CH M1.1 User manual

M1.1 Two-channel Reference Power Amplifier
User Manual

Dear Valued Customer,
e are honored that you chose the M1.1 Power Amplifier for your audio system. Our team devoted every effort to design and
manufacture this top quality versatile and future-proof product and is proud to present it to you. e hope your M1.1 Amplifier will
bring you uncountable hours of emotion from your music collection.
But before you embark on your musical journey, we kindly request your attention to the information contained in this manual. The
M1.1, 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.
e hope you will enjoy your M1.1 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 Operation modes............................................................................................................................................... 8
1.1.2 Feedback ratio control........................................................................................................................................ 9
1.1.3 Gain control...................................................................................................................................................... 9
1.1.4 Bias circuitry (ExactBias).................................................................................................................................... 9
1.2 Advanced monitoring circuit........................................................................................................................................ 9
1.2.1 Power monitoring.............................................................................................................................................. 9
1.2.2 Temperature monitoring.................................................................................................................................. 10
1.3 Careful construction.................................................................................................................................................. 10
1.4 Modular architecture and slot-in boards..................................................................................................................... 10
1.4.1 Monaural analog inputs: ANALOG_IN board...................................................................................................... 11
1.4.2 Firmware update and control: CONTROL board................................................................................................... 11
1.5 Power supply........................................................................................................................................................... 11
2 Read carefully 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
3.2 Positioning your unit................................................................................................................................................ 15
3.3 Connections.............................................................................................................................................................. 16
3.3.1 CONTROL board............................................................................................................................................... 18
3.3.1.1 USB port................................................................................................................................................. 18
3.3.1.2 Ethernet port.......................................................................................................................................... 18
3.3.2 ANALOG IN board............................................................................................................................................ 18
3.3.3 Power cord receptacles and voltage selection..................................................................................................... 19
3.4 Amplifier modes....................................................................................................................................................... 19
3.4.1 Stereo mode.................................................................................................................................................... 19
3.4.2 Monaural mode............................................................................................................................................... 19
3.4.3 Bridge mode................................................................................................................................................... 20
3.4.4 Passive bi-amplification mode........................................................................................................................... 20
3.4.5 Active bi-amplification mode............................................................................................................................ 21
3.4.6 Daisy-chain mode............................................................................................................................................ 22
4 Operation......................................................................................................................................................................... 23
4.1 Front panel controls.................................................................................................................................................. 23
4.1.1 Front panel..................................................................................................................................................... 23
4.1.2 Front panel push buttons.................................................................................................................................. 24
4.2 Operating modes...................................................................................................................................................... 24
4.2.1 Normal mode.................................................................................................................................................. 24
4.2.2 Shortcuts......................................................................................................................................................... 26
Rev 3.0 M1.1 User Manual 5

4.2.3 Menu mode..................................................................................................................................................... 28
4.3 Configuration........................................................................................................................................................... 31
4.3.1 M1.1 configuration menu items........................................................................................................................ 32
4.3.1.1 AUDIO SETTINGS..................................................................................................................................... 32
4.3.1.2 DISPLAY SETTINGS................................................................................................................................... 33
4.3.1.3 SHORTCUTS............................................................................................................................................. 34
4.3.1.4 FACTORY SETTINGS.................................................................................................................................. 35
4.3.1.5 INSTALLED OPTIONS................................................................................................................................ 36
4.3.1.6 NET ORK............................................................................................................................................... 36
4.4 Returning to factory defaults..................................................................................................................................... 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
6 M1.1 User Manual Rev 3.0

1 Technical highlights
CH products are proudly designed and manufactured in Switzerland by CH Precision Sàrl. Our engineers put together all their
know-how, expertise and ingeniousness to bring you the M1.1, a top performance future-proof modular two output channels
power amplifier with USB flash-drive firmware update and Ethernet control capabilities. Like all CH Precision products, the M1.1is
highly versatile: up to 5 setups are possible: stereo mode (one M1.1 driving a pair of loudspeakers), monaural mode (the power
transformer of the M1.1is dedicated to one loudspeaker, only one output board is used), bridge mode (to nearly four times the
available power), passive bi-amplification (each channel powers a specific loudspeaker driver or group of drivers) or active bi-
amping (an active loudspeaker crossover is to be inserted between the preamplifier and the pair of M1.1s)
For increased flexibility, the M1.1 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 loudspeaker on the
market. The amplifier gain can also be adjusted over a 24 dB wide range in 0.5 dB steps. This greatly helps 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
Ohm load can be engaged to help reduce signal reflections as well as to improve external noise immunity, therefore improving the
overall signal transmission. A pass-through XLR line-level output is also provided to daisy-chain multiple M1.1 and A1.5 amplifiers.
M1.1 main components
Rev 3.0 M1.1 User Manual 7
(5) (6)
(13)
(3)
(2)
(8)
(9)
(9)
(9)
(9)
(10)
(10)
(11) (11)
(14)(14) (15)(15) (16)(17)
(4) (7)
(18)
(12)
(2)
(3)
(2) (2)
(1)
(1)
(1)
(1)

