Orban 622B User manual

622 Parametric Equalizer
OPERATING MANUAL

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Performance Specifications
Specifications apply to each channel
except as noted. All specifications apply
when equalizer drives 600 ohm or higher
impedances. All noise specifications
assume a20-20,000 Hz bandpass filter
with 18 dB/octave Butterworth skirts.
Operating Controls: EQUALIZATION,
EQUALIZATION IN/OUT, BAND
WIDTH, and TUNING for each of four
bands. MASTER EQUALIZATION
IN/OUT, GAIN, POWER ON/OFF.
Frequency Response: (EQ controls set
mechanically flat) ±0.25 dB, 20-20,000 Hz.
Available Gain: +12 dB, adjustable to -oo
by means of front-panel GAIN control.
Input: (RF suppressed)
Impedance: (each leg) 100K in parallel
with lOOOpF, electronically balanced.
Driving impedance should be 600
ohms or less.
Absolute Overload Point: +26dBm.
Output: (RF suppressed)
Level: greater than +19 dBm into 600
ohms, 20-20,000 Hz
Impedance: 47 ohms in parallel with
lOOOpF, unbalanced. (Option 01
provides atransformer-balanced
output for both channels)
Equalizer is unconditionally stable and
will not ring with any captive load.
Risetime: less than 4microseconds.
Slew Rate: greater than 6V/microsecond.
Internal bandlimiting assures that slew
rate limiting will not occur with even the
most severe equalization and program
material.
Square Wave Response: Square wave
exhibits no spurious ringing at any output
level. The only ringing observable is that
theoretically associated with any given
equalization curve.
Circuitry: active RC, utilizing FET-input
IC opamps. The output line driver utilizes a
discrete transistor current booster.
Total Harmonic Distortion (+ 18 dBm
output): less than 0.025%, 20-20,000 Hz.
Typically less than 0.002% at 1kHz, +18
dBm.
SMPTE Intermodulation Distortion:
Typically 0.008% at +18 dBm equivalent
peak output, using 60 Hz/7 kHz; 4:1.
Noise: At Output, GAIN control adjusted
for unity gain, all EQ switches IN, all EQ
controls FLAT: Less than -84 dBm;
-87 dBm typical.
Overload-to-noise Ratio of Single
Parametric Bandpass Filter: greater
than 102 dB for any combination of
TUNING and BANDWIDTH settings.
Interchannel Crosstalk, 622B dual-
channel equalizer: less than -90 dB,
20-20,000 Hz.
Equalization Characteristics: Figure 1
shows curves corresponding to the
maximum and minimum bandwidths for
each band. DB equalization contributions
of the individual bands add without inter-
action. BANDWIDTH, TUNING, and
EQUALIZATION controls are all contin-
uously variable.
Range of Adjustment of “Q”: 0.29 to 3.2.
Range of Adjustment of Peak Equal-
ization: +16 dB to -oo .Typical notch
depth obtainable is 40 dB.
Tuning Range (per band): 20-500 Hz,
68-1700 Hz, 240-5850 Hz, 800-20,000 Hz.
Tuning dials are calibrated at ISO preferred
frequencies.
Power Requirements: 115/230 volt 50-60
Hz AC, approximately 4watts (622A), 7
watts (622B). Captive “U-Ground” power
cord. Option 02 eliminates the AC power
supply. Power requirements for the Option
02 version are ±18 to 28 volts DC at
60 ma per equalizer channel. Option 02 is
supplied on special order only, and is
recommended only for users planning to
install alarge number of 622 channels
in agiven installation.
Overload Lamp: will light for approxi-
mately 200 mS if the instantaneous peak
output of any amplifier in the equalizer
is driven within 1dB of its clipping point.
Size: 19" (48.3 cm) wide x3.5" (8.9 cm)
high x 5.2" (13.3 cm) deep.
Shipping Weight: 10 lbs. (4.5 kg).
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1525 Alvarado Street. San Leandro, CA 94577 USA
Phone: [phone]; Fax: [phone]; E-Mail: [email protected]; Site: www.orban.com
P/N: 95013.000.10

Table of Contents
Specifications
Registration Card ^
Warranty 13
Is
IPart A: Installation and Operation
IIntroduction
1Performance Highlights
2Front Panel Description '
°
2Rear Panel Description
3AC Power
3Mechanical Installation
Balanced Output Tranformer Installation
4Electrical Installation
Input
Output ^
Wiring With Two-Conductor Shielded Cable
Grounding Diagram
Typical Input/Output Connection Rules
6OPERATING INSTRUCTIONS
Using the EQ Section
Boost/Cut Curve Familes
Headroom
Part C: Maintenance
Introduction
Performance Evaluation and Alignment
General
Power Supply
Signal Processing Circuitry
Maintenance and Service
Preventive Maintenance
Control Replacement
Replacement of Components on Printed Circuit Boards
Troubleshooting 1C Opamps
Factory Service
Shipping Instructions
Circuit Description
General
Input Buffer
Equalizer Sections
EQ IN/OUT Switch
Overload Indicator
Output Buffer
Power Supply
8Part B: Specific Applications 24 Appendix: Interconnections And Grounding
8Stereo
9Sound Reinforcement
House Tuning
Notch Filtering
Stage Monitors
Individual Driver Equalizer
10 Dance Bars
IIRecording Studios
I I Motion Picture Sound
12 Broadcasting
12 Electronic Music
24 Driving the Input From High-Impedance And/Or High-
Level Sources
24 Grounding
26 PARTS LIST
30 PARTS LOCATOR
31 SCHEMATIC

