Wohler SUM Series User manual

World Leader of In-Rack, Audio, Video, Data Monitoring, and Closed Captioning Solutions
CONFIDENCE IS EVERYTHING.™
SUM Series
•AMP1ASUM6/RD •VMDA-SUM8
1RU Summing Audio Monitors
User Guide
Part Number 821025, Revision C

© 2010 Wohler Technologies, Inc. All rights reserved.
ii
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© 2010 Wohler Technologies, Inc. All rights reserved. 1
SUM Series User Guide
Introduction
Overview
The SUM Series of audio monitors provide self-powered, full-fidelity
stereo or monaural monitoring in a single (1U) industry standard rack-
space mount. The AMP1A-SUM6/RD model features speakers driven
by three power amplifiers: two amplifier/driver combinations to
handle midrange and high frequency information in stereo, while a
third center channel reproduces information below the 500 Hz
crossover point for reproduction through the woofer. The
AMP1A-SUM6/RD model, has two midrange and one woofer speaker
in a 6.5” depth. The VMDA-SUM8 provides either analog or AES
digital inputs, summed as mono or stereo through two amplifier/
drivers in an ultr-shallow 4.5” depth.
Topics
Topics Page
Introduction 1
Safety Instructions 2
Installation Recommendations 3
Features 4
Applications 6
Specifications 6
Front Panel Controls 7
Rear Panel Connectors 10
Technical Functional Overview 12

© 2010 Wohler Technologies, Inc. All rights reserved.
2
SUM Series User Guide
Safety Instructions
Safety Instructions
1. Read, keep, and follow all of these instructions; heed all warnings.
2. Do not use this equipment near water or moisture.
3. Use only a dry cloth to clean the equipment.
4. Do not block any ventilation openings. Install only in accordance
with the instructions in the section entitled, “Installation
Recommendations” on page 6.
5. Do not install near any heat source such as a radiator, heat register,
amplifier, or stove.
6. Do not attempt to plug the unit into a two-blade outlet (with only
two prongs of equal width).
7. Protect the power cord from being walked on or pinched,
particularly at plug’s source on the equipment and at the socket.
8. Use only the attachments/accessories specified by the
manufacturer.
9. Unplug the equipment during lightning storms or when unused
for long periods of time.
10. Refer all servicing to qualified service personnel. Servicing will be
required under all of the following conditions:
•The equipment has been damaged in any way, such as when
the power-supply cord or plug is damaged.
•Liquid had been spilled or objects have fallen onto the
equipment.
•The equipment has been exposed to rain or moisture.
•The equipment does not operate normally.
•The equipment has been dropped.
IMPORTANT: By design, these monitors will only plug into a three-prong outlet for
your safety. If the plug does not fit into your outlet, contact an
electrician to replace the obsolete outlet.

© 2010 Wohler Technologies, Inc. All rights reserved. 3
SUM Series User Guide
Installation Recommendations
Installation Recommendations
Mounting
The unit is designed to install into a standard 19" rack mounted at eye
level for best visual observation of the monitor screens.
Heat Dissipation
The ambient temperature inside the mounting enclosure should not
exceed 40°Celsius (104°Fahrenheit). Adjacent devices can be rack
mounted (or stacked) in proximity to the unit if the above temperature
is not exceeded. Allow a 1RU (1.75”/44.45mm) space above and below
the unit for air circulation.
Power
The unit comes with a standard 24VDC/3.0A internal power supply
and connects an A/C mains power source (65W, 100 to 240 VAC, 50/
60Hz) to the IEC connector provided on the rear panel of the unit.
Sympathetic Vibration
Sympathetic vibration from other equipment (cables, etc.), in the rack
may be serious enough to interfere with the unit’s sound quality out in
the listening area. The use of thin card stock and/or felt or foam
weather-stripping type materials between adjacent vibrating surfaces,
or tying up loose cables, etc., may be required to stop vibrations
external to the unit.
Important: To reduce noise, the monitor have any fans. As a result, the heat
generated by the class D power amplifiers, power supplies, and other
components is vented by slots in the side of the unit. Therefore, as a
safety precaution, we advise you to be sure to allow proper ventilation
on both sides of the unit.