(1) Customized Argento Audio speaker terminals
(2) Output coil for HF immunity
(3) Monaural analog input boards (each M1.1 can be equipped with 1 or 2 such boards)
(4) Small signal power transformer
(5) Mains switch, low power section fuse and power cord receptacle
(6) High power section fuse and power cord receptacle
(7) Standby power transformer (ensures green mode Standby)
(8) USB (firmware update) and RJ-45 (control) board
(9) Adjustment shafts and spikes
(10) Power supply regulation boards
(11) Heatsink-mounted amplifier boards
(12) Shielded small-signal analog ground
(13) User interface push buttons
(14) Rectifying diode bridges, mounted onto the front panel
(15) Custom ultra-low ESR/ESL rectifying capacitors
(16) Main analog ground oxygen-free copper plate
(17) Display (on front panel)
(18) High power section transformer
1.1 Unmatched lexibility
The M1.1 offers unmatched system integration flexibility. Not only does it provide multiple modes of operation (stereo, monaural,
bridge and bi-amplification modes) but also allows adjustments to match the loudspeaker impedance and sensitivity through
feedback and gain controls. The operating modes can be selected from the M1.1 front panel user interface or from the Android
app.
1.1.1 Operation modes
The M1.1 integrates two power amplification channels and provides the option to support a single or dual input boards. In its
default configuration, the M1.1 is delivered with a single input board and provides following modes of operation:
•Monaural mode: In this mode, the entire power of the power transformer is dedicated to a single output channel and the
M1.1 can deliver up to 2200 . It is optimal for low impedance speakers, requiring large amount of current.
•Passive bi-amplification mode: In this mode, the M1.1 operates its two power amplification channels, each channel
driving a different loudspeaker terminal with an identical signal. Feedback and gain can be adjusted independently for
each channel to best match the individual speaker sections. In Bi-Amplification Mode, each channel delivers 200 under
8 Ohm (350 under 4 Ohm or 600 under 2 Ohm). It is optimal with speakers with more than one pair of binding
posts.
•Bridge mode: In this mode, the M1.1 operates as a very high power monaural power amplifier, where both amplification
channels are used in balanced mode from a single audio signal. hen configured in Bridge Mode, the M1.1 can deliver
up to 700 under 8 Ohm. It is optimal for high impedance speakers in large rooms, requiring large voltage swings.
By adding a second input board, the M1.1 provides following additional operating modes:
8 M1.1 User Manual Rev 3.0

•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
M1.1 delivers 200 under 8 Ohm per channel. It is the configuration used when a single M1.1 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 M1.1 delivers 200 under 8 Ohm on each channel. It is optimal if the speaker has an external active
crossover filter network.
1.1.2 Feedback ratio control
One of the M1.1's most unique features is its user controllable feedback ratio. This feature provides control over the ratio between
global and local feedback applied in the M1.1'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 M1.1 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. e
recommend to start with pure local feedback and increase the global feedback until the bass are tight enough to your personal
taste. Feedback ratio settings can be adjusted on the fly from the M1.1 front panel user interface.
1.1.3 Gain control
The M1.1 provides an integrated gain control with a 24 dB range in 0.5 dB steps. It allows optimal matching of the loudspeakers
sensitivity, room size, and preamplifier output level. In multi-amplification systems it can be used to match the sensitivity of the
individual loudspeaker sections. Gain is conveniently accessed from the front panel user interface and can be set on the fly.
1.1.4 Bias circuitry (ExactBias)
The M1.1 provides a patent-pending advanced bias control circuitry called the ExactBias that does not only follow 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 output voltage and current of each M1.1
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 loudspeakers, and detect malfunctions such as short-circuits or
amplifier damage.
Rev 3.0 M1.1 User Manual 9

1.2.2 Temperature monitoring
The DSPs also monitor both the power transistors and the heatsink temperatures. If the temperature becomes excessive, the M1.1
will protect itself by entering standby mode.
1.3 Care ul construction
The M1.1 power amplifier chassis is made of high grade aluminum alloy and steel elements with no visible screws on the front, top
and side panels. The front panel, side panels and top cover are machined from aluminum, while the base plate is machined from
solid steel, ensuring optimal mechanical reference and magnetic shielding. First class mechanical and chemical surface treatments
provide the luxury finish of the M1.1.
Pin assembly of all chassis elements enables smooth joints between metal parts while screws every 6cm ensure protection against
electromagnetic interferences.
Four stainless steel feet support the unit. Each foot ends with an elastomer ring to sit on delicate surfaces but is also equipped with
height adjustable hardened steel spikes to fine tune the unit position. Horizontal leveling is accomplished using the provided
screwdriver through the four adjustment shafts accessible from the top of the unit. Moreover, the steel spikes serve as vibration
evacuation channels for stacked units. Special covers are provided to interface with the spikes of the unit above. 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 M1.1, ensuring the electronic
circuitry is protected from gradually gathering dust.
1.4 Modular architecture and slot-in boards
The M1.1 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. Optional boards
provide audio functionality and connectivity to other equipment. There are two types of slot-in boards:
•ANALOG_IN: provides mono single-ended RCA and BNC (both configurable as either high impedance or 300 Ohm
terminated) and balanced XLR analog audio input. One (left or right) or two (left and right) such boards can be fitted
into the M1.1. By default, the M1.1 is factory delivered with a single ANALOG_IN board.
•CONTROL: provides a USB port for software upgrade and an Ethernet port for command. The CONTROL board is factory
mounted in each M1.1.
There are three slots in the M1.1. Two of them can be populated with a left ANALOG_IN and/or a right ANALOG_IN board. The
last slot is dedicated to the CONTROL board. Note that optional boards MUST be installed by a qualified technician. Failure to do so
will void any warranty.
10 M1.1 User Manual Rev 3.0