SPL Passeq User manual

PASSEQ
Passive Mastering Equalizer
• Test Report
• Manual / Handbuch

PASSEQ
Passive Mastering Equalizer
Manual

Content
PASSEQ
Version 1.2 – 12/2017 2
Package Contents 2
Introduction 3
King of the passive equalizers 3
Technical Aspects 4
120 Volt Technology 4
120 Volt Technology - Diagrams 5
The Basics of Frequency Filtering 6
Filter Types 6
Shelf Filters 6
Peak Filters 6
Bandwidth 6
Passive EQs 7
Installation 8
Voltage Selection 8
First Steps 8
Cabling: Rear Side 9
XLR inputs and outputs 9
Control Elements 11
Layout of Control Elements 12
Frequency 12
LF+ and LF- 12
MF+ and MF- 13
HF+ and HF- 13
Q (HF+ Band) 13
Gain 14
Output 14
Channel Switch 14
Auto Bypass 14
Recommendations on using Equalizers 15
Basic Approaches and Working Techniques 15
EQ Yin & Yang 15
First cut, then boost 15
Specications 16
Measurements 16
Security Advices 17
Contact 19

2
Version 1.2 – 12 / 2017
Developer: Wolfgang Neumann
This manual includes a description of the product but no guarantee as for specific charac-
teristics or successful results.
Unless stated otherwise, everything herein corresponds to the technical status at the
time of delivery of the product and user manual by SPL electronics GmbH.
The design and circuitry are under continuous development and improvement.
Technical specifications are subject to change.
Package Contents
PASSEQ Passive Mastering Equalizer
Power cord
Manual
The PASSEQ Equalizer is available in different colors.
Black: Modell 1650
Red: Modell 1654
Do consider keeping the original packaging. It can come in very useful whenever you need
to transport your gear. If there is ever the need to send it in for repair, the original packag-
ing guarantees a safe shipment.
The SPL PASSEQ Mastering Equalizer was designed, developed and manufactured in
Germany.

3
Introduction
King of the passive equalizers
The PASSEQ Mastering Equalizer is a dual-channel, passive equalizer.
The PASSEQ Mastering Equalizer – Model 1650/1654 is a new revised edition of the well-
known SPL Passeq – Model 2595.
Both units are based on our 120V Rail Technology. The new PASSEQ Mastering Equalizer
features the same high-quality characteristics as the previous model, though it was
revised and optimized to fulfill all requirements of a Mastering Equalizer.
The Passeq of the first generation was the first passive equalizer which provides three
separate frequency ranges for the boost and the cut stages. With 12 switchable frequen-
cies per band, totaling 36 boost and 36 cut frequencies, the Passeq was the most power-
ful passive EQ system ever made. The new PASSEQ Mastering Equalizer features the same
amount of cut and boost frequencies, though the choice of frequencies was changed and
the Q-factor was individually newly adjusted for every selectable frequency with an opti-
mal coil, condenser, resistor combination. Each boost and cut frequency now got an indi-
vidual optimized Q factor. Especially the mid bands are much more harmonious for work-
ing on program material than they were on the previous model. When we were fine-tun-
ing, through component selection, within countless listening sessions, the focus was on
receiving musically sounding curves, which are clearly on par with legendary devices like
the Pulteq EQ from the decades of the 1950’s and 60’s, but without all disadvantages
of a 60-year-old original, like a high noise level and most of all a very limited choice of
frequencies.
All passive filter components (variable resistor, capacitor and coil) deliver excellent sonic
characteristics. An important part of this process is played by coil and condenser loading
and saturation characteristics. The resulting inertia in contrast to the characteristically
extremely fast reaction of active filters is the reason for pleasant, beneficial sonic char-
acteristics. We tend to perceive these attributes in terms of an increased suppleness and
transparency, with perceptibly improved, silky highs and warm and punchy basses.
Another highlight of the new PASSEQ is the HF+ Band, which was expanded with the fre-
quencies 25kHz and 35kHz, sounding so incredibly good, that you don‘t want to turn it off
anymore.
Thanks to the big detented output control, you can increase or attenuate the output level
by 10dB, to reach following devices with the perfect desired level. This is important, espe-
cially when it comes to mastering. A fader ranging from 0dB to limitless, like the previous
model provided, would not be helpful in this case. With the PASSEQ you can also adjust
the parameters Gain, Q (HF +) and Output in 41 steps with the detented potentiometers.
All other parameters can be adjusted with 12-position switches. Thanks to these switches
and detented potentiometers, a precise recall is very easy to realize.
In addition to that, the handling of the PASSEQ Mastering Equalizer was improved through
small corrections of the positioning and naming of the control elements. Like all new
SPL Mastering devices, the new SPL PASSEQ provides an Auto Bypass. Of course each
of the two channels can also be manually activated or deactivated with the big illumi-
nated pushbuttons. Thanks to the Auto Bypass, this can also be realized automatically in
a freely selectable time frame.

