aci VGM-804 Guide

VGM-804 Gated Microphone Mixer
Installation and Use
ACI-AppliCAD, Inc.
Version 2.0
[phone] www.aci-applicad.co

Table of Contents
Introduction ---------------------------------------- 1
Features & Benefits
Quick Start Guide --------------------------------- 2
Connecting Your Co ponents
Installation Issues
Microphone Settings
Setting Audio Levels
Operator’s Guide ---------------------------------- 6
Basics
Managing Microphones
How Sound Gating Works
Opti izing The Sound Gating
In Case of Difficulty -------------------------------11
Troubleshooting
Phone Support & Warranty
Specifications -------------------------------------- 12

1
Introduction
Congratulations on your purchase of the VGM-804 Gated Microphone Mixer.
Because its design targets sound reinforce ent applications, your audience will enjoy higher
quality sound than with generic ixers or consoles. At first, you’ll find a refreshingly si ple
exterior. It’s straightforward to set up, and easy to use. Soon, however, you’ll co e to
appreciate how the ixer allows you to ake better use of your sound syste . Its rugged
construction should provide you with years of reliable service.
Features and Benefits
The challenges often encountered running a sound reinforce ent syste inspired
the features of this ixer, as shown below:
VGM-804 Feature What It Does User Benefit
Mic Sound Gating
with Last Mic ON &
Adaptive Threshold
Quiets idle ics by gating active
ones ON. The last live ic
re ains ON until another is used.
Reduces distracting noise,
allows ore volu e with less
reverberation.
Gate/Clip LEDs Green shows inputs gated ON,
red indicates clipping.
Identifies ics in use. Warns of
excessive levels.
Co pression Li its unusually loud sounds. Listeners re ain co fortable.
Co press LED Lights when loud sounds trigger
co pression.
Helps the operator keep levels
under control.
Balanced Lo-Z
Microphone Inputs
Rejects electrical noise picked up
by icrophone cables.
Reduces “hu ” and “buzz.”
Mic input bass rolloff Reduces bass response of ic
inputs only.
Mini izes “pop” and “boo ”
while preserving vocals.
Industrial-quality level
controls
Designed to withstand illions of
rotations.
Controls re ain s ooth and
quiet for any years.
Gain presets Adapts to any source level. Makes level setting easier.
LED Level eter Indicates overall sound level. Assists setup & operation.
Balanced Output Drives professional gear. Yields quiet, stable operation.

2
Quick Start Guide – Connecting Your Co ponents
Gather your input and output cables and ake the connections you need :
MIC 1
MIC 2
MIC 3
MIC 4
MIC 5
MIC 6
MIC 7
MIC
LINE OUT
POWER
AUX OUT
AUX 2
AUX 1
Line Output
Balanced line output connects to
pro-audio a plifiers, equalizers, etc.
1 – Ground (Shield)
2 – White wire
3 – Black wire
1 2
3
1 – Ground (Shield)
2 – White wire
3 – Black wire
12
3
Microphone Input Jacks 1 –
Inputs are Lo-Z, balanced XLR
Phanto power available for condenser ics (See page 4)
Standard wiring for microphone cables:
Auxiliary Inputs 1 – 2
RCA jacks to play line-level ono sources:
•CD player
•Telephone interface (receive)
Co bine stereo sources with “Y” adapters
(see page 3)
16 VAC Power
Plug in supplied AC
adapter here.
Auxiliary Output
RCA jack for connecting:
•A plifier with unbalanced RCA input
•Recording devices
•
Telephone interface, FM trans itter
Use “Y” adapters to connect additional devices

