DM Engineering AUDIO-POD IFB User Manual

USER GUIDE

AUDIO-POD IFB

Microphone Control and

Integrated Headphone

Amplifier System with IFB Receive

Version 1.0

DM Engineering

2174 Chandler St.
Camarillo, CA 91345-4611
805-987-7881 800-249-0487
www.DMEngineering.com

Overview:

The “Audio-Pod System with IFB Receive” is a microprocessor controlled Microphone
On-Off control system with an integrated headphone amplifier and IFB Receive
capabilities which is ideal for remote and talk studio applications. The Mic ON/OFF
buttons may be top or front mounted depending on the application. The latching
Microphone On-Off circuitry incorporates a high quality, low noise pre-amplifier with
available switched 48VDC phantom power. The IFB received audio has a separate
input amplifier for isolation and is applied to the headphone amplifier mixing buss.
Individual gain controls for Program and IFB audio are provided. The stereo program
audio is connected using a 3.5mm mini jack on the rear panel, and the IFB single ended
audio is applied at the rear terminal block. (Refer to figure 1) “Cough” muting is
controlled by depressing and holding the “Mic ON” button.

An Audio-Pod system consists of from one to four Audio-Pod modules and a Power
Supply. One Power Supply will supply power for up to four Audio-Pod modules, and the
modules may include any of the available variety of options. 10 foot Power Supply
cables, mounting screws for the power supply module and a trim-pot adjustment tool
are supplied.

Optional permanent table top tilt mounting brackets for the Audio-Pod modules are also
available.

The Microphone circuit and Mic on-off control portion includes the following features:

• Large LED differentially lighted Mic-On and Mic-Off and constantly lit
Talk-Back long life reed type silent push buttons

• Cough-mute function integrated with Mic-On button (Operational with
local control mode enabled)

• Local Mic On-Off feature may be disabled and controlled remotely

• Remote control of Mic on-off function with a logic low or contact closure

may be accomplished with either local control enabled or disabled

• Microphone XLR in and XLR out connectors as well as Eurostyle screw

terminal block termination of Mic out connection for permanent

installations

• Solid State Relay driving voltage, continuous or flashing, to drive a

DME Solid State Relay Pack or customers own solid state relay for
ON-AIR lamps or for external LED indicator (multiple Audio-Pod SSR

outputs may be connected in parallel in the continuous mode only)

• Precision metal film resistors used throughout audio chain for low noise

and stability

• Quality low noise mic preamp with user adjustable rear panel variable

gain control with output ranging from mic to line level

• Phantom power supplied with rear panel switch and LED indicator

The integrated headphone amplifier section includes the following features:

• Voltage Controlled Amplifier (VCA) circuitry employed (no “dirty” pots)
for the program audio.

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• Power Op-Amp headphone output providing both the power and P-P
voltage required to drive headsets ranging from 8 to 600 ohms

• Rear panel output phase switch (0-180

O

) to address bone conduction

cancellation issues sometimes experienced by users

• ESD protected front panel 3.5mm and ¼” stereo headphone output
jacks

• Rear panel maximum headphone gain set control to restrict the

maximum headset output to prevent possible hearing damage and

liability issue avoidance

• Stereo Program audio input via a rear panel 3.5mm jack

• Single ended IFB audio input via rear terminal block

• Precision metal film resistors used throughout the audio chain for low

noise and stability

Installation:

1. Mount the Audio-Pod Power Supply within 10’ of the Audio-Pod locations.
Mounting may be table top or under the desk mounting using the supplied
mounting screws and “keyhole” slots located on the bottom of the power supply
cabinet. (3” center to center mounting holes) Orientation may be in two
different axes depending upon user preference.

2. The Audio-Pod modules are normally desk top mounted using the supplied
rubber feet. If the optional permanent table top tilt mounting bracket is used,
refer to the installation instructions that accompany the bracket.

Fig. 1

3. Connect the Power Supply to the Audio-Pods using the supplied 8 pin Mini-Din
cables. The orientation of the connector has the flat side facing the top of the

enclosures. IMPORTANT: Assure that the Mini-Din connectors are fully

engaged with the sockets. Insert, wiggle and press firmly! Failure to
completely insert the power cables will result in hum or non-operation of the
Audio-Pod module.