4
Technical Aspects
120 Volt Technology
SPL‘s goal was to push analog signal processing to the limits. That‘s why we combined the
best possible components with a high-grade optimized circuit design.
We have been using the in-house developed 120-volt technology - the highest-ever oper-
ating voltage used for audio applications - in all our products from the Mastering series
for years. Some of the most highly respected Mastering studios today revolve around
SPL consoles and signal processors from our Mastering series (Bob Ludwigs Gateway
Mastering & DVD in the USA, Simon Heyworth‘s Super Audio Mastering in the UK, Galaxy
Studios in Belgium, and the legendary Wisseloord in the Netherlands, for instance).
The 120-volt technology is based on op-amps developed internally by SPL‘s co-founder
and Chief Developer Wolfgang Neumann. The PASSEQ features the most advanced gen-
eration of these op-amps. They boast with even better tech specs thanks to the thermal
behavior optimization they underwent under the hands of Bastian Neu.
Ultimately, the supply voltage is key for the overall dynamic response of a processor.
Voltage is to an electrical circuit what cylinder capacity is to an internal combustion
engine:
You can‘t replace cylinder capacity with anything else, except more cylinder capacity.

5
Technical Aspects
120 Volt Technology - Diagrams
These diagrams clearly show the advantages of our 120-volt technology in comparison to
other circuits with a lower operating voltage. The direct relation between operating level
and maximum level is fundamental for the classification: the higher the operating level,
the higher the maximum level a circuit can handle. And since virtually all essential acous-
tic and musical parameters depend on this relation, a higher operating voltage also
has a positive impact on the dynamic range, distortion limit and signal-to-noise ratio. The
result is a clearly more laid-back and natural sound with less unpleasant coloring.
Do bear in mind that dB scales do not represent linear but rather exponential increases. A
3 dB increase corresponds to doubling the acoustic power, +6 dB correspond to twice the
sound pressure level, and +10 dB correspond to twice the perceived loudness.
When it comes to volume, the 120-volt technology exhibits a performance that is twice
that of common components and circuits, in regard to maximum level and dynamic range,
with values that are approximately 10 dB higher. THD measurements of the SPL op-amps
show a difference of more than 3 dB compared to the OPA134 at 36V — in terms of sound
pressure level, that corresponds to an improvement of more than 50%.
The operating level most commonly used for audio equipment is 30 volts.
120
125
130
135
140
145
dBu Dynamic Range
OPA 134@30 VOPA 134@36 VSPL-OP@120 V
124,2
129,1
141,4
0
5
10
15
20
25
30
35
dBu
OPA 134@30 VOPA 134@36 VSPL-OP@120 V
21,5 22,5
33,2
Maximum Levels
0
20
40
60
80
100
120
Volt
+/- 15 Volt +/- 18 Volt +/- 60 Volt
30 V
36 V
120 V
Operational Voltages
-115
-113
-111
-109
-107
-105
dBu TL 071@30 VOPA 134@36 VSPL-OP@120 V
106
111,7
114,2
THD&N

