White Instruments 4100 User manual

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Model 4100
Two Channel
Active LC Octave Band Equalizer
NOTE: This document was reconstructed from the original printed Users' Manual.
Specifications: Models 4100, 41OORM.............................................................................2
ELECTRICAL ................................................................................................................2
MECHANICAL..............................................................................................................3
OPTIONS........................................................................................................................3
MODEL 4100 STEREO EQUALIZER USER'S MANUAL .............................................4
INTRODUCTION...........................................................................................................4
UNPACKING .................................................................................................................4
CONNECTION TO THE SYSTEM...................................................................................4
CONTROLS....................................................................................................................8
POWER ON-OFF: ......................................................................................................8
EQ IN-OUT:................................................................................................................8
LEVEL:.......................................................................................................................8
OVERLOAD:..............................................................................................................8
ACCESSORY SOCKET:............................................................................................9
ADJUSTMENT AND EQUALIZATION......................................................................9
BI-AMPLIFICATION ..................................................................................................11
OTHER APPLICATIONS............................................................................................12
CIRCUIT DESCRIPTION............................................................................................13
WARRANTY:...............................................................................................................18
Damage in Shipment:....................................................................................................18
Return Shipment: ..........................................................................................................18
Schematic Diagram:..........................................................................................................19

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Specifications: Models 4100, 41OORM
ELECTRICAL
CIRUITRY: 2 IC quad amplifiers, 2 IC regulators, 2
transistors, 2 zener diodes, 6 diodes, and 3
LED's. Precision-tuned inductors in all
negative feedback circuit, magnetically
shielded for low hum pickup.
OPERATING RANGE (FREQUENCY): 20 Hz (-3 dB) to 20 kHz (-1 dB).
CONTROL AANGE(FREGUENCY): Ten bands (each channel) on one octave
I.S.O. centers from 31.5 Hz to 16 kHz.
CONTROL RANGE (AMPLITUDE): -10 dB to +10 dB, continuously variable.
LOW-CUT CONTROL: 12 dB/octave active high-pass filter,
continuously variable from 20 Hz to 160
Hz.
GAIN: Unity gain with all controls in flat position.
Calibrated attenuator at input of each
channel for level setting.
OPERATING LEVEL (INPUT): 0 dBm (approximately 0.8 Vrms)
recommended.
MAXIMUM OUTPUT: +18 dBm with all controls in flat position.
OVERLOAD DETECTOR: Peak level detector set approximately 2 dB
below maximum peak output. LED
indicators.
DISTORTION (THD):
(IM):
Less than .08% at 0 dBm, worst case
control settings; less than 0.1% at
+18 d Bm.
Less than .004% (SMPTE).
NOISE: Better than -92 dBm (19 microvolts) over
20 kHz bandwidth.
DYNAMIC RANGE: 110 dB.
INPUT IMPEDANCE: Greater than 40 kilohms, single ended, AC
coupied.
OUTPUT IMPEDANCE: Approximately 100 ohms.
OUTPUT LOAD: 600 ohms or greater.
FREGUENCY TOLERANCE: ±6% of center frequency.

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POWER: 115/230 Vac nominal, 50-60 Hz. Fused for
1/2 am . Front anel ilot li ht.
MECHANICAL
CONTROLS: Rotary potentiometers, sealed MIL-SPEC
type. EQ IN-OUT switch, power switch.
CONNECTIONS: Standard phono type plus chassis ground
terminal.
DIMENSIONS: 18-1/2 inches by 6-3/4 inches by 3-1/2
inches (47 cm x 17.2 cm x 8.9 cm).
WEIGHT: 7-1/2 pounds (3.4 kg).
FINISH: Black anodized aluminum with solid
walnut trim.
SEGURITY COVER: Furnished with either standard table model
or with rack mount option.
OPTIONS
BI-AMP NETWORKS: Plug-in networks provide crossover
separation for bi-amp systems.
Order 4101-frequency for 12 dB/octave or
4102-frequency for 18 d8/octave.
RACK MOUNTING: Specify Model 4100 RM.
! W A R N I N G !
TO PREVENT FIRE OR SHOCK HAZARD
DO NOT EXPOSE THIS APPLIANCE TO
RAIN OR MOISTURE.

