Alesis MULTIMIX 12R User manual

ALESIS
Studio 12R
Reference Manual

Table of Contents
Studio 12R Reference Manual 1
TABLE OF CONTENTS
Table of Contents.................................................................1
Important Safety Instructions................................3
Safety symbols used in this product............................................................3
Please follow these precautions when using this product:....................3
Introduction.............................................................................5
The Alesis Studio 12R Microphone Preamplifier/Mixer......................5
Using this manual..........................................................................................5
Grounding Instructions.................................................................................6
Installation...............................................................................7
Unpacking........................................................................................................7
AC power..........................................................................................................7
Grounding............................................................................................7
Use clean power..................................................................................8
Power switch........................................................................................8
Mounting..........................................................................................................8
Connections.............................................................................9
Inputs.................................................................................................................9
Cable common sense..........................................................................9
Microphone Inputs...........................................................................10
Phantom power.................................................................................11
Line-level devices (synthesizers, CD players, video)................12
TAPE IN jacks....................................................................................14
Phonograph turntables....................................................................15
Do not connect any of the following to any input of the
Studio 12R!.........................................................................................15
How to connect effect devices and signal processors............................16
Effects via Aux Send and Aux Return.........................................16
In-line processing using the INSERT jacks (compressors &
equalizers)...........................................................................................17
Outputs............................................................................................................20
To a stereo PA system or instrument amplifier.........................20
To a mono system.............................................................................20
To a stage monitor (foldback) system...........................................20
To another mixer..............................................................................21
To a stereo tape recorder..................................................................21
To an ADAT multitrack recorder..................................................22
Phones.................................................................................................25
Monitor Out.......................................................................................25

Table of Contents
Studio 12R Reference Manual 2
Operating Instructions......................................................27
Before turning the mixer on, "zero out' the controls...........................27
Setting input trim levels.............................................................................28
PEAK LED method ...........................................................................28
Metering/Unity Gain method.......................................................29
Typical Fader and Control Levels..............................................................30
Proper gain staging of other equipment ......................................31
AUX System: Effects Send/Receive .........................................................32
How to Set Aux Send and Return Levels....................................32
Using the meter.............................................................................................34
Avoiding noise..............................................................................................35
System noise (ground loops, hum, induced noise)...................35
Applications...........................................................................39
Multitrack recording ....................................................................................39
Tracking/Overdubbing....................................................................39
Mixdown.............................................................................................40
Using the HIGH and LOW EQ controls ...................................................41
Monitoring AUX 1 in the PHONES jack .................................................42
Troubleshooting.................................................................. 43
Troubleshooting Index................................................................................43
Maintenance/Service...................................................................................45
Exterior cleaning...............................................................................45
Obtaining Repair Service................................................................45
Specifications....................................................................... 47
Frequency Response.....................................................................................47
Connectors......................................................................................................47
Levels...............................................................................................................48
Impedance......................................................................................................48
Noise performance (typical) .......................................................................49
Distortion (THD+N).....................................................................................49
Power...............................................................................................................49
Mounting........................................................................................................49
Dimensional Drawing ........................................................50
Block diagram ...................................................................... 51
Level diagram................................................................................................52
Index ........................................................................................53
Warranty ............................................................................... 54

Important Safety Instructions
Studio 12R Reference Manual 3
IMPORTANT SAFETY
INSTRUCTIONS
Safety symbols used in this product
This symbol alerts the user that there are important operating and
maintenance instructions in the literature accompanying this unit.
This symbol warns the user of uninsulated voltage within the
unit that can cause dangerous electric shocks.
Please follow these precautions when
using this product:
1. Read these instructions.
2. Keep these instructions.
3. Heed all warnings.
4. Follow all instructions.
5. Do not use this apparatus near water.
6. Clean only with a damp cloth. Do not spray any liquid cleaner onto the
faceplate, as this may damage the front panel controls or cause a
dangerous condition.
7. Install in accordance with the manufacturer's instructions.
8. Do not install near any heat sources such as radiators, heat registers,
stoves, or other apparatus (including amplifiers) that produce heat.
9. Do not defeat the safety purpose of the polarized or grounding-type plug.
A polarized plug has two blades with one wider than the other. A
grounding-type plug has two blades and a third grounding prong. The
wide blade or the third prong are provided for your safety. When the
provided plug does not fit into your outlet, consult an electrician for
replacement of the obsolete outlet.

