear panel (each 6-pin input connector receives two
channels). See page 19 for an interconnect block diagram of the signal paths through the input/display sections.
Although the bargraph displays are arranged in groups of two on the front panel, each "input section" is comprised of four
inputs (two 6-pin connectors). Each input section (four inputs) is user adjustable for Referrence Level,Display Mode,
Peak Hold,PPM Ballistics, and Alternate Bargraph Scales via DIP switches on the rear panel and inside the unit. See
pages 12 and 16 for more information regarding DIP switch settings.
Power Indication LED
This LED glows GREEN to indicate the unit is connected to mains power and an operation voltage is present.

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© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-ASection 2: Operation
Figure-2a: Front Panel Features

12 © 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
C
A
Please refer to Figure-2b on the following page to familiarize yourself with the rear panel features of the LM25 Analog Series units. The
following sections describe these features and are referenced, by letter, to Figure-2b.
DIP Switch - Rear Panel
Each rear panel DIP switch sets the Line Level Calibration,Reference Level, and PPM/VU Display Mode for each
input section (four channels). See the descriptions and diagram below for setting information.
Line Level (Auto) Calibration:
The unit is calibrated at the factory. To recalibrate:
1) Turn on the power.
2) Apply the desired reference level (nominal 0) signal to all channels.
3) Make sure the Reference Level DIP sections (2and 3) are set to the nearest level of the input signal being applied for
calibration (i.e., 0, +4, +6 or +8). The user should make sure that the signal applied to all four channels is within +/- 4
dB of the reference level selected by DIP switch sections 2and 3.
4) Place DIP section 1in the DOWN position.
5) Wait 10 seconds. The unit will remove the previous calibration and the new calibration will be applied.
6) Place DIP section 1in the UP position and return unit to service.
7) Only ONE auto-calibration attempt may be made for each cycling of AC power to the unit. Once the Line Level
Calibration DIP switch has been placed in the CAL position, it is necessary to cycle the power before that DIP switch
will be functional again, EVEN if a calibration attempt was unsuccessful.
If one wishes to calibrate again, turn off the power to the unit and repeat steps 1 through 6.
LEVEL METER CALIBRATION NOTE: For more accurate indication of signal levels, meters are tuned to effect a
“rounding” function, which occurs BETWEEN the thresholds of any two bargraph segments. This means the level meter
zero LED segment will turn on before that segment’s scale indication, the amount being one-half the smallest spacing
between LED segments (mid-scale resolution) or 0.5 dBu, whichever is smallest. For example, using the Analog (extended
VU) scale, a meter calibrated for a +4 dBu nominal level will actually turn the zero LED segment of the level meter on at 3.5
dBu and all segments will turn on at 0.5 dBu before each segment’s silk-screened scale indication.
Reference Level:
DIP switch sections 2and 3determine the Reference Level, which adjusts the level of the input signal and the resultant level
displayed on the LED bargraphs. Factory setting is +4 dB. See diagram below for settings.
Bargraph Display Mode:
DIP switch sections 4and 5determine how peak levels are displayed for the associated meters on the front panel. There are
four possible settings; VU-VU Floating Segment,VU-PPM Floating Segment,PPM Only, and PPM-PPM Floating
Segment. The VU floating segment is visible when a Peak Hold time (other than zero) is selected using the Internal 10-
Position DIP Switch Module (see page 16). The PPM-PPM Floating Segment selection has a PPM floating segment
visible when a Peak Hold time (other than zero) is selected. The factory default setting is VU-PPM Floating Segment.
See diagram below for settings.
Analog Input Connectors
Each 6-pin male “mini” Phoenix connector accepts two channels of standard Analog audio signals and is configured for
balanced connections (27k Ωimpedance ). Connector pinout information is silk-screened below each connector on the
rear panel.
Power Connector
Attach the supplied IEC-320 power cord between this connector and mains power (100 - 240VAC nominal, 50/60 Hz). The
front panel Power Indication LED (Item 3, page 10) will glow GREEN to indicate operating voltages are present.
Section 2: Operation
Rear Panel Features
B

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© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-ASection 2: Operation
Figure-2b: Rear Panel Features

14 © 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-ASection 2: Operation
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© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
Technical Information
Level Meter Internal 10-Position DIP Switch Settings
Level Meter DIP Switch Locations
Level Meter Alternate Scales
LM26 Analog Interconnect Block Diagram
Section 3

16 © 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-AOperation
Level Meter Internal 10-Position DIP Switch Settings
PPPM Characteristics (Ballistics):
The PPM characteristics determine the Integration Time (rise time) and Return Time (fall time) of the level meter. The
Integration Time is the time it takes for the lighted segments of the level meter, after application of a 5 Khz tone at a certain reference
level, to rise within a specified number of dB of that level. Return Time is the time it takes for the lighted segments of the level meter
to fall a certain number of dB after removal of a 5 Khz tone of a certain reference level. The PPM characteristics available for
selection using DIP switch sections 7and 8of the 10-position Internal DIP Switch (as shown in the above diagram) are as follows:
Integration Time is 5 ms (-2 dB),
Return Time is 1.7 seconds (20 dB)
Integration Time is 10 ms (-2 dB),
Return Time is 2.8 seconds (24 dB)
Integration Time is 5 ms (-2 dB),
Return Time is 1.5 seconds (20 dB)
Integration Time is a single sample,
Return Time is 1.5 seconds (20 dB)
IEC268-10, Type 1:
IEC268-10, Type 2:
DIN 4506:
Single Sample:
This 10-position DIP switch is accessed by removing the top cover of the LM unit and is located on the 919174 PCB (the same PCB
on which the 6-position rear panel DIP switch is located). See Figure-3a, page 17 for a diagram of the 919174 PCB and the DIP
switch location.

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© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
Level Meter DIP Switch Locations
Internal Level Meter
10-Position DIP Switch
Module (see page 16)
Rear Panel Level Meter 6-
Position DIP Switch Module
(see page 12)
Figure-3a:
DIP Switch Locations on

18 © 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-ASection 3: Technical Information
Level Meter Alternate Scales
The standard scale used on the ALM25 Analog Series of level meters is the Extended VU scale. However, if alternative scale
characteristics are selected for the level meters by setting the Alternate Scale section of the Level Meter Internal 10-Position
DIP switch (see page 16), it is recommended that a label with the appropriate scale be applied to the front panel LED bargraph level
meters. Alternate scales for the LM25 level meters include the VU,BBC,NORDIC, and DIN scales. The Extended VU scale is
the standard scale for all LM Analog Series models. See the diagrams below for the 26-segment Alternate Scales. Contact
Wohler Technologies for more information about Alternate Scale labels.

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© 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
LM26 Analog Interconnect Block Diagram
Section 3: Technical Information

20 © 2004 Wohler Technologies Inc. ALL rights reserved
LM25 Analog Series User Manual P/N 821612 Rev-A
NOTE:
PCB layout and schematic support documentation is available upon request.
Wohler Technologies, Inc.
713 Grandview Drive
South San Francisco, CA 94080
650 589-5676 Fax: [phone]
web: www.wohler.com
e-mail: [e-mail]
Wohler Technologies, Inc.
31055 Huntwood Avenue
Hayward, CA 94544
Phone: [phone] Fax: [phone]
US Toll-Free: 1-888-596-4537
www.wohler.com [e-mail]