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MODEL 4100 STEREO EQUALIZER USER'S MANUAL
INTRODUCTION
Congratulations'. You have purchased the finest one octave stereo equalizer that money
can buy. White Instruments stands behind this product, as we do all products we
manufacture, in guaranteeing that the highest standards of quality and craftsmanship have
gone into the construction of your Model 4100 Stereo Equalizer. Properly installed, this
unit will provide you with years of trouble-free operation. Please read the instructions
carefully – by following them you will realize a standard in music reproduction that
previously could only be hoped for.
UNPACKING
Your Model 4100 Stereo Equalizer has been carefully packaged to minimize the
possibility of damage during shipment. When you receive your unit, unpack and carefully
inspect it. If there is any obvious damage, report it immediately to the dealer from whom
you purchased it or to the carrier who delivered it. Save all packing materials for
inspection by the dealer or carrier. As all products from White Instruments are shipped
F.O.B. Factory, we are not responsible for damage incurred during shipment; however,
we will assist you in obtaining rapid repairs or replacements.
Inside the plastic foam shipper you will find the following:
l. One Model 4100 Stereo Equalizer
2. One Security Cover
3. Two hi-fi stereo patch cables
4. One 3-wire line cord adaptor
5. One User's Manual
6. One set of hardware (if you ordered the 4100RM (rack mounting) unit)
We recommend you retain all packing materials in case the unit must be returned to your
local service center or the factory for repair.
CONNECTION TO THE SYSTEM
NOTE: Even if you do not like to read instructions, please read the section,
CONNECTION TO THE SYSTEM, to protect your investment in your music system. It is
possible to damage some high frequency loudspeakers or tweeters by excessively
boosting the upper portions of the spectrum.
The Model 4100 Stereo Equalizer is designed to be connected between your preamplifier
and your power amplifier. The instructions for doing this follow.
The input impedance of the Model 4100 is high – greater than 40,000 ohms. This means
that it will not appreciably "load" the output. circuit of modern high fidelity preamplifiers
and may be connected without consideration of impedance matching methods. The output

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impedance of the Model 4100 is very low – less than 100 ohms. The output stages are
capable of driving following circuit impedances as low as 600 ohms without exhibiting
any loading effects. Most high fidelity power amplifiers have input impedances of 50,000
ohms or greater and loading of the Model 4100's output circuit will not have to be
considered.
The average signal level between the preamplifier and the power amplifier at the loudest
volume setting you intend to use should be considered. The Model 4100 is capable of
putting out levels as high as +18 dBm (about 6.0 volts). If it happens that you have used
one of the cut/boost controls to boost a particular band by +10 dB, then the input signal
must not exceed +8 dBm or it is possible to overdrive the output circuit. To allow head
room for average program material, you do not want the average input level to exceed 0
dBm. However, there are these considerations: First, the average modern high fidelity
power amplifier is generally driven to full output by signals on the order of +8 dBm (2
volts) or less. Second, in the following explanations on equalization you will see that
most of your adjustment is done in the cut mode. We recommend that the average signal
level of the circuit into which the Model 4100 is inserted by between -20 dBm (.078
volts) and 0 dBm (0.78 volts) for the best head room and signal-to-noise considerations.
This will be easily achieved with practically all receivers or component systems.
In the event the maximum output level of the Model 4100 is approached, the
OVERLOAD lamp on the front panel will begin flashing at an output level of
approximately +16 dBm.
Insertion of the Model 4100 into your system is simple. In a RECEIVER or
INTEGRATED AMPLIFIER type system it is only necessary to remove the jumper
cables or plugs between the PREAMP OUT and the POMER AMP IN jacks on the rear
of the chassis (see Figure 1). The PREAMP OUT is connected via the supplied hi-fi patch
cable to the INPUT jacks on the rear of the Model 4100. Be sure to observe the order of
the left and right channel connections. OUT 1 (NORM) of the Model 4100 is then
patched back into the POWER AMP IN of the receiver, again observing the order of the
left and right channels.
A chassis grounding terminal is provided on the rear of the Model 4100. In some
instances it may be necessary to connect a wire from this terminal to a similar terminal on
your preamplifier or receiver. The internal circuit ground is not connected to the chassis
at any point.
To insert your Model 4100 into a component system, the same procedure is followed:
Connect the OUTPUT of the preamplifier to the INPUT of the Model 4100. The OUT 1
(NORM) of the Model 4100 then goes to the power amplifier INPUT (see Figure 2).
If you have purchased an optional BI-AMP CROSSOVER NETWORK (Type 4101-f or
4102-f ) with your Model 4100, you will use the following procedure: Connect the
INPUT to the Model 4100 as previously described. The OUT 1 (NORM) will be
connected to the pair of amplifiers associated with the LOW frequency speakers or
woofers. OUT 2 will be connected to the amplifiers associated with the HIGH frequency
speakers or horns (see Figure 3). CAUTION: Do NOT reverse OUT 1 and OUT 2 as this
will cause the LOW frequency signal to be fed into the HIGH frequency speakers or
horns and may damage or destroy them!