6
The Basics of Frequency Filtering
Filter Types
There is basically only one type of filter used in the PASSEQ: The bell-filter or peak-filter.
But since the center frequency of the peak-filter, concerning the HF and LF bands, is only
marginally within the perceptible hearing range, these filters auditorily and visually rather
correspond to shelf-filters.
Shelf Filters
A shelf filter increases or decreases the energy of all frequencies above or below a chosen
frequency. Depending upon the direction of processing one refers to high frequency (HF)
or low frequency (LF) shelf filters. Beginning with the threshold frequency, the frequency
band is boosted or cut much like a shelf. The maximum boost or cut achieved at the point
furthest from the threshold frequency. The threshold frequency is usually about 3 dB less
(with the overall increase set to maximum). This gives the typical rising form of the shelf
filter’s response curve.
Peak Filters
A peak filter boosts or cuts a chosen frequency‘s energy with a maximum amplitude and a
definable frequency range around this frequency with a fall off of up to 3dB to both sides.
The chosen frequency with the maximum amplitude is called center frequency—it takes
place in the middle at the peak of the response curve. The response curve forms a bell,
thus peak filters are also often referred to as bell filters
Bandwidth
The width of a frequency range or band is musically defined in octaves. The technical
counterpart to this is the “Quality” of a filter, and the abbreviated “Q” is the most com-
mon value for the bandwidth of a filter.
A high Q value means a narrow bandwidth while a smaller Q factor corresponds to a wider
one:
Bandwidth 2 Octave: 0.7 Q
Bandwidth 1 1/3 Octave: 1 Q
Bandwidth 1 Octave: 1.4 Q
Bandwidth 1/2 Octave: 2.8 Q.

7
The Basics of Frequency Filtering
Passive EQs
A filter in a passive network got no amplification elements and therefore does not need
any external power. That is why you can only attenuate the energy of the frequencies.
However, to change the energy of the frequencies of a passive filter network in both ways
(attenuate and increase), the signal level of the filter input signal gets reduced by a certain
value. Proceeding from this value, an additional attenuation (cut) or an increase (boost)
of the reduced condition can be put into effect. A passive filter is always followed by an
amplifier which regains the initial energy of the attenuated signal level – though it is not
part of the actual filter circuit.
Passive filters react differently than active filters, mostly due to the saturation and load-
ing characteristics of its coils and condensers. The characteristics of passive filters often
are very advantageous in their ability to create a musically pleasing sonic result: they
sound comparably very smooth and harmonious.
Schematic of a passive frequency filter
Block diagram of passive filter set flat
Blockdiagrammofapassivelterat+18dBboost
dB
0
-2
-20
-36
-50 Hz 20 kHz
Input signal level
Filter output level
(when set for flat response)
Bass cut at 50 Hz by -18 dB
Bass boost at 50 Hz by +18 dB
Input Output
0 dBu 0 dBu-20 dBu
Filter (flat):
-20 dBu
Amp
+20 dBu
Input Output
0 dBu +18 dBu-2 dBu
Filter +18 dB
boost
Amp
+20 dBu

8
Installation
Voltage Selection
Before connecting the PASSEQ to the mains, make sure that the voltage selection corre-
sponds to the values of your local power grid (230 or 115 volts). Inside the power connec-
tor, to the right, next to the on/off switch, there is an opening that displays the voltage
selected. If the voltage indicated does not correspond to the one required, change it by
following this procedure:
Open the power connector lid with a small screwdriver (use the tiny slots on the right hand
side). Use the screwdriver to lever the red fuse holder from above until you can grab it.
Take the fuse holder out and replace the fuse with one corresponding to the local power
grid specifications. You can find the adequate values on the rear of the unit or on page 16
of this user‘s manual. Turn the fuse holder around 180 degrees and place it back again.
When you close the lid again, you should see the correct voltage displayed in the opening.
First Steps
Before turning on the PASSEQ you must first connect the included 3-pin power cord to the
3-pin IEC socket. The transformer, power cord and IEC socket all comply to the VDE, UL
and CSA regulations.
The PASSEQ should not be installed in close proximity to equipment that emits magnetic
fields or emanates heat. Avoid exposure to heat, moisture, dust, and vibrations. Do not
install the PASSEQ close to any power amps or digital processors. Instead, install it in a
fully „analog rack” where any interferences can be avoided (Word Clock, SMPTE, MIDI
etc.).
The unit should be powered off before connecting or disconnecting any cables or equip-
ment to it.
Use the On/Off switch on the rear panel to turn the unit on or off. The illuminated red LED
in the middle of the front panel indicates the unit‘s operating status. The On/Off switch
was placed on the rear panel to avoid any emissions due to voltage-carrying conductors
running across the unit and affecting sound. When powering on or off, there‘s no need
to observe a specific sequence regarding the connected devices. However, like with any
audio signal chain, power amplifiers should always be powered on last and powered off
first. The PASSEQ can be powered on and off with the use of a circuit breaker, as long as
the total load does not exceed the rating of the latter.

