Jeff Rowland Design Group very desirable Remote Controlled Concentra 2 with optional Phono option, truly like new, with optional Cardas Radio Frequency Reduced Production caps 6 XLR's and 16 RCA's value $234 alone.

Classic cost no object very desirable classic 2001-2004

One owner truly like new with factory remote, cloth bag, owners papers and this is highly recommended by those in the know and all of here art Weinhart Design.

Serial # E-01209

The Concentra II (1/2001 through
10/2003) is a 150 watt per channel integrated amplifier. It has a
completely different power supply layout and design, in fact much more
similar to the 112 power amplifier. The new layout is a much quieter
source of power, and also has a separate front-end supply. The amplifier
section has been derived from the model 10 and 112 power amplifiers,
incorporating LM3886 integrated amplification circuits instead of
bipolar transistors. See model 10, 12 and 112 for more info. The input
section of the Concentra II is derived from the Synergy II preamplifier
and utilizes a pair of audio input transformers. The Concentra II can be
identified by its blue display and indicators.

INCLUDES: Optional high-quality internal phono preamp modules were available for 1000 euro.

Specifications :

Output Power..................................150 watts at 8 ohms, 250 watts at 4 ohms
Bandwidth.......................................0.1Hz to 160kHz, -3 dB
Slew Rate.......................................30 volts per microsecond
THD..................................................Less than 0.01% at rated power
Damping Factor...............................>60, 20Hz to 20kHz
Gain Structure.................................14dB Preamplifier section
..........................................................26dB Amplifier section
Volume Control Range......................99.5dB
Volume Control Resolution................0.5dB +/- 0.05dB over entire range
Input Impedance...............................36k ohms balanced or unbalanced
Common Mode Rejection Ratio........Greater than 60dB, 20Hz to 20kHz
Power Consumption.........................150 watts idle; 550 watts maximum
Inputs.................................................Balanced 3 x XLR per channel
............................................................Unbalanced 3 x RCA per channel
Outputs..............................................1 pair 5-way binding posts per channel
.............................................................1 pair balanced pre-out via XLR
.............................................................1 pair unbalanced pre-out via RCA
Dimensions(w x d x h)........................44.5 x 39 x 15.5 cm
Weight...................................................24kg

A good friend of mine has the Concentra
II and I have heard it many times in his setup but somehow we never got
around to comparing it to my model sixes. Nevertheless, because I know
his system so well, I can safely say that the Concentra II indeed sounds
like the ingredients that it is made of: a combination of the Synergy
2i preamp and 112 poweramp. It has all the finesse, low-level resolution
and the fluid, airy and gentle treble as well as a colorful and
romantic character. It is important to understand that although it
really is marvelous, the Concentra II is not a universally applicable
amp. Much like the Synergy 2i preamp, it can lack propulsion, speed and
attack if the system it is placed in is unsympathetic. But match it with
fast and open sounding speakers and the combination is stunning.

All Concentras have a balance control which makes sense because they
contain a version of the Synergy preamp inside. Using the remote
control, the balance will work but this just is not indicated on the
front panel. To reset the balance, press “Mute” for a couple of seconds.

Although the C2’s mute function dims the
display, and supposedly puts the unit in a low-power state, my friend
still measured a power consumption of around 100 watts in that state.
Compared to my Model sixes that use around 25 watts per side in standby,
that seems really high.

The early Concentras had no possibility
of putting it into standby or “sleep”. There is an option to upgrade
early Concentra units with a “standby” mode that allows the unit to run
cool and lower power consumption when not in use. Later models had this
mode as standard. Standby mode is then engaged by pressing the “mute”
switch after which the power transistors shut off and the unit consumes
only a few watts. However, the original Concentra cannot be upgraded to
Series II status.

Above: Input transformer mounted on the rear panel, on the input/output board

Above: LM3886 integrated amplification
circuit up close. You can see that it has 11 pins, indicating that there
is going on more inside besides simple amplification.

Concentra Technology

The text below has been re-published from content that was formerly available on the official Jeff Rowland website.

The amplifier output section of the
Concentra II contains six power amplifier circuits per channel, each
capable of 150 watts of peak power, incorporated in a novel “Intelligent
Power Transistor with Gain” configuration. These output circuits are
used in place of standard output transistors to provide unprecedented
audio performance, stability, and reliability virtually impossible to
achieve with conventional discrete components.

These integrated power output devices,
or transistors, despite greater cost in comparison to their more
commonly used discrete transistor counterparts, occupy very little
circuit “real estate,” dramatically reducing capacitive and dielectric
storage effects, as well as simplifying the overall signal path. Because
of these lower capacitive and dielectric effects, open-loop bandwidth
is approximately ten times greater than comparable discrete circuit
designs and mid and high frequency distortion is lowered an order of
magnitude while output impedance is also lowered dramatically, resulting
in a much more accurate and musical presentation.