REGISTRATION The original purchaser should have received apostpaid Registration Card packed
CARD with this manual.
Registration is of benefit to you because it enables us to tell you of new
applications, possible performance improvements, service aids, etc., which may be
developed over the life of the product. It also provides us with the date of sale so
that we may more promptly respond to possible claims under Warranty in the
future (without having to request acopy of your Bill of Sale or other proof of
purchase).
Please fill in the Registration Card and return it to us.
If the Registration Card has become lost or you have purchased the unit used,
please photocopy the image of the card reproduced below and send it to us in an
envelope. Use the address shown on the title page.
Model #Serial #
Name or Title
Organization
Street
City/State/Country
Zip or Mail Code .
Purchased from City Date of Purchase
Nature of your application
How did you hear about it?
Comments:
Fig. I: REGISTRATION CARD
WARRANTY The Warranty, which applies only to the first end-user of record, is stated on the
Warranty Certificate on aseparate sheet packed with this manual. Save it for
future reference.
Details on obtaining factory service are provided in Part C.

Part A: Installation and Operation
INTRODUCTION The Orban 622A/B are parametric equalizers of high professional quality. The
622A is asingle-channel equalizer; the 622B is adual-channel equalizer. Each
channel contains four parametric equalization bands.
Isolation of the two channels in the 622B is extremely high (greater than -90dB,
20-20, 000Hz). Therefore, each channel may be used independently without danger of
audible crosstalk.
The 622 is equipped with rotary-type EQ controls providing up to lodB of boost
and better than 40dB of cut. The controls are non-reciprocal, providing musically
useful "constant-Q" characteristics, and permitting the equalizer to be used as a
notch filter. The center frequency and bandwidth of each band are continuously
variable to enable precise control of the audio spectrum.
Each channel of the 622 has an electronically-balanced bridging input and an
unbalanced output which can be balanced by the addition of an optional output
transformer. Input, output, and power line connections all contain effective RF
filtering. l2dB of gain is available. Aj| potential overload points in the equalizer
are monitored by an extremely fast "peak -stretching" overload detector, so that
peak clipping can be detected and corrected before it becomes audible.
The flexibility offered by the 622 makes it aparticularly powerful tool in nearly
all areas of audio: sound reinforcement, public address, recording studio,
broadcasting, motion picture sound, dance bars (discos), theater...
The 622 easily meets the quality, performance, and reliability requirements of the
demanding professional, and is also well-suited for use in semi-pro or audiophile
applications.
The controls and features of the 622 are fully described in this manual. It will
familiarize you with the unit's potential and enable you to imaginatively use the
622 for your specific installation and application.
PERFORMANCE
HIGHLIGHTS EQ Section
Four bands, each with TUNING and BANDWIDTH control
True parametric operation: non-interacting control over all three equalization
parameters
+l6dB, -infinity equalization range
"Constant-Q" curves
Each band tunes over 25: 1frequency range
"Q" is variable between 0.29 and 3.2
Bands are totally non-interacting
In/out switches for each equalizer band

Circuitry highly resistant to performance deterioration caused by control wear
FRONT PANEL
DESCRIPTION
REAR PANEL
DESCRIPTION
General
l2dB available gain
Very low noise and distortion
High slew rate for minimum TIM (SID)
"Peak-stretching” overload lamp warns of clipping anywhere in equalizer before
distortion is audible
Industrial-grade parts and construction
Extremely easy service access
RFI suppression on input, output, and power leads
Balanced output optional (order retrofit kit as required)
The INPUT control adjusts the drive level to the equalizers.
The OVERLOAD indicator monitors all critical points to warn of excessive signal
amplitude due to excessive input amplitude or to large amounts of peak boost
equalization. It indicates peak clipping substantially before any audible effects are
perceived. Overloads are eliminated by turning down the INPUT control.
The CHANNEL EQ IN/OUT switch defeats the entire EQ section, but retains the
input buffer and output amplifier so that no gain changes (other than those
associated with large amounts of equalization) occur. In the OUT position, the
OVERLOAD LAMP will still operate as if full equalization were occurring.
Input/output polarity is constant regardless of the position of this switch.
The BAND EQ IN/OUT switches defeat the equalization action of agiven
equalizer band by disconnecting the output of the bandpass resonator from its
summing amplifier. Putting unused bands in the OUT position will eliminate any
noise contribution from the resonators and will assure accurate flat response.
The EQ controls adjust the maximum peak or dip in each band over arange of
+!6dB, -infinity dB.
The TUNING controls adjust the center frequency of each of the four bands, and
have atypical calibration accuracy of +1/3 octave.
The BANDWIDTH controls adjust the "Q" (sharpness) of each band. The "Q"
becomes broader when turned clockwise; sharper when turned counterclockwise.
Calibration tolerance is typically +10% of the nominal "Q" value.
The FUSE used in the 622 is a3AG slo-blo type: 1/8 amp for either I15V or
230V operation. Replace with the same type only.
The INPUT and OUTPUT connectors provided allow connection via barrier strip (//5
screw).
2

