QSC UF-2 User manual

12
UF-2
Universal
Filter
*TD-004031-00*
Rev. A
Owner’s
Manual
®
A U D I O

1
I. DESCRIPTION
The UF-2 is a Mini-Slot accessory dual-channel universal filter for use with QSC amplifiers using the Level
1orLevel2OpenInputArchitecture,suchastheEXandMXaSeries.Dependingonhowyousetandselect
theresistornetworksandprogrammingjumpersandswitches,youcanconfiguretheUF-2tobeasubsonic
or ultrasonic filter, a bandpass filter, or an active crossover.
Using the UF-2 as a crossover is ideal for rental sound systems, since it virtually eliminates the possibility
of unauthorized tampering with crossover settings or incorrect crossover output connections, and the
loudspeaker damage that may result from such user errors.
The UF-2, as does any other Mini-Slot accessory, mounts to an input module (the standard input module,
orany ofthe OpenInput Architectureaccessory modulesthat directlyreplaces thestandard inputmodule)
with a 10-pin header and a 12-pin header that solder to the corresponding holes on the input module. The
installationprocessinvolvessoldering, so onlyqualifiedtechnicalpersonsshould attempt toinstalltheUF-
2 to the input module; ideally, you should enlist QSC’s Customer Service Department or an authorized
service center to perform the task. The installation section of this manual offers more information about
installing the UF-2.
II. FEATURES
The UF-2 allows independent filtering of the two audio channels. You can select high-pass, low-pass, or
bandpass filtering, as well as the frequencies of the filtering.
Eitherchannel’scircuitrycontainselectronicallybalancedinputcircuitryandbypassablelow-passandhigh-
pass circuitry. Each filter circuit has a four-pole (24 dB/octave) Linkwitz-Riley alignment and a “x10” range
switch. Figure 1 shows a block diagram of the UF-2.
(+) Input
(-) Input
Input
Differential
Amplifier
Programmable
Linkwitz-Riley
Low-Pass Filter
Optional
CD Horn
Boost
Programmable
Linkwitz-Riley
High-Pass Filter
Low-Pass Filter Bypass High-Pass Filter Bypass
Channel
Output
3-pin
jumper block 3-pin jumper block
1
2
3
1
2
3
Figure 1—Block diagram of UF-2 (1 of 2 channels shown)
UF-2 UNIVERSAL FILTER

2
III. PROGRAMMING THE UF-2
The UF-2 circuit board has four switches, six 3-pin headers, and four SIP resistor network sockets (see
Figure 2). All these are used for programming the module. The circuitry for the two channels is identical,
sotheswitches,headers,andsocketsaredividedbetweenthem:thosedesignatedbyathree-digitnumber
startingina“1”(switchesS101andS102;headersJ101,J102,andJ103;andSIPresistornetworksockets
RN102andRN104)areforChannel1,whilethosewithathree-digitnumberstartingina“2”areforChannel
2. The following instructions will use an “x”in place of the first digit, except where a specific channel
reference is necessary.
RN102 RN104 RN204 RN202
S101 S102 S202 S201
J101 J102
J103
J202 J201
J203
Figure 2—UF-2 Circuit board switch, jumper and resistor network locations
Notes on Stereo, Bridged, or Parallel Operation
The input board or accessory on which the UF-2 is installed has provisions—switches or headers—for
setting the operating mode of the amplifier, i.e., stereo, parallel-mono, or bridged-mono. In the signal flow,
theMini-Slotaccessoryislocatedsomewhere after these switchesorheaders,soyoumustconfigureboth
channels of the UF-2 accordingly, regardless of the operating mode selected. Usually you would use
identicalsettingson both channelsin stereo orparallelmode, depending ontheapplication. If theamplifier
is in bridged mode, bypass Ch. 2 of the UF-2 and use the Ch.1 input and processing only.
Bypassing the Filtering
Tocompletely bypass thefilteringcircuitryofachannel,setthejumperson bothJx01andJx02acrosspins
1and2, which aretheupper two pinsontheir headers(seeFigure3). Note:Ifyou neglect toplacejumpers
on either header, no signal will pass on that channel.
1
2
3
1
2
3
Pins 1 & 2
shorted together
Pins 2 & 3
shorted together
1
2
3
Figure 3—Jumper positions
Programming the Low-Pass Filter
Tousethe low-passfilter,set the jumperon Jx01 acrosspins2 and3,which are thelower two pinsontheir
header.If, however,you do not wish to use the low-pass filter and wantto bypassit instead,set thejumper
across pins 1 and 2.

