CH A1 User manual

A1 Power Amplifier
User Manual

Dear Client,
We are honored that you have chosen the CH A1 Power Amplifier. ur team has put all his efforts into designing and
manufacturing this top quality versatile and future-proof product and is proud to present it to you. We hope your A1 will bring you
uncountable hours of emotion from your musical collection.
But before starting your musical journey, we kindly ask you to pay attention to the information contained in this manual. The A1,
as you will discover in the following pages, is a Swiss precision product designed for ultimate performance and flexibility. However,
reaching sonic excellence requires your unit to be setup and operated correctly and this what this manual is all about. If you have
any questions or require assistance, please don't hesitate to contact your authorized dealer.
We hope you will enjoy your A1 amplifier for many years.
The Concert has just begun...
Cossy F.
Heeb T.

Table of contents
1 Technical highlights.............................................................................................................................................................. 7
1.1 Unmatched flexibility.................................................................................................................................................. 8
1.1.1 peration modes................................................................................................................................................ 8
1.1.2 Feedback control................................................................................................................................................ 9
1.1.3 Gain control....................................................................................................................................................... 9
1.1.4 Bias adjustment.................................................................................................................................................. 9
1.2 Advanced monitoring circuit......................................................................................................................................... 9
1.2.1 Power monitoring............................................................................................................................................... 9
1.2.2 Temperature monitoring.................................................................................................................................... 10
1.3 Mechanical construction............................................................................................................................................. 10
1.4 Modular architecture and slot-in boards...................................................................................................................... 10
1.4.1 Monaural analog inputs: ANAL G_IN board....................................................................................................... 11
1.4.2 Firmware update and control: C NTR L board.................................................................................................... 11
1.5 Power supply............................................................................................................................................................ 11
2 Before use......................................................................................................................................................................... 12
2.1 Package content........................................................................................................................................................ 12
2.2 Safety notice............................................................................................................................................................. 12
2.3 User manual............................................................................................................................................................. 13
2.4 Mains supply............................................................................................................................................................. 13
2.5 Transport and packaging............................................................................................................................................ 13
2.6 Cleaning................................................................................................................................................................... 14
2.7 Maintenance and service............................................................................................................................................ 14
3 Installation........................................................................................................................................................................ 15
3.1 Unpacking................................................................................................................................................................ 15
3.1.1 Removing the security screws............................................................................................................................ 15
3.2 Unit positioning......................................................................................................................................................... 15
3.3 Connections............................................................................................................................................................... 17
3.3.1 C NTR L board................................................................................................................................................ 18
3.3.1.1 USB port.................................................................................................................................................. 18
3.3.1.2 Ethernet port........................................................................................................................................... 19
3.3.2 ANAL G_IN boards.......................................................................................................................................... 19
3.3.3 Power cord receptacle and voltage selection....................................................................................................... 19
3.4 Amplifier modes........................................................................................................................................................ 19
3.4.1 Stereo mode..................................................................................................................................................... 19
3.4.2 Bridge mode.................................................................................................................................................... 20
3.4.3 Monaural mode................................................................................................................................................ 20
3.4.4 Passive bi-amplification mode............................................................................................................................ 21
3.4.5 Active bi-amplification mode............................................................................................................................. 21
3.4.6 Chained mode.................................................................................................................................................. 22