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NOTE: The EQ IN-OUT switch on the front panel does NOT switch the BI-AMP
crossover networks out of the circuit when in the OUT position; only the equalizing
portion of the Model 4100 is switched out, thus still enabling you to utilize the electronic
crossover portion of the system even though all of the equalization has been removed.
This allows you to "A-B" your bi-amped system without fear of putting low frequency
signals into delicate horns or tweeters.
CONTROLS
POWER ON-OFF:
This switch controls the power to the unit. The Model 4100 may be connected to the
switched power plugs provided on the rear of most receivers and preamplifiers. In this
manner, the POWER switch of the Model 4100 may be left in the ON position and the
unit controlled from the main switch of the system. A pilot lamp in the center of the front
panel indicates whether or not the unit is on.
EQ IN-OUT:
This switch inserts or removes the frequency shaping controls of the Model 4100 from
the system. This allows you to go from your "raw" or unequalized system to the
equalized system for comparison. This switch will not affect the bi-amp crossover
network if inserted in the rear accessory socket.
LEVEL:
The level controls are used when excessive signal levels are encountered which may
overdrive the Model 4100 or the following components in the system. By using these
calibrated attenuators which are at the input to the Model 4100, incoming signals may be
attenuated to a suitable level. These controls may also be used for balancing the system
after equalization to assure the system volume is the same in both the left and right
channels.
OVERLOAD:
These panel lamps indicate if the Model 4100 is driven by signals exceeding +16 dBm (5
volts). While the full output of the Model 4100 is +18 dBm, the indicating point of the
overload circuit is set about 2 dB below this level to warn the user he is approaching
overload conditions.
LOW CUT:
The LOW CUT controls are very important to the proper operation of your music
reproduction system. These controls vary the cutoff point of a 12 dB/octave high-pass
filter from 20 Hz to 160 Hz. By proper adjustment unwanted and distortion-causing low
frequency transients are kept from the power amplifier and speakers. (See curves in
CIRCUIT DESCRIPTION section.)

