Rane MM 12 Operating instructions

MM 8z
Here are a few basic “plug and play” steps to get you performing. If you are a first-time DJ mixer user, please do
yourself a favor and at least read this section.
Begin by making sure your amplifier is off before making connections. The MM 8z has all unbalanced connectors,
except for the ¼" balanced Main Outputs and XLR Mic Inputs. Plug a source component, such as a CD player, into one of
the four LINE Inputs on the rear. Connect the MAIN OUTPUTS to your amplifier. Set all front panel controls to the
middle of their travel and all pushbuttons to their out position. Slide the MASTER LEVEL down to 0. Set the INPUT
SELECT switch to your active Source Input. Plug in the MM 8z’s power supply and see the PWR indicator illuminate.
Turn on your source and amplifier. Slowly turn up the MASTER LEVEL, as the meters light and music is heard from the
You can get tripped up at two places. If you have a phono signal into one of the four PH/LN Inputs, be sure the PH/LN
switch is in the PHONO position (in); likewise, when using a tape deck or CD into these Inputs, be sure the switch is in the
LINE (out) position. If you plug into the PROGRAM LOOP, the internal signal path is broken. Be sure that a complete
loop is made, to and from an outside device.
Couldn’t be easier, right?
With the CROSSFADER CONTOUR set to full
counter-clockwise position, it operates as a typical constantpower crossfader. Set to clockwise position, the crossfader
has the very steep slope as indicated in Figure 1 to the right.
Now that was a pretty quick start, right?
Never connect anything except a Rane RS 1 to the
thing that looks like a red telephone jack on the rear of the
MM 8z. This is an AC supply and requires some special
attention if you do not have an operational power supply
exactly like the one that came with your unit. Consult the
Rane factory for a replacement or substitution.
This product contains the following wear part subject to
the ninety (90) day warranty period described on page
Service-1: (1) Active Crossfader Assembly F 60.
Figure 1. Crossfader Contour control
MAIN MIC ON switch: puts the Main Mic signal into the mixer signal path. When the switch is pressed in, the Main Mic
is on and the adjacent red indicator blinks.
Front panel MAIN MIC input: accepts a balanced microphone with an XLR connector. A parallel Main Mic Input is on the
rear of the unit. Do not connect microphones to both front and rear Main Mic inputs.
MAIN MIC LEVEL control: adjusts the level of the Main Mic Input.
MIC OVERLOAD indicator: monitors both Main and Aux Mic Inputs, before and after the Mic EQ. It lights when the
signal exceeds the Mic section’s output capability (3 dB below clipping). Occasional flickering is acceptable; however,
steady lighting requires a reduction in the Mic LEVEL control to prevent distortion.
AUX MIC ON switch: puts the Aux Mic signal into the mixer signal path. The adjacent red indicator blinks when the
switch is pressed in, indicating that the Aux Mic is on.
AUX MIC LEVEL control: adjusts the level of the Aux Mic Input.
MIC EQ controls: contour the frequency response of the summed Main and Aux Mic Inputs.
Source Input Select switch: selects either a Phono/Line or Line Input for the Source. In the center position the Source
Input is muted.
Source EQ controls: contour the frequency response of the selected Input.
Source Input fader: controls the level of the selected Input.
Source ASSIGN PRE/POST CROSSFADER switches: are provided for Inputs 1 and 4. In the PRE (up) position, this
Input is routed to the Crossfader. In the POST (down) position the Input bypasses the Crossfader.
ACTIVE CROSSFADER: controls the relative output level from the summed A and B Mixes. When the fader is at its far
left, only the A Mix is heard from the Outputs. As the fader is moved toward the right, the amount of B Mix is increased and
the amount of A Mix is decreased. When the fader is centered, equal amounts of A and B Mixes are routed to the Outputs.
Fully right is all B Mix at the Outputs.
m CROSSFADER CONTOUR control: Allows adjusting the “shape” of the Crossfader response from a gentle curve for
smooth, long running fades, to the steep pitch required for top performance cut and scratch effects. See Figure 1 on page
Meter and Mode switch: This peak-dBu reading meter displays one of two modes, depending on the switch position. In the
LEFT/RIGHT (out) position, the meter indicates the stereo level in the LEFT and RIGHT Main Outputs. In the CUE/PRG
(in) position, mono CUE level is displayed on the Left meter and mono PROGRAM level is displayed on the Right meter.
