Protech 870B User Manual
PROTECH
®
1/03
INSTALLATION & OPERATION
MANUAL
AUDIO MIXER CARDS
MODELS COVERED
870B*
871B*
872B*
873B*
*Microphone Level
874B
875B
876B
877B
Input
www.protechaudio.com
The 800 Series Mixer/Preamplifiers and Mixer/Line Amplifiers are designed for use in professional audio applications. Each model is designed to accept multiple microphone
signals in, and combine the individual signals into one
common output signal.
Typical applications are public address announcements,
with different paging stations, program material that must
be combined from different studios, headphone listening
systems where the user can directly interface with various
program sources, or audio recording systems, where
different program material must be fed to the recorders at the
same time.
The actual application of the mixers is found in buildings
such as airports, courthouses, factories, casinos, convention centers, libraries, racetracks, training systems, and corporate boardrooms, to mention just a few.
The 800 Series mixer cards are designed to incorporate a
combination of features that will allow the units to deliver
maximum reliability. Each circuit is designed with a minimum of components, to reduce the possibility of failure,
while still maintaining performance and feature criteria.
INTEGRA III SYSTEM
Model 877B Shown
Each of the 800 Series mixer cards, is designed with the same
combination of features. The input level type, the link feature
(not available on 5 input units), and number of inputs are the
only variables between models.
The gain structure of the 800 Series mixer cards allows the
output level to be adjusted from off to +55dB, with respect to
the input level. The trimpots used to adjust the input gains, are
mounted on the backplane assembly. The alignment procedure
is described on page two of this manual.
The input sections, and the output section of each model are
individually isolated using the highest quality audio
transformers. In addition, each input, and the output section
on every model has individually adjustable operational
amplifiers. These features provide the maximum in isolation.
Each model may be mixed or matched with other INTEGRA III
SYSTEM audio cards, to create a complete audio system.
These products are designed to provide the user with high
quality audio, for years of uninterrupted service.
Protech Audio Corporation, PO Box 597, 192 Cedar River Road, Indian Lake, New York, 12842, Voice 518-648-6410 Fax 518-648-6395
INSTALLATION
The 800 Series Mixer are designed to be mounted in the Model
857B Card Frame Package, or the Model 858B Card Frame
Package. The Model 857B Card Frame Package will accomodate
up to 10 audio cards, and requires an external power supply
(Model 66708). The Model 858B Card Frame Package will
accomodate up to 9 audio cards, and has a built-in, unpluggable
power supply card.
Both card frame assemblies bus the DC power to the individual
card slots, and provide screw-type barrier termination points for
audio and DC connections.
The determination as to which backplane assembly to use in
your project, was made prior to our factory receiving the order.
The backplane assembly you have received will
accommodate the group of cards you or your designer have
specified.
The actual steps necessary for installation of the 800 Series
Mixer cards, are comparable to those necessary for any of
the 800 series cards. They are as follows:
1- Mount the card frame in an appropriate EIA 19" width rack,
using 4 screws of sufficient tensile strength to provide secure
mounting.
2- A determination has been made as to which type of power
supply will be used on your system. Follow the instructions for
the type of power supply you will be installing.
EXTERNAL POWER SUPPLY. If an external power supply
is to be used, terminate the proper supply
connections to pins 1, 2, & 3 of the DC barrier connector, as
shown in the card frame layout drawing. Turn on the power
supply, and using a DC voltmeter, check for correct voltage and
polarity at pins 1, 2, & 3 of the barrier connector.
INTERNAL POWER SUPPLY. If a plug-in power supply card
is to be used, plug in the supply card, and check for proper
illumination of both the positive and negative voltage LED's, on
the power supply card front edge.
4- Unpack each individual card, inspect for shipping
damage, and assuming none is found, slide the card
half-way into the appropriate slot. After all cards have been
installed half-way into the card frame, plug in one card at a time
and turn on the power supply. Make sure no unusual loading is
noticed at the power supply. If loading is noticed, turn off the
power supply, unplug the card and recheck terminations. If no
loading is noticed, continue inserting each card in the card
frame, checking power supply loading as each card is plugged
in. When all the cards have been plugged in, the installation is
complete, and all that remains is the alignment.
ALIGNMENT
Each 800 Series card with microphone level inputs has been
shipped from the factory aligned for 45dB of gain. Mixer cards
with line level inputs have been aligned for unity gain. This
alignment optimizes headroom. Ifadditional gain is required,
the following alignment procedure is recommended;
1- Apply a signal representative of the actual signal level to
be used, to input #1.
2- While monitoring the output channel, turn the input
gain trimpot clockwise until the output signal reaches the
desired level.
3- Repeat steps 1 & 2 for each input on your mixer/pre amplifier.
This completes the installation and alignment of your 800 Series
mixer cards. The cards may be expected to deliver years of
uninterrupted service.
Note 1The alignment procedures for 800 Series cards, differ from
card type to card type. Therefore it is necessary to consult the
alignment procedure for each type of card being installed, to
properly align a card frame using different card types.
PROTECH
MORE GAIN
CW
INPUT #5 GAIN
INPUT #4 GAIN
INPUT #3 GAIN
INPUT #2 GAIN
INPUT #1 GAIN
OUTPUT GAIN
NOTE: For Link Capability Strap Pins 14 Together, and remove IC
from socket nearest card handle, on unit to be used as slave.
®
857B & 858B BACKPLANE CONNECTIONS
H
L
H
L
H
L
H
L
H
L
H
L
INTEGRA III SYSTEM
CONNECTOR & TRIMPOT DRAWING
MODELS 870B Through 877B
OUTPUT HI
OUTPUT LO
GROUND
INPUT #1 HI
INPUT #1 LO
INPUT #2 HI
INPUT #2 LO
GROUND
INPUT #3 HI
INPUT #3 LO
INPUT #4 HI
INPUT #4 LO
GROUND
INPUT #5 HI
INPUT #5 LO
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
3- Terminate all audio input and output connections, using the
card connection drawing on the facing page. Double conductor
shielded cable is recommended for all audio connections.
Terminate each unused input with a 1K ohm resistor.
Page 2
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