CH L1 User manual

L1 Dual Monaural Line Preamplifier
User Manual

Dear Valued Customer,
We are honored that you chose the L1 Dual Monaural Line Preamplifier. Our team made every effort to desi n and manufacture
this top quality versatile and future-proof product and is proud to present it to you. We hope your L1 preamplifier will brin 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
L1, as you will discover in the followin pa es, is a Swiss precision product desi ned for ultimate performance and flexibility.
However, reachin 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 L1 preamplifier for many years.
The Concert has just be un...
Cossy F.
Heeb T.

FCC-Notice
Note: This equipment has been tested and found to comply with the limits for a Class B di ital device, pursuant to Part 15 of
the FCC Rules. These limits are desi ned to provide reasonable protection a ainst harmful interference in a residential
installation. This equipment enerates, uses and can radiate radio frequency ener y and, if not installed and used in
accordance with the instructions, may cause harmful interference to radio communications. However there is no uarantee that
interference will not occur in a particular installation.
If this equipment does cause harmful interference to radio or television reception, which can be determined by turnin the
equipment off and on, the user is encoura ed to try to correct the interference by one or more of the followin measures:
•adjust or relocate the receivin antenna
•increase the separation between the equipment and the receiver
•connect the equipment into a mains outlet on a circuit different from that to which the receiver is connected
•consult the dealer or an experienced ratio/TV technician for help
Disposal – Environmental care
Directive 2002/96/EG of the European Parliament requires consumer electro-technical appliances to be
disposed separately and have to be indicated with the followin symbol. Should you dispose this
component please do so in conformity with local and lobal le al and environmental re ulations and
accordin to best practices. We stron ly encoura e you to recycle any batteries used with this component.

Table of contents
1 Technical Hi hli hts.............................................................................................................................................................. 8
1.1 Unmatched flexibility.................................................................................................................................................. 9
1.1.1 Confi urations.................................................................................................................................................... 9
1.1.2 Input sta e....................................................................................................................................................... 10
1.1.3 Volume control................................................................................................................................................. 10
1.1.4 Output sta e.................................................................................................................................................... 10
1.2 Advanced DC offset cancellation................................................................................................................................. 10
1.3 Careful Metal Work Construction................................................................................................................................ 10
1.4 Power supply............................................................................................................................................................ 11
2 Read carefully before use................................................................................................................................................... 12
2.1 Packa e content........................................................................................................................................................ 12
2.2 Safety notice............................................................................................................................................................. 12
2.3 User Manual............................................................................................................................................................. 13
2.4 Mains supply............................................................................................................................................................. 13
2.5 Transport and packa in ............................................................................................................................................ 13
2.6 Cleanin ................................................................................................................................................................... 13
2.7 Maintenance and Servicin ........................................................................................................................................ 13
3 Installation........................................................................................................................................................................ 15
3.1 Unpackin ................................................................................................................................................................ 15
3.1.1 Removin the security screw.............................................................................................................................. 15
3.2 Positionin your unit................................................................................................................................................. 15
3.2.1 Unit level adjustment........................................................................................................................................ 15
3.2.2 Shaft covers..................................................................................................................................................... 16
3.3 Connections............................................................................................................................................................... 17
3.3.1 CONTROL Section.............................................................................................................................................. 18
3.3.1.1 USB port.................................................................................................................................................. 18
3.3.1.2 Ethernet port........................................................................................................................................... 18
3.3.2 Sin le-channel preamplification board............................................................................................................... 19
3.3.3 Power cord receptacle and volta e selection....................................................................................................... 20
3.3.4 External DC Power Supply Connector.................................................................................................................. 20
3.4 Preamplifier Confi uration......................................................................................................................................... 20
3.4.1 Dual Monaural confi uration............................................................................................................................. 21
3.4.2 True Monaural Confi uration............................................................................................................................. 21
3.4.3 True Monaural Extended Confi uration.............................................................................................................. 22
4 Operation.......................................................................................................................................................................... 24