MASTER LEVEL fader: adjusts the level at the rear panel Main Outputs.
AUX INPUT: This stereo pair of RCA connectors is an extra line level Input which sums with the other signals before the
Master Level fader.
AUX IN LEVEL control: adjusts the level of the front panel Aux Inputs.
AUX OUTPUT: This stereo pair of RCA connectors provides an extra line level output mix. This is the same signal as the
Main Outputs, but with a separate Level control.
AUX OUT LEVEL control: adjusts the level of the front panel Aux Outputs. This control is independent of the Master
Level fader and Main Outputs.
CUE switches: Pressing in any or all of the CUE pushbuttons routes the respective Source to the Headphone and Meter Cue
sections. The adjacent yellow indicator illuminates when the switch is depressed.
HEADPHONE PAN control: adjusts the relative levels of Cue and Master signals mixed together in stereo for the headphones. Counterclockwise rotation increases the amount of Cue signal; clockwise rotation increases the amount of Master
HEADPHONE LEVEL control: adjusts the volume for the headphones.
HEADPHONE Output jack: This stereo ¼" TRS (Tip-Ring-Sleeve) jack accepts ¼" TRS stereo headphone plugs (do not
use mono plugs).
POWER “ON” indicator: When the yellow indicator is lit, the MM 8z is ready to go.
Fader Cleaning
With heavy use in harsh environments, the faders may
need lubrication. This treatment extends longevity and can
make used faders as good as new. The fader assembly must
be removed from the MM 8z for proper cleaning. We recommend any of the following cleaning solutions:
Caig Cailube MCL 100% spray lubricant
Caig Cailube MCL 5% spray cleaner
CRC 2-26
Order CaiLube MCL® from:
CAIG Laboratories, Inc.
12200 Thatcher Ct.
Poway, CA 92064
Phone 619-486-8388
Fax 619-486-8398
Web http://www.caig.com
The Crossfader may be removed without any disassembly
of the MM 8z itself, and may be performed while the unit is
operating with no interruption of the audio signal.
F 60 and F 45 Fader Kits are available from your local
retailer or the factory. The kit includes full assembly including knobs, ribbon, and face plate.
1. Remove the two (2) outer screws attaching the crossfader
assembly to the front panel.
2. Pull the Crossfader Assembly forward and unplug the
ribbon from the connector on the bottom board.
3. Proceed with Cleaning Instructions, or install the replacement assembly by reversing the above instructions.
1. Hold the fader assembly away from the mixer.
2. Position the fader at mid-travel.
3. Spray cleaner/lubricant into both ends of the fader.
4. Move the fader over its full travel back and forth a few times.
5. Shake excess fluid from the fader assembly.
6. Wipe off excess fluid.
Remote POWER Supply Input: The unit is supplied from the factory with a Rane Model RS 1 remote power supply
suitable for connection to this input jack. The power requirement of the unit specifies an 18 volt AC center-tapped transformer only. This is not a telephone jack. Never use a power supply with your unit other than the one supplied or a
replacement approved by Rane Corporation. Using any other type of supply may damage the unit and void the warranty.
Chassis ground point: This screw is provided for grounding purposes. This unit comes with an outboard power supply
which does not ground the chassis through the line cord. The MM 8z can be grounded either to another chassis which is
earth grounded, or directly to the grounding screw on an AC outlet cover with a wire connected to this chassis screw.
PHONO GROUND screw: These screws provide a place to connect the ground wire from a turntable.
PHONO/LINE switch: These switches change the Input from a PHONO (pushbutton in) to a LINE (pushbutton out).
PHONO/LINE INPUTS: These stereo pairs of RCA connectors are an Input for a PHONO (RIAA) stage for magnetic
cartridges or a LINE stage suitable for any device, such as a CD player.
LINE INPUTS: These stereo pairs of RCA connectors are an Input for any LINE level device.
PROGRAM LOOP jacks: These ¼" TRS (Tip-Ring-Sleeve) jacks allow stereo external processing of the Program signal.