Important Safety Instructions
Studio 12R Reference Manual 4
10. Protect the power cord from being walked on or pinched, particularly at
plugs, convenience receptacles, and the point where they exit from the
apparatus.
11. Use only attachments or accessories specified by the manufacturer.
12. Use only with a cart, stand, bracket, rack, or table designed for use with
professional audio or music equipment. In any installation, make sure
that injury or damage will not result from cables pulling on the apparatus
and its mounting. If a cart is used, use caution when moving the
cart/apparatus combination to avoid injury from tip-over.
13. Unplug this apparatus during lightning storms or when unused for long
periods of time.
14. Refer all servicing to qualified service personnel. Servicing is required
when the apparatus has been damaged in any way, such as when the
power-supply cord or plug is damaged, liquid has been spilled or objects
have fallen into the apparatus, the apparatus has been exposed to rain or
moisture, does not operate normally, or has been dropped.
15. This unit produces heat when operated normally. If this unit is installed
in a rack, make sure that there is proper ventilation when operated. Do
not operate with the rack covers on. If there are other units in the rack
that generate a large amount of heat, spread them apart. Do not
sandwich this product between to large heat-producing units.
16. This product, in combination with an amplifier and headphones or
speakers, may be capable of producing sound levels that could cause
permanent hearing loss. Do not operate for a long period of time at a
high volume level or at a level that is uncomfortable. If you experience
any hearing loss or ringing in the ears, you should consult an audiologist.

Introduction
Studio 12R Reference Manual 5
INTRODUCTION
The Alesis Studio 12R Microphone
Preamplifier/Mixer
The Alesis Studio 12R is a high-quality, rack-mountable 12-input,
stereo output audio mixer. It is designed to handle eight
microphones, two stereo line inputs, and to route signal to and
from external effect processing devices. As a basic, easy-to-
understand mixer, it can be used in a wide variety of applications
from sound reinforcement to multitrack recording. It may also be
used as an accessory or submixer to a larger console.
Using this manual
To get the most out of your Studio 12R, please read this manual.
While the mixer is not complicated to operate, the manual contains
information that will help you get the highest level of performance
from it. We’ve included creative alternative techniques that aren't
obvious at first glance.
To find what you need quickly, refer to the index at the back of the
manual, or the Table of Contents.
We appreciate your feedback. If you have any suggestions on how
to improve this manual, please write to us at:
Technical Communications Dept.
Alesis Corp.
3630 Holdrege
Los Angeles, CA 90016
or via email at: [email protected]
Conventions
The buttons, knobs, and rear panel connectors are referred to in this
manual just as their names appear on the Studio 12R, using all
capital letters (Example: [TRIM] control, [PAN] knob, [PHONES]
jack, etc.).
✪When something important appears in the manual, an icon (like
the one on the left) will appear in the left margin. This symbol

Introduction
Studio 12R Reference Manual 6
indicates that this information is vital when operating the Studio
12R.
Grounding Instructions
This product must be grounded. If it should malfunction or break
down, grounding provides a path of least resistance for electric
current to reduce the risk of electric shock. This product is equipped
with a cord having an equipment-grounding conductor and a
grounding plug. The plug must be plugged into an appropriate
outlet that is properly installed and grounded in accordance with all
local rules and ordinances.
DANGER - Improper connection of the equipment-grounding
conductor can result in a risk of electric shock. Check with a
qualified electrician or serviceman if you are in doubt as to whether
the product is properly grounded. Do not modify the plug provided
with the product; if it will not fit the outlet, have a proper outlet
installed by a qualified electrician.