9
Cabling: Rear Side
XLR inputs and outputs
We used exclusively Switchcraft/Neutrik XLR input and output plugs to guarantee perfect
connectivity in the studio. They provide an optimal connection thanks to their electrome-
chanical design and large contact surface.
The image shows the XLR connectors pinout. They are balanced and have three conductors
or wires. Conductor 2 (Pin 2) corresponds to the (+) or hot Signal.
In case an unbalanced connection is necessary, the correct polarity of the conductors
needs to be observed.
Ground Lift switch to avoid ground loops
On the rear panel of the PASSEQ Mastering Equalizer (see page 10) is also a „GND LIFT“
(Ground Lift) switch to avoid any ground loops. Ground loops take place when gear con-
nected in the same network have different potentials.
The GND LIFT switch disconnects the equipment ground from the service ground to avoid
such problems. The Ground Lift function is activated (= equipment ground disconnected)
when the switch is depressed.
Input Output
balanced unbalanced balanced unbalanced
1=GND
2=hot (+)
3=cold (-)
1
2
3
1
2
3
12
3
12
3

10
Cabling: Rear Side
1Input
2Output
3 Ground Lift (see details on page 9)
4 Voltage (see details on page 8)
GND LIFT
GND LIFT
GND LIFT
GND
INPUT 1
INPUT 1
OUTPUT 1
OUTPUT 1
INPUT 2
INPUT 2
OUTPUT 2
OUTPUT 2
TO REDUCE RISK OF FIRE OR ELECTRIC SHOCK.
DO NOT EXPOSE THIS UNIT RAIN OR MOISTURE.
DISCONNECT MAINS BEFORE REMOVING COVER.
THIS EQUIPMENT MUST BE EARTHED.
AC MAINS
AC MAINS
XLRs:
Balanced +4dBu
1 = GND
2 = HOT (+)
3 = COLD (–)
WARNING
AVIS: RISQUE DE CHOC ÉLECTRIQUE • NE PAS OUVRIR
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION
Serial
Number
Made in Germany
~ 115V AC / ~230VAC, 50Hz / 60Hz, P max. 45W
Fuses:
Voltage Selection:
115V AC: T 1 A L 250 V
230V AC: T 500 mA L 250 V
1. Remove Fuse Holder
2. Change Fuses
3. Flip Over
4. Reinstall
PASSEQ
230
GND LIFT
GND LIFT
GND LIFT
GND
INPUT 1
INPUT 1
OUTPUT 1
OUTPUT 1
INPUT 2
INPUT 2
OUTPUT 2
OUTPUT 2
TO REDUCE RISK OF FIRE OR ELECTRIC SHOCK.
DO NOT EXPOSE THIS UNIT RAIN OR MOISTURE.
DISCONNECT MAINS BEFORE REMOVING COVER.
THIS EQUIPMENT MUST BE EARTHED.
AC MAINS
AC MAINS
XLRs:
Balanced +4dBu
1 = GND
2 = HOT (+)
3 = COLD (–)
WARNING
AVIS: RISQUE DE CHOC ÉLECTRIQUE • NE PAS OUVRIR
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION
Serial
Number
Made in Germany
~ 115V AC / ~230VAC, 50Hz / 60Hz, P max. 45W
Fuses:
Voltage Selection:
115V AC: T 1 A L 250 V
230V AC: T 500 mA L 250 V
1. Remove Fuse Holder
2. Change Fuses
3. Flip Over
4. Reinstall
PASSEQ
230
1122
3
4