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OCTAVE BOOST/CUT:
These controls are the heart of your Model 4100 Stereo Equalizer. It is with these
controls that the electrical response of your system is adjusted to complement the
acoustics of the listening environment. Each of these controls is centered on an
International Standards Organization (I.S.O.) octave center from 31.5 Hz to 16 kHz. Each
control allows you to cut the signal level within its band by as much as 10 dB or to boost
it as much as 10 dB. With the control center at the 0 dB position the response in that band
is not affected. Most importantly, adjacent octaves are buffered from one another
electronically to minimize reactive tuning effects between channels. In addition, White
Instruments' unique all negative feedback circuitry gives mirror image response in both
the boost and cut modes for the utmost in control.
ACCESSORY SOCKET:
This socket on the rear of the Model 4100 chassis allows insertion of special bi-amp
crossover networks for sophisticated four-amplifier bi-amplified stereo systems. These
networks are available in either 12 dB/octave or 18 dB/octave slopes to match the
response of the system loudspeakers. Please note that for operation without a crossover
network inserted, jumpers must be inserted between pins 4 and 8, and pins 2 and 9. The
units are shipped from the factory with these jumpers installed.
ADJUSTMENT AND EQUALIZATION
Before beginning the adjustment of your Model 4100 Stereo Equalizer, the rest of your
music reproduction system must be in good order. Speaker placement is most important.
While there are no firm rules to follow in this regard, it will at least be assumed that the
speakers are located to give adequate coverage to the listening area. To begin the
equalization process, set the OCTAVE BOOST/CUT controls of the Model 4100 to the
FLAT or 0 dB position. The LOW CUT control should be set to the lowest frequency
(extreme counterclockwise) position. The EQ IN-OUT switch should be in the IN
position. LEVEL controls should be set at their 0 dB positions unless attenuation is
necessary to prevent overloading.
To properly adjust the Model 4100, equipment capable of making acoustic measurements
is necessary. The preferred method utilizes a REAL TINE ANALYZER. To carry out the
following procedure utilizing a real time analyzer, we suggest you consult with your
equipment dealer or high fidelity consultant for either rental of the necessary equipment
or the hiring of his services in assisting you in installing your equalizer.
Since all high quality components of a sound reproduction system will faithfully
reproduce the program material fed through them, it follows that equalization is
principally for the part of the system that is not under full control -- the room in which
you will listen.
In equalization procedures it has been found sufficient to measure and then control the
"average" response of a room over a specific interval. In professional systems for large
rooms the one-third octave (i.e., about the space covered by four consecutive notes in the
scale) is the amount of frequency interval that each adjustment will control. In a personal

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music system in a normal room, adjustment over full octave intervals is satisfactory.
Ways to measure and adjust the average response for each octave interval follow.
The most commonly used procedure of measurement and adjustment is to connect a pink
noise generator to an appropriate input into the preamplifier. The system then generates
acoustic noise in the room that excites all octaves with equal power. Analysis of the room
sound is then made with a standard microphone and a real time analyzer. To carry this
out, first connect the pink noise generator to one channel only of the stereo system. Make
certain that your preamplifier's or receiver's tone controls and loudness control are in the
FLAT position. START OUT AT A VERY LOW LEVEL AND ADJUST THE GAIN
CONTROLS CAREFULLY TO A CONVENIENT MEASURING LEVEL. MAKE
CERTAIN THAT ALL HIGH FREQUENCY BOOST CONTROLS IN THE MODEL
4100 ARE IN THE FLAT POSITION. HIGH FREQUENCY DRIVERS CAN BE
BURNED OUT BY ENERGY THAT THE EAR DOES NOT HEAR.
Next, a standard microphone compatible with the analyzer is placed in the center of the
listening area. With this pickup feeding the real time analyzer you are ready to begin
some adjustment of the individual controls. First, you must consider what type of house
curve (i.e., the room response) you prefer. Under some circumstances you might want all
octaves to have equal response, or a flat house curve. This is not necessarily the best
choice. Since high frequency sound is absorbed preferentially in most rooms, the natural
condition to which we are accustomed is a gradual roll-off above 2 kHz. If the sound
system is forced to make the room response appear flat, you will probably not be satisfied
with the excess high frequency acoustic level that results. The response curve to which
you try to make the system conform will probably fall off at a rate of about 3 dB in each
octave above 2 kHz (see Figure 4). In the end, listening will determine the choice. The
owner must satisfy his own ear in making the choice of what to do with the high
frequency end of the spectrum. He should not hesitate to make the measurements drop off
smoothly above 2 kHz at whatever rate he finds pleasing.
When the real time analyzer has indications in one-third octave intervals, some averaging
of the three readings that make up an octave must be made. It will probably be acceptable
to average the readings in dB's since all three should be nearly the same. If there are large
variations from one channel to the next in the one-third octave analysis, there evidently
are some room resonances that will cause trouble later on and, if possible, some
experiments in speaker placement should be made. After taking an average reading for
Figure 4