4. Connect the microphone XLR in and out connectors to the respective
receptacles. A more permanent wired output connection, balanced or
unbalanced, may be made using the Eurostyle screw terminal connector “MIC
OUT +”, “MIC GND”, and “MIC OUT –“ terminals.

5. Connect the single ended headphone inputs to the 3.5mm “PHONES IN”
connector, (left=tip, right=ring, common=sleeve).

6. Connect the single ended IFB audio input to the “IFB COMMON” and “IFB IN”
terminals of the rear terminal block.

7. If desired, connect the “SSR/LED out” and the “GND” terminals to your DM
Engineering Studio Solid State Relay or users’ solid state relay (3-15VDC input)

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for lighting incandescent ON AIR or RECORDING lights. Outputs may be
connected in parallel for multiple Audio-Pods driving one SSR if all modules are

set for constant SSR operation. IMPORTANT: Maintain SSR output polarity

considerations between the Audio-Pods or damage may result. If multiple
Audio-Pod SSR outputs are used for driving a single LED indicator, a 220 ohm
series resistor between the positive outputs and the LED is recommended.
See note at the end of the “OPERATION” section below.

8. If desired, connect the remote control wiring to the “RMT CONT ON/OFF” and
“GND” terminals. Either a logic low or contact closure will turn the microphone
on. A logic high or open contact will turn the microphone off unless local
control has it locked on. It is recommended that an “open collector” logic
interface or isolated normally open contacts be used.

9. The “LOC CONT ENABLE” jumper that is connected to “GND”, with the factory
installed jumper, enables the front panel push buttons and “COUGH” function.
To disable the local microphone on-off switch and cough functions, remove the
jumper between the “LOC CONT ENABLE” and “GND” terminals. The Mic ON­OFF function will now only work using the remote control input.

10. If phantom powered microphones are to be used, set the “PHANTOM POWER”
switch to the “ON” position. (switch to the left position) The amber LED will
indicate that phantom power is on. This switch setting may be changed at any
time.

Setup

Connect the AC power cord to an 115VAC outlet. The LED indicator on the power

supply should light as well as the “MIC OFF” and “MIC ON” buttons on the Audio
Pods.

1. The Audio-Pod microphone gain is factory preset for the average Condenser

microphone and there may not be need for any adjustment. If the gain is set
too high the rear panel “MIC GAIN” control setting will need to be reduced.

A. If a Condenser or Electret type of microphone is being used turn the

Phantom Power switch to ON. The LED indicator will light when the
switch is in the ON position. It is advisable to disable the phantom power
supplied by the mixing console unless other such microphones are being
used directly connected to the console. The presence of up to 48 volts
DC on the output of the Audio-Pod will do no damage.

B. Set your mixing console for normal input and output, press the Audio-Pod

Plus “MIC ON” button. Adjust the “MIC GAIN” control, using the supplied
trim-pot tool, counter-clockwise (less gain) for the proper VU indication on
your console. Note that the “MIC GAIN” control is very sensitive to
adjustment at the most clockwise end of its range.

C. IMPORTANT: Due to the large amount of available gain in the Mic pre-

amp section it is possible to overpower the FET Mic On-Off switching

circuit if the “MIC GAIN” control is set for excessive

gain. To assure that
you have not exceeded the capabilities of the switch, press the “MIC OFF”
switch and speak loudly into the microphone. If modulation peaks cause
an output, you have the gain set too high and it should be reduced
accordingly.

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Headphone Section:

1. Insert the headphone jack into the appropriate “Phones” receptacle. The rear
panel “PHONES MAX GAIN SET” is factory pre-set to about mid range and
may be adjusted to the users desired maximum level. This adjustment affects
Program audio only.

2. To reset the maximum headset level, have the headset audio input source
active, slowly adjust the front panel “GAIN” control to maximum while using the
trim-pot adjusting tool to set the rear panel “PHONES MAX GAIN SET” to the
maximum level that you feel is safe for the user. This feature is included to
protect the user from possible damaging volume levels to their hearing which
may lead to possible litigation issues in the future.