AC POWER The power transformer can be strapped for I15 volt or 230 volt 50 or 60Hz AC
operation. If the unit was ordered for 230 volts, a tag on the power cord warns of
the modification.
The two primary windings of the power transformer are connected in paral lei for
115 volt operation, and in series for 230 volt operation. (See the Schematic
Diagram at the back of this manual.)
To strap the power transformer for adifferent voltage, remove the top cover of
the 622. Strapping instructions are found on the insulating fishpaper around the
power tranformer. It is not necessary to rearrange the heavy insulated wiring; all
strapping can be performed with bare jumper wire. Take care not to burn the
insulation.
The power cord is terminated in a"U-Ground" plug to USA standards. The green
(or green/yellow) wire (which is connected to the long prong) is connected directly
to the 622 chassis. If it becomes necessary to lift this ground to suppress ground
loops, this should be done with athree-prong to two-prong adapter plug, rather
than by damaging the power plug. It is not recommended that this ground be
defeated unless absolutely necessary because it eliminates the intrinsic safety
feature of the three-wire system.
WARNING!
IF THE GROUND IS DEFEATED, CERTAIN FAULT CONDITIONS IN
THE UNIT OR THE SYSTEM TO WHICH IT IS CONNECTED CAN
RESULT IN APPEARANCE OF FULL LINE VOLTAGE BETWEEN
CHASSIS AND EARTH GROUND. SUCH VOLTAGE IS CAPABLE OF
CAUSING SEVERE INJURY OR DEATH!
MECHANICAL Vertical space of two standard rack units (3 l/2"/8.9cm) is required.
INSTALLATION Mounting the unit directly over large heat-producing devices like avacuum-tube
power amplifier may shorten component life and is not recommended. Ambient
temperature should not exceed 113 degrees F(45 degrees C) when equipment is
powered.
Balanced Output Transformer Installation: If transformers were not installed at
the factory, refer to the installation instructions furnished with the transformer
retrofit kit, available directly from Orban. The transformers supplied with this kit
have been designed to have anegligible effect on published specifications. Should
you wish to use some other transformers, it would be wise to make careful
performance measurements with special attention to LF distortion and HF response
at high output levels, thus determining the output level achievable with
performance acceptable for your application. Atransformer meeting Orban
standards should produce approximately +20dBm (limited by clipping in the output
amplifier) without significantly compromising performance.
The Electrical Installation section describes grounding procedures in the event
transformers are used.
3

ELECTRICAL Connecting the 622 Equalizer to other equipment is quite straightforward.
INSTALLATION Relatively uncomplicated systems (such as home playback systems, "semi-pro"
recording studios, electronic music studios, dance bars, etc.) tend to come together
without serious grounding problems even if the wiring practices are somewhat
casual, provided that high RF fields are not present. Unusual situations can be
analyzed if you are familiar with the standard rules governing grounding and
interfacing between balanced and unbalanced systems.
The instructions below will apply to the majority of cases. Acomprehensive
discussion of interconnections and grounding can be found in the Appendix.
Input
The electronically-balanced input of each channel of the 622 equalizer is
compatible with most professional and semi-professional sound equipment, balanced
or unbalanced, whose source impedance is 600 ohms or less. If it is greater (as in
some vacuum-tube audiophile preamps), aminor modification may be made to the
input to accomodate the situation. Please refer to the Appendix for further details.
Nominal input level is between -10 and +4dBm. The absolute overload point is
+26dBm.
Output
The two outputs of each channel of the 622 are unbalanced (unless fitted with the
optional transformers), and the source impedance is 47 ohms in parallel with lOOOpF
to the chassis (for RFI suppression).
Wiring the 622 With Two-Conductor Shielded Cable
We recommend wiring with two-conductor shielded cable (such as Belden 8451 or
equivalent) because signal current flows through the two conductors only. The shield
does not carry signal, is used only for shielding, and is ordinarily connected to
ground at one end only. The following table and diagram are applicable to agreat
majority of installations.
4

TABLE I:
TYPICAL INPUT/OUTPUT CONNECTION RULES
INPUT
Always use "+" and as the two input terminals to the 622.
When the 622 is driven from an unbalanced source, connect shield both to
circuit ground of source, and to chassis ground of 622.
When the 622 is driven from abalanced source, connect shield at source end
to chassis ground. Do not connect shield at 622 end.
OUTPUT
On the 622 output, connect shield at 622 end to chassis ground (whether
driving balanced or unbalanced). Do not connect shield at other end.
When driving abalanced load, jumper circuit ground to chassis ground on 622
(on rear panel). When driving an unbalanced load, do not attach jumper.
622 chassis should always be earth-grounded (i.e. through third wire in power
cord or through rack.) For maximum protection from shock, float this ground
only as last resort.
If optional output transformer(s) are installed on 622, jumper the circuit
ground to chassis ground on the 622.
Because it is not always possible to determine if the pieces of equipment driving
or being driven by the 622 have their circuit grounds internally connected to their
chassis grounds (which are always connected to the ground prong of the AC line
cord), and because the use of the AC power line ground often introduces problems
because it can be noisy or otherwise imperfect, the wiring techniques in the
diagram are not universally applicable.
If you follow the diagram and hum or noise appears, don't be afraid to
experiment. If the noise sounds like alow-level crackling buzz, then probably there
isn't enough grounding. Try connecting the input of the 622 to achassis ground
terminal on the 622's barrier strip and see if the buzz goes away. You can also try
strapping the 622's chassis and circuit grounds together, and see if this helps.
Aground loop usually sounds like asmooth, steady hum rather than acrackly
buzz. If you have aground loop, you can often break it by disconnecting the
jumper between circuit and chassis grounds on the 622's rear-panel barrier strip. In
either case, think carefully about what is going on, and keep in mind the general
principle: one and only one circuit ground path should exist between each piece of
equipment! (Bear in mind that the circuit grounds of the two channels of a622B
are connected together internally, and could conceivably introduce aground loop if
you do not take this connection into account in planning your wiring.)
5

