Conex UM-33 User manual

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UM-33
Cue Amplifier

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UM-33
Cue Amplifier
Conex Electro-Systems, Inc. Bellingham, WA 98226
•

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SPECIFICATIONS
S iz e
Weight
Mo
unting
Power Re qu irements
Audio Input Level
Lin e Buffer Am pl ifi er
No ise:
D
ist ortion:
Sp
ea ker Amplifier
Output p
ower :
Noise:
Di
st orti on:
O
sc ill a tor
Level:
Frequen cy :
D
is tortion:
Level Meters
Type:
Ca li br ati on :
Internal Speakers:
1 9" X 1.75" X 6"
2 Lb
Standard Rack Mount
115 VAC, 60 Hz , 10 watts max
+20 dB nominal maximum
1 OK ohm transformerless bridging
-7 0 dB with respect to 0 dB in.
.2% THO max at O dB in .
2 watts p er channel into 8 ohm load
-60 dB with re spect to 100 mw out.
0.1% THO max.
Adjustible from off to +1OdBm
Selectable 40 Hz, 400
Hz , and 7500 Hz
0.1% THO max.
12 LED stereo bar -graph
Front panel adjustable for -10 to +24
db lull scale
with -20
dB point adjustment.
3" diameteron sloping baffles.
Co nex Electro-Systems. I nc . P. O. Box 1342 Bellingham, WA 98227

