AW-250 DUAL MONO
BALANCED POWER AMPLIFIER
Owner’s Manual
WARNING:To reduce risk of fire or electric shock, do not expose this appliance to
rain or moisture.Verify line voltage before use.
Do not remove cover. No user serviceable parts inside. Refer servicing to qualified
service personnel. The warranty in void if the product is tampered with by non
authorised personnel. Use only authorised Electrocompaniet service station.
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The design features of Ampliwire 250 DMB
After the Electrocompaniet 25 watt amplifier had established a new standard for transistor
amplifiers, research was undertaken to find ways to make the amplifier even better, and to
extend its highly musical sound quality to more powerful amplifier designs. The engineers
at Electrocompaniet were not satisfied by only reducing the commonly recognised types of
distortion to low levels. They recognised that distortion appears in many forms, and that
distortion was still audible in listening tests even when conventional categories of distortion
were at astonishingly low levels.
Traditionally, designers increased feedback to make a larger portion of the output signal
control the amplifiers response. Our listening tests showed us that simply applying more
feedback was not the answer. In fact, as one kind of distortion went down, other parame-
ters would be adversely affected, leading to an overall degradation of sound quality. We
knew that the other conventional design approach of eliminating feedback completely was
not the answer either, because this would cause high distortion levels, and as a result
would produce a “woolly” sound.
The answer to the dilemma was found in a novel approach to feedback theory. We
developed a feedback concept that allowed local feedback to be applied around individual
stages of the amplifier circuit. This approach allowed us to avoid the sonic disadvantages of
overall feedback from output to input. The concept was further developed to reduce phase-
and interphase distortion between stages of the amplifier as well. We were able to concent-
rate the loop feedback on the stages of the amplifier where it resulted in audible
improvement.
Stability margins were also expanded because feedback no longer affected the frequency
response. The use of this concept of individual gain blocks - complex in design but simple
in function - allowed us to reduce distortion to minute values in all the products.
The amplifier is divided into two separate sections or gain blocks. The input block is a
transconductance amplifier without overall feedback. This avoids large output current being
fed back to the input, and mixed with the minute input signal. The output block is a
transresistance amplifier with parallel feedback. This is done to prevent higher frequencies
than the feedback loop can handle, from entering the loop. An approach like this will
prevent Transient Inter modulation Distortion (TIM) and Slewing Induced Distortion (SID),
eliminating the need for an extremely wide bandwidth.
All stages work in Class A with an efficiency of less than 0,1%. The power supply of the AW
250 DMB consists of two 650 VA toroidal transformer. Furthermore, the power supply
consists of a 120.000 micro farad reservoir divided into twelve 10.000 micro farad
capacitors in parallel with 4,7 and 0,1 micro farad polycarbonate- and polypropylene
capacitors.
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Unpacking the amplifier:
Immediately upon receipt of the amplifier, inspect the carton for possible damage during
shipment. If the carton is visibly damaged, a claim must be filed with the carrier as soon as
possible.
Unpack the unit carefully, and please do remember to save all packaging materials for
future shipment. The carton and packaging have been designed to offer the safest possible
protection when transporting your amplifier.
The content of the carton is as follows:
1 pcs Electrocompaniet Ampliwire 250 DMB
1 pcs AC power cord
1 Owners Manual
1 pcs Spare fuse,
10.0 AT slow-blow 5x20mm (120V AC)
5.0 AT slow-blow 5x20mm (240V AC)
The actual spare fuse is located inside the AC 3 pin receptacle.
Connecting the AW 250 DMB
Connecting to mains
Check that the mains voltage printed on the rear panel of the amplifier corresponds with
the line voltage in the territory were you intend to use your amplifier.
How to avoid damages
A good operating practice is to turn off all equipment before any connections or
disconnection’s are made. Do not under any circumstances connect or disconnect
equipment when power is turned on. If you insist on connecting or disconnecting while
power is turned on, you should be aware that the design of the RCA plug generates a large
transient when inserting the plug. This could damage both the speakers and the amplifier.
The rear panel
The rear panel of the Ampliwire AW 250 DMB is equipped with two sets of RCA input
sockets, marked + and -, and one XLR female socket, for each channel.
Single-ended (normal) input and operation
Upon arrival, the amplifier is set for single-ended use with a shorting plug in the negative
RCA input.This will short the negative (-) input of the amplifier to ground. With shorting
plugs in position, the amplifier is ready to be connected in a normal way with a single
ended preamplifier.
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Balanced XLR input and operation
The balanced mode can only be used if the preamplifier has a balanced output. In order to
use the balanced XLR- input, turn off the amplifier, and remove the shorting plugs from
the negative (-) RCA inputs.Use an XLR interconnect with GND on pin 1, + on pin 2 and
- on pin 3.