3
Tosetthecornerfrequency(atwhichtheoutputis6dBdown)ofthelow-passfilter,choosetheappropriate
value and switch setting for RNx02 and Sx01, respectively. (Sx01 is a “x10”range switch. In its upper
position,thefrequencyrangeisx10,intheloweritisx1.)Usethetablebelowtoselecttherightcombination.
Sx01 = x1
80 Hz
100 Hz
120 Hz
160 Hz
200 Hz
250 Hz
500 Hz
800 Hz
1600 Hz
2000 Hz
Sx01 = x10
800 Hz
1000 Hz
1200 Hz
1600 Hz
2000 Hz
2500 Hz
5000 Hz
8000 Hz
16000 Hz
20000 Hz
RNx02
120K
82K
68K
56K
47K
33K
18K
12K
5.6K
4.7K
Ifthereisaresistor network already installedinthesocket,carefullypull it straight out.Insertthepinsofthe
newresistornetworkintothesocketholesandcarefullypressthenetworkintothesocket.Becarefultoavoid
bending the pins of the resistor network. Orientation of the resistor network is unimportant, as long as all
eight pins are well seated in the socket.
Programming the High-Pass Filter and CD Horn Equalization
Touseeitherthehigh-passfilterortheconstant-directivityhornequalization,orboth,setthejumperonJx02
acrosspins2and 3, whicharethelower two pinsontheirheader. If, however,youdonot wish touseeither
one and want to bypass them instead, set the jumper across pins 1 and 2.
Tosetthecornerfrequency(atwhichtheoutputis6dBdown)ofthehigh-passfilter,choosetheappropriate
value and switch setting for RNx04 and Sx02, respectively. (Sx02 is a “x10”range switch. In its upper
position,thefrequencyrangeisx10,intheloweritisx1.)Usethetablebelowtoselecttherightcombination.
Sx02 = x1
20 Hz
30 Hz
40 Hz
50 Hz
80 Hz
100 Hz
120 Hz
150 Hz
200 Hz
400 Hz
500 Hz
800 Hz
Sx02 = x10
200 Hz
300 Hz
400 Hz
500 Hz
800 Hz
1000 Hz
1200 Hz
1500 Hz
2000 Hz
4000 Hz
5000 Hz
8000 Hz
RNx04
120K
82K
56K
47K
27K
22K
20K
15K
12K
5.6K
4.7K
2.7K
Ifthereisaresistor network already installedinthesocket,carefullypull it straight out.Insertthepinsofthe
newresistornetworkintothesocketholesandcarefullypressthenetworkintothesocket.Becarefultoavoid
bending the pins of the resistor network. Orientation of the resistor network is unimportant, as long as all
eight pins are well seated in the socket.