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UM-33 Cue Amplifier
INTRODUCTION
The Conex Electo-Systems cue amplifier is a general purpose audio switcherand monitoramplifier. With its eight
stereo input channels and one stereo output channel, the UM-33 provides the easiest, least expensive and most
compact way of handling common audio switching and monitoring problems.
The general nature
of the UM-33 lends itself to a variety of applications Including:
• Tape Recorder InputSelector
• Console Input Expander:
• Automation Cue Amplifier:
• Program Line Selector:
• General Purpose Monitor:
The built in oscillator makes head alignment and record equalization
easy.
Expand a console input
by 8 channels.
Check levels
of audio sources feeding automation. Simplifies cueing
tapes and checking head alignment.
Connect sourcesthat could teed the program line as inputs to the UM33.
Selecting what feeds the transmitterthen becomes as easy as
pushing a button. (Great forfreeing the console for otheruses.)
Connect audio sources that you would like
to monitor ,.. network.
program line, news r
oo m, etc. Use the UM-33 to check audio levels and
tnonitoraudio equality with external speakers.
As you can see,
th e UM-33 has potential use in every studio in a radio station.
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INSTALLATION
The UM-33 is designedto be rack mounted. It is suggested that it be placed in a rack with th e rear terminal strip
can be easily accessed. If
th e LED VU meters are to be used in your application, the unit should be placed at a
height that makes viewing easy.
For the highest quality speakeraudio, we recommend connecting external speakers to the UM-33 Relatively high
efficiency bookshelf type speakerswould be appropriate. If you choose to use the internal speakers, the unit
should be placed in a rack th
at has other equipment above and below it to provide proper baffling. The internal
speakers were designed to
pr ovide a simple self contained method of monitoring audio sources wh ere quality is
not critical.
CONNECTING INPUTS
Up to eight stereo sources can be connected to the UM-33. Connections are made to inputs 1 thru 8 as indicated
on the backpanel. Notethat each input has provision for balanced inpu
ts and a shield connection. If unbalanced
sources areto be connected,
the'+' input terminal should be used forthe audio input with the common and/or
shield connected to the '.· and 'G' terminals Input levels should be in the range of -1O
dB to +8 dB for prop er
operation. Standard pr actice should be followedto prevent ground loops.
CONNECTING OUTPUTS
The UM- 33 has two se parate stereo outputs. The 'direct out' output is simplythe input switched directly to the
output through the
me chanical contacts of the front panel switch.
The 'buffer out' output is audio that is isolated from the
inp ut by bufferamplifiers. Its output impedance is 600
ohms and can be used in either a balanced
or unbalanced configuration. Note that when using unbalanced
inputs, the outputswill be unbalanced. The circuit has been designed to provide unity gain between input and
output. Formost applications, the buffered output should be used.
INTERNAL/EXTERNAL SPEAKER CONNECTION:
To use the internal speakers, it is necessary to putjumpers from EXT L to INT L and EXT R to INT R on the
te rminal strip. The ground connections are internally connected. '
Whether the internal speakers are connected
or not, the external speakers are connected to the EXT speaker
outputs. The external speakers should be rated at 8 ohms and should be relatively efficient. The UM-
33 will drive
external speakers at 2 watts
per channel.
OPERATION
FRONT PANEL CONTROLS: (See Figure 1)
1. Internal speakers ... left and right.
2 SpeakerON/OFF switch. When in the
OFF position, both internal and external speakers are off.
3. Headphone jack. Headphone audio is always present regardless of the position of the speakerON/OFF
switch.
4. LED UV meter.
5. •20
dB LED VU meter calibration controls (see ADJUSTMENTS).
6. O
dB LED VU met er calibration cont ro ls.
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7. Stereo/MONO switch. Affects speaker/headphone audio on ly. When in STEREO mode, speakers and
headphones are fed stereo audio. When in MONO mode, the inputs to the speaker amplifier are tied
together for mono audio.
8. LE
Fr SPEAKER VOLUME CONTROL.
9. OSCILLATOR FREQUENCY SELECT SWITCH. This switch determineswhethertheoscillatorwill
operate at 40 Hz, 400
Hz or 7500 Hz. Note thatthe oscillatoroutput is switched directly to the switched
input bus. This means thatthe oscillator will feed the selected input aswell as the output. This could be
desirable in some applications, but forthe most pan, the inputs should be deselected while using
the
oscillator. To deselect all inputs, lightly press any non-selected ted input until all buttons are releases.
See figure 2.
10 . RIGHT SPEAKER VOLUME CONTROL.
11 . OSCILLATOR LEVEL CONTROL. Determines amplitude of oscillator.
12 . OSCILLATOR ON/ OFF SWITCH. Push this switch to turn the oscillator on. Push again to
turn it off.
13 . INPUTSELECTOR SWITCHES. These are in terlocking switches that select the input to the
monitoramplifier.
14. INPUTLEGEND. This legend strip allows the labeling
of the input switches. F or conve For convnienc e,
the strip may be taken out of the holderforlabeling.
15,16 INPUT/OUTPUT JACKS: These jacks are tied directly to the input stereo bus. (The upper jack is left
channel. the lowerIs right channel.) These jacks are useful tor checking distortion
or frequency response
of an audio source from the front panel of the UM-33. Also...because the jacks are connected directly to
the stereo bus before any amplifiers. audio can be fed into the jacks and out the selected input... as we
ll
as the outputs.
F IG URE 1
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ADJUSTMENTS:
The only adjustment provided in the UM-33 is the calibration of the VU meter. The procedure is simple and can
be performed from
th e front panel
First decide what yourzero level signal out should be. For example,
if you would like youroutput signal to be +4
dB, feed a tone
to the left input. (or use t he built in oscillator .) Using an audio voltmeter, adjust the tone level until
a +4 signal is indicated
on the voltmeter. Now adjust the left "O" calibration pot on the front panel until the "O" Db
LED just lights. Next, reduce the input
by 20 dB as indicated on the volt meterand adjust the -20 dB calibration
pot untilthe -20
dB LED just lights.
Repeat the above for the fight channel.
The meter calibration is now complete
CIRCUIT DISCRIPTION: (refer to figures 1 & 2)
A built in three frequency tone oscillatorcan be connected to the switched input bus by pressing the OSC ON/
OFFbutton on the fr
ont panel. (# 12 , figure 1 ). A gain control (#11 , figure 1) allows the setting of the oscillator
output level. The frequency
(40,400 or 7500 Hz) is selected by a three position toggle switch (#9, figure 1).
Note: The oscillatoroutput is switched directly to the switched input bus. This means that the oscillator will feed
the selected input as well as the output. This could be desirable in some applications, but for the most pan, the
inpu
ts should be deselected while using the oscillator. To deselect all inputs, lightly press any non selected input
until all buttons are released.
See figure 2.
The speaker amplifierwill drive external speakers (two
walls per channel) by connectingthem to the rear panel
terminal strip. Use of the internal speakers requires jumpers on the panel speakerswitch (#2, figure 1} leaving
the amplifierconnected only to the stereo headphone jack.
The stereo VU meters have front panel screwdriveradjustments that allow calibration over a
full-scale range ol -
10
to +24 dB. (To allow forsufficient headroom, it is recommended that in put signals in the range of - 10 to +8 dB
be used.
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Conex
Electro-Systems, Inc.
REV
A UM33 VU METER MOD
SCALE DATE 8/22/91
ENG
BH
DW
G#
001-05-2
DRAFT JP MATL

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