4 peration.......................................................................................................................................................................... 23
4.1 Front panel controls................................................................................................................................................... 23
4.1.1 Front panel...................................................................................................................................................... 23
4.1.2 Front face push-buttons..................................................................................................................................... 23
4.2 perating modes....................................................................................................................................................... 24
4.2.1 Normal mode................................................................................................................................................... 24
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4.2.2 Shortcuts.......................................................................................................................................................... 26
4.2.3 Menu mode...................................................................................................................................................... 28
4.3 Configuration............................................................................................................................................................ 31
4.3.1 A1 configuration menu items............................................................................................................................. 32
4.3.1.1 AUDI SETTINGS...................................................................................................................................... 32
4.3.1.2 DISPLAY SETTINGS.................................................................................................................................... 33
4.3.1.3 SH RTCUTS.............................................................................................................................................. 34
4.3.1.4 FACT RY SETTINGS................................................................................................................................... 35
4.3.1.5 INSTALLED PTI NS................................................................................................................................. 36
4.3.1.6 NETW RK................................................................................................................................................ 37
5 Firmware update............................................................................................................................................................... 38
5.1 Preparing the USB stick............................................................................................................................................. 38
5.2 Updating the unit's firmware..................................................................................................................................... 38
5.3 Emergency firmware update procedure....................................................................................................................... 39
6 Troubleshooting................................................................................................................................................................. 40
7 Specifications..................................................................................................................................................................... 41
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1 Technical highlights
CH products are proudly designed and manufactured in Switzerland by CH Precision Sàrl. ur engineers have put all their know-
how into bringing you the A1, a top performances future-proof modular two output channels power amplifier with USB flash-drive
firmware update and Ethernet control capabilities. As all CH Precision products, the A1 is highly versatile: a single A1 can be used
as a stereo power amplifier (with two mono input boards), or a pair of A1 can be used as mono power amplifiers. Even in
monaural mode, 4 setups are possible: left /right mono mode (the transformer of each A1 is dedicated to a loudspeaker, but only
one output board is used), bridged mode (to nearly quadruple the available power per channel), passive bi-amp (each channel
powers a specific speaker driver) or active bi-amp (when an active crossover network is placed between the preamplifier and the
A1). Moreover, multiple A1s can be chained for ultimate performance, using multiple A1s per speakers.
For increased flexibility, the A1 also provides two unique features: global/local feedback ratio and gain adjustments. The amount
of global feedback in the amplifying loop of each channel can be adjusted to best match virtually any speaker on the market. The
amplifier gain can also be adjusted over a 24 dB wide range, by 0.5 dB steps. This also greatly helps in matching the output level
of the preamplifier, the efficiency of the connected loudspeakers and the listening room. Three standard input connectors are
available (balanced XLR, single-ended RCA and BNC). Unbalanced inputs can be configured as high impedance input, or a 300
hm load can be engaged to match the output of 50 or 75 hm D/A controllers or preamplifiers. A pass-through XLR line-level
output is also provided for daisy-chaining multiple A1s.
A1 main components
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(1) utput coil for HF immunity
(2) Argento Audio speaker terminals
(3) Monaural analog input boards (each A1 can be equipped with 1 or 2 such boards)
(4) Mains switch and power cord receptacle
(5) USB (firmware update) and RJ-45 (control) board
(6) Adjustment shafts and screws
(7) Power supply regulation boards
(8) Heatsink-mounted monaural amplifier boards
(9) User interface buttons
(10) Rectifying diode bridges, mounted onto the front panel
(11) Custom rectifying capacitors
(12) Main analog star-ground oxygen-free copper plate
(13) AM LED display (on front panel)
(14) Standby power transformer (ensures green mode Standby)
(15) Main power transformer
1.1 Unmatched flexibility
The A1 offers unmatched system integration flexibility. Not only does it provide multiple modes of operation (stereo, mono,
bridged and active or passive bi-amp) but is also provides adjustments to match speaker impedance and sensitivity through
feedback and gain controls. perating modes can be selected by the user from the A1's front panel. In addition, multiple A1s can
be daisy-chained for ultimate performance in multi-amplification systems.
1.1.1 Operation modes
The A1 integrates two power amplification channels and provides the option to support a single or dual input boards. In its default
configuration, the A1 is delivered with a single input board and provides following modes of operation:
•Bridge mode: In this mode, the A1 operates as a very high power mono power amplifier, where both amplification
channels are used in balanced mode for a single audio channel. When configured in Bridged Mono Mode, the A1 can
deliver up to 350 W under 8 hm. It is optimal for high impedance speakers in large rooms, requiring large voltage
swings.
•Monaural mode: In this mode, the entire power of the transformer is dedicated to a single output channel. In Left or
Right Mono Mode, the A1 can deliver 550 W under 1 hm. It is optimal for low impedance speakers, requiring large
amount of current.