The tips connect the sends to the processor inputs, and the rings connect the returns from the processor. These are switching
jacks—always complete the loop when connecting a send and return, or no sound will be heard.
MAIN OUTPUTS: These ¼" TRS jacks provide a balanced line level output.
TAPE OUTPUTS: This stereo pair of RCA connectors is a line level Output of Mix program (without Mic or Aux Inputs).
The signal is unaffected by the MASTER LEVEL fader. It is intended for use with a tape recorder, but is not restricted to
that purpose.
PRE/POST LOOP switch: With the switch pressed in the PRE (in) position, the TAPE OUTPUTS have the signal before
processing by an external device connected to the PROGRAM LOOP. Releasing the switch to POST (out) provides the
TAPE OUTPUTS with the signal that has been processed by an external device connected to the PROGRAM LOOP. If no
plugs are inserted in the PROGRAM LOOP, this switch has no effect.
MAIN MIC LOOP jack: This ¼" TRS jack is for inserting external mono signal processing in the MAIN MICROPHONE
circuit path only. The tip connects the send to the processor inputs, and the ring connects the return from the processor. This
is a switching jack—always complete the signal loop when connecting a send and return, or no sound will be heard.
AUX MIC jack: This ¼" balanced TRS Input accepts wireless mics or another line-level mono source.
Rear panel MAIN MIC input: This XLR Input connects a balanced microphone. The same MAIN MIC Input is on the
front of the unit. Do not connect microphones to both front and rear MAIN MIC Inputs.
With the MM 8z’s ability to accommodate a wide variety
of systems, these basic guidelines will assist the user in
incorporating this mixer into their equipment setup.
Since most source components (e.g., turntables, disc
players, tape decks) used with the mixer are consumer grade,
the MM 8z features unbalanced RCA Source Input connectors.
When using the PH/LN inputs, be sure the adjacent switch
is in the correct position for the connected device: pushbutton
in for phono, out for line level. Ground screws attach the
turntable ground wires, which help eliminate hum or buzz.
The front and rear panel Main Mic Inputs are XLR
connectors, for use with a balanced output microphone of any
impedance. Use only one mic at a time in the front or rear
jack. Effects can be inserted in the Main Mic signal path thru
the ¼" unbalanced TRS MAIN MIC LOOP jack. Use a
special TRS send/return cable: tip = send, ring = return,
sleeve = ground. Refer to the wiring diagram below. The
Auxiliary Mic input is ¼" balanced TRS jack, useful for
wireless mics and other high-impedance sources.
The MAIN OUTPUTS are ¼" balanced TRS connectors,
which provide good hum rejection and allow long (greater
than 10 feet) lengths of interconnect cable without significant
losses (see Sound System Interconnection on page Manual-10
for proper wiring of connector/cable). The PROGRAM LOOP
has left and right ¼" unbalanced TRS connectors for sending
the Source program signal to an external effects device and
returning the signal back to the mixer. Use a special TRS
send/return cable: Tip = send, Ring = return, Sleeve = ground.
Refer to the wiring diagram below. Remember, these are
switching jacks—always complete the loop when connecting
the send to and return from an external device.
Two sets of outputs can provide convenient connections
for recording equipment. The TAPE OUTPUT unbalanced
RCA jacks provide an output for recording program material.
If you want signal processing via the Program Loop to have
an effect on the recording, let out the PRE/POST Record
push-button to the POST position. The TAPE OUTPUT does
not contain any signal from the Mic or Aux In sections. If you
need to record the mics, use the Aux Out for your recording
signal; this output is a composite of the Program, Microphone, and Aux Inputs.
Send-Return Cable Wiring
The MM 8z is able to mix together four Sources. Each
Source is switchable between two line Inputs, one of which
may be switched to a Phono Input. The center OFF position
of the Source Input Select switch mutes it.
The ASSIGN switch for Source 1 in the PRE position
combines PH/LN 1 or LINE 2 with PH/LN 3 or LINE 4 for
the A Mix. Likewise, the ASSIGN switch for Source 4 in the
PRE position combines PH/LN 5 or LINE 6 with PH/LN 7 or
LINE 8 for the B Mix. These Mixes are routed to each side of
the Crossfader, A & B. Either ASSIGN switch in the POST
position routes Source 1 or 4 directly to the Master Level
control, and routes Source 2 or 3 through the Crossfader
before going to the Master Level control.
