Marihart Audio ACRH-1.2 User Manual
Hybrid Integrated Amplifier ACRH-1.2
The ACRH1.2 is an integrated and complete stereo amplification and
preamplification system. It offers the features of a high-end unit designed in a userÂfriendly, convenient, easy to use system. Its tube-based preamplifier offers
outstanding detail in sound and scope. This, along with its semiconductor output
stage, creates a musically dazzling performance.
It is well known that a good preamplifier is the heart of a sound system. With this in
mind, Margules Audio fronted challenge of developing a hybrid integrated amplifier
combining an extraordinary tube preamplifier with excellent solid state amplifier.
Description:
Preamplifier
The preamp section of the unit is based on two dual triodes (12AU7) per side that
acts as coupling circuit from the signal source to the power amplifier. The circuit is
based on the knowledge and experience gained in the development of the acclaimed
Margules SF220 line stage.
This topology allows the frequency response to be further wider than the audio
bandwidth, maintaining the fase and amplitude constant with a very low distortion
together with an extremely fast transient response.
High Voltage Power supply
The Bias power supply of the preamplifier is fully regulated. Good regulation
reduces the loss of signal integrity.
The filament supply is also regulated and has active damping control to avoid noise
and microphonics.
Remote operation
The remote control is unusually versatile. Besides the input selection, volume, power
on and off
You will also be capable of switching the AC power any associated equipment having
load up to 15
amps (1800 watts). Additionally switching control can be accomplished by means of
the RS232 connection or with an external web server(optional)
All switching is made by mechanical high quality relays avoiding the audio signal to
go through semiconductor device, thus ensuring maximum signal purity.
Amplifier Section
The totally discrete semiconductor amplifier has Direct coupling topology, designed
so that the entire interstage is direct, avoiding capacitors , results faster transient
and lower distortion.
The output stage bias is designed with a proprietary circuit optimizes the operating
point of the semiconductor to avoid the typical overheating found in other designs
Class A while avoiding the problems of distortion in Class B.
The innovative design of ACRH-1.2 complements metal film resistors and printed
circuit silver coating.
Connections:
All inputs and outputs of the preamplifier are unbalanced RCA connectors.
The back panel is organized by blocks from left to right: the first RCA block contains
the inlets to the amplifier, the second is for the preamp, the third has four inputs,
which have the same gain and impedance; and the fourth section is direct avoiding
the volume control, so you can use the ACRH together with a 5 channel preamplifier
for a high end multichannel. It can also be used as an input and output circuit for a
processor.
The phono preamplifier is external and is not included.
The preamplifier has two outputs per channel, they are connected in parallel.
One will be connected to the amplifier input, completing the integrated system. The
other is available to connect an active subwoofer or perhaps an adapter multi-room
extension or surround system.
To wire the speakers, connect the 5 ways binding post of the amplifier terminals to
corresponding speaker, use a good cable with a 12 gage or more, it is
recommendable to avoid long runs, less than 10 meters.
Connect the speakers red to the red and the black to the black, it is VERY important
to avoid any short circuit, this will lower the life expectancy of the ACRH.
The output stage has big current capability and it is protected by fuses, if a fuse
blows, it might be because the ACRH was overdriven or the speaker cable has a short
circuit.
Check for proper connections before turning the ACRH on.
The minimum loudspeaker impedance is 4 Ohms, avoid paralleling speakers that can
lower the speakers below this recommended impedance.
When the power line is connected to the ac wall outlet the filaments of the tubes and
the remote control receiver will be turned on.
The filament will be on as long as the AC is connected, so the unit will be in standby
mode, and can be turned on and use immediately, also the life expectancy of the
tubes will be longer.
Avoid turning the unit on immediately after you connect the ACRH to the wall outlet,
let it warm the filaments for a couple of minutes.
Operation:
When your ARCH 1.2 is plugged for first time, or when the current wall is absent for
a few seconds, it is good to allow the tube filaments to be preheated for 2 minutes,
verify that the volume is at a low level to avoid a blow sudden sound can damage
your speakers.
Turn on your ACRH 1.2 with the on /off switch in the remote or the front panel.
This will activate a blue light in the upper left corner indicating that the unit is active,
now the high voltage in the preamplifier and power amplifiers are operational.
To select the input source press the selector switch in the front panel or at the
remote control, the red light on the front panel indicates the selected source.
To turn on or off the unit presses the power switch on the front panel or the remote
control.
The filaments are always on, so the ACRH is instantly operative. Tube life expectancy
increases if the instructions are followed.
The ACRH has an AC outlet for associated equipment interrupted with a capacity of
15 amps, so you can control the switching on and off of associated components by
the remote control.
Troubleshooting:
There is no sound: Verify the connections
Make sure the unit is turned on verifying the on light.
Verify that the input signal is connected in the correct
input.
Verify that the source is working properly.
One channel has no output
Verify the connections
Verify the jumper from the preamp to the Amp.
Verify that the source is working properly.
Check the output fuses
General Comments:
The unit is always warm, so that should be placed in well ventilated area.
Always place the unit on a firm platform to avoid external vibrations.
You can alter the tonal characteristics by placing the unit in different types of
surfaces such as feet, spikes etc.’
Cables
The cabling quality changes the tonal characteristic of the ACRH, so choosing proper
ones will let bloom its characteristics.
To minimize unwanted noise in the system:
Avoid excessive in long interconnect cables.
Avoid having signal cables near the AC. power line
Avoid ground loops between components, only one physical ground should be used
Breaking in period:
150 hours of music playback are required. Having the lit without music unit does not
work for a proper seating.
TubesLife Expectancy:
For optimum performance we recommend changing both tubes every three to four
years, even if should last for longer period.
The unit has 12AU7 or 12AT7 tubes but these can be exchanged with 12AX7 or
similar ones without
any adjustment.
Never remove the tubes from the circuit while the ACRH is connected to the wall.
Specification
Integrated: Frequency Response 10-50 KHZ
Power at 8 Ohms 100w. / Channel
Total noise <0.3mV.
THD .03%
Weight 15KG.
Consumption: Stand Buy 17 W.
At maximum power at 8 ohms. 380W
Preamplifier:
Frequency Response 4-80KHZ
Noise <0.1mV
Gain 1DB
Harmonic distortion 0.02%
Amplifier:
Input voltage for maximum power 0.8V
Frequency Response 10-50KHZ
Noise <0.2mV
Harmonic distortion 0.02%
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