Installation
Studio 12R Reference Manual 7
INSTALLATION
Unpacking
The Studio 12R box should contain:
1. The mixer itself
2. A packet of literature along with this manual
3. An AC power cable
4. An Alesis warranty card
Please send in your warranty card right away. Your warranty is not registered
with Alesis until the card is returned. Please save your sales receipt as your ultimate proof
of purchase and warranty date. By sending in your warranty card, you will receive the
Alesis First Reflection magazine free of charge, and we will be able to notify you of special
programs and offers from Alesis. Should repair ever become necessary, having the unit
registered will make it faster and easier to obtain service.
Note that the warranty is valid only in the country of purchase; i.e., units purchased in the
United States must be serviced in the United States.
AC power
READ ALL SAFETY WARNINGS IN THE PREVIOUS SECTION OF THIS MANUAL
TO ENSURE SAFE OPERATION OF THIS UNIT. Connect the Studio 12R to the
specified power using the AC cable supplied with the unit. The AC cable is removable. If
the distance to your AC outlet is longer or shorter than the supplied cable, you may
substitute an approved standard NEMA-to-CEE power cable of the correct length, available
from most electronics stores.
Grounding
CONNECT THE STUDIO 12R TO A PROPERLY GROUNDED OUTLET ONLY. DO
NOT USE ADAPTERS WHICH REMOVE THE SAFETY GROUND PROTECTION OR
CUT OFF THE GROUNDING PRONG ON THE POWER CORD. Proper grounding is
essential for user safety and low noise. If you experience 60-cycle hum in your sound
system as a result of different ground potentials between different units in your system,
plug all units into the same AC circuit (if the total power load allows) and make sure other
devices in the system are properly grounded themselves. The Studio 12R features balanced
inputs and outputs, so if it is properly connected to other balanced units, AC ground
potentials will not affect the audio. If you cannot get rid of ground loops, consult a
professional electrician familiar with sound system power designs.
Use clean power
The Studio 12R's internal power supply is designed to filter out most AC line noise.
However, it is still good practice to plug your sound equipment into an AC circuit that is
not shared with lighting dimmers, refrigerators, air conditioning units, or other appliances
that may induce noise into the power system.

Installation
Studio 12R Reference Manual 8
Power switch
The POWER switch is located on the back panel. A power indicator
is on the front panel next to the meter. Avoid turning the power
switch on or off while the Studio 12R is connected to a live
amplifier.
Mounting
The Studio 12R may be rack mounted in a standard EIA 19" rack, occupying three standard
1.75" rack spaces. Any angle of orientation is acceptable. Note that (as with most audio
equipment) if it is mounted into metal rack rails, the chassis ground of all units in the rack
will be connected together by the rail. In some cases this is desirable, but if hum is a
problem in the system, you may need to install non-conductive rack screws and washers on
the Studio 12R or other equipment in the rack to isolate the chassis grounds from each
other.
The mixer may also be used on a table top. To avoid scratching a tabletop surface, apply
rubber or felt feet to the bottom of the Studio 12R.

Connections
Studio 12R Reference manual 9
CONNECTIONS
Inputs
Cable common sense
Make all connections to the Studio 12R with the power turned off wherever
possible. If you must connect or disconnect inputs while power is on, make sure the
channel fader and [TRIM] are turned all the way down to avoid sudden pops and clicks
which may damage speakers or other equipment.
Use good-quality cable: 99% of all mixer problems turn out to be
cable or connector problems. Use the best quality cable you can, for
highest reliability and lowest noise. If something goes wrong, check
the cable and its connection to the mixer first. If the connectors are
dirty or corroded, clean them with isopropyl alcohol or other
approved electrical contact cleaner before inserting them into the
Studio 12R. High quality cables are low-capacitance shielded cables
with a stranded (not solid) internal conductor and a low-resistance
shield. Although quality cables cost more, they do make a
difference.
Route cables in your system correctly by observing the following
precautions:
• Do not bundle audio cables with AC power cords.
• Avoid running audio cables, or placing the Studio 12R itself,
near sources of electromagnetic interference such as
transformers, monitors, computers, etc.
• Never unplug a cable by pulling on the wire itself. Always
unplug by firmly grasping the body of the plug and pulling
directly outward.
• Do not place cables where they can be stepped on. Stepping on a
cable may not cause immediate damage, but it can compress the
insulation between the center conductor and shield (degrading
performance), or reduce the cable’s reliability.
• Avoid twisting the cable or having it make sharp, right angle
turns.
Microphone Inputs
The Alesis Studio 12R features eight studio-grade, low-noise hybrid microphone
preamplifiers. These [MIC] jacks are designed to work with almost any low-impedance