Each selected Source’s frequency spectrum can be
contoured with the Treble, Mid, and Bass controls. These are
intended to provide EQ between varying program material.
The Treble and Bass controls offer 15 dB of boost or cut; the
Mid control offers 8 dB of boost or cut. Positioning any
control to the “12 o’clock” position turns that equalization
band off.
The Source faders control the level of the selected Input.
They also provide a means to set relative levels for each Input
to A and B Mixes. Set the Source faders near their maximum
levels (0 dB) instead of increasing the gain later at the Master
Level control or power amp. You achieve optimum noise
performance by having the majority of the gain at the input
stages. Taking the least amount of gain at the output ensures
that the system doesn’t have to amplify the unavoidable noise
generated by the input buffers and summing amplifiers. Unity
gain for Line Inputs is achieved with the faders positioned at
the “0 dB” marking.
Depending on the position of the Pan control, a mix of
stereo Cue or stereo Master is heard through the headphones.
Fully counterclockwise, the sum of selected Cue Sources is
heard. This allows previewing of the full equalized Source
signal even while the fader is down. Clockwise rotation
increases the amount of Master signal. The Level control
adjusts the headphone output.
With the ASSIGN switches in the PRE position, Sources 1
and 2 create the A Mix and Sources 3 and 4 create the B Mix.
The output of these Mixes are under control of the Active
Crossfader. When the appropriate ASSIGN switch is in the
POST position, only Source 2 and/or 3 is routed to the
When the Crossfader is in its left-most position, only A
Mix (PRE) or Source 2 (POST) appears at the Output. In the
center, both Mixes are present in equal levels, and only B Mix
(PRE) or Source 3 (POST) is heard once the Crossfader
reaches its far right position. With the ASSIGN switches in
POST, Source 1 and 4 are still active, unaffected by the
With the CROSSFADER CONTOUR set to the full ccw
position, the sound pressure level does not change as this
transition progresses. See Figure 1 on page Manual-1 for
response curves.
Active Crossfader technology dramatically increases the
service life of the crossfader. In the unlikely event of crossfader failure, there is no loss of signal—all Sources are
present in equal levels, as if the crossfader was in its center
position. Use the Source Input faders to set the audio levels
while the Crossfader is out of service. If a Crossfader becomes rough or noisy, it is possible to remove and replace
(“hot swap”) the control during a performance with no
interruption of the audio signal.
The output signal from the Crossfader and Source Input
faders is routed to the Program Loop jack. The signal can be
fed to external effects units and returned to the MM 8z. The
Program Loop return signal is combined with the Mic and
Aux Input signals and presented to the Master Level fader,
Aux Out Level control, headphone amplifier, and peak meter.
The Master Level fader should be set at the lowest position
while still achieving overall desired sound output level. The
least amount of gain in the output stage will avoid amplifying
unavoidable noise and provide the cleanest output. For unity
gain in the output stage, set the Master Level fader at the “0
dB” marking.
Connect the microphone to the appropriate connector. The
Main Mic Input on the front panel allows a gooseneckmounted microphone. The connector is rotated such that a
right angle connector may be used when connecting via mic
cable. Use only one of the front or rear Main Mic Inputs, both
are not operable simultaneously. Leave the Master Level
fader in roughly the same position as it was for music. Press
in the Mic On switch, lighting the adjacent indicator, and
adjust the Main Mic (or Aux Mic) Level. The tonal balance of
the Main and Aux Mic Inputs may be adjusted via the Mic
EQ controls. Modifying the sound of the mic in this way
won’t affect the EQ of the music. When the mic is not in use,
release the Mic On switch to its out position to disconnect the
mic signal. Should the mic preamp become overloaded, the
Overload indicator will light. By reducing the appropriate
Mic Level control and increasing the Master Level fader, the
desired microphone level may be restored without overload
The TAPE OUTPUT does not contain any signal from the
microphone section. If you need to record the mics, use the
Aux Out for your recording signal; this output is a composite
of the Program, Microphone, and Aux Inputs.
The Auxiliary Input is an insertion point for added signals.
