JEFF ROWLAND Concentra User manual

JEFF ROWLAND
DESIGN GROUP

Concentra
Stereo Integrated Amplifier
Owner’s Manual

Introduction
Welcome to the Jeff Rowland Design Group “family” and congratulations on your purchase of what is unquestionably
one of the world’s finest audio amplifiers. þ With its combination of industrial grade active and passive devices,
precision electronic circuitry and accurately machined chassis components throughout, your Concentra Integrated
Amplifier will offer you many years of musically satisfying enjoyment. þ Please take a few moments to read the
remainder of this Owner’s Manual. A thorough understanding of the operational features will allow you to gain the
maximum performance and ease of use for which this Amplifier was designed. þ Your Amplifier’s serial number is
located on the rear panel and also recorded below. Please include this number with any correspondence regarding your
Concentra Integrated Amplifier. þ It has been my joy to create an audio component of enduring value which will reflect
a higher ideal of musical and artistic expression. It is my hope that these qualities will enrich your experience of
ownership.
Enjoy the music!
Jeff Rowland
President
þJeff Rowland Design Group, Inc.
2911 North Prospect Street
Colorado Springs, CO 80907
Phone: [phone]
Fax: [phone]

Product Features
þThree balanced XLR inputs per channel plus three unbalanced (RCA)
inputs per channel.
þPreamp Out in both balanced XLR output and unbalanced (RCA)
outputs per channel.
þTape input and output jacks allow tape recording from any source and
monitoring of tape recorder output.
þRear panel handles assist moving and transport of unit.
þChassis and all chassis components, precision machined from 6061
aluminum plate, reduce distortion resulting from mechanical resonance
and thermal instabilities.
þAll operational functions under microprocessor control. Within five
seconds of any function selected, the microprocessor reverts to a non-
clocking “sleep” mode which eliminates any possibility of digital noise
contamination.
þNon-multiplexed, zero electrical noise generating numerical display
indicates volume level over entire range of 99.5 decibels.
þ‘Display off after five seconds’ option available for non-intrusive, low
light listening environments.
þDual range volume control allows large volume level changes when
knob is rotated abruptly, yet permits precise small volume level changes
when knob is rotated slowly.
þOptional plug-in phono cards (installed internally) convert Line Input 1
to high performance phono inputs. Four gain and input loading options
standard for moving magnet and moving coil cartridge types.
þFull electronic and thermal protection modes guard against output
overloads and short circuits.
þHigh current preamp outputs (balanced XLR and unbalanced RCA)
allow simultaneous driving of external power amplifiers for subwoofers,
vertical bi-amping, etc.
þAll inputs are transformer-coupled to provide maximum immunity from
RF contamination and system ground loops and enhance compatibility
with a wide variety of interconnected components.
þSpeaker outputs are fully balanced to provide maximum sonic
performance and immunity from RF contamination due to high output
common mode noise rejection.
þOptical encoder type volume control maintains quiet, trouble-free
performance and accuracy over entire lifetime of product.
þSix-function hand-held IR remote control.
Introduction / Product Features

2
4
Contents
1
3

Initial Inspection
Inspect the shipping container for damage. If the shipping container,
packing material, amplifier or accessories are damaged or missing, notify
your dealer and the shipper (if a claim is to be made). Note: Many shippers
require notification and an inspection within twenty-four (24) hours of
delivery to ascertain the nature of damages incurred.
Your Concentra Integrated Amplifier has undergone extensive performance
evaluations, listening tests, quality control inspections and a minimum
seventy-two (72) hour burn-in period prior to shipment and should be in a
perfect operational condition upon receipt. If the Amplifier does not operate
correctly, please notify your dealer immediately.
We strongly suggest that you save all packing materials. If the Amplifier is
returned to your dealer or Jeff Rowland Design Group, the original packing
materials must be used for shipment. Neither Jeff Rowland Design Group
nor the shipper can be held responsible for damages incurred during transit
if the original factory packing is not used. All factory returns require that a
Return Authorization number be issued by Jeff Rowland Design Group
prior to shipment.
Contents
Ensure that all of the auxiliary components listed below are enclosed
within the accessory box. Refer to the diagrams illustrated above and
verify the components included.
1Handheld remote transmitter
2Four (4) compliant isolation interface supports
3AC power cable
4One (1) warranty card (in some countries warranties are provided by
the respective importer)
Initial Inspection / Contents

Front Panel Function Controls
CONCENTRA
SOURCE
123456TAPE MON MUTE VOLUME
JEFF ROWLAND
DESIGN GROUP
A
E
B
C
D