3
Quick Start Guide – Installation Issues
Low-i pedance icrophones with standard cable wiring plug directly into the
icrophone jacks without any odifications. Here’s how to handle so e circu stances that
ay affect your installation:
Replacing an old mixer – If your installation has fixed icrophone jacks with cables run as
part of the building (though walls, under floor, above ceiling), exa ine how these cables
ter inate at your old ixer. If they have ale XLR connectors, si ply ove the to your
new ixer. If they ter inate as screw ter inals, you’ll need to attach XLR plugs. We
reco end Neutrik NC3M connectors because they are easier to work with. If these are
not available, Switchcraft type A3M will do. Whether new or existing, connector wiring ust
atch the standard shown on page 2.
Mounting – The ixer fits into a standard 19" rack, taking up one space. It needs no support
beyond the panel ounting screws. Be sure to place it where it’s easily accessible to the
operator. It akes little heat, but allow one rack space between the ixer and equip ent
that does generate significant heat, such as power a plifiers.
Wireless mics – Most wireless icrophone receivers allow you to select a balanced,
icrophone-level output. Choose this output and connect each wireless receiver to a
icrophone input of the ixer. This way, the ixer handles each wireless ic as it does
other icrophones, providing the gating and selectable co pression features. Set any level
controls on the wireless receivers to atch their level to that of your wired icrophones.
Condenser microphones – Condenser icrophones feature excellent sound quality, but
require a power source to operate. So e use built-in batteries. Others expect to receive
power fro the ixer’s icrophone connection (this is called, phantom power). Your ixer
can provide phanto power at any or all icrophone jacks. To select phanto power, see
Mixer Settings, next page. Many condenser ics have a “hot” (loud) output – adjust your
ixer’s presets (see page 5) as needed.
Stereo Sources – Use a “Y” adapter to co bine the Left and Right channel of stereo sources
(such as CD players). Connect the resulting ono output to one of the two auxiliary inputs
at the ixer.
Multiple sources – If you have ore than two auxiliary (non- icrophone) sources, we
reco end using an external selector switch to select a ong the . Different sources ay
not perfor properly if paralleled with “Y” adapters.

4
Quick Start Guide – Microphone Settings
The ixer allows you to tailor operating features for each icrophone. Make these
selections with the botto -panel switches shown below:
The COMPRESSION and Phantom Power switch banks each have nu bered switches
corresponding to the eight icrophone channels (1-8). Set each switch using a pen or
si ilar pointed tool. So e suggestions for each feature:
Compression – The ON position is reco ended for ost situations. Co pression li its
unusually loud sounds fro each ic, increasing audience co fort. It works unobtrusively, so you can
enable co pression with confidence. However, we reco end you select no co pression (switch
OFF) for any icrophone where its user ay need extra level – for exa ple, speaking above the noise
to bring a eeting to order. Often this eans choosing co pression OFF for the “ ain” ic.
Phantom Power – Leave OFF for dyna ic or wireless icrophones. Select ON for each input
fro a condenser icrophone. If a particular icrophone input is used with a variety of icrophones
including condenser ics, choose ON. Most condenser icrophones require phanto power.
Dyna ic ics don’t need it, but should tolerate it.
Quick Start Guide – Setting Audio Levels
This ixer has a balanced line output for professional equip ent, and an auxiliary
output for consu er-grade a plifiers and other devices. The balanced output is capable of
a high level: +28dBv. Following equip ent should be capable of a si ilar axi u level.
When any equip ent is driven beyond its axi u level, it “clips”, flattening audio peaks –
resulting in a characteristic distorted sound. You get the least noise fro your equip ent
(best signal-to-noise ratio) when everything clips at the sa e level. Thus, it’s best if
following equip ent can handle at least +28dBv.
Check the specifications of following gear. If for exa ple your equalizer can handle
only +22dBv at its balanced input, you need to reduce your ixer’s output by 6 dB. Since
your ixer has an output i pedance of 600 oh s, you can reduce its output by loading it
with a resistor. A 600 oh load lowers the output by 6dB. Other values can be used, as
shown next page. Wire this resistor into the connector at either end of the cable between
the ixer’s balanced output and the balanced input of the next device, as shown:
Gating
Threshold
Compression
Phantom
Power
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
ON