4
Inadditiontoenablingthehigh-passfilteratJx02,ifyouoptforCDhornequalizationyoumustplaceajumper
at Jx03 as well. The UF-2 offers two equalization curves for CD horn correction: one with +6 dB of boost
at 20 kHz (place the jumper across pins 1 and 2 of Jx03), and one with +10 dB of boost at 20 kHz (place
the jumper across pins 2 and 3). If you do not place a jumper in one position or the other, the CD horn
equalization circuit will be inactive.
The table below is a summary of jumper settings for the UF-2.
IV. TYPICAL APPLICATIONS
Subsonic Filter
Subsonic filters are commonly used in sound installations to filter out rumbles and other inaudible or
unwanted low frequency signals and to protect speaker drivers. Vented speaker enclosures in particular
often exhibit a phenomenon in which the acoustical damping on the driver(s) drops at extremely low
frequenciesbelowtheirown resonant frequency.Ina situation likethis,asubsonic filter willhelptoprevent
damage from over-excursion of the speaker cone.
Program settings:
1. Set the jumper on Jx01 to bypass the low-pass
filter (across pins 1 and 2).
2. Set the jumper on Jx02 to enable the high-pass
filter (across pins 2 and 3).
3. No jumper on Jx03.
4. InsertaresistornetworkinRNx04thatisappropri-
ateto the desired roll-off frequency—typically20,
30, 40, or 50 Hz.
Typ. 20–50 Hz
Subsonic roll-off
Figure 4—UF-2 as a subsonic filter
2&1sniP3&2sniPenoN
noitcnuFredaeH
:1lennahC
ssap-wolssapyB101JX
ssap-wolelbanE101JX
ssap-hgihssapyB201JX
ssap-hgihelbanE201JX
tsoobnrohDCelbasiD301JX
zHk02@Bd6+,tsoobnrohDC301JX
zHk02@Bd01+,tsoobnrohDC301JX
:2lennahC
ssap-wolssapyB102JX
ssap-wolelbanE102JX
ssap-hgihssapyB202JX
ssap-hgihelbanE202JX
tsoobnrohDCelbasiD302JX
zHk02@Bd6+,tsoobnrohDC302JX
zHk02@Bd01+,tsoobnrohDC302JX

5
Ultrasonic Filter
An ultrasonic filter is useful for minimizing RF interference, oscillations, leakage or aliasing from digital
devices, and other signals that are too high in pitch to hear but may wreak havoc in an amplifier system.
Program settings:
1. Set the jumper on Jx01 to enable the low-pass
filter (across pins 2 and 3).
2. Set the jumper on Jx02 to bypass the high-pass
filter (across pins 1 and 2).
3. InsertaresistornetworkinRNx02thatisappropri-
ate to the desired roll-off frequency—typically 16
or 20 kHz.
Bandpass Filter
A bandpass filter may be useful if the speaker system driven by the amplifier has a limited bandwidth.
Minimizing the out-of-the-passband energy may result in reduced distortion and better intelligibility.
Program settings:
1. Set the jumper on Jx01 to enable the low-pass filter (across pins 2 and 3).
2. Set the jumper on Jx02 to enable the high-pass filter (across pins 2 and 3).
3. No jumper on Jx03.
4. Insert a resistor network in RNx04 that corresponds to the lower limit of the desired
frequency passband.
5. Insert a resistor network in RNx02 that corresponds to the upper limit of the desired
frequency passband. This frequency must be higher than the one selected for the
previous step.
CD Horn Equalization Filter
A constant-directivity horn requires a 6 dB per octave high-frequency boost from about 3.5 kHz to provide
aflat frequencyresponse. Onthe UF2you must use the CD horn equalizationin conjunctionwith thehigh-
pass filter.
Program settings:
1. Set the jumper on Jx01 to bypass the low-pass filter (across pins 1 and 2).
2. Set the jumper on Jx02 to enable the high-pass filter (across pins 2 and 3).
3. Set the jumper on Jx03 to select the EQ curve you desire: across pins 1 and 2 for +6 dB
at 20 kHz, or across pins 2 and 3 for +10 dB at 20 kHz.
4. InsertaresistornetworkinRNx04thatcorrespondstothedesiredlow-frequencyroll-off.
Typ. 16–20 kHz
Ultrasonic roll-off
Figure 5—UF-2 as an ultrasonic filter