OPERATING The operating controls of the 622 have been configured to permit easy, intuitive
adjustment. The EQ and BANDWIDTH controls are concentric; the EQ control
protrudes further from the front panel. The TUNING control for each band is
located below its associated EQ and BANDWIDTH controls.
To provide best value, the 622 uses controls of high reliability but modest
calibration accuracy. Calibrations are approximate, and are intended primarily as
reference guides. Accurately defeating the equalization in agiven band is best done
with the BAND IN/OUT switch. When operating with narrow bandwidths, accurate
stereophonic matching of several 622 channels on the basis on panel calibrations
alone is impractical. However, if the BANDWIDTH controls are set on, or more
clockwise than, "5", then no problems will occur. (See the subsection on Stereo
Matching in Part Bfor matching instructions.)
Using the EQ Sections
To use the EQ section, switch the CHANNEL EQ section switch IN, and switch IN
the BAND EQ switch for each band you wish to use.
For those who have never used aParametric Equalizer before, the easiest way to
become familiar with the 622 is to center the TUNING controls, and adjust the
BANDWIDTH controls to "6". The 622 will now behave like an ordinary "four-knob"
console channel equalizer. Once you have gotten the "feel" of the 622 in this mode,
try experimenting with the TUNING and BANDWIDTH controls to see how they
affect the sound.
When you boost the EQ, discover the subtle shelving effects available from
broadband peaking (BANDWIDTH control close to full clockwise; EQ control
clockwise of "0"). Contrast this with the "ringy", colored quality of setting the
BANDWIDTH control toward narrow (ccw).
When you cut the EQ observe the effects you now achieve. Narrowband dips are
essentially inaudible, but permit suppressing sounds of fixed frequency (like hum),
typically better than 40dB in each band. (If the sound to be suppressed is rich in
harmonics, use one band per dominant harmonic.)
The EQ curves are not reciprocal: boost provides awider bandwidth than cut
because of the "Constant-Q" configuration of the equalizer. Experience has shown
this curve family to be more musically useful than the more common "reciprocal"
curves. The "Constant-Q" family also permits infinite-depth (in practice, greater
than 40dB) notches to be created which are highly useful for eliminating hum or
other interference of fixed pitch.
Specified "Q" range for any setting of the TUNING control is 0.29 to 3.2. When
varying the BANDWIDTH control, the peak gain remains constant while the skirts
of the curve vary.
Despite the non-reciprocal nature of the "Constant-Q" curves, agiven amount of
EQ (in recording atrack, for example) can be precisely cancelled later by passing
the track through the equalizer with all TUNING controls set as they were during
the original recording, with all EQ controls set equal but opposite to their original
settings, and with the BANDWIDTH controls readjusted (by ear) to provide acurve
which is reciprocal to the one used to make the recording. If aboost is to be
cancelled, use abroader "Q" setting (more clockwise); if acut is to be cancelled,
the converse is true. When the BANDWIDTH control is correctly adjusted, such a
curve will be precisely reciprocal to the original.
6

HZ
Fig. 3: CONSTANT-Q CURVE FAMILY
More boost or cut can be achieved by tuning adjacent bands to the same
frequency. Typically, -80dB of cut (which is seldom more useful than the -40dB cut
provided byasingle band), and +32dB of boost are then available. But beware of
overload and noise buildup when boosting!
While in the narrowband boost mode, aband's TUNING control can be continuously
swept to give asound similar to "phasing".
Notes On Headroom
The overload-to-noise ratio available from the 622 is typically l05dB, and depends
somewhat on the settings of the controls. To minimize audible noise while driving
power amplifiers, for example, the overload point of the 622 should be matched to
the overload point of the power amplifier. This is done by adjusting the INPUT
ATTENUATOR settings on the power amp(s) to make the amp(s) barely clip when a
sinewave input to the 622 is adjusted in level such that it just barely lights the
622 OVERLOAD lamp. Clipping in the amplifier may be detected by means of an
oscilloscope, power output meters, or other overload indicator, depending on the
amplifier used. This procedure assures minimum noise and distortion from the
622/power amp combination.
WARNING!
PRIOR TO TESTING, BE SURE THAT THE POWER AMP LOAD (SUCH
AS ALOUDSPEAKER) IS NOT DAMAGED BY FULL-POWER SINEWAVE.
IF YOU THINK THAT IT MIGHT BE, USE ADUMMY LOAD OR ATEST
SIGNAL WITH AHIGHER PEAK-TO-AVERAGE RATIO (LIKE PINK
NOISE LOWPASS FILTERED AT IKHZ) SO AS NOT TO BURN OUT
TWEETERS.
7

Part B: Specific Applications
This part of the manual provides very specific instructions and suggestions on how
to use the 622 in the fields of Sound Reinforcement, Recording Studios, Motion
Picture Sound, Broadcasting, Dance Bars, and provides comments on Electronic
Music. We recommend that anyone involved in pro audio (and certainly those
involved in its more eclectic aspects, such as Theater) read all the sections. The
applications information in each will undoubtedly provide much food for thought.
I: STEREO For broadband equalization (BANDWIDTH controls at or clockwise of "5"), no
difficulty should result when the channels are matched on the basis of panel
calibrations alone. In applications other than monitor tuning or sound reinforcement,
however, if any BANDWIDTH control is adjusted "narrowband" (i.e., 0through 5),
then test instruments should be used to assure matching between stereo channels,
assuring precise stereo imaging and accurate mono summing of the channels. (See
the section on Dance Bars below for a discussion of matching requirements in
monitor tuning and reinforcement applications.)
The following procedure assumes that both channels have been adjusted by ear to
achieve the desired equalization, and that both are adjusted identically with
reference to panel calibrations. One channel must be arbitrarily chosen as the
"reference", and the other channel's controls must then be slightly tweaked to
achieve aprecise instrument-match to this reference. This is most readily done by
the "differential method": the reference channel and the channel under adjustment
are swept out-of-phase, and their outputs are summed. The channel under
adjustment is tweaked to minimize the amplitude of the sum. This method is very
sensitive because it automatically indicates both phase and amplitude mismatches.
It is performed as follows:
1) Connect asinewave sweep generator with logarithmic sweep to the input of
the reference channel such that the hot output is connected to the reference
channel's (+) input, and its (-) input is grounded.
2) Connect another output from the sweep generator to the channel under
adjustment. Connect the hot output to this channel's (-) input; ground its (+)
input.
3) Sum the outputs of the two channels by connecting each (+) output to one
side of a22K 5% 1/4 watt carbon resistor (the value is not particularly
critical). Connect the other side of both resistors to the vertical input of an
oscilloscope.
4) Sweep the channels from 20-20,000Hz, and adjust the scope sensitivity to
easily see the swept component.
5) Switch aU IN/OUT switches on both channels OUT. Adjust the GAIN control
on the channel under adjustment to null the output observed on the scope.
6) Switch all IN/OUT switches IN (unless some of these switches are normally
out on the reference channel).
7) Slightly adjust the various controls on the channel under adjustment to
minimize the amplitude of the differential component as observed on the scope.
8