Connections
Studio 12R Reference manual 10
microphone using standard 3-conductor XLR connectors. The [MIC] jacks also feature 48
volt phantom power, which may be turned on and off by the [PHANTOM] switch on the
back panel, for condenser microphones which require external powering.
Balanced Mic Input
GroundHot
12
3
Cold
Socket (female)
The MIC Input is designed to accept a wide range of balanced or unbalanced low
impedance input signals, with up to 60 dB of amplification available (which is 10 to 20 dB
more than many other rack-mount mixers). It is wired with "pin 2 hot" according to the
accepted standard.
✪Use only one input per channel. The LINE IN jack and the MIC IN jack of a
channel can’t be used at the same time. If you turn up the level of a line source to hear it at
the same time a microphone is connected, you may damage the microphone.

Connections
Studio 12R Reference manual 11
Phantom power
Certain types of microphones (called condenser microphones) require a DC power supply
from the mixer. “Phantom power” sends 48 volts of DC through the microphone cable. If
any of your microphones need phantom power, turn on the [PHANTOM POWER] switch
on the Studio 12R’s back panel to connect all the XLR MIC IN jacks to the Studio 12R’s
internal 48 volt phantom power source. Since the power is applied equally to pins 2 and 3,
phantom power should not affect dynamic microphones (which do not require phantom
power). However, make sure that your microphone cables have no short circuits or
intermittent connections to avoid damage to the system.
✪Avoid connecting or disconnecting any microphones while [PHANTOM
POWER] is turned on. Make all connections with the Studio 12R powered off. If this
is not possible, make sure the channel's fader and [TRIM] are down, make the
connections, then turn on the [PHANTOM POWER] switch on the back panel before
bringing the fader and [TRIM] back up. Many microphones make a loud "pop" when first
powered, so make sure your faders are down to avoid damaging your speakers or hearing.
Never connect the MIC jack to an UNBALANCED source or to a
line-level device (such as a tape recorder or synthesizer) when
phantom power is being used.
If none of your microphones need phantom power, leave the phantom power switch off.

Connections
Studio 12R Reference manual 12
Line-level devices (synthesizers, CD players,
video)
The Studio 12R features line-level inputs on 1/4" phone jacks which accept standard
unbalanced or balanced signals.
AA
AA
AA
AA
AA
AA
A
A
Tip
Sleeve
Signal
Ground
Tip
Sleeve
Unbalanced Line Input
A
A
A
A
A
A
A
AA
Tip
Sleeve
Hot
Ground
Tip
Sleeve
Balanced Line Input
Ring
Ring
Cold
Unbalanced -10 dBV line level sources: Most synthesizers, drum machines, effect
devices, cassette decks and CD players operate at this level. Their average signal level is
about 1/3 of a volt. They have a 2-conductor output jack that is either a 1/4" phone or
"RCA phono" type. These may be plugged directly into any of the Studio 12R’s [LINE
IN] jacks, with the [TRIM] level set at approximately the 1 o'clock position. Plug stereo
sources such as synthesizers, CD players, and drum machine main outputs into the
STEREO LINE channels (9/10 and 11/12) if possible.
Electric guitars and basses may be plugged directly into the [LINE IN] jacks, if you
raise the [TRIM] level. The Studio 12R has more than enough gain (up to 50 dB when the
channel fader and trim are set to maximum) for guitars, although some pickups may sound
better if they're plugged directly into a high-impedance preamp designed for guitar use.
Plug the output of such preamps into any [LINE IN] jack.
A reminder: do not plug a line input and a microphone input into the same
channel. The inputs are not designed to handle two sources at the same time. If you
crank up the line level input to extremes to compensate for the level loss, you may damage
the microphone.