6
Subsonic Filter with CD Horn EQ
Use settings 1, 2, and 4 from the Subsonic Filter, and setting 3 from the CD Horn Equalization Filter. This
would be suitable only if the loudspeaker system uses passive crossovers.
CD Horn boost
Subsonic roll-off
Figure 6—UF-2 as a subsonic filter with CD horn EQ
Subsonic and Ultrasonic Filter
Use settings 2, 3, and 4 from the Subsonic Filter along with 2 and 3 from the Ultrasonic filter.
Typ.
20–50 Hz
Typ. 16–
20 kHz
Figure 7—UF-2 as a subsonic and ultrasonic filter
2-Way Active Crossover
This configuration routes the frequencies below a particular frequency to amplifier Channel 1, which shall
drive the low-frequency speakers, and the frequencies above to Channel 2, which shall drive the high-
frequency speakers. Using the UF-2 as a crossover requires that you drive both amplifier inputs with the
same full-band signal.
Fc
Channel 2
Channel 1
Amp
HF Driver
LF Driver
Channel 2
Channel 1
SPA-2
Figure 8—UF-2 as a 2-way active crossover

7
Program settings:
1. On the input module, set the amplifier mode to parallel. Alternately, you could use a Y-
cable to provide the same signal to both channel inputs.
Steps 2 through 5 configure Channel 1.
2. Jumper J101 to enable Channel 1’s low-pass filter (across pins 2 and 3).
3. No jumper on J103.
4. Insert a resistor network into RN102 that is appropriate to the desired crossover
frequency.
5. Ifyouneedsubsonicfiltering,setajumperonJ102toenableChannel1’shigh-passfilter
(across pins 2 and 3) and insert a resistor network into RN104 that corresponds to the
roll-offfrequencyyoudesire.Ifyoudonotwantsubsonicfiltering,setJ102tobypassthe
high-pass filter (across pins 1 and 2).
Steps 6 through 9 configure Channel 2.
6. Set J202 to enable Channel 2’s high-pass filter.
7. Insert a resistor network into RN204 that is appropriate to the crossover frequency you
set in #4.
8. If you need equalization for a constant-directivity horn, set a jumper on J203 for the
amount of boost you need. If you do not want CD horn equalization, do not place any
jumper on J203.
9. Ifyouneedultrasonicfiltering,setajumperonJ201toenableChannel2’slow-passfilter
(across pins 2 and 3) and insert a resistor network into RN202 that corresponds to the
desired roll-off frequency. If you do not want any ultrasonic filtering, set the jumper on
J201 to bypass the low-pass filter (across pins 1 and 2).
Multi-way Crossover System
The UF-2 allows you to set up 3- and even 4-way systems. Of course, this also requires that you use more
than one amplifier and more than one UF-2. The other basic requirement of using the UF-2 as a crossover
is that you must feed each amplifier with the same full-range signal and use the UF-2 to filter the signals
in the individual channels.
Figure8depictsanexampleofa4-waysystem.Becauseofthemultitudeofpossiblesystemconfigurations,
the fundamentals of the technique used in the example will be explained below, with a few specifics. The
actual crossover frequencies you should use will depend on your speaker system.