Balanced RCA input and operation
The balanced mode can only be used if the preamplifier has a balanced output. Be sure
the amplifier is turned off. Remove the shorting plugs. Use 2 single (1 stereo) interconnect
cables from the preamplifier to the power amplifier, connecting + and - outputs from the
preamplifier to the + and - inputs of the corresponding channel on the amplifier.
Make sure the + and - are not interchanged, as this will cause the system to operate out of
phase, with very poor bass response as a result.
Operating instructions:
How to turn on your system
You should always turn on your equipment in this order: Signal source devices (CD, tuner,
etc) and preamplifier are turned on first. Allow 30 seconds of preheating before you turn on
your power amplifier.When turning your system off, you should start by switching off your
power amplifier, then the preamplifier, and finally your signal source devices
After switching on the power amplifier, there will be a 5 seconds delay before the speakers
are connected. This will prevent large turn on/off transients to reach the speakers.
Replacing a blown main fuse:
Always remove the AC cord from the Inlet
The main fuse is located inside a small drawer in the AC inlet of the unit. If, for some
reason the fuse blows, turn the unit off, and remove the AC cord from the inlet.
Open the drawer with a small screwdriver and remove the broken fuse. The spare fuse is
located in the hole in front of the main fuse. Push the new fuse gently out of the hole, and
place it in correct position (where the blown fuse was removed). Push the drawer gently
back to the closed position, connect the power cord and turn the unit on.
Never replace a blown fuse with other values than printed on the unit.
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Warning:
The amplifier will be warm.
Due to the high class A operating point used in the Electrocompaniet design, it is normal
that the amplifier feels warm. Proper ventilation will be needed, and the amplifier should not
be covered in. A good rule is to allow 1 - 2 inches of air sidewise, and 2 - 3 inches above
the amplifier.
If placing the amplifier on the floor, be aware of carpets that can obstruct the ventilation
underneath the amplifier.
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Service Policy:
When service is needed
Your dealer will have all relevant information about the service centers in your area, and
will ensure that your unit is serviced without delay. It is our general policy to have your
amplifier returned to you within 5 working days. This is an average time, and could vary
locally, depending on the work load at the service center.
If, for some reason, there are no service facilities available in your country, please ship the
amplifier to the following address:
ELECTROCOMPANIET A/S
SOLHEIMVEIEN 36
N-1473 SKAARER, NORWAY
FAX +47 67911760
E-mail : [email protected]
You are responsible for all shipping charges, insurance, re-importation to your country, and
duty arrangements. When shipping a product to the factory for service, always include the
following:
1)
2)
3)
4)
A sales slip or other proof of purchase if repair is claimed under
warranty.
A proforma invoice with value of the goods, stating that the amplifier
is returned to Norway for repair.
An accompanying letter describing faults, symptoms, or problems
with the amplifier.
Always ship the amplifier in its original carton and packaging
material to prevent damage in transit.
Electrocompaniet will not accept responsibility for any damage caused in transit, no matter
how ever caused.
If you require further information concerning the amplifier operation, or if you have any
questions related to service, please do not hesitate to contact your dealer or national
Electrocompaniet distributor.
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Technical Specifications AW250DMB :
The following technical data were measured on randomised test objects and are typical
data. All measurements are made with the following equipment:
Distortion analyser: Tektronix AA501
Oscilloscope:
Oscillator:
Tektronix 468
Tektronix SG505
Frequency counter: Rascal 9838
Phase meter:
Hewlett Packard 3575A
Amplifier section
Main voltage 120 V / 240 V. Clipping point of the amplifier is set to a level where total
harmonic distortion (THD) is 0.2 %.
Output Impedance (20 Hz - 20 kHz)
RCA (single) input impedance
XLR (balanced) input impedance
Input sensitivity for rated output
Max. peak current
< 0,008 Ohm
220 kOhm
110 kOhm
1 V
> 100 A
THD (measured at 1 kHz half power, 8 Ohm)
THD (measured at 1 kHz -1 dB, 8 Ohm)
Noise (measured with both inputs shorted)
400 Hz - 30 kHz :
< 0,001 %
< 0,001 %
90 µV
10 Hz - 30 kHz :
100 µV
Rated output power
10 % change in line voltage will give app. 20 % change in output power.
8 Ohm2 x 250 W
4 Ohm2 x 380 W
2 Ohm2 x 625 W
1 Ohm2 x 1100 W
Power consumption (no load or signal) 230 W
Dimensions
Width 483 mm / 19 inches
Depth 450 mm / 17 inches
Height 210 mm / 8.2 inches
Weight39 kg. / 85.8 lbs.
The manufacturer reserves the right to alter these specifications without further notice.
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