•Passive bi-amplification mode: In this mode, the A1 operates its two power amplification stages in parallel, each channel
driving a different speaker terminal with the same signal. Feedback and gain can be adjusted independently for each
channel to best match the individual speaker sections. In Passive Bi-Amp Mode, each channel delivers 100 W under 8
hm. It is optimal with speakers with more than one binding post pair on its passive crossover filter network.
By adding a second input board, the A1 provides following additional operating modes:
•Stereo mode: In Stereo Mode, each amplification stage is driven by its dedicated input board and the amplifier operates
as a standard stereo power amplifier. Feedback and gain settings are shared among both amplification channels and the
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A1 delivers 100 W under 8 hm per channel. It is the configuration used when a single A1 drives a pair of speakers.
•Active bi-amplification mode: As for Stereo Mode, Active Bi-Amp Mode links each amplification stage to its dedicated
input board. Feedback and gain can however be adjusted individually for each channel in order to best match the
requirements of each driver. An active cross-over is generally used to split the signal into different frequency bands
between the system controller/preamplifier (such as CH Precision's L1) and the power amplifiers. In the Active Bi-Amp
Mode, the A1 delivers 100 W under 8 hm on each channel. It is optimal if the speaker has an external active crossover
filter network.
1.1.2 Feedback control
ne of the A1's most unique features is its user controllable feedback. This feature provides control over the ratio between global
and local feedback applied in the A1's amplification stage. Global feedback takes a portion of the output signal after the power
stage and feeds it back to the input of the amplifier. This ensures a very low output impedance and low distortion figures. Local
feedback, on the other hand, does not include the output stage and lets the latter operate in open loop mode. This favors small
signal details and timing. As a rule of thumb, a higher ratio of global feedback is preferred for grip and control in the low
frequencies whereas a lower ratio is preferred for speed and details in the high frequencies. This rule is however not absolute as
each speaker and cross-over are different and we highly recommend to try out various settings to find the best match with the
connected loudspeakers, especially if the A1 is driving a complete full bandwidth loudspeaker. In multi-amplification systems,
different feedback settings are commonly used for the various speaker sections opening a whole new level of performance. We
recommend to start with pure local feedback and increase the global feedback until the bass are tight enough for your personal
taste. Feedback settings can be adjusted on the fly from the A1's front panel.
1.1.3 Gain control
The A1 provides an integrated gain control with a 24 dB range and 0.5 dB steps. This gain control allows for optimal matching of
speaker sensitivity, room size, and preamplifier output level. In multi-amplification systems it can be used to match the sensitivity
of the individual speaker sections. Gain is conveniently accessed by a front panel control and can be set on the fly.
1.1. Bias adjustment
The A1 provides an advanced bias control circuitry that not only follows slow temperature variations, but also accurately takes into
account all the dynamic aspects induced by transients in the musical content.
1.2 Advanced monitoring circuit
1.2.1 Power monitoring
Each power amplifier board is equipped with a DSP that monitors the instantaneous voltage and current output of each A1's
channel. Both values are sampled at around 100 kHz, ensuring peak values are properly detected. This circuitry has several
purposes: give the user a feedback of the peak power fed to the speakers, and detect malfunctions such as short-circuits or
amplifier damage.
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1.2.2 Temperature monitoring
The DSPs are also responsible for reading both the power transistors and the radiators temperatures. If the temperature gets
excessive, the class-A polarization is turned off, forcing the A1 to work in pure class-B. If removing the output stage bias current is
still not enough, and the temperature keeps rising, the A1 will protect itself by entering standby mode. Please note that under
normal conditions, none of the above should happen.
1.3 Mechanical construction
The A1 power amplifier is assembled from high-quality aluminum and steel elements with no visible screws on the front, top and
side panels. The front panel, base, side panels and top cover are machined from aluminum. The power supply is based on a fully
shielded 1200 VA toroidal transformer and custom rectifying capacitors sitting in the central position of the unit. Argento Audio
internal wiring is used throughout the unit and binding posts from the same manufacturer provide the best possible interface to
your speaker cables. The area where the air flows to cool down the amplifier is isolated from the rest of the A1, ensuring all
electronics are preserved from dust accumulation. Pin assembly of all chassis elements provides smooth joints between elements
while screws every 6cm ensures protection against electromagnetic interferences. First class mechanical and chemical surface
treatments provide the luxury finish of the A1.