Front Panel Function Controls
Before attempting any system interconnection, please familiarize yourself
with the front panel controls of the Concentra Integrated Amplifier. The
descriptions below refer to the letters associated with the features in the
diagram above.
Front Panel
AVOLUME control: Rotating the VOLUME control clockwise increases
volume, while rotating the knob counter clockwise decreases volume.
The VOLUME control provides a fixed range of 99.5 dB in increments of
0.5 dB throughout a rotation of 330 degrees. If the VOLUME control is
rotated abruptly, the full range of 99.5 dB will be achieved within 110
degrees of rotation.
BDISPLAY: Contains the IR receiver for receiving commands from the
remote control. Also displays the numerical Volume control position
from 0 to 99.5 dB in increments of 0.5 dB. If desired, your dealer can
internally configure the display to turn off after five seconds from
initiating any front panel command (Input Select, Volume, etc.) Please
contact your dealer for details.
CMUTE push button: Momentarily pressing this push button mutes the
amplifier PRE OUT and SPEAKER OUTPUTS. The lamp above the MUTE
button illuminates. Pressing the push button again restores the normal
condition of the amplifier outputs. The MUTE lamp is not illuminated.
Pressing and holding in the Mute push button for five seconds, then
releasing, will reset the microprocessor and automatically recalibrate
internal circuitry. Initiate this function in the unlikely event of control
‘lock-up’ (caused by AC line brown-outs) or to reset the channel balance
to ‘center’ position if it has been changed via the remote control.
DSOURCE push buttons 1-6: Momentarily pressing one of these buttons
selects the source (CD, tuner, etc.) connected to the associated rear
panel input (see Signal Connections). The lamp above the selected
source illuminates. In addition to being selected for listening, the
selected source signal is also routed to the PRE OUT and TAPE OUT
jacks on the rear panel (see Signal Connections).
ETAPE MON push button: Momentarily pressing this button routes the
signal source (tape recorder) connected to the TAPE INPUT jacks to the
PRE OUT and SPEAKER OUTPUTS for monitoring and listening
purposes. The lamp above TAPE MON illuminates. Pressing the button a
second time restores normal operation. The TAPE MON lamp is not
illuminated. Note: The TAPE OUT outputs are unaffected by TAPE MON.
Front Panel Function Controls

Signal Connections
AE
C
C
DDA
BB
E
F
G
GH
H
I
I

Signal Connections
AINPUT 1/PHONO (RCA unbalanced): Connect any unbalanced line
source (CD, Tuner, D/A Converter, Laser Disk, etc.), unless the PHONO
option has been installed. If the PHONO option is installed, the low
level output from the PHONO source (turntable) MUST be connected
only to this input, and line level sources MUST NOT be connected to
this source.
BINPUTS 2 and 3 (RCA unbalanced): Connect any line level source with
unbalanced (RCA) type connectors.
CINPUTS 4-6 (Female XLR balanced): Connect any line level source using
balanced XLR connectors. Each INPUT connector conforms to a Pin #1
ground, Pin #2 negative, Pin #3 positive standard. For lowest possible
noise, both positive and negative terminals of each INPUT connector
are isolated from ground by several megohms which restores maximum
common mode noise rejection regardless of source impedance
imbalances.
DTAPE IN (RCA unbalanced): Connect the output from a tape recorder to
this input to allow monitoring of recording via the TAPE MON push
button (see Front Panel Function Controls).
ETAPE OUT (RCA unbalanced): Connect to the input of a tape recorder
to allow recording from the selected SOURCE.
FGND: When using the phono option, this thumbscrew provides a
convenient ground connection for turntable grounding. To use, unscrew
the knurled knob several turns, insert the uninsulated or spade terminal
end of the ground wire from the turntable underneath the thumbscrew
and firmly re-tighten.
GPRE OUT BAL (Male XLR balanced): When using an additional amplifier,
such as for subwoofers or for additional speakers, this connector
provides fully balanced volume-controlled output to drive the additional
amplifier. This PRE OUT conforms to a Pin #1 ground, Pin #2 negative,
Pin #3 positive standard. Balanced output signals are always provided
regardless of input selected (balanced or unbalanced). Note: The gain
structure (internal power amplifier gain) from PRE OUT BAL to
SPEAKER OUTPUT is 26 dB.
HPRE OUT UNBAL (RCA unbalanced): This connector provides volume
controlled output to drive an auxiliary amplifier (as above) requiring
unbalanced RCA connections.
ISPEAKER OUTPUT: Unscrew the + and - SPEAKER OUTPUT connectors
and install the positive and negative loudspeaker cable spade connec-
tors. Retighten the output connectors. Red is normally positive; black is
normally negative. ALWAYS USE THE SUPPLIED SPEAKER TERMINAL
HAND WRENCH WHEN CONNECTING OR DISCONNECTING LOUD-
SPEAKER CABLES. DO NOT OVER TIGHTEN THE TERMINALS. Note:
The signal polarity between either PRE OUT BAL or PRE OUT UNBAL
and speaker output is inverted. For example: PRE OUT BAL, Pin #3
(positive polarity) and PRE OUT UNBAL (RCA center pin) corresponds
to SPEAKER OUTPUT - (negative).
WARNING: Both positive and negative SPEAKER OUTPUTS are
electrically active with respect to chassis and/or system ground
potential. It is important that both of these outputs are electrically isolated
from system ground potential. This precludes the use of this Amplifier in
certain loudspeaker switching configurations (sometimes used in retail
demonstrations) and testing or servicing situations where either positive or
negative outputs can be connected to ground potentials. Failure to observe
these precautions may result in damage to the Amplifier and may void your
warranty. Consult the factory first if the Amplifier is to be used under these
conditions.
Signal Connections
!