11
Control Elements
1
2
3 4
5
6
7
8
9
11
12
14
15
16
17
13
10
Auto Byp.
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1
0
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9
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5
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8
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5
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6
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7
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2
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2
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2
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1
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1
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1
k
1
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2
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2
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3
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5
4
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3
6
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1
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6
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I
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dB
dB
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Hz Hz
Hz
HzHz
Hz
passive
mastering
equalizer
PASSEQ
Sound Performance Lab
Model 1650
A Wolf
Neumann
Design
Q
HF - HF +
MF
- MF +
LF
- LF +
Output
120V DC Audio Rail
17
-
1
0
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9
.
5
-
8
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5
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6
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7
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5
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2
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2
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2
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1
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5
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1
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2
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1
dB
dB
dB
dB dB
dB
dB
Hz Hz
Hz
Hz
Hz
Hz
Q
HF - HF +
MF
-
MF +
LF
- LF +
Output
1HF- Frequency
2HF- Gain
3 MF- Frequency
4 MF- Gain
5 LF- Frequency
6 LF- Gain
7 HF+ Frequency
8 HF+ Gain
9 HF+ Q
10 MF+ Frequency
11 MF+ Gain
12 LF+ Frequency
13 LF+ Gain
14 Output
15 Power LED
16 Auto Bypass
17 Channel Switch

12
Control Elements
Layout of Control Elements
Initially one might be struck by the circular arrangement of the PASSEQ’s control ele-
ments. As unusual as this first appears, the more understandable and clearer this layout
becomes when one looks closer.
Along with the fact that we simply like this design from an aesthetical view, this layout
makes even more sense with respect to the idea of the passive EQ concept itself: In a pas-
sive design, filters for boosting and cutting a frequency range are physically separated
from each other. Reflecting this fact, the elements left of the central output control per-
form level cuts, while controls to the right of this central regulator serve as signal boost
controls. Cut and boost switches are positioned next to the appropriate frequency band
selector and frequency bands are arranged from low to high from the standpoint of both
physical and frequency range layout.
Frequency
Each channel provides three cut and three boost frequency switches. You can choose 12
different frequencies per switch. The workable frequency range stretches from 10 Hz to
35 kHz.
Frequency Range:
• LF- (Low Frequencies Cut): 30 Hz bis 600 Hz
• LF+ (Low Frequencies Boost): 10 Hz bis 550 Hz
• MF- (Mid Frequencies Cut): 200 Hz bis 6 kHz
• MF+ (Mid Frequencies Boost): 220 Hz bis 4,8 kHz
• HF- (High Frequencies): 580 Hz bis 22 kHz
• HF+ (High Frequencies): 5 kHz bis 35 kHz
LF+ and LF-
The LF- frequency range extends from 30 Hz to 600 Hz. The low boost LF+ band encom-
passes a range of 10 Hz to 550 Hz. The maximum available increase in this LF+ boost band
is 17 dB, while the maximum reduction of the LF- band is 22dB. Optically these filter
bands may be represented as having a shelving characteristic with an 6dB slope. Passive
filters do not allow for direct alteration of the slope gradient because this quality is pre-de-
termined by component selection and not, as with active filters, by a variable value. The
lowest frequencies begin here with 10 Hz, then follow with 15 Hz, 18Hz, 26Hz, 40 Hz, and
so on. At this point one might think that such a lavish set of frequency choice in this range
might be a bit overdone, as there is acoustically a rather limited amount of audio mate-
rial of any real significance below 26Hz. However, these choices are anything but arbi-
trary. These frequencies represent a consistent -3 dB point of a sloping down response
curve. That is, the gentle 6dB slope also allows frequencies above 10 Hz to be processed.
As mentioned in other parts of this text, special condenser/coil/resistor filter networks
have been designed for each frequency range. The choice of one or the other inductances
produces differences in sonic coloration even when limited differences between frequen-
cies such as 10 Hz or 15 Hz play a subordinate role. Along with this differing phase rela-
tionships may come into play and affect tonal color. Because modern productions often
demand a definite number of choices in an engineer’s options for achieving an optimal
result in bass emphasis, the PASSEQ has been designed with a very complete set of low
frequency options to insure realizing these goals.