WARNING: Listening to earphones too loudly may cause hearing loss. To prevent

hearing loss, adjust the volume to comfortable levels and avoid prolonged use.

Operation:

The Audio-Pod IFB front panel control functions are as follows:

MIC ON (COUGH): Turns on the microphone function (latching) and displays a

brighter switch illumination on the active button. Depressing and holding this button
while in the “ON” position will mute the microphone output.

MIC OFF: Turns off the microphone function. The OFF button will illuminate

brighter.

IFB GAIN: Adjusts the headphone audio level from the IFB input.
PROGRAM GAIN: Adjusts the Program audio headset level.
PHONE JACKS: Both ¼” and 3.5mm stereo headphone jacks are supplied. The

jacks are connected in parallel and employ ESD protection circuitry for protection
from static build-up on the earphone plug that is being connected.

The Audio-Pod IFB rear panel headset control adjustments are as follows: (refer to

Fig. 1)

PHASE: Depressed for 180° phase shift in the headphone output to correct for bone

conduction issues that may arise, and left in the outermost position for 0° phase
shift.

PHONES MAX GAIN SET: Factory pre-set to approximately mid range and may be
adjusted to the users desired maximum level. (Refer to headphone section setup

instructions above.)

All other rear panel connections and functions are discussed in the INSTALLATION

section starting on page 3.

Note: The SSR output mode may be changed between continuous and flashing by

moving an internal jumper located on the lower microphone PCB. It is imperative

that the “PHASE” switch be depressed prior to opening the Audio-Pod
enclosure or damage to the switch will result. This damage is not covered by
the warranty.

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Warranty Information:

The DM Engineering Audio-Pod IFB system is warranted for a period of one year from
the date of purchase. This warranty covers materials and workmanship only. Any
misapplication, physical or electrical damage from outside sources or by the customer is
not covered. For factory warranty repairs, the customer must pay shipping costs to the
factory, and DME will pay standard ground transportation shipping costs to return the
warranted equipment to the customer. Any priority shipping costs are to be the
responsibility of the customer as ground service only is standard. Please contact the
factory for an RMA number prior to any returns. Items returned without an RMA may be
sent back to the customer unopened.

Technical Support

If you have questions, experience difficulties with the product or require further
information please contact DME at: 805-987-7881, toll free 800-249-0487, or E-mail
technical support at: [email protected], or visit www.dmengineering.com for
the latest User Guide.

Specifications:

Case dimensions: Audio-Pod module and Power Supply: 5.09" W X 5.95" L X 2.2" H
Case material and color: ABS flame retardant plastic, black
Power supply to Audio-Pod DC power connection method: 8 pin mini-din cable
AC input operating voltage: 105-125 VAC, 60 Hz
Solid State Relay drive output voltage: 5VDC current limited by 330 ohms
Microphone and talk-back buttons: Silent long life reed type with differential LED
illumination for microphone on-off functions
Microphone input impedance: 150-250Ω
Microphone pre-amplifier output impedance: 600Ω (balanced)
IFB input impedance: 10KΩ
IFB input level: -10db nominal

Microphone user gain adjustment: > 43dBm (overall gain ≅58dBm)
Microphone pre-amplifier absolute maximum output level: +20dBu
Headphone program gain control circuitry: VCA (voltage controlled amplifier)
Headphone amplifier input level: Stereo L & R, -20dBu to +4dBu
Headphone amplifier input impedance: 10KΩ
Headphone output: (ESD protected) 160MW per channel, 20VP-P max per channel).
Power supply AC cord length: approx. 6 ft. total
Power interface cables: 10 ft. 8 pin mini-din M-M
Mounting method: Power supply and Audio-Pod modules are supplied with rubber feet.
Screws for “key hole” type mounting of the power supply are supplied. An optional
desk-top mounting brackets and flush mounting brackets for permanently mounting the
Audio-Pod modules are available.
Operating temperature: 32 to 110F
Humidity: 0 to 95% non-condensing

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