8
Ch. 2
Ch. 1
UF-2
EX4000
(stereo mode)
Ch. 2
Ch. 1
UF-2
EX2500
(parallel mode)
Ch. 2
Ch. 1
UF-2
EX4000
(bridged mode)
Ch. 1:
Ch. 2 LP @ 150 Hz; HP @ 20 Hz Bypassed
UF-2: Subwoofer
Ch. 1:
Ch. 2 LP @ 1000 Hz; HP @ 150 Hz LP @ 1000 Hz; HP @ 150 Hz
UF-2: Woofers
Ch. 1:
Ch. 2 LP @ 5 kHz; HP @ 1000 Hz LP @ 20 kHz; HP @ 5 kHz
UF-2: Mids & Highs
Subwoofer
Thesubwoofersubsystemin the example is driven
byabridgedamplifier.Channel1oftheUF-2inthis
amplifierissetwiththehigh-passfilter at 20 Hz (for
subsonic filtering) and the low-pass at 150 Hz,
which is the crossover point to the woofers. Chan-
nel 2 of the UF-2 is bypassed.
Woofer
Thewoofersaredrivenbyanamplifier operating in
theparallelmode.BothchannelsofitsUF-2areset
with the high-pass filter at 150 Hz (the crossover
pointfromthesubwoofers)andthelow-passfilterat
1 kHz.
Midrange and High Frequencies
The remaining speakers are driven by the same
amplifier: the mids by channel 1, and the highs by
channel 2. The settings for channel 1 of the UF-2
are: high-pass at 1 kHz (the crossover from the
woofers) and low-pass at 5 kHz (the crossover
point to the high-frequency drivers).
Channel2ofthe UF-2 issetforhigh-passat 5 kHz.
For ultrasonic protection, the low-pass is set at 20
kHz.
Figure 9—Multiple amplifiers with UF-2s,
set up for 4-way crossover operation
V. INSTALLATION
InstallingtheUF-2requiresPCboardsolderingskills,soonlyqualifiedservicetechniciansshouldattempt
it. Any authorized QSC service center—or, for an additional installation fee, the QSC factory service
center—can perform the installation.
TheUF-2installsontheamplifierinputPCboardofanyQSCEXSeriesamplifier.SomeolderEXamplifiers
may require an upgrade to the current input board. Contact the QSC Service Department for details on
compatibility with older EX amplifiers.
Wheninstalled,theUF-2settingsandadjustmentsarenotexternallyadjustable;thiscanpreventtampering
by unauthorized users.
Tools and materials you will need:
Soldering iron
Desoldering iron or other suitable desoldering equipment
Phillips screwdriver
Wire cutters
Rosin-core solder
Do not use desoldering braid because it may damage the Mini-Slot socket solder pads on the input board,
and it also might not adequately remove solder.

9
The UF-2 contains active components which can be damaged by electrostatic discharge (ESD). Be sure
to practice standard ESD precautions and always ground yourself and your workstation before handling
exposed circuit cards.
CAUTION: Preparing the input board for installation of the UF-2 involves removing
solderfromfeed-throughholesonatwo-sidedcircuitcard.Excessiveheatcaneasily
damage the solder pads you will be working on. Proper equipment and experience
with desoldering delicate PC board circuitry is essential to successfully perform the
following procedure. Please contact the QSC Customer Service Department if you
feel you might not be qualified to perform the installation yourself. One last warning:
damage caused by an improper installation will void the warranty.
Before you start any work, turn off the amplifier power switch and disconnect the AC power cord from the
AC source. Disconnect all cables from the amplifier’s input panel.
Position the amplifier so the rear of the chassis is facing you. The input panel is located on the left side of
the rear panel. See Figure 10.
Begin the installation by locating and removing the screws securing both the upper blank and lower input
panelstotherearsideofthechassis(twoscrewsoneachminipanel).SeeFigure10.Theupperblankpanel
will simply drop off when its screws are removed.
Gently pull the lower input panel out from the amplifier. Once it is removed, you will notice a ribbon cable
connecting the input PC board to the amplifier. Disengage the locking wing clamps on the ribbon header
and carefully remove the ribbon head from the socket on the board. Now the input panel assembly is
completely free from the amplifier. See Figure 11.
Next, desolder and remove the wire jumper pairs W305/W306 and W405/W406 (W303/W304 and W403/
W404onMXaSeriesamplifiers).Underwherethejumperswerearetworowsofsolderpadholes,onewith
10 holes and another with 12. These are the Mini-Slot “sockets.”See Figure 11.
Figure 10
Figure 11
CH1
CH2
CH1
CH2
BRIDGE
MONO
BRIDGE
MONO
LOW IMPEDANCE
LOW IMPEDANCE
DIR. OUTPUT
DIR. OUTPUT
ISOL.OUTPUT
ISOL.OUTPUT
AUDIO TRANSFORMER
AUDIO TRANSFORMER
70V
70V
25V
25V
100V
100V
070100
070100
00
-dB -dB
10 10
88
66
44
22
24 24
18 18
14 14
STEREO
12 12
CH2 INPUT CH1
CH2 CH1
PARALLEL BRIDGE LEVELLEVEL
GROUND
INPUT
Input card