These devices also allow the added
benefit of extremely accurate bias control and stability, whereas most
other amplifier circuits must rely on “thermal bias.” Thermal bias is a
process where a temperature sensor, most often a diode or transistor
mounted to the heat sink, mimics the behavior of the output transistors
and adjusts the bias current accordingly as it heats or cools – less
current when hot and more current when cool. The greatest drawback with
thermal bias is that there is a time delay of several seconds between
the time the temperature of the output transistor changes and the
temperature sensor reacts, as heat from the output device must slowly
travel through the heat sink before it will arrive at the sensor.
Typically, under conditions such as when music is playing, where the
signal is changing instantaneously and bias requirements will vary
quickly and continually, the bias adjustment will almost never be
optimal for low distortion and the best possible sound quality since the
bias adjustment will never catch up to the changing needs of the output
transistors. Within the Concentra II, the temperature sensing is all
performed directly within the output transistors themselves. This system
allows the device to react as soon as demands change so that any and
all bias adjustments are performed instantly and optimally along with
the music – there is no delay between the time the temperature of the
device changes and the sensor detects the change, as the sensor is an
integral part of the device itself. In this way, distortion is lowered
and reliability is dramatically increased to best serve the music while
at the same time-saving cost.

One common question is whether the
output section of the amplifier is biased into Class-A operation.
Technically, the answer is “yes,” as the exceptional linearity of the
output section design achieves the advantages of pure Class-A operation.
Using the “Intelligent Power Transistor with Gain” system keeps the
output section properly biased at all times to eliminate crossover
distortion caused by the output transistors during turn-on and turn-off,
as opposed to the brute force Class-A biasing techniques used in other
inadequate amplifier designs to compensate for poor linearity that
result in low efficiency, excessive heat, electrical waste, and the need
for power management.

Yet another advantage of the output
devices Jeff Rowland Design Group has chosen is that they have no
inherent current limiting – only thermal limiting. Most amplifier
designs use a monitoring system to detect current draw. If the
transistors are drawing too much current, the output section will shut
down so as not to destroy itself. Within the Concentra II, the output
transistors have no limit to the amount of current they can safely draw:
unless thermally challenged, the output transistors have no power
limit. If the device is driven hard and detects an unsafe temperature,
it will simply lower the bias until a safe temperature is reached and
then resume at the optimal bias setting.

The output transistors within the
amplifiers are securely clamped to a massive, non-resonant, machined
aluminum heat sink via a rigid, custom machined aluminum bar. The heat
sinks have been designed with a specific height, depth, and width in
proportion to the front panel, rear panel, and top and bottom covers of
the amplifier so that when all of the various parts of the unit are
assembled, the amplifier as a whole does not resonate or vibrate. It
also means that the entire chassis acts as a heat sink for better heat
dissipation. This allows optimal and efficient heat transfer from the
output devices and prevents any mechanical resonance or vibration under
high power conditions from affecting the signal. During demanding
musical passages, the amplifier is able to play cleanly and smoothly
with no chance for excessive heat or ringing heat sinks to interfere
with or affect sound quality.

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It is best to call David and visit: www.weinhartdesign.com with questions
in Los Angeles Showroom 310-472-8880 or on my cell after hours and
weekends 310-927-2260 any time from 10AM - 10PM.

Weinhart Design has lots of other items new and used and if you're in Los
Angeles or visiting please accept my invitation to experience our World
Class Audio Showroom and please visit our web site @ 
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All sales out of California are State Sales Tax exempt.

California State Sales Tax of 9.5% applies for items picked up or shipped to a California address.

We accept payments by Bank Wire Transfers without fees and is the only
form of payment on all sales out of the U.S. and Canada. We prefer this
method of payment and also makes shipping to addresses other than
billing agreeable.

VISA,
MC and Papal are gladly accepted within the U.S. and Canada as long as
the charge is approved and shipping to the billing address on record and
adds 3% to cover costs for VISA or MC best to call David.

Please call me directly in my world class showroom in Los Angeles weekdays @
310-472-8880 or any reasonable time on my cell including weekends @
310-927-2260 and I can answer your questions and help you with all of
your new and pre owned needs.

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 Changing the Way You Listen, 

         
          David Weinhart 
       Weinhart Design, Inc.
         President & CEO
 david@weinhartdesign.com
  www.weinhartdesign.com
The Audio and Video Expert
2337 Roscomare Road, Studio #1
 Los Angeles, California 90077
   Showroom) 310-472-8880
      Cell) 310-927-2260