4.1 Front panel controls................................................................................................................................................... 24
4.1.1 Front panel...................................................................................................................................................... 24
4.1.2 User control knob............................................................................................................................................. 24
4.2 Operatin modes....................................................................................................................................................... 26
4.2.1 Normal mode................................................................................................................................................... 26
4.2.2 Shortcuts.......................................................................................................................................................... 27
4.2.3 Menu mode...................................................................................................................................................... 29
4.3 Confi uration............................................................................................................................................................ 32
4.3.1 L1 confi uration menu items............................................................................................................................. 33
4.3.1.1 AUDIO SETTING........................................................................................................................................ 33
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4.3.1.2 DISPLAY SETTING...................................................................................................................................... 35
4.3.1.3 SHORTCUTS.............................................................................................................................................. 36
4.3.1.4 FACTORY SETTING..................................................................................................................................... 37
4.3.1.5 INSTALLED OPTIONS................................................................................................................................. 38
4.3.1.6 NETWORK................................................................................................................................................ 39
4.4 Remote control.......................................................................................................................................................... 40
4.4.1 Remote control operation.................................................................................................................................. 40
4.4.2 Chan in the remote control batteries................................................................................................................ 41
4.5 Returnin to Factory defaults..................................................................................................................................... 41
5 Firmware update............................................................................................................................................................... 42
5.1 Introduction.............................................................................................................................................................. 42
5.2 Firmware Update procedure....................................................................................................................................... 42
5.2.1 Preparin the firmware ima e........................................................................................................................... 42
5.2.2 Updatin the firmware (Firmware Update procedure).........................................................................................43
5.2.3 Emer ency Firmware Update procedure............................................................................................................. 43
6 Troubleshootin ................................................................................................................................................................. 45
7 Specifications..................................................................................................................................................................... 46
7.1 Specifications............................................................................................................................................................ 46
7.2 Dimensions............................................................................................................................................................... 47
7.3 Factory settin s......................................................................................................................................................... 47
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1 Technical Highlights
CH products are proudly desi ned and manufactured in Switzerland by CH Precision Sàrl. Our en ineers put to ether all their
know-how, expertise and in eniousness to brin you the L1, a top performance future-proof modular two channel preamplifier
with USB flash-drive firmware update and Ethernet control capabilities. Like all CH Precision products, the L1 is hi hly versatile: 3
confi urations are possible: Dual Monaural (the L1 holds two channels in a sin le chassis), Monaural (two L1s work to ether, each
one processin a sin le channel, one board in each chassis) and finally the Monaural Extended (two L1s work to ether, each one
processin a sin le channel, however with two boards in each L1 chassis, allowin twice the amount of inputs). All these
confi urations can be further enhanced by addin the X1 External power supply.
The L1 is a fully symmetrical desi n, pure Class A discrete transistor based circuitry. This results in ultra low noise, hi h bandwidth
and hi h slew rate performances. The si nal stays in the analo domain all the way throu h. By default, the L1 is confi ured for
no series capacitor throu hout the si nal chain. The volume control is based on a discrete 20 bits R-2R resistor network circuit
topolo y, providin a ran e of 118dB in 0.5 steps. The output sta e is desi ned to be able to deliver ample current to drive heavy
loads and/or multiple pieces of equipment simultaneously. The L1 uses ti ht tolerance, hi h- rade metal film resistors throu hout
the audio si nal path.
Balanced XLR, sin le-ended RCA and BNC connectors are available at both the input and output. All the inputs can be confi ured as
hi h-impedance input, or a 600 Ohm load can be en a ed on balanced inputs (300 Ohm for sin le-ended inputs) to reduce
reflections as well as to improve external noise immunity, therefore improvin the overall si nal transmission.
L1 main components
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(1) External power supply input. For X1 optional external power supply only
(2) Mains switch and power cord receptacle (on back panel)
(3) Adjustment shafts and screws
(4) Mains filter board
(5) Power supply section
(6) Main power transformer
(7) Standby power transformer (ensures reen mode standby)
(8) Front panel power supply board
(9) Display (on front panel)
(10) Balanced and sin le-ended outputs
(11) Balanced and sin le-ended inputs
(12) Control board (USB plu for firmware update and Ethernet RJ-45 plu for control from Android App)
(13) Sin le-channel preamplification board (one or two per unit)
(14) Backplane board
(15) Power supply re ulation board
(16) Dual concentric control knob with pushbutton
1.1 Unmatched flexibility
The L1 offers unmatched system inte ration flexibility. Not only can it be used in multiple confi urations (Dual Monaural,
Monaural, and Monaural Extended) but it also allows adjustments to match the impedance of the upstream unit, improvin the
overall si nal transmission with the surroundin pieces of equipment.