© 2010 Wohler Technologies, Inc. All rights reserved.
4
SUM Series User Guide
Features
Mechanical Bracing
The chassis is securely attached to the front panel at eight points along
its surface, not just at the four corners of the chassis ears. This feature
will reduce or eliminate rear bracing requirements in many mobile/
portable applications. The weight of internal components is distributed
fairly evenly around the unit.
Audio Connections
Connection of the audio feeds is straightforward. Please refer to the
system interconnect block diagram on page 15 for clarifi cation of the
general signal paths into and out of the VMDA-SUM8 unit. Care should
be exercised to avoid mismatched cable types and other similar causes
of undesired refl ections in RF signal systems.
Electrical Interference
As with any audio equipment, maximum immunity from electrical
interference requires the use of shielded cable; however, satisfactory
results can sometimes be obtained without it. The internal circuitry
common is connected to the chassis.
Features
Common
•Only one rack space high
•Separate volume control for each channel
•Headphone output jack
•Fits in a 1U standard 19" rack space with a depth of only 4.5"
•Minimal power dissipation for a low operating temperature

© 2010 Wohler Technologies, Inc. All rights reserved. 5
SUM Series User Guide
Features
•Low power consumption
•Power indication LED
•Excellent high frequency response for positive detection of
background whine and noise
•Audible indication of phase/polarity problems
•Thorough magnetic shielding for placement next to video monitors
•Quick and easy installation: simply slide in the rack and connect
audio and AC power
VMDA-SUM8 Features
•Master volume control
•Balanced mono output of the selected channels on a 1/4" phone jack
•LED indication of input signal type (digital or analog)
•LED indication of digital input signal lock status
•Analog inputs on a DB-25 connector
•Digital inputs on four female BNC connectors
•Termination select for each digital input connector
•Gain calibration adjustment of digital input signal pairs
AMP1A SUM6/RD Features
•Separate volume controls for each of the six inputs a on a DB-25
connector
•98 dB SPL at two feet

© 2010 Wohler Technologies, Inc. All rights reserved.
6
SUM Series User Guide
Applications
Applications
The SUM Series monitors are ideally suited for use in VTR bays, mobile
production vehicles, teleconferencing installations, multimedia
systems, satellite links and cable TV facilities, and on-air radio studios.
Specifications
Table 1–1 SUM Series Specifications
Specification AMP1 SUM6/RD VMDA-SUM8
AES/EBU Inputs — 4 on BNC (Unbalanced)
Digital Input Termination — 75 
Digital Input Sampling
Rate —Auto detection between 32 and 96 kHz
Digital Input Level for Full
Output — -20 dBfs
Analog Inputs 6 on DB-25 (Balanced) 8 on DB-25 (Balanced)
Analog Input Impedance 200k Balanced) 100k (Balanced)
Analog Input Level for
Full Output
0 dBv Balanced
-10 dB Unbalanced 0 dBv
Balanced Program Output
1/4" Phono Jack, Mono, retains mix balance, 0 dBv out at
0 dBv in under balanced conditions/max volume
settings.
Hum and Noise Better than -68 dB below
full output
Better than -70 dB below
full output
Electrical Distortion: < 0.15% at any level below
limit threshold
<0.3% below limiting
threshold
Acoustical Frequency
Response
80 Hz - 16 kHz ± 7 dB)
(-10 dB @ 50 Hz, 22 kHZ) 300 Hz to 10k Hz (± 6 dB)
Acoustical Distortion 8% or less worst case;
typically < 2% above 180 Hz
Typically <2% at operating
levels below limiting
threshold, 300 Hz to 10k Hz
Peak Acoustical Output 90 dB SPL at 2 feet 80 dB SPL at 2 feet