This Input combines with the program mix and microphone
signal to provide a final mixer output. Leave the Master Level
fader in roughly the same position as it was for program
music. Adjust the Aux In Level control for the desired sound
The Aux Out provides a separate final mixer Output,
unaffected by the Master Level fader, for external devices
such as tape recorders and video cameras, or for additional
zone feeds. The Aux Out Level control varies the output
signal level.
The MM 8z’s meter displays signal level in peak dBu.
Two display modes are provided, Stereo Master and Mono
Cue/Mono Program. The mode is selected with the meter
mode switch. With the switch in the out position (LEFT/
RIGHT), the meter indicates the level of the left and right
Main Outputs as measured at the output jacks (what you see is
what you hear). The Master signal is the sum of Program,
Microphone, and Aux Input signals.
With the switch in the in position, the left meter indicates
the sum of selected Mono Cue levels and the right meter
indicates Mono Program level. Mono Cue levels are measured
at the output of the Source Input fader (just before the
Crossfader). The Input fader of a cued Source will need to be
advanced to see level indication on the meter. Mono Program
level is measured at the output of the Crossfader and Source
Input faders (Pre Master summing and Master Level fader).
This arrangement allows matching of Source levels and beat
prior to Crossfading. Note that if two Sources are to be in an
A or B mix, both need to be cued for the meter to reflect the
combined levels.
Two Pre/Post Crossfader ASSIGN switches add to the
flexibility of the MM 8z. By placing these in the POST
position, the Crossfader is bypassed, allowing the Source 1 or
4 to be a separate mixer or other device, while still using the
MM 8z's Crossfader with Sources 2 and 3. This powerful new
feature greatly increases the flexibility of the MM 8z, making
it one of the most capable mixers in it’s price range.
It is now possible to have a pair of booth turntables on
Source 2 and B Mix Source 3, each sent to the Crossfader,
while having the output of a 2nd Performance Mixer connected
to Source 1 and summed post Crossfader. Source 4 could be
summed Pre-crossfader for use with a 3rd booth turntable, or
Post-crossfader to allow use of a 3rd mixer, a wireless
microphone, a drum machine, etc... you get the idea. The
examples shown below illustrate some of the many possibilities. Any of the turntables can be replaced with CD players by
switching the Phono Input to Line level.
Rane’s policy is to accommodate rather than dictate.
However, this document contains suggestions for external
wiring changes that should ideally only be implemented by
trained technical personnel. Safety regulations require that all
original grounding means provided from the factory be left
intact for safe operation. No guarantee of responsibility for
incidental or consequential damages can be provided. (In
other words, don’t modify cables, or try your own version of
grounding unless you really understand exactly what type of
output and input you have to connect.)
Use balanced lines and tie the cable shield to the metal
chassis (right where it enters the chassis) at both ends of the
A balanced line requires three separate conductors, two of
which are signal (+ and –) and one shield. The shield serves
to guard the sensitive audio lines from interference. Only by
using balanced line interconnects can you guarantee (yes,
guarantee) hum-free results. Always use twisted pair cable.
Chassis tying the shield at each end also guarantees the best
possible protection from RFI [radio frequency interference]
and other noises [neon signs, lighting dimmers].
The quickest, quietest and most foolproof method to
connect balanced and unbalanced is to transformer isolate
all unbalanced connections. Your audio dealer can recommend such a transformer.
The goal of transformer adaptors is to allow the use of
standard cables. With these transformer isolation boxes,
modification of cable assemblies is unnecessary. Virtually
any two pieces of audio equipment can be successfully
interfaced without risk of unwanted hum and noise.
Another way to create the necessary isolation is to use a
direct box. Originally named for its use to convert the high
impedance, high level output of an electric guitar to the low
impedance, low level input of a recording console, it allowed
the player to plug “directly” into the console. Now this term is
commonly used to describe any box used to convert unbalanced lines to balanced lines.
If transformer isolation is not an option, special cable
assemblies are a last resort. The key here is to prevent the
shield currents from flowing into a unit whose grounding
scheme creates ground loops (hum) in the audio path (i.e.,
most audio equipment). Do not be tempted to use 3-prong to
2-prong “cheater” adapters to lift grounds. This is a dangerous and illegal practice.