2: SOUND The 622 is aversatile sound reinforcement equalizer which can function as a
notch filter and broadband equalizer.
Man/ reinforcement systems are mono. In these installations, particularly powerful
results can be obtained by connecting both 622B channels in series .Atotal of
eight bands are then available for notch filtering or equalization.
House Tuning: In an economy installation, the 622B (with both channels connected
in series) can do asurprisingly effective job of tuning areinforcement system to a
room without the use of athird-octave filter set. Use three or four of the bands
in their narrowband notching mode (BANDWIDTH full counterclockwise) to notch
out the major ring modes. This is most effectively and safely done if there is a
limiter or compressor in the circuit before the power amplifier to prevent speaker
damage. Advance system gain until it feeds back at asingle frequency. Make sure
that the limiter is in gain reduction to protect the speakers. Estimate the
frequency of the feedback, and choose aband on the 622 which covers it. Turn the
BANDWIDTH control to broad,and turn the EQ control down to -infinity. Adjust
the TUNING control until the feedback changes frequency. Continue to adjust the
TUNING control until the feedback returns at its original frequency. Set the
TUNING control half-way between the two settings where the feedback was
observed to change frequency. Now reduce the BANDWIDTH to full CCW
(narrowband), and readjust the TUNING as necessary to keep the notch centered on
the ring frequency. Finally, turn the EQ control up toward "0" (or flat) until the
ring frequency reappears. Back off about 4dB, This will leave headroom so that the
ring frequency will not reappear when the system gain is increased when more ring
modes are tuned out later. This procedure may be repeated with the new ring
frequencies as they appear. Usually after the first four ring frequencies have been
eliminated, the "point of diminishing returns" is reached.
The remaining bands on the 622B are now available to perform broadband
equalization of the system. Use apink-noise generator and third-octave real-time
analyzer for most precise results. However, if your budget doesn't permit athird-
octave analyzer, use your ears. Fortunately, you only have four or five bands to
deal with —not awhole third-octave set!
Notch Filtering: If athird-octave filter set is available for broadband equalization,
the 622B may be used solely as a narrowband notch filter set to eliminate up to
eight ring modes. The notches obtainable are somewhat sharper than those created
by athird-octave equalizer.
Stage Monitors: The 622 is an effective stage monitor equalizer because of its
low cost per channel and notching capabilities. Follow the instructions in House
Tuning above.
Individual Driver Equalizer: Some practitioners have discovered that there are
substantial advantages to equalizing each driver in acomplex sound reinforcement
system with its own parametric equalizer. It is claimed that this is the best way
to correct for individual driver response anomalies without having the corrective
equalization affect other drivers.
9

If the 622 is used in this way, simply connect each channel of 622 equalization
between the appropriate output of the electronic crossover and the input of the
appropriate power amplifier. If phase reversal of an individual driver is necessary,
this can be accomplished either at the power amplifier output or at the 622 input
(exploiting the 622's balanced input feature.)
3: DANCE The sound generally desired in adance bar is one that will make the customers
BARS get out and boogie (or sit down and drink...). This usually implies a large bass boost
in the region of 40-80Hz, and asmaller amount of treble boost. The LF and HF
bands of the 622 can be employed for this purpose, leaving the remaining bands
available for "house tuning". In this case, we mean smoothing out midbass and
midrange acoustic response of the loudspeakers in the room.
The amount of bass boost is primarily limited not by subjective considerations but
by available amplifier power and loudspeaker bass power-handling capacity. For
maximum capability, bi-amping is recommended because the bass amplifier can be
clipped occasionally without causing obvious harshness. In this case, an external
electronic crossover is necessary.
In all cases, the setting of the 622 low frequency TUNING and BANDWIDTH
controls is quite critical in obtaining bass that is punchy, "tight", and sensual,
without being "boomy" (like "jukebox bass"). Correct settings will vary considerably
with loudspeaker type and room acoustics. In particular, satisfactory results cannot
be obtained with ahorn-loaded bass system with acutoff frequency above 40Hz.
Trying to boost bass below the cutoff frequency of the horn will cause severe
distortion and also has the potential of damaging the drivers.
We do not recommend that the D.J. be permitted to operate the 622 in the
course of his normal activities. The 622 should be adjusted once by the installing
contractor to the manager's specifications, and then locked up. If the D.J. is to be
provided with equalization, sufficient power to correct the sound of inadequate
records can be supplied by asimple 5-band graphic equalizer with more limited
range.
If the sound contractor has access to athird-octave real-time analyzer and pink-
noise source, these can be of substantial aid in adjusting the MLF and MHF bands
for flat acoustic response in the midbass and midrange. Coloration here is
undesirable, and can cause customer edginess. It can also interfere with
conversation. For the same reason, excessive treble boost should be avoided because
of its potential for subliminal irritation.
If athird-octave analyzer is available to monitor the acoustic response of the
system, it is not necessary or desirable to exactly match the channels in the
frequency range below 200Hz according to Stereo Matching above. This is because
different loudspeaker locations will ordinarily produce different bass balances ]n
the room unless the room has been acoustically designed and is symmetrical (like a
good recording studio control room). In adance bar, the chances of fhis occuring
are slight, to say the least!
It is quite acceptable to adjust the two 622 channels substantially differently
below 200Hz to smooth out standing waves, resonances, and the like. Above 200Hz,
equalization is much more useful in correcting the response of the loudspeaker than
in correcting room acoustics. If the loudspeakers are reasonably well-matched, the
equalizer channels should therefore be adjusted to also be well-matched above
10