© 2010 Wohler Technologies, Inc. All rights reserved. 7
SUM Series User Guide
Front Panel Controls
Front Panel Controls
Common Controls
•Speakers (Left and Right): The VMDA-SUM8 internal speaker
system is comprised of two mid-range speakers capable of stereo or
mono reproduction. The internal speaker system for the AMP1A-
SUM6/RD model, to accomodate the reduced depth dimension, is
comprised of two woofer speakers (center) and two mid-range
tweeter speakers (left and right). The two mid-range speaker
channels reproduce, in stereo, only the mid and high frequencies
while the woofer speaker(s) monorally reproduce the low
frequencies.
•Headphone Jack: Select the headphone audio sources as you
would for the internal speakers. When you plug in headphones, the
speakers will mute. This jack accepts a standard 1/4” phone type
stereo plug as shown in Figure 1–1 below.
•Power LED: This LED glows green to indicate that the mains
powered 24V power supply is connected to the power connector on
the rear panel.
Power output:
RMS Each Side
RMS Bass
10 W transient / 5 W
continuous
10 W transient / 5 W
continuous
10 W transient / 5 W
continuous
Power (CE and UL
approved) 100 to 240VAC, 50/60 Hz
Power Consumption 35 W 45 W
Dimensions 1.75 x 19 x 6.5 inches
(44.5x 483 x 165.1 mm)
1.75 x 19 x 4.5 inches
(44.5x 483 x 114.3 mm)
Weight 5 lbs. (2.27 kg ) 2.75 lbs. (1.25 kg)
Magnetic Shielding <1 gauss any adjacent
surface
<2 gauss any adjacent
surface
Table 1–1 SUM Series Specifications
Specification AMP1 SUM6/RD VMDA-SUM8

© 2010 Wohler Technologies, Inc. All rights reserved.
8
SUM Series User Guide
Front Panel Controls
AMP1A SUM6RD-Specific Controls
Figure 1–1 AMP1A SUM6/RD Front Panel
•Volume(Channels 1 to 3): These three controls independently affect
the loudness of each of the first three source channels (1, 2 and 3),
which are electronically summed together for reproduction from
the left internal speaker (or left headphone, if connected).
•Volume (Channels 4 to 6): These three controls independently
affect the loudness of each of the second three source channels (4, 5,
and 6), which are electronically summed together for reproduction
from the right internal speaker (or right headphone, if connected).
VMDA SUM8-Specific Controls
Figure 1–2 VMDA SUM8 Front Panel
•Master Volume Control: Turning this recessed trim-pot clock-wise
increases the volume of the entire mix; when turned counter-
clockwise it is decreased. Note that this control comes after the mix
as set by the individual Input Source Volume Controls, so that the
volume balance between channels (the mix) is maintained
throughout master volume adjustment. Factory setting is full
volume.
Speakers
Volume
Headphones
Power
Speakers
Volume
Headphones
Analog/Digital Select and AES Lock
Power
Master Volume

© 2010 Wohler Technologies, Inc. All rights reserved. 9
SUM Series User Guide
Front Panel Controls
•Input Source Volume Control (1 through 8): Each of these volume
controls affects the loudness of only the selected audio source for
the channel it is associated with (1 through 8). Channel numbers are
silk-screened above each control. When the unit is set for mono
operation, all channels are summed together (at their respective
levels) monaurally across both speakers. When set for stereo
operation the left speaker reproduces the mix of channels 1, 3, 5, and
7 and the right speaker reproduces the mix of channels 2, 4, 6, and 8.
Mono or stereo operation is selected by placing the 4-wire audio
harness on one of two headers internal to the unit.
Note that the Input Source Volume Controls are positioned so that
when operating the unit in stereo mode, the volume controls for
channels 1/2, 3/4, 5/6, 7/8 are arranged in four left/right pairs.
These pairs also correspond to the AES input channel pair
designations of A, B, C, and D.
Digital Gain Calibration for each of the eight AES audio source
channels is adjustable, allowing calibation relative to the analog
input levels. Digital gain calibration is accomplished by adjusting
eight trim-pots internal to the unit. Digital gain calibration is factory
set at -20 dBfs digital to +4 dBu analog for all eight channels. See
page 10 for setting instructions.
A Mute on Data feature is available allowing the unit to mute any of
the four AES inputs when a datastream (i.e. Dolby) is detected at the
AES input. Factory setting is for this feature to be activated. See
page 10 for setting instructions.
The unit may be configured (with internal jumpers) to mute the AES
input(s) and indicate an error (A/D Input Select Button glows red
on front panel) when a set validity bit is detected at the input(s).
Factory setting is for this feature to not be activated.
•A/D Input Select Buttons and AES Input/Lock Indication LEDs
(1 through 8): Each of these buttons is used to select the source
signal for the associated channel. Channel numbers are silk-
screened below each button. Each button features an integrated bi-
color LED (green/red) used for button status indication. When an
analog source is selected, the button is unlit. When a locked AES
source is selected the button glows green. When the selected AES