Four steel feet support the unit. Each feet ends with a elastomer ring to sit on delicate surfaces but is also equipped with a height
adjustable steel spike to fine tune unit positioning. Horizontal adjustment is done with the provided screwdriver through the four
adjustment shafts accessible from the top of the unit. In addition to providing convenient horizontal adjustment from the top of the
unit, the shafts also serve as vibration evacuation channels for any stacked unit. Special shaft covers are provided to interface with
the spikes of the stacked unit. Any vibration from the upper unit is transmitted by the shaft cover to the shaft of the lower unit and
from there to the lower unit's feet or spikes, forming a privileged path for vibrations evacuation.
The area where the air flows to cool down the amplifier is hermetically sealed from the rest of the A1, ensuring the electronic
circuitry is protected from gradually gathering dust.
1. Modular architecture and slot-in boards
The A1 benefits from a fully modular architecture. It features separated sections for power rails, analog and digital power supplies,
front panel, signal routing and central host processor, monaural analog input boards and single channel amplification boards. This
modular architecture combined with the USB plug for firmware update allows for easy servicing and upgrade should one section
become faulty or obsolete.
The slot-in boards section consists in a vertically mounted mother board with optional boards plugged into it. ptional boards
provide audio functionality and connectivity to other equipment. There are two types of slot-in boards:
•ANAL G_IN: provides mono single-ended RCA and BNC (both configurable as either high impedance or 300 hm
terminated) and balanced XLR analog audio input. ne (left or right) or two (left and right) such boards can be fitted
into the A1. By default, the A1 is factory delivered with a single ANAL G_IN board.
•C NTR L: provides a USB port for software upgrade and an Ethernet port for command. The C NTR L board is factory
mounted in each A1.
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There are three slots in the A1. Two of them can be populated with a left ANAL G_IN and/or a right ANAL G_IN board. The last
slot is dedicated to the C NTR L board. Note that optional boards MUST be installed by a qualified technician. Failure to do so will
void any warranty.
1. .1 Monaural analog inputs: ANALOG_IN board
The ANAL G_IN board features a user selectable mono analog input on three different connectors: single-ended RCA, single-ended
BNC and balanced XLR. Both the RCA and BNC inputs can be configured for high-impedance or 300 hms load. In addition to its
inputs, the ANAL G_IN board includes an XLR output providing a pass-through of the input signal.
1. .2 Firmware update and control: CONTROL board
The C NTR L board is factory installed into the A1. It provides a USB port for software updates using a flash drive and an Ethernet
port for controlling the unit over a network.
1.5 Power supply
The power supply of the A1 is a linear supply with multiple independent local regulations. It is based on an oversized magnetically
shielded toroidal 1200 VA mains transformer. A secondary (also toroidal) transformer is used as Standby transformer to ensure
green Standby mode, meeting the latest energy saving regulations. Both transformers have static shields between primaries and
secondaries. They are mounted on a separate steel plate which is isolated from the main base steel plate by silent blocks.
Custom made 4-poles capacitors are used for rectification. These capacitors exhibit exceptionally low ESR, high speed and high
capacitance, providing instantaneous response to current draws from the output stage.
Discrete (power-transistor and op-amp based) ultra low noise regulators are used throughout the power supply to ensure the purest
low noise DC feed possible to the different sections. The input stages of the power section are also fully regulated to avoid any
coupling distortion. A massive oxygen-free copper plate is used for signal ground.
Input AC voltage to the power supply can be set to 100V, 115V or 230V AC depending on your local mains voltage.
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2 Before use
Please read this manual carefully before making connections or operating your A1. After reading this manual, please store it in an
accessible place for future reference. If after reading this manual you feel unsure about how to make connections or how to
operate the unit, please contact your authorized dealer for assistance.