200Hz. If the "A" and "B" channel curves differ greatly, this often results in the
system's being well-equalized at only one place in the room (where the measuring
microphone was located) at the expense of other locations which may have their
problems exaggerated!
4: RECORDING The 622 can be used in the recording studio just about anywhere that a
STUDIOS conventional equalizer is used. Most studios find at least two channels of patchable
Parametric Equalization to be invaluable in cleaning up "difficult" tracks that the
internal console equalizers can't handle.
If atrack is plagued by hum or other interference of fixed pitch, the 622 can be
used in its narrowband notching mode (BANDWIDTH full CCW; EQ at -infinity) to
substantially eliminate the sound with negligible effect upon desired program
material. The notching of each harmonic requires use of a separate band.
The 622 is capable of producing awide variety of special effects. Sweeping
wideband notches gives atrue "phasing" sound. Sweeping narrowband peaks gives a
different sound with asimilar flavor.
Telephone, transistor radio, and "old-time" recording effects are most easily
generated by adjusting the MLF and MHF bands close together in frequency (around
1.3kHz, for example). The BANDWIDTH controls are adjusted to give moderately
narrow bandwidths and both EQ controls are set for l6dB boost. This produces the
sound of aringy bandpass filter with approximately 12dB/octave slopes and gives
the distinctive sound desired. Authentic-sounding distortion can be generated by
overdriving the input of the 622 beyond the point where the OVERLOAD lamp
flashes.
The 622 can also be effectively employed as amonitor system equalizer,
particularly when athird-octave equalizer is too costly. See the Sound
Reinforcement section above.
5: MOTION PICTURE The 622 can be used to particular advantage as adialog equalizer because of its
SOUND many versatile features, such as:
1) Fine-tuning capability, allowing the mixer to obtain the best possible sound for
difficult or poorly-recorded location recordings;
2) Instant notch filtering which can reduce hum and camera whine;
3) Increase in flexibility when both 622B channels are cascaded to make asingle-
channel 8-band equalizer.
The scoring mixer can similarly benefit from the fine adjustability of the 622.
The 622 can be used to equalize the motion picture monitoring environment by
adjusting the "B" chain in the re-recording theater to the studio's accepted acoustic
response standard. The music scoring stage monitoring system can be similarly
adjusted.
Those interested in motion picture applications should also review the section on
Recording Studios immediately above.

6: BROADCASTING in AM, FM, and TV broadcasting applications, the integral RF suppression will
greatly facilitate installation of the 622. The optional output transformers are
particularly recommended for stations with studio and transmitter at the same site.
Normal precautions regarding grounding and shielding should be followed when the
622 is installed.
The 622 is invaluable in the production studio. It can be used to "sweeten"
records, and to equalize the announce microphone for maximum punch.
If sibilance is aproblem, the best solution is the use of an Orban Dynamic
Sibi lance Controller. If one is unavailable, tuning a622 band to 6kHz, adjusting the
BANDWIDTH close to approximately "5", and turning down the EQ control as
necessary will help control sibilance -- although at the expense of vocal presence.
Use of narrowband peaking, and sweeping can create some wild gimmicks.
However, be aware that excessive high frequency boost can saturate the 7.5ips tape
cartridges usually used. This can be avoided by following the 622 with the Orban
Stereo Compressor/Limiter, which assures clean carts under all EQ conditions.
The 622 can also be used to enhance the sound of telephone calls, remotes,
satellite feeds, shortwave broadcasts, and network feeds. The LF and HF bands may
be used in their shelving mode (both BANDWIDTHs at "10", LF TUNING at 20Hz
and HF TUNING at 20kHz) to remove out-of-band noise. Presence and intelligibility
can often be enhanced by boosts in the 4-5kHz region.
The 622 is amost effective phone line equalizer. Unlike simpler phone company
equalizers, the 622's flexibility can effectively deal with minor response "glitches".
In the main studio, the 622 can be used to notch out cart or tape machine motor
hum and ventilation system noise with minimal effect on voice quality. Use one
band for each major 60Hz harmonic, with BANDWIDTH control adjusted to "0".
The 622 may also be used in the AM program line to equalize the air sound, thus
partially compensating for the inadequacies of typical consumer AM radios. A
certain amount of high frequency boost is essential to counteract the extremely
rolled-off performance of such radios. However, extreme boosts can cause problems
with conventional compressors and limiters (such as severe pumping, "gulping" on
material with large amounts of high frequency energy, and audibly obvious de-
essing). Therefore, for ultimate performance, we recommend using the Orban
OPTIMOD-AM, which is acomplete signal processor including adjustable
equalization.
7: ELECTRONIC The 622 is ahighly valuable adjunct to any electronic music synthesizer. It is
MUSIC particularly useful as aformant filter, and can be used as a resonator to simulate
certain instrument body sounds. (If both channels of a622B are connected in series,
up to eight high "Q" resonances can be simulated.)
The synthesist will find the more extreme equalization settings to be particularly
useful in approaching live instrument sound and getting away from the raw sound of
typical synthesizer systems.
As this whole area is highly specialized, we will not explore it further. We suggest
that the beginner familiarize himself with the literature on musical instrument
physics.
12

