Model 7PX3.5 & 7PX3.5/B
RIAA Phono Preamplifier
Operating Manual
After Unpacking ·
Remove the Model 7PX3.5 from the protective plastic bag and check for
any signs of shipping damage. Although the heavy construction and modern packaging of the
7PX3.5 make shipping damage highly unlikely, any claim must be reported immediately to
your dealer or carrier. Save all packing materials for future use. At this time, carefully read
through this operating manual to be sure that you understand the many unique features of the
7PX3 before placing it into your system and applying power.
CAUTION: IMPROPER
OPERATION OF THE INTERNA L G AIN SETTING SWITCHES CAN CAUSE DAMAGE TO YOUR
LOUDSPEAKERS. SEE THE SECTIONS ON PHONO GAIN SETTING B EFORE OPERATING THESE
SWITCHES. ALSO, READ THE SECTION ON SERVOS BEFORE USING THE 7PX3 IN YOUR SYSTEM.
Circuit Highlights
·
The circuits of the Model 7PX3.5 preamplifier represent the very latest
in our evolution of Phono preamplifier design which began with our highly acclaimed SK-1
MC Step-up amplifier. The 7PX3.5 employs our new amplifier module called “Music
Module™”. We call them “Music “ modules because of their exceptional musical qualities of
tonal accuracy and harmonic integrity. The Music Modules™ are built with discrete
components and are “universal” in application. Each module is optimized with selection of
external components for its respective circuit function. The overall circuit configuration uses
two low noise amplifier blocks separated by a passive RIAA equalization network.
Components used in the RIAA network have been carefully selected for their exceptional
sonic characteristics of tonal accuracy, their ability to preserve both low-level and high-level
dynamics and detail; and, their ability to present a natural soundstage.
The power supply for each amplifier block is independently regulated, using high speed op-
amps, selected for their exceptional sonic neutrality, in series regulation configurations. DC
servos are used for each of the amplifier modules to allow direct coupled outputs and still
maintain zero volts DC at the outputs under all operating conditions. See the section titled “DC
Servos” for further details.
All components used in the 7PX3.5 have been selected only after extensive listening tests.
Criteria for selection has been only the very finest sonic performance without regard to cost.
Model 7PX3.5/B
·
Specifications and operation of the Model 7PX3/B are identical to the
Model 7PX3.5. The Model 7PX3.5/B includes balanced outputs via XLR connectors with an
output impedance of 600 Ohms. (See section on System Polarity on page 5.
Front panel Controls
·
The
push button
“mute”
control alternates between muted and non-
muted main outputs. (see “Turn-on Delay” section below for more details).