Connections
Studio 12R Reference manual 13
Balanced +4 dBu line level sources: Professional recording and processing
equipment typically provides a balanced, 3-conductor signal output that is a higher voltage
(1.24 volts nominal level) than most synthesizers and stereo equipment. The Studio 12R’s
[LINE IN] jacks are designed to handle these balanced inputs.
Balanced sources often feature XLR outputs. However, they should NOT be connected to
the XLR [MIC] inputs of the Studio 12R unless absolutely necessary, because the higher
gain of the MIC jacks gives you less headroom than the LINE IN jacks do (also, the source
could be damaged by phantom power if it's turned on). Connect them to the [LINE IN]
jacks using an XLR-to-1/4 inch phone TRS (tip-ring-sleeve) cable, as shown below:
If the proper connector cable or adapter is not available, +4 dBu line level sources may be
connected to the [MIC] jacks ONLY IF PHANTOM POWER WILL NOT BE
USED!!
Connecting a line-level output to a phantom-powered XLR input
on the Alesis Studio 12R may cause damage to the external unit.
Alesis cannot be responsible for any damages caused by this kind of
misuse.
The nominal trim setting for a +4 dBu signal plugged into a line input is approximately 11
o'clock (12 o'clock on the stereo channels). This will give you plenty of headroom to start
with.
Maximum levels: The maximum level the [MIC] jack can receive with the [TRIM]
control full counter-clockwise is +12 dBu before clipping, so there’s only 8 dB of
headroom if you plug a +4 dBu line source into the mic jack. The [LINE IN] jack on
channels 1-8 may receive levels up to +32 dBu without clipping, a headroom advantage of
20 dB. The stereo channels may receive a +22 dBu (balanced or unbalanced) maximum
input.

Connections
Studio 12R Reference manual 14
TAPE IN jacks
The [TAPE IN] jacks on the rear panel are designed for playback of a
stereo tape deck (or any other -10 dBV level signal) through the
[MONITOR OUT] and [PHONES] jacks only. A signal at the [TAPE
IN] jacks cannot be heard from the [MAIN OUT] jacks.
This allows you to use the Studio 12R to monitor a mixdown to a 2-
track deck through your headphones. (If you plugged your
mixdown deck into the line inputs on the channels, it would cause
feedback when you press “record”.) By placing the
[PHONES/MONITOR] switch in the TAPE position, you will hear
the mixer's output after it has been passed through the mixdown
deck, so you can make sure that it is recording correctly.
• Another use for the [TAPE IN] jacks is to play a CD or tape into a
PA system, automatically turning off all the microphones into
the main PA system when the front panel MSTR/TAPE switch
is set to the TAPE position. Note that in this application, the PA
system must be fed from the MONITOR OUT instead of the
MAIN OUT jacks, and will be affected by the level of the
[PHONES/MONITOR] control as well as by the [MASTER]
control fader.

Connections
Studio 12R Reference manual 15
Phonograph turntables
If you're using a record turntable, you may not plug it directly into the line inputs of the
Studio 12R (well, you can, but it will sound very thin and noisy). Obtain a phono preamp
from your dealer or an electronics specialty store.
1. Plug the outputs of the phonograph pickup into the RIAA-
equalized phono preamp.
2. Plug the outputs of the preamp into the LINE IN 9-10 or 11-12
inputs of the Studio 12R.
Do not connect any of the following to any
input of the Studio 12R!
•The speaker output of any power amplifier.
•Any source that is too loud for the input (no more than 3 volts
RMS into a [MIC] jack or 13 volts RMS into a [LINE IN] jack).
•Any unshielded cable.

Connections
Studio 12R Reference manual 16
How to connect effect devices and signal
processors
Alesis and other companies make many different types of signal processors which may be
connected to the Studio 12R mixer. There are two ways to connect these units: using the
AUX system or via the INSERT jacks.
Effects via Aux Send and Aux Return
If you want to add an effect such as reverb, chorus, or delay to several different inputs at
once, you will use the AUX system.
1. Connect the AUX 2 (POST) AUX SEND output of the 12R to the
input of the effect device. If the effect has a stereo input, check
the manual of the effect to see which jack is the mono jack. (In
most cases, you won't need to connect anything to the other
input jack of the device, but you will still get a stereo effect
output).
2. Connect the left and right outputs of the effect device to the
[STEREO AUX RETURN] jacks of the Studio 12R.
• Alternatively, you may connect the output of the effect device to
either of the STEREO LINE channels ([9-10 or 11-12].) This will
allow you to control the effect with a large fader, send the effects
to the Aux 1 output for monitoring, and use EQ on the effect.
About stereo effect devices
✪If your effect unit has two inputs, in most cases you need to connect
from only ONE Aux Send to the left (mono) input of the effect unit,
but you will still connect both the left and right outputs of the effect
to the STEREO AUX RETURN.