Part C: Maintenance
Introduction: This part of the manual provides instructions on how to maintain the
622, how to make sure that it is working according to specifications, and how to
repair it if something goes wrong.
Factory service is available throughout the life of the 622. Please refer to
Factory Service subsection of MAINTENANCE AND SERVICE below for further
information.
1: PERFORMANCE General
EVALUATION This section provides aseries of thorough, definitive bench tests which will verify
whether or not the 622 is operating normally. Each band of the 622 has two
alignment controls which are adjusted at the same time that the performance
evaluation procedure is executed.
Power Supply
Equipment Required:
1) VTVM or DVM
2) Oscilloscope
The following tests will verify correct operation of the Power Supply:
1) Using the DC voltmeter, measure the voltage from circuit ground to both
positive and negative unrequ la ted supplies. This can be readily measured across
the two large filter capacitors. This voltage may be expected to vary widely
depending on line voltage; it should measure between +18 and +26 volts DC.
2) Measure the voltage between circuit ground and the outputs of the positive
and negative voltage regulators, IC70I and IC702. The supplies should put out
between +14.25 and +15.75 VDC. If either supply exceeds 15.75 VDC, it
implies that its associated 1C regulator is defective. If either supply is lower
than 14.25 VDC, refer to the Power Supply portion of Part 4in this section
for troubleshooting hints.
3) Using the oscilloscope, measure the ripple and noise on the regulated positive
and negative power busses. Ripple and noise should be less than 2mV peak on
each bus.
Signal Processing Circuitry
Equipment Required:
1) Oscilloscope with DC-coupled display
2) Audio sweep generator with sinewave output and logarithmic sweep (A
Tektronix 5L4N Low-Frequency Spectrum Analyzer in aTektronix 5111
Bistable Storage mainframe may be substituted for items (I) and (2).)
3) 20-20,000Hz bandpass filter, !8dB/octave slopes
4) VTVM or DVM
5) Harmonic distortion analyzer with built-in 400Hz and 80kHz filters and
residual THD below 0.0015%
6) Low-distortion oscillator with residual THD below 0.0015%
(A Sound Technology I700A or H-P 339 will satisfy (5) and (6))
For the following tests, a600 ohm load must be provided across each 622 output.
620 ohm 1/2 watt 5% carbon resistors are suitable.
PERFORMANCE
HIGHLIGHTS
13

IN THE CASE OF THE DUAL-CHANNEL 622B, THE TEST PROCEDURE BELOW
SHOULD BE FOLLOWED FROM BEGINNING TO END FOR CHANNEL "A", THEN
REPEATED FOR CHANNEL "B".
I) Signal Passage Test
a) Connect the high (+) side of the 622 main output to the input of the
harmonic distortion analyzer, and also to the vertical input of the
oscilloscope. Connect the ground side of the 622 to instrument ground.
b) Ground the (-) input of the 622 and connect the output of the low-distortion
oscillator to the (+) input of the 622.
c) Move a|| IN/OUT switches to OUT, and center all EQ controls.
d) Adjust the GAIN control clockwise, and verify that an undistorted sinewave
appears at the output.
e) Continue to advance the GAIN control until clipping is barely visible. Verify
that this clipping level exceeds +l9dBm for 20Hz, IkHz, and 20kHz input
signals.
f) Verify that the OVERLOAD lamp flashes at, or slightly below, the clipping
level at IkHz.
2) DC Offset
a) Disconnect the oscillator from the 622 input.
b) Move the CHANNEL IN/OUT switch to IN. Measure the DC voltage
appearing at the output of the 622. The voltage should not exceed 30mV DC.
3) Distortion and Inverting Operation
a) Ground the (+) input of the 622 and connect the low-distortion oscillator to
the (-) input of the 622. Adjust the oscillator to IkHz.
b) Center all operating controls, and move al] BAND IN/OUT switches to the
IN position.
c) Using the same procedure as in the Signal Passage Test above, verify that
the gain is the same as previously measured +0.3dB.
d) Apply a20kHz signal and adjust the output level of the oscillator and the
622's GAIN control until +l8dBm is observed at the 622 main output.
e) Measure the Total Harmonic Distortion, using the 400Hz and 80kHz filter on
the distortion meter. The THD should not exceed 0.025%.
f) Repeat at 20Hz; +l8dBm output; 400Hz filter OUT. The THD should not
exceed 0.025%.
4) Noise
a) Adjust the 622 GAIN control to produce unity input/output gain.
b) Switch OUT the 400Hz and 80kHz filters in the analyzer. Connect the
20-20,000Hz bandpass filter between the 622 output and the analyzer input.
c) Disconnect the oscillator from the 622, and connect both (+) and (-) 622
inputs to circuit ground.
d) Center all controls except for GAIN (adjusted in step (a)), and place all
IN/OUT switches IN.
e) Measure the noise at the main output of the 622. With the test setup as
described, it should not exceed -84dBm. If only the 80kHz filter internal to
the analyzer is available, the noise will measure somewhat higher.
5) HF, MHF, and MLF Equalizer Swept Response and Alignment
The following procedure should be performed in turn on the HF, MHF, and MLF
bands. The alignment procedure for the LF band is slightly different and is
described immediately below. As you perform the tests, be sure that the BAND
IN/OUT switches of the bands not under test are OUT. If the OVERLOAD lamp
flashes at any time, reduce the GAIN.
14