13
Control Elements
MF+ and MF-
The midrange bands elevate the PASSEQ to a complete combination of filter options that
classic passive designs do not offer. Both midrange bands exhibit peak filter character-
istics, that is, when viewed from the boost band, the frequency curve appears as bell-
shaped slopes above and below the chosen frequency range. The slope or Q-value is,
again, not variable, but attuned through the choice and configuration of the passive fil-
ter‘s components for a maximum in musical ef ciency, relying in the PASSEQ on its devel-
oper, Wolfgang Neumann‘s years of musical experience. The middle bands‘ peak struc-
ture is chosen for a clean separation of LF and HF bands. Were the choice here to be for a
shelving filter design, too many neighboring frequencies would be processed, with result-
ing undesirable influences extending into LF and HF bands. Along with this is the simple
fact that a midrange peak filter characteristic is accompanied by a more easily focused
center point processing of critical voice and instrument fundamental frequencies.
HF+ and HF-
PASSEQ’s high frequency bands have a different layout for the cut and boost ranges: The
HF- cut band exhibits a (wide-band) shelving characteristic, while the HF+ boost band
exhibits a variable Q, peak filter characteristic.
As seen above, one can also note and intensification in choice of frequencies in the
high range. Here the same reasons apply as in prior cases: Individually designed and
constructed coil-condenser-resistor configurations result in slightly differing sonic
characteristics.
Q (HF+ Band)
Like already mentioned in the last chapter, with the HF+ Band you got the possibility to
change the Q-factor (value), thus the bandwidth, thanks to the Q-control. The control
range here ranges between 0.1 Q and 1.0 Q. Again all settings can be adjusted through a
41 step detented potentiometer.
With the proportional or variable Q principle, boost control settings would apply only if
the HF+ Q were to be set at Q=1.0 (control set fully clockwise). Were the value to be re-
duced (thus increasing the bandwidth), the boost would also be reduced. This can lead to
a situation wherein, for example, a HF+ Q setting of 0.1 and a boost of 3dB would result
in effectively no audible boost in the chosen frequency—at this value the Q value resides
at about 0.3dB. With this Q value, don’t hesitate to turn turn up the HF+ band boost con-
trol to its full 12.5 dB setting—this results in an actual overall increase of around 3.5 dB.
Narrower Q settings, for example, to 0.6, result in further level boosts again. The advan-
tage of a Proportional-Q design compared to Constant-Q design rests with the musically
superior way it functions. The acoustic energy below the bell-shaped curve remains es-
sentially the same and thereby it retains the balance of high frequencies in relation to the
entire frequency spectrum while experimenting with different Q values. While it is true
that one must think independently of the scaled gain dB values of the HF+ boost switch
in such cases (because these only apply to a Q value of 1), the result is a simpler, more
musically sensible and worthwhile way to work that does not require continual additional
corrections of the Q values.

14
Control Elements
Gain
The maximum increase or attenuation of the amplitude is adjusted to the according fre-
quency range for each frequency band. The setting can be selected with detented poten-
tiometers in 41 steps.
Maximum change in amplitude:
• LF- (Low Frequencies Cut): 22 dB
• LF+ (Low Frequencies Boost): 17 dB
• MF- (Mid Frequencies Cut): 11,5 dB
• MF+ (Mid Frequencies Boost): 10 dB
• HF- (High Frequencies): 14,5 dB
• HF+ (High Frequencies): 12,5 dB
Output
Located at the center of both sides, you will find the Output controls. The Output controls
serve as an output level regulator for the respective side, to increase or attenuate the out-
put level up to 10dB. These controls are also 41 step detented potentiometers.
Channel Switch
The two, centrally located, orange-lit switches activate or deactivate the corresponding
left and right channels.
Auto Bypass
To be able to make an objective judgment of the processed material, it is best not to have
to be toggling between the original and processed signals by yourself, but rather have it
done automatically. Plus, the fact that you do not have to move from the sweet spot and
can concentrate better on the music to optimally assess the processing is a huge advan-
tage. The Interval control determines the time that needs to elapse before the compressor
toggles between the processed and unprocessed signals. Hard left is the shortest set-
ting. To increase the interval, turn the knob clockwise.