1.1.1 Configurations
A sin le L1 can be fitted with one or two channel boards, dependin on the desired confi uration. The followin confi urations can
be realized:
•Dual Monaural: In this confi uration, a sin le L1 is used to hold the two channels (Left and Ri ht, Center and Sub or Left
and Ri ht surround). Two boards are fitted inside its chassis, each one independently processin a sin le channel. The
mains power supply section is common to both the board, however separate dedicated DC re ulation circuits are provided
to each board.
•True Monaural: In this confi uration, two L1s are used to hold a sin le channel each (Left resp. Ri ht, Center resp. Sub or
Left resp. Ri ht surround). One board is fitted inside each chassis, each L1 processin a sin le audio channel. In this
confi uration, the entire power supply of the L1 is dedicated to one channel, further enhancin the system performances.
•True Monaural Extended: The confi uration is identical to the True Monaural confi uration, with the addition of a second
board in each chassis. The two boards in a chassis work to ether, as if it was only one board with twice as many inputs
(and outputs). This confi uration will be used when more inputs are required than the amount a sin le board can
provide.
For ultimate results, one/two X1 External Power Supply unit(s) can be connected to the L1(s) in all the above confi urations,
addin a second sta e of power supply re ulation to the preamplifiers, further improvin the system performances.
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1.1.2 Input stage
The L1 input sta e is equipped with both balanced and sin le-ended types of connections, 4x XLR, 2x RCA and 2x BNC. A hi h
bandwidth, hi h performances discrete amplifier buffers the si nal prior to applyin the volume. A DC blockin capacitor can be
en a ed to remove unwanted DC offset comin from sources connected to the L1's inputs. For more information about this
feature, please refer to section 1.2 Advanced DC offset cancellation.
1.1.3 olume control
The L1 volume control is based on a discrete 20 bits R-2R resistor network circuit topolo y, providin a ran e of 118dB in 0.5
steps. The volume set by the user from the front panel rotary knob or from the remote control is translated by the main controller
into commands that open or close analo switches, creatin a different combination of resistors for each of the volume steps,
therefore applyin the required attenuation. A ain of up to 18dBs is available for sources providin low output levels. A Mute
function is also available.
1.1.4 Output stage
The L1 output sta e is equipped with both balanced and sin le-ended types of connections, 2x XLR, 1x RCA and 1x BNC. A
powerful, hi h bandwidth, hi h performances discrete amplifier provides with ample current to drive one or more outputs
simultaneously.
1.2 Advanced DC offset cancellation
DC (continuous) volta e in an R-2R resistor network circuit topolo y translates into audible clicks in the audio si nal when a
volume chan e is applied. In order to remove the clicks, DC offsets must be canceled. The L1 features an advanced DC offset
cancellation system allowin to reduce the DC volta es to insi nificant levels, preventin audible clicks from happenin . The DC
offset cancellation system works in parallel with the audio path. It acts on the DC component of the audio si nal only, leavin the
audio content unaltered, but DC free. Ei ht pick up points are measured and corrected in real time throu hout the si nal path,
ensurin all sta es includin the L1 outputs are DC free.
DC offset wise, if there is one thin the L1 cannot control, it is the DC inherited from the pieces of equipment connected to its
inputs. Althou h care has been taken to try and counteract a fair amount of DC offset from upstream pieces of equipment
connected the its inputs, if these pieces of equipment exhibit hi h levels of DC at their outputs, the L1 will reach a state where it
can't counteract the inherited DC any more. If this condition happens, clicks mi ht start to become audible when a volume chan e
is applied. The only way to remove the excessive DC offset is to add a capacitor in series with the si nal path. The L1 front panel
display indicates that it cannot counteract DC any further and recommends to en a e the DC blockin capacitor. By default, there is
no capacitor in series inside the si nal chain, however the lar e value hi h- rade polypropylene capacitor can be en a ed when
excessive DC comin from the upstream piece of equipment has been detected at the input. Please note that en a in the
capacitor is a recommendation only, it is up to the user to en a e the capacitor or not. It is done from the unit's menu, but in no
circumstances will the unit en a e the DC blockin capacitor automatically. The DC blockin capacitor is en a ed on a sin le input
basis, it is not a lobal settin for all the inputs.
1.3 Careful Metal Work Construction
The L1 preamplifier chassis is made of hi h rade aluminum alloy with no visible screws on the front, top and side panels. First
class mechanical and chemical surface treatments provide the luxury finish of the L1. Pin assembly of all chassis elements enables
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