2.1 Package content
Make sure that the package content is complete. If not, please contact your authorized dealer. Your package should contain:
•A1 power amplifier with one (mono bridged or mono passive bi-amp modes only) or two input boards, depending on the
ordered configuration
•A power cord
•Four adjustment steel spikes
•A suction cup (used to unscrew the top covers)
•An accessory box containing:
◦a spike adjustment screwdriver
◦an Allen key
◦a Torx 10 screwdriver
◦four stacking covers
◦a USB stick containing the latest CH Precision firmwares.
◦a set of four CH Support Discs
Please store the packaging for future use. Check your A1 for any apparent damage. In case of a damage, immediately contact
your authorized dealer. If your A1 is cold due to transport, please let it warm up to room temperature before powering it up.
2.2 Safety notice
Make sure to observe the following rules:
•Install your A1 power amplifier on a stable base
•Do not install your A1 power amplifier near water
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•Always handle with care. The A1 power amplifier is heavy, so have someone help you when moving it around
•Do not expose the unit to any kind of liquid
•Do not install in direct sun light or near any heat source such as radiators or other apparatus generating heat
•Do not install in a confined space and make sure sufficient air can flow around the unit, including under the unit.
•Never install your A1 power amplifier directly on a carpet or any soft material, as fresh air flow from openings under the
unit to the side apertures is required for proper cooling of the unit.
•Do not operate under high ambient temperature (>40°C) or with extremely high humidity such as in humid cellars
•nly use options and accessories specified or recommended by the manufacturer
•Do not open the unit nor try to service it by yourself. Do not try to install any option board by yourself. Always refer to a
qualified technician for service, maintenance or upgrades. Failure to do so will void the unit's warranty
2.3 User manual
Please read this manual carefully before making connections or operating your A1 power amplifier. After reading, store the
manual in an accessible place for future reference. If, after reading this manual, you feel unsure about how to make connections
or how to operate the unit, please contact your authorized dealer.
2. Mains supply
Make sure to use 3 terminals (phase, neutral and earth) power cords with ground conductor. Make sure that the mains voltage
selection of the unit matches your mains voltage.
Make sure your A1 power amplifier is disconnected from AC wall power in the following cases:
•When making connections (it is also recommended to disconnect the rest of the system from AC wall power)
•When cleaning
•During thunder storms
•When unused for a long period
2.5 Transport and packaging
The A1 power amplifier must always be stored in its original packaging for transportation. Doing so will ensure optimal level of
protection of your unit. Therefore, keep all the packaging material in a dry and clean place for future use.
Rev 2.0 A1 User Manual 13

In addition, the transformer base plate must be secured for transportation to avoid excessive constraints on the silent blocks
isolating the chassis from transformer vibrations. This is done by the insertion of three security screws on the bottom of the unit.
Failure to do so will void the warranty as it may cause the silent blocks to tear up and the heavy transformer module to move
inside the A1, resulting in severe damages to all A1 components. Do not forget to install these screws for transportation and to
remove them at installation of the unit in its new location.
Finally we recommend to remove the adjustment spikes and to put them into the A1 box for transportation. Indeed, vibrations
during transport may cause the adjustment spikes to move from their fully retracted position. There is risk of scratching the
installation base if the spikes are not fully retracted when installing the unit.
2.6 Cleaning
Use a soft, dry towel or cloth for cleaning. Never use any solvent or liquids as they may damage the surface treatment or
penetrate inside the unit.
2.7 Maintenance and service
The A1 power amplifier contains no user serviceable parts. Do not try to open, modify or repair your A1 by yourself. This will void
any warranty. Your A1 power amplifier must be checked by a qualified technician in any of the following cases:
•The unit is not functioning properly
•The mains cable or the power cord receptacle is damaged
•The unit has been dropped to the floor or presents external damage
•The A1 power amplifier has been exposed to liquids (such as rain) or unknown substances
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3 Installation
3.1 Unpacking
Unpack the A1 power amplifier and store the packaging for future transportation. Be careful when lifting the A1 as the unit is
heavy (over 40kg). Get someone to help you if necessary. When unpacking and installing the A1, take care not to damage the
high quality surface treatments.