Rear Panel Power Connections
2
1

Installation
Locate the amplifier as close as possible to its final installation point.
Allow access to the rear panel for making connections.
The Concentra Integrated Amplifier is convection cooled, eliminating the
need for a fan or forced air cooling. When operating, the chassis should
have at least two inches of air space around the heat sink areas.
Supplied with your Concentra Integrated Amplifier are four compliant
interface supports which can be easily installed underneath the chassis
near the corners. This will help attenuate the transfer of spurious energy
from the supporting structure into the Amplifier chassis.
Rear Panel Power Connections
Important:Please strictly follow the steps in order as outlined below
before operating your Amplifier
1Verify that the VOLTS 50/60 Hz INPUT identified on the rear panel
corresponds to the AC mains voltage of your service area.
2Install the AC power cable between the amplifier and an active AC
mains outlet
Note: The Concentra Integrated Amplifier is designed to be powered from
AC mains at all times with no degradation of durability or service life. An AC
power switch for interrupting AC mains has not been provided. However, if
desired, the AC power cord can be plugged into a ‘switched’ AC mains
outlet or suitable device to facilitate AC mains switching in the interest of
energy conservation. Please note that the Concentra power consumption is
approximately 100 watts average. Depending on various operating
conditions during use, power consumption can increase up to 550 watts for
short periods.
Installation / Rear Panel Power Connections

Remote Control Features
AThe six-function, hand-held, IR remote transmitter permits remote
operation of Input Selection, Volume Up/Down, Balance L/R and Mute
functions.
BThe Concentra volume display simultaneously receives transmitted data
and displays a numerical Volume control position from 0 to 99.5 dB in
increments of 0.5 dB.
The remote transmitter handset operates on a standard 9 volt battery
available from a wide variety of sources. This battery is accessed by
removing the two Phillips-head screws on the back side of the handset.
Two (2) different data rate transmission codes can be selected if
interference from other IR remote transmitters become an issue. Please
contact your Jeff Rowland Design Group dealer or distributor for
information on selecting different data codes.
B
A

Concentra Performance Specifications
Output Power Continuous RMS Watts
@ 8 ohms 100 watts
@ 4 ohms 150 watts
Bandwidth 0.5 Hz to 160 kHz, -3 dB
Slew Rate 30 volts per microsecond
THD and Noise Less than 0.06% at rated power
Damping Factor 60, 20 Hz to 20 kHz, 8 ohms
Output Current 16 amps continuous, 28 amps peak
Gain Structure
Preamplifier Section 14 dB
Amplifier Section 26 dB
Volume Control Range 99.5 dB
Volume Control
Resolution 0.5 dB ± 0.05 dB over entire range
Input Impedance 36k ohm
Common Mode
Rejection Ratio Greater than 60 dB, 20 Hz to 20 kHz
Power Consumption 100 watts idle; 550 watts maximum
Inputs
Balanced Line 3 per channel (XLR)
Unbalanced Line 3 per channel (RCA)
Record 1 per channel (RCA)
Unbalanced Phono (optional) 1 per channel (RCA)
Outputs
Balanced Pre Out 1 per channel (XLR)
Unbalanced Pre Out 1 per channel (RCA)
Record 1 per channel (RCA)
Speaker 1 pair binding posts per channel
Dimensions 17.5 in (W) x 14.35 in (D) x 5.75 in (H)
44.5 cm (W) x 36.2 cm (D) x 14.6 cm (H)
Weight 50 lbs (23 kg)
Because Jeff Rowland Design Group is constantly analyzing new
design improvements, we reserve the right to change or modify product
specifications without notice or obligation.

If you have any additional questions regarding installation or operation,
please contact your authorized Jeff Rowland Design Group Dealer.
JEFF ROWLAND
DESIGN GROUP