5
2
3
1
3
2
1
R value: Atten.:
600 oh 6 dB
300 oh 10 dB
200 oh 12 dB
Because the VGM-804 can be set to co press excessively loud sounds to a consistent
level, you need to ad ust the rest of your system (power amplifier, etc.) to spot this level as
required. This is easy to do if you follow the procedure below. In fact, we reco end
following this procedure to get your levels “in the ballpark” even if you don’t plan on using
co pression in nor al operation (te porarily co press one ic input to perfor it):
•Start with your power a plifier’s volu e control at a low level.
•If your syste has an equalizer, set it to Bypass or Flat ode.
•Have so eone speak (reading a book works well) into a icrophone connected to any
channel that has co pression ON.
•Increase this ic channel’s gain control until you see the COMPRESS LED glow yellow and
red with the speaker’s voice. At this point, the ixer output has reached its
consistent co pressed level. The level display should peak within its yellow range.
•Now, turn up your power a plifier’s gain until your assistant’s voice fills your auditoriu
to a fully satisfying, but still co fortable, listening level.
•Enable your equalizer. The overall level shouldn’t change uch, but adjust as needed.
•You ay find that under actual use, when the auditoriu is filled, slightly ore volu e is
required. In that case, increase your power a plifier gain as needed.
Once you have found the right setting for your power a plifier, it should need little further
adjust ent. Instead, use your ixer to anage the volu e of all your sources. We suggest
you write down or ark the proper positions of EQ and a plifier controls for future
reference. To prevent unauthorized adjust ents, ount security covers over these panels.
In any installations, you’ll need ready access only to the ixer and your sound sources.
Your VGM-804 features a gain preset for each input. You can adjust these with a fine slot
screwdriver, to bring differing source levels into agree ent. These are factory set to
idrange, so si ply adjust any “low” inputs upward, and any “hot” inputs downward. Many
condenser ics, as well as so e wireless ics, output a very high level – go ahead and
“ta e” the with the presets. Ideally, you can adjust the presets to bring each source to a
usual, co fortable level when its knob is set to around “5”.
C OMPRESS
MIC
AUX 1 AUX 2
VGM804
AUX 1
Preset
AUX 2
Preset
MIC
Preset

6
Operator’s Guide – Basics
The power a plifier and preset adjust ents you’ve just co pleted, along with the VGM-
804’s icroprocessor “brain”, ake operation as si ple as it can be!
POWER Switch – At the far right of the panel. Switch ON for use. Many users prefer to plug
the ixer’s AC adapter (as well as the rest of their audio gear) into a switched outlet strip,
leaving the POWER switch on. Either way, the first green LED of the level display lights when
the ixer is powered up.
Gain controls – adjust as needed for good listening levels. You can apply labels on a blank
panel above or below your ixer (as shown above) to describe their actual use. Depending
on the icrophones and their place ent, about halfway up should provide good usable
level. If needed, adjust the presets (see the previous page). The gating and co pression
features ean you’ll do less knob-turning than would be needed with non-auto atic ixers.
Gate/Clip LEDs – under each icrophone gain control. Each lights green when the ixer
gates that icrophone ON. Use these LEDs to identify live ics. For exa ple, during a walk-
though test before the progra , have your assistant speak into each ic in turn – the LEDs
show which ixer channels are in use. These LEDs light red when their input channels are in
danger of clipping – reduce their gain to re edy this condition.
Clip LEDs – under the two AUX gain controls. Lights red when these channels are near
clipping. To prevent audible distortion, reduce gain should you see the clip indicators light.
If you still need ore sound, turn up your power a plifier instead.
The ic and aux input channels all feature sufficient headroo so you should rarely if ever
see red (clipping) lights.
C O M P R E S S
MIC AUX 1 AUX 2
VGM804
Gated
ON
Clipping!
POWER
Switch
Stage Left
CD Player
Phone