15
Recommendations on using Equalizers
Basic Approaches and Working Techniques
While we would never assume that in creative and artistic work there should be absolute
rules, and this also applies to work with EQ: There is no such thing as “The Voice” or “The
Kick Drum” or “The Piano”. The following is thus offered strictly as a basic orientation or
starting point for such work, and should not be misconstrued as dogma or any other kind
of absolute.
Nonetheless, in order to achieve sometimes hard-to-define goals when applying EQ, it
really is important to be aware of and be able to use a few accepted basic musical and
technical guidelines.
EQ Yin & Yang
1) A small reduction in the lower middle range around 250Hz can have a similar effect as
an increase in the presence region of 5 kHz.
2) Added energy in the very high region of 15-20 kHz can create the impression of having
made the bass and lower mids thinner.
3) Adding warmth to a voice will reduce its mix presence.
Working with EQ and this Yin and Yang principal means ideally to consider always such
implied repercussions of work in one frequency—for example, that in working to enhance
warmth, that one might want to avoid losing presence.
Harshness in the upper middle to lower high range can be countered with more than one
approach: A harsh trumpet section may be improved through a reduction around 6-8 kHz,
oder with an increase at around 250 Hz. Both of these measures result in a warmer sound,
but the decision of which to use should depend on which of the two also works best in the
entire mix.
Moreover, one should never forget how easy it is, while working intensely with isolated
elements of a mix, to fall into the trap of forgetting how such elements can influence, for
better or worse, the rest of the mix.
First cut, then boost
“The ear” is more used to energy reductions in a frequency range, thus boosts attract
more attention. That is, a 6 dB boost is perceived to be similar in amount to a 9 dB cut.
Therefore when wishing to emphasize one frequency, it is typically better first to consider
a reduction in others. The result will bring more transparency and clarity as well as reduce
possible unwanted coloration of the signal.

16
Specications
Measurements
Inputs
Max. Input Level ..................................... + 32,5dBu
Input Inpedance ..................................... 20kOhms (balanced)
Outputs
Max. Output Level .................................. + 32,5 dBu
Output Inpedance .................................. ‹ 600 ohms (balanced
Harmonic Distortion: at -30 dBu: 0,076%
at -20 dBu: 0,026%
at 0 dBu: 0,026%
at +10 dBu: 0,0086%
at +30 dBu: 0,0012%
Noise (unweighted, Gain +0 dBu, EQ = 0dB B/C) ................................ - 91,8 dBu
Noise (A-weighted, Gain +0 dBu, EQ = 0dB B/C) ................................ - 95,2 dBu
Noise (CCIR, Gain +0 dBu, EQ = 0dB B/C) .......................................... - 86,2 dBu
THD & N ( Gain +0 dBu, EQ = 0dB B/C) ............................................... › 102 dB
Common-Mode-Rejection:................................................................. › -60dBu
(at 1 kHz, Gain +0 dBu, EQ = 0dB B/C)
Transmission Bandwidth: 10 Hz-200 kHz
(-3 dB)
Frequency Range: 30 Hz-35 kHz
Power Consumption: ............................... 0,06 Amp, 230V/50Hz, 9,5Watt, 13,6VA
0,09 Amp, 115V/60Hz, 9,5 Watt, 13,6VA
Fuses ..................................................... 230 V/50 Hz: 0,5 Amp
115 V/60 Hz: 1 Amp
Dimensions
Standard EIA 19 Inch Housing/4U ............ 482 x 177 x 311,5 mm / ca. 19“ x 7“ x 12,25“
Weigh ..................................................... 10,2kg / 22,5 lb