It is true that connecting both ends of the shield is theoretically the best way to interconnect equipment – though this
assumes the interconnected equipment is internally grounded
properly. Since most equipment is not internally grounded
properly, connecting both ends of the shield is not often
practiced, since doing so can create noisy interconnections.
A common solution to these noisy hum and buzz problems
involves disconnecting one end of the shield, even though one
can not buy off-the-shelf cables with the shield disconnected
at one end. The best end to disconnect is a matter of personal
preference and should be religiously obeyed; choose inputs or
outputs and always lift the side you choose (our drawings
happen to disconnect the outputs). If one end of the shield is
disconnected, the noisy hum current stops flowing and away
goes the hum — but only at low frequencies. A one-end-only
shield connection increases the possibility of high frequency
(radio) interference since the shield may act as an antenna.
Many reduce this potential RF interference by providing an
RF path through a small capacitor (0.1 or 0.01 microfarad
ceramic disc) connected from the lifted end of the shield to
the chassis. The fact that many modern day installers still
follow this one-end-only rule with consistent success indicates this and other acceptable solutions to RF issues exist,
though the increasing use of digital and wireless technology
greatly increases the possibility of future RF problems.
See the following page for suggested cable assemblies for
your particular interconnection needs. Find the appropriate
output configuration from either your mixer output or the MX
22 output (down the left side), and then match this with the
correct balanced or unbalanced input to the MX 22 or the
amplifer (down the right side.) An “off-the-shelf” cable may
be available or modifiable. Soldering should only be attempted by those trained in the art.
If you are unable to do things correctly (i.e. use fully
balanced wiring with shields tied to the chassis at the point of
entry, or transformer isolate all unbalanced signals from
balanced signals) then there is no guarantee that a hum free
interconnect can be achieved, nor is there a definite scheme
that will assure noise free operation in all configurations.
• Use balanced connections whenever possible.
• Transformer isolate all unbalanced connections from
balanced connections.
• Use special cable assemblies when unbalanced lines cannot
be transformer isolated.
• Any unbalanced cable must be kept under ten feet (three
meters) in length. Lengths longer than this will amplify
the nasty side effects of unbalanced circuitry's ground
This information was condensed from Rane Note 110,
“Sound System Interconnection”. If you would like the
complete note, call or email the factory, download it from
Rane's web site (addresses on page Manual-12), or ask your
dealer for a copy.
balanced line The recommended method of interconnecting audio
equipment. A balanced line requires three conductors: a twisted-pair
for the signal (positive and negative) and an overall shield. The
shield must be tied to the chassis at both ends for hum-free interconnect.
bandwidth Abbr. BW The numerical difference between the upper
and lower -3 dB points of an audio band.
clipping What occurs when a unit tries to produce a signal larger
than its power supply. The signal takes on a flat-topped, or clipped
shape. When an amplifier tries to go above its max power, it clips.
compressor A signal processing device used to reduce the
dynamic range of the signal passing through it. For instance, an
input dynamic range of 110 dB might pass through a compressor and
exit with a new dynamic range of 70 dB. The modern usage for
compressors is to turn down (or reduce the dynamic range of) just
the loudest signals. Other applications use compressors to control the
creation of sound. When used in conjunction with microphones and
musical instrument pick-ups, compressors help determine the final
timbre by selectively compressing specific frequencies and waveforms.
connectors Audio equipment uses different styles:
RCA An unbalanced pin connector commonly used on
consumer and some pro equipment; aka phono plug
XLR A 3-pin connector common on pro audio equipment.
Preferred for balanced line interconnect; aka Cannon plug
¼" TRS 1. Stereo ¼" connector consisting of tip (T), ring (R),
and sleeve (S) sections, with T = left, R = right, and S =
ground/shield. 2. Balanced interconnect with the pos & neg
signal lines tied to T and R respectively and S acting only as an
overall shield. 3. Insert loop interconnect with T = send, R =
return, and S = ground/shield. [Think: ring, right, return]
¼" TS Mono ¼" connector consisting of tip (T) [signal] and
sleeve (S) [ground & shield] for unbalanced wiring.
constant-Q equalizer (also constant-bandwidth) The
bandwidth remains constant for all boost/cut levels. Since Q and
bandwidth are interrelated, the terms are fully interchangeable.