3.1.1 Removing the security screws
The transformer base plate must be secured during transportation to avoid damage to the isolating silent blocks. Three security
screws are located on the bottom of the unit. To remove the security screws, tilt the unit on its side and unscrew. Do not tilt the unit
on the front or back panels as this may damage the front plate or the connectors.
Security screw location
(1) Security screws. Must be mounted for transport and removed at installation
3.2 Unit positioning
We recommend to locate the A1 close to the loudspeaker it drives, using short loudspeaker cables.
For best transmission and immunity to external noise, we recommend to connect the A1 input to the upstream unit (preamplifier)
using a balanced XLR cable.
When delivered from factory, the A1 amplifier's four feet sit on elastomer rings, ensuring both scratch-protection for the base on
which the unit sits, as well as safe anti-slipping unit positioning.
But a more advanced vibration-channeling mechanical coupling can be implemented, thanks to the steel spikes and the polymer
Rev 2.0 A1 User Manual 15

support discs provided with the A1. To use this optimal coupling, simply go through the following steps:
1. Place the A1 unit on a stable base at its approximate final position, for instance in your preferred audio rack. Make sure
cooling air is able to freely flow around the unit.
2. Gently lift the unit's corners and insert a support disc under each foot. The foot's elastomer ring should disappear in the
support disc's groove when properly placed. Carefully check all four feet perfectly fit in each support disc before pursuing
any further. The unit should stably rest on its feet at that point.
3. Unscrew the four top covers from the A1's shafts with the provided suction cup. Be careful not to scratch their delicate
finish.
4. Insert the adjustment spikes into each adjustment shaft.
5. Softly screw clockwise each adjustment spikes into the shaft with the provided screwdriver, until any resistance is felt (just
before the unit's corner starts to lift).
6. Then screw clockwise each spike by the same amount (for instance two full turns).
7. If the base is flat, the unit should be stable and horizontal. If not, correct the unit's stability and horizontality by turning
clockwise or anti-clockwise the required spikes.
8. If no CH Precision unit is to be stacked on top of the A1, screw the four top covers back. therwise, screw the four
polymer stacking caps instead, and gently lay down the unit to be stacked on top of it. Be very careful that both units are
perfectly aligned in order not to scratch the A1's top plate with the other unit's feet. Repeat steps 3 to 8.
Adjustment shafts, feet and spikes
(1) Adjustment shafts. Insert adjustment spikes and use screwdriver to secure and adjust individual feet spikes
(2) Feet
(3) Adjustment spike heads (when inserted into adjustment shafts)
(4) Adjustment spike
Never stack any component other than CH's on your A1. Never use the aluminum shaft covers (top covers) when another CH
component is to be stacked on top of your A1.
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Shaft covers (left: stacking cover, right: top cover)
3.3 Connections
This section provides information about how to connect your A1 power amplifier to your system. As the A1 is a modular design with
different optional boards, the description applies to the example configuration presented below. For details about how to integrate
you A1(s) in a specific setup, please refer to the Amplifier modes section of this user manual. If you don't feel secure with the
connections to be applied to your configuration, please contact your authorized dealer for assistance.
The example configuration is a stereo-ready (2 input boards) power amplifier. Your configuration could only contain a single input
board.
A1 rear panel connections
(1) Argento Audio right positive (or bridged mono positive) speaker terminal
(2) Ethernet port for command interface [C NTR L board]
(3) Power on/off switch
(4) Analog ground connectors. Bottom one can be connected to digital ground (Earth) using provided jumper
(5) RCA single-ended analog input for right channel [Right ANAL G_IN board]
(6) BNC single-ended analog input for right channel [Right ANAL G_IN board]
(7) RCA single-ended analog input for left channel [Left ANAL G_IN board]
(8) BNC single-ended analog input for left channel [Left ANAL G_IN board]
(9) Argento Audio left positive (or bridged mono negative) speaker terminal
(10) Argento Audio left negative speaker terminal
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(11) XLR balanced analog output (pass-through for A1 chaining) for left channel [Left ANAL G_IN board]
(12) XLR balanced analog input for left channel [Left ANAL G_IN board]
(13) Transportation security screws (to be removed once A1 is placed in its definitive position)
(14) XLR balanced analog input for right channel [Right ANAL G_IN board]
(15) XLR balanced analog output (pass-through for A1 chaining) for right channel [Right ANAL G_IN board]
(16) Earth connector. Internally connected to digital ground
(17) Power fuse and voltage selection and power cord receptacle
(18) USB port for software upgrades. [C NTR L board]
(19) Argento Audio right negative speaker terminal
The C NTR L board is mandatory in any A1 configuration and is always factory installed. Depending on arrangement of optional
boards in the A1's expansion slots, connector arrangement may slightly differ on your unit. Each A1 unit provides 2 expansion
slots, each supporting a monaural analog input (ANAL G_IN) board.