The procedure below specifically refers to the HF band. The procedure should be
repeated for the MHF and MLF bands by substituting the analogous controls for
each band as appropriate.
a) Connect the sweep generator output to the (+) input of the 622, and the
sweep generator ramp output to the horizontal input of the scope. Connect
the 622 output to the vertical input of the scope. Adjust the sweep generator
to produce a20-20,000Hz log sweep.
b) Switch the CHANNEL IN/OUT switch IN, and all BAND IN/OUT switches
OUT.
c) Adjust the 622 INPUT control for full-scale deflection on the scope screen.
d) Move the HF BAND IN/OUT switch to the IN position.
e) Adjust the HF EQ control to -infinity, and note that anotch appears in the
swept response.
f) Adjust the HF BANDWIDTH control throughout its range (from "0" to "10")
and note the change in the depth of the null. The null should remain constant
throughout the range. If null depth varies appreciably, adjust RI05 for
minimum change in null depth as the BANDWIDTH control is varied.
g) Adjust the HF BANDWIDTH control to "10" (broad) and verify that the null
is better than -25dB when the HF TUNING control is adjusted throughout its
entire range. If the null is less than -25dB, adjust RI25 for amaximum null
at all settings of the HF TUNING control.
NOTE:
It may be necessary to fine-tune RI05 as described in step (f)
above.
h) Repeat steps (d) through (g) for the MHF and MLF bands.
6) LF Band Test and Alignment
a) Connect the output of the low-distortion oscillator to the (+) input of the
622, and adjust the oscillator's frequency to 60Hz (50Hz if that is the mains
frequency in your country).
b) Switch the LF BAND IN/OUT switch IN, and all other BAND switches OUT.
c) Adjust the LF EQ control to -infinity.
d) Adjust the LF BANDWIDTH control to 10 (broad).
e) Adjust the LF TUNING control for maximum null. (Be as precise as possible).
f) Adjust the LF BANDWIDTH control throughout its range and note the change
in the depth of the null. The null should remain constant. If the null varies
appreciably, adjust R405 for aminimum change in the depth of the null.
g) Adjust the LF BANDWIDTH control to "0" (sharp), and verify that the null is
better than -25dB when the LF TUNING control is adjusted throughout its
range. If the null is less than -25dB, adjust R425 for best null at all settings
of the LF TUNING control.
NOTE:
It may be necessary to fine-tune R405 as described in step (f)
above.
7) Tuning Control Calibration Test and Alignment
a) Connect the output of the low-distortion oscillator to the (+) input of the
622.
b) Switch all BAND IN/OUT switches OUT except for the band being tested.
c) Adjust the EQ control on the band being tested to -infinity.
d) Adjust the TUNING control on the band being tested to approximately I
o'clock.
15

e) Adjust the oscillator frequency to the frequency appearing on the 622
TUNING dial calibration close to the Io'clock position.
f) Adjust the 622 TUNING control for anull in the 622 output level, indicating
that the position of the TUNING control corresponds to the oscillator
frequency set in step (e). If the TUNING control reads correctly, +1/3 octave,
go on to the next band and repeat steps (b) through (f) above. If the TUNING
knob is outside the +1/3 octave tolerance, loosen the TUNING knob and
readjust it until it reads the correct frequency. Retighten the TUNING knob
by alternately tightening its two Allen setscrews until both are tight.
2: MAINTENANCE Preventive Maintenance
AND SERVICE The front panel may be cleaned with amild household detergent. Stronger solvents
should be avoided, as they may damage the paint, the silk-screened lettering, or
the plastic control knobs.
The interior of the 622 should be kept free of dust and dirt, since dirt buildup
inside the chassis can cause loss of cooling and can also cause high-resistance
short-circuits if the dirt absorbs moisture from the air. It is particularly important
in adusty or humid environment that the covers be periodically removed and the
interior of the chassis cleaned.
Maintenance of Operating Controls
Anew parametric bandpass resonator was designed for the 622 which is essentially
immune to the effects of ordinary wear of the BANDWIDTH and TUNING controls.
Wear on the TUNING control is manifested almost completely as a slight change
in bandwidth as the TUNING control is operated. However, the available notch
depth is not compromised.
Wear on the BANDWIDTH control changes its calibration slightly, but does not
compromise notch depth.
Wear on the EQUALIZATION control (such that its total resistance is changed)
will compromise the notch depth. Therefore, with heavy use, we recommend
periodic alignment of RI25, 225, 325, 425, which will maximize the null depth when
the EQ controls are placed in their -infinity positions. Refer to section I
(PERFORMANCE EVALUATION AND ALIGNMENT), subsection 5(Equalizer Swept
Response and Alignment) for instructions.
The controls of the 622 are not hermetically sealed, and can therefore readily be
cleaned with acommercial spray-type contact cleaner if they become noisy. If a
replacement is needed, it should be ordered directly from Orban Associates, Inc.
(see section below on Factory Service), as the controls have no commercial
equivalents.
Replacement of Components on Printed Circuit Boards
It is important to use the correct technique for replacing components mounted on
PC boards. Failure to do so will result in possible circuit damage and/or
intermittent problems.
The circuit board used in the 622 Equalizer is of the double-sided plated-through
variety. This means that there are traces on both sides of the board, and that the
through-holes contain ametallic plating in order to conduct current through the
16