decibel Abbr. dB (named after Alexander Graham Bell). The
preferred method and term for representing the ratio of different
audio levels. Being a ratio, decibels have no units. Everything is
relative. So it must be relative to some 0 dB reference point. A suffix
letter is added to distinguish between reference points:
0 dBu A reference point equal to 0.775 V
+4 dBu Standard pro reference level equal to 1.23 V
0 dBV A reference point equal to 1.0 V
-10 dBV Standard reference level for consumer and some pro
audio use, equal to 0.316 V. RCA (phono) connectors are a
good indicator of units operating at -10 dBV
dynamic range The ratio of the loudest signal to the quietest signal
in a unit or system as expressed in decibels (dB).
expander A signal processing device used to increase the dynamic
range of the signal passing through it. Expanders complement
compressors. For example, a compressed input dynamic range of 70
dB might pass through a expander and exit with a new expanded
dynamic range of 110 dB. Modern expanders usually operate only
below a set threshold point, i.e., they operate only on low-level
audio. The term downward expander describes this type of application.
ground Any electrical reference point for measuring voltage levels.
Usually a large conducting body, such as the earth or an electric
circuit connected to the earth. Chassis should always be at earth
Never use an AC line cord ground-lift adapter or cut off the 3rd
pin. It is illegal and dangerous.
headroom The level in dB between the typical operating level and
clipping. For example, a nominal +4 dBu system that clips at +20
dBu has 16 dB of headroom.
hum Unwanted sound contaminating audio paths due to EMI
(electro-magnetic interference) caused by AC power-lines &
transformers getting into unbalanced, poorly shielded, or improperly
grounded connecting cables. Hum has a definite smooth (sine wave)
repetitive sound based on the harmonics of 50/60 Hz such as 100/
120 Hz and 150/180 Hz.
interpolating Term meaning to insert between two points. If a
graphic equalizer’s adjacent bands, when moved together, produce
a smooth response without a dip in the center, they are interpolating between the fixed center frequencies.
levels Terms used to describe relative audio signal levels:
mic-level Nominal signal coming directly from a microphone.
Very low, in the microvolts, and requires a preamp with at least 60
dB gain before using with any line-level equipment.
line-level Standard +4 dBu or -10 dBV audio levels.
instrument-level Nominal signal from musical instruments
using electrical pick-ups. Varies widely, from very low mic-levels
to quite large line-levels.
limiter A compressor with a fixed ratio of 10:1 or greater. The
dynamic action prevents the audio signal from becoming larger than
the threshold setting.
Linkwitz-Riley crossover The most preferred active crossover
design. It features steep 24 dB/octave slopes, in-phase outputs, and
flat amplitude response. Due to the in-phase outputs the acoustic
lobe resulting when both loudspeakers reproduce the crossover
frequency is always on-axis (not tilted up or down) and has no
noise 1. Interconnect. Unwanted sounds contaminating audio paths.
RFI (radio frequency interference) caused by broadcast signals
leaking into unbalanced, poorly shielded, or improperly grounded
connecting cables. Also by light dimmers, motor controls and
computers. 2. Music. A random mix of audio frequencies not
harmonically related, sounding like radio static.
polarity A signal’s electromechanical potential with respect to a
reference. For example, a microphone has positive polarity if a
positive pressure on its diaphragm results in a positive output
voltage. polarity vs. phase shift: polarity refers to a signal’s
reference NOT to its phase shift. Being 180 degrees out-of-phase and
having inverse polarity are DIFFERENT things. We wrongly say
something is out-of-phase when we mean it is inverted. One occurs
over a period of time; the other occurs instantaneously.
Q (upper-case) Quality factor. Defined to be the ratio of the center
frequency f divided by the bandwidth BW for a bandpass filter.
signal-to-noise ratio The ratio in dB between a reference level
and the noise floor. For example, a signal-to-noise ratio of 90 dB re
+4 dBu, means the noise floor is 90 dB below a +4 dBu ref.
unbalanced line An audio interconnect scheme using one wire
with an overall shield. The shield must perform two functions: act as
the return signal path (ground) and to protect the conductor from
noise (shield). Consequently this method is vulnerable to hum &
noise problems.
unity gain A gain setting of one. The level out equals the level in.
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