ANAL G_IN boards provides 3 monaural user-selectable analog input connectors (balanced XLR, single-ended high impedance (Hi-
Z) / 300 hm RCA and BNC) as well as an XLR output monitoring the input signal. This output is used to daisy-chain multiple A1s
in multi-amplification systems.
Installation and removing of optional boards must be done by a qualified technician only. Do not attempt to install or remove any
optional board by yourself as this would void the unit's warranty.
3.3.1 CONTROL board
The C NTR L board is factory installed into the A1. It provides a USB port for software updates and an Ethernet port for controlling
the unit over a network. Following drawing shows the layout of the back panel of the C NTR L board:
CONTROL board back panel layout
3.3.1.1 USB port
The USB port on the C NTR L board is dedicated to the firmware update of the A1 unit. Do not use it for any other purpose. For
more information on unit firmware update, please refer to the corresponding section of this manual.
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3.3.1.2 Ethernet port
The Ethernet port on the C NTR L board is dedicated to network based control of the unit. This functionality is currently not
implemented, thus leave the Ethernet port unconnected. A future A1 firmware release will provide this functionality.
3.3.2 ANALOG_IN boards
ANAL G_IN boards feature a user selectable mono analog input on three different connectors: single-ended RCA, single-ended
BNC and balanced XLR. The analog stage design is fully discrete and balanced. Both the RCA and BNC inputs can be configured for
high-impedance or 300 hms load, the later allowing for optimal signal transmission when connected to the outputs of 50 or 75
hm D/A controllers or preamplifiers. In addition to their inputs, ANAL G_IN boards include an XLR output providing a pass-
through of the input signal. This output can be used to daisy-chain multiple A1s in multi-amplification systems for ultimate
performance. Balanced connections are recommended for optimal performance. Following drawing shows the layout of the
connectors on the ANAL G_IN boards:
ANALOG_IN panel layout
3.3.3 Power cord receptacle and voltage selection
Make sure that the voltage selection is set to the correct value with respect to the AC voltage in your location. Connect the power
cord to the power cord receptacle and plug the power plug to an AC wall outlet only after all other connections have been made.
3. Amplifier modes
This section describes most standard setups in which one or multiple A1s can be integrated into.
3. .1 Stereo mode
A single A1 equipped with two analog input boards can be used as a stereo power amplifier. This is the simplest configuration that
already allows to enjoy the unique sound of the A1 amplifier. The picture below shows how it should be connected in this case.
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Stereo mode
3. .2 Bridge mode
A pair of A1s, each equipped with a single analog input board can be used as a pair of high power with high voltage swing
monoblocks. This configuration should be used when low efficiency high impedance speakers are used in large rooms to achieve
higher sound level than possible with a single stereo A1. This configuration also exhibits a better signal-to-noise ratio. The picture
below shows how they should be connected in this case.
Bridge mode
3. .3 Monaural mode
A pair of A1s, each equipped with a single analog input board can be used as a pair of high power with very high current capability
monoblocks. This configuration should be used when low efficiency low impedance speakers are used in large rooms to achieve
higher sound level than possible with a single stereo A1. The picture below shows how they should be connected in this case.
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C1 D/A Controller
A1 Stereo Power Amplifier Left Speaker Binding Post
Right Speaker Binding Post
Balanced XLR cables
C1 D/A Controller
A1 Left Mono Power Amplifier
Left Speaker Binding Post
Right Speaker Binding Post
Balanced XLR cables
A1 Right Mono Power Amplifier