Connections
Studio 12R Reference manual 17
You don’t need to connect anything to the other input of the effect,
because most effect units use the stereo inputs only to provide a
path for the “dry” stereo signal when the effect is connected directly
between an instrument and an amplifier. In mixing applications
such as with the Studio 12R, you will set the effect’s wet/dry balance
all the way to “wet” (effects only, no direct signal). The effect device
will generate an artificial stereo output from the signal input.
Check the manual for your effect device for more information.
On the other hand, true dual-channel effects processors (such as the
Alesis QuadraVerb 2) may be connected to two different sends to
take advantage of the dual processing capability. Dual-channel
processors allow the left and right inputs to be used for different
kinds of effects (for example, the left input to a stereo chorus while
the right input is used for a stereo reverb).
Using Aux 1 as an effects send
Note that [AUX 1] may also be used as an extra effects send.
Although Aux 1 is a pre-fader send, and normally used for stage
monitoring or a separate headphone mix while recording, it may
also be used as an effects send so you can add different effects to
different channels. Just remember that the “PRE” under [AUX 1]
means that when you move a fader up or down you won’t change
the level going to an effect from Aux 1. If you change fader levels,
you will need to adjust Aux 1 levels to maintain the same balance
between dry and effected signal.
In-line processing using the INSERT jacks
(compressors & equalizers)
Some signal processors are designed to be used on one signal at a time, with the entire
signal being processed instead of a mix of effected and uneffected signal. The purpose of
the INSERT jacks on channels 1-8 is to allow you to insert a compressor, equalizer, or
other effect into the signal path of a single channel after its preamplifier and [TRIM]
control, but before the Studio 12R's own EQ, aux sends, and fader. The INSERT jacks
may also be used as direct outputs to a recorder.
The INSERT connector is a TRS (tip/ring/sleeve) 1/4" jack which
consists of an insert send (the tip of the TRS plug) and an insert
return (the ring of a TRS plug). A special Y-cable consisting of a
TRS 1/4" plug on one end and two mono 1/4" plugs on the other
end is required.

Connections
Studio 12R Reference manual 18
Tip
Ring
Sleeve
Send
Return
Ground
Tip
Ring Sleeve
Insert Points
Note that you will not hear any signal through the Studio 12R if the
INSERT jack is plugged in and the signal is interrupted in that loop (by the
other cables being disconnected, the processor being turned off, or the volume turned off in
the processor).
Connecting an in-line processor
1. Obtain a "stereo splitter" insert cable from your dealer.
2. Connect the stereo (TRS) end to the INSERT jack of the Studio
12R.
3. Connect the mono plug from the tip connector to the input of
the processor.
4. Connect the mono plug from the ring connector to the output of
the processor.
If you're not sure which mono plug is from the tip and which is from the ring, check to see
if the cable is labeled. If not, simply try it one way and if the signal doesn't pass through,
swap the input and output plugs the other way.
• The [INSERT] jack may also be used as a direct output to a
multitrack recorder such as the ADAT. The send from the insert
jack is where the cleanest mic preamp signal may be obtained,
without passing through the EQ or channel circuitry. Simply insert
the plug to the first "click" (the ring connector) and it will not
interrupt the flow through the mixer, while providing a direct
output. Or, put the recorder into INPUT mode and insert the plug
all the way, connecting the input and output of each track of the

Connections
Studio 12R Reference manual 19
recorder into each channel path of the mixer. This will allow
playback monitoring of the recorder. See the Applications chapter
for more information.
For more information on using the AUX and INSERT systems, see the
“Operating Instructions” chapter of this manual.