Jeff Rowland Coherence 1 Pre Owners manual

COHERENCE ONE PREAMPLIFIER

TABLE OF CONTENTS

Introduction
Features
Unpacking Instructions
Installation
Phono Cartridge Loading
Basic Troubleshooting
Technical Specifications

Introduction

OWNER’S MANUAL

Congratulations on your purchase of the Jeff Rowland Design Group Coherence One Series II
Preamplifier.

Please take a few moments to read this owners manual. Contrary to popular belief, there is actually quite a
bit of useful information in an owner’s manual. The Coherence One Series II offers tremendous
interconnection flexibility regardless of the amplifier used. A thorough understanding of your preamplifier
now can save you a lot of anxiety later.

PLEASE NOTE: THE COHERENCE ONE SERIES II IS IN NO WAY COMPATIBLE WITH EARLIER
COHERENCE ONE PREAMPS. DO NOT INTERCHANGE OLD AND NEW POWER SUPPLIES FOR ANY
REASON!

Features

• The preamplifier is designed to rest on top of its power supply so the user-friendly pair can be handled
easily. Special shielding techniques allow for this configuration, and "hum field" contamination has been
eliminated.

• Lighted, feather-touch mode switches electronically control signal. The front panel switches do not alter
sonic integrity, since signal switching is accomplished at the preamplifier input stage. Absolute phase
reversal and full muting are other essential front panel control functions.

• A selectable tape output section allows simultaneous recording from one source while listening to
another. "Record Out: Off" position disconnects tape recorder inputs from tape out jacks, eliminating
loading problems when tape recorder is not in use.

• Volume controls are chosen for their sonic neutrality. Separate right and left trim potentiometers provide 6
dB adjustment for full rotation, permitting precise channel balance.

• Input and output jacks are gold-plated, ground-fault protected connectors, which provide tight, corrosion­free connections. Simultaneous normal and inverting outputs allow for balanced cable operation.

• Extremely low-noise phono sections eliminate the need for extra circuitry when using low output moving
coil cartridges. The phono modules of the Coherence One Series II have been optimized for use with
moving coil cartridges; for moving magnet cartridges, a module exchange can be easily accomplished by
the user. Please contact Jeff Rowland Design Group from more details.

• All main outputs are muted temporarily during initial power application, power drop or disruption. DC
potential across outputs, regardless of source, will also cause a muted condition.

• All signal amplification utilizes high-voltage, high-current, Class A field effect transistor technology.

• All inputs and outputs are direct-coupled, thus eliminating the deleterious effects of capacitors in the
signal path.

• Precise RIAA equalization is the result of a split-passive network in the phono section.

• Incorporation of two-stage power supply regulation: A separate outboard power supply provides tight
regulation regardless of power company extremes. Additionally, this discrete component design is
optimized for excellent transient behavior, thus providing very low output impedance beyond 100 kHz.

• DC power is routed, via a power cable with a locking connector, to the main preamplifier circuit board.
Compensating for power cable and circuit board inductance effects, sixteen (16) feedback-free discrete
regulators adjacent to each module complete DC power distribution. This total system, in addition to
separate channel balance controls, provides dual mono operation and precise regulation at
each stage throughout.

• Time-related distortion, particularly in low-level phono stages, is eliminated by a totally feedback-free
design.

• Mil-spec circuit board material, with oxygen-free copper traces and high-temperature mask provides
superior electrical characteristics.

• All signal switching is accomplished with hermetically sealed, gold- contact signal relays.

• AC power line filter offers excellent line noise rejection.

• All critical circuitry is encapsulated in a thermally-conductive epoxy to ensure excellent thermal stability,
mechanical integrity and to facilitate ease of service