© 2010 Wohler Technologies, Inc. All rights reserved.
10
SUM Series User Guide
Rear Panel Connectors
source is unlocked, the button will glow red. Refer to the chart
below for button LED indication.
Rear Panel Connectors
Common Connectors
Power Connector: Attach the included 24V power supply between this
connector and mains power connector. The Power LED on the front
panel will glow green to indicate operating voltages are present. For
polarity orientation, refer to the silk-screened diagram to the right of the
connector.
AMP1A SUM6RD-Specific Connectors
Figure 1–3 AMP1A SUM6/RD Rear Panel
•Balanced Analog In (1 through 6): This balanced (200K) female
DB-25 connector accepts standard analog audio signals. Only the
top row of pins are used for audio input. See Figure 1–4 below for
pin-out information including polarity.
Table 1–2 Button/Indication Descriptions
Selected Source Button/LED Indication
Analog Unlit
AES (Locked) Green
AES (Unlocked) Red
+-
Wohler
Technologies
[phone]
[phone]
www.Wohler.com
Fax
Tel
AMP1A-SUM6 / RD
253348-01
24VDC
AUDIO 2 AUDIO 5 AUDIO 6
GND
AUDIO 4 AUDIO 3 AUDIO 1
25
13
N/C
14
1
YEAR
MONTH
SERIAL NO.
MADE IN U.S.A.
Power Balanced Analog In

© 2010 Wohler Technologies, Inc. All rights reserved. 11
SUM Series User Guide
Rear Panel Connectors
Figure 1–4 Balanced Analog In - DB-25 Pin-Out
VMDA SUM8-Specific Connectors
Figure 1–5 VMDA SUM8 Rear Panel
•Analog In: This DB-25 connector accepts eight channels of
standard analog audio signals and is configured for balanced 100k
impedance connections. For channel and pin-out information of
this connector, refer to Figure 1–6 below or to the silk-screened
diagram for the connector on the rear panel.
2.0A typical
24VDC
3.5A max
+-
VMDA-SUM8
SERIAL NO.
6
13
25
+
2
-
3
-
+
1
-+
4
-
5
+
-
+
www.Wohler.com
Fax
Tel
Technologies
Wohler
[phone]
[phone]
14
1
++
-
7
+
-
8
-
ANALOG IN
OFF
ON TERM.
OFF
A
AES
B C
ON
D
Analog In
Power
AES Termination
AES In

© 2010 Wohler Technologies, Inc. All rights reserved.
12
SUM Series User Guide
Technical Functional Overview
Figure 1–6 Balanced Analog In - DB-25 Pin-Out
•AES In (Athrough D): These four female BNC connectors accept
two channels each (eight channels total) of AES/EBU digital audio
signals and are configured for unbalanced 75 impedance
connections. These input connectors are referred to as A, B, C, and D
from left to right (see silk-screened diagram at left of rear panel).
Each of the inputs provides the following channels:
•Input A - Channels 1/2
•Input B - Channels 3/4
•Input C - Channels 5/6
•Input D - Channels 7/8
•AES Input Termination Select (A through D): These two two-
position DIP switch modules allow termination selection for each of
the four AES inputs. Each switch affects the connector to which it is
closest. If an input is connected to downsream equipment, remove
its termination by placing the associated switch in the up (off)
position. If not connected, apply termination by placing its switch in
the down (on) position. For settings, you can also refer to the
diagram silk-screened to the left of the AES input connectors.
Technical Functional Overview
Figure 1–7 below and Figure 1–8 on page 14 illustrate the overall
functionality of the SUM Series monitors.

© 2010 Wohler Technologies, Inc. All rights reserved. 13
SUM Series User Guide
Technical Functional Overview
Figure 1–7 AMP1A SUM6/RD Block Diagram
Right Input
Left Input
123
SOURCE LEVEL
5
6
2
3
1
456
SOURCE LEVEL
4
Right
Left
Right
Summing
Circuitry
Left
Summing
Circuitry
Right
Left
Source 1
Source 2
Source 3
Source 4
Source 5
Source 6
Left
Speaker
Woofer
Speaker
Right
Speaker
Woofer
Speaker
Stereo Analog
Amplifier
Headphone

© 2010 Wohler Technologies, Inc. All rights reserved. 14
SUM Series User Guide
Technical Functional Overview
Figure 1–8 VMDA-SUM8 Block Diagram
Stereo Analog
Amplifier
Master
MONO
STEREO
Balanced Program Output
(Mono Mix of Selected Source)
12345678
12 345 6 78
Volume
Right
Speaker
Headphone
Left
Speaker