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Passeq
Advantages of Passive Filtering
• Typically coil inductance in virtually all active lters is achieved through simulation. True
passive coil lters, on the contrary, can only deliver the genuine, characteristic sound asso-
ciated with inductive components.
• Inherent distortion elements of active lters are ruled out by passive lter design.
• For any number of reasons stemming from design and component advantages over active
lters, passive lters achieve a very natural aural quality and through their harmonic treat-
ment (THD, distortion, phase response, etc.), offering at the very least, a clear sonic alter-
native, which our ears often perceive as an extremely attractive one.
• All passive lter components (variable resistor, capacitor and coil) work in concert to
produce this beautiful sonic result. An important part of this process is played by coil
and condenser loading and saturation characteristics. The resulting difference in latency
from characteristically extremely fast reaction of active lters provides for more pleasant,
musical sonic qualities. We tend to perceive these attributes in terms of an increased
suppleness and transparency, with perceptibly improved, silky highs and robust basses.
72 passive Filters with 120 Volt Makeup Ampliers
With 72 passive lters (36 x boost, 36 x cut per channel), the Passeq surpasses all previous
designs of this type by a wide margin. Each channel is divided into three cut and three boost
bands, each offering 12 switchable frequency ranges. The cut and boost ranges are not iden-
tical; crossovers are designed to work with like a precise mechanic cogwheel so as to allow the
engineer access to the largest possible number of optimal, wide-band S-curves with variable
slopes. A further noteworthy Passeq feature is its individual sonic adaptation of each induc-
tive lter through separate coil/condenser/resistor combinations: In stark contrast to earlier
lter design and construction, each Passeq lter is optimized for the frequency assigned. To
insure the best possible signal warmth, richness and musicality in processing, coils for critical
voice frequencies are custom-made for the Passeq. This achieves the widest possible range
and tonally appealing sound color palette from any passive EQ.
Filter Types
The Passeq employs two distinct lter types: One of these functions much like traditional
shelving lters, while the other, as a peak lter, and together, they provide the combined char-
acteristics of wide-band control in low and high ranges with more specic frequency range
control in mids. This selection minimizes mutual inuences between low, mid and high bands
while providing a more selective control in the mids is often useful.
Single Core Coils
Until now design approaches have involved individually wound coils, but multiple coils have
nonetheless been placed on a single core. The Passeq design places each coil on separate
cores. This eliminates any possible unwanted mutual inuence transmitted through common-
core windings and thus, among other improvements, results in better THD values.
Peak and Shelving Filters
Mid boost and cut, as well as HF boost lers have been set up in a peak (bell) conguration,
while the hi cut, low cut and low boost lters function in a shelving conguration. The HF
boost band offers variable values from Q=1 to 0.1.
Introduction