Audio Note L2 Line Preamplifier Instruction Manual

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Manual Version 2.3 - May 2008

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Summary of Contents for Audio Note L2 Line Preamplifier

Page 2: Table Of Contents
Table of Contents Section1: Introduction................................4 General Information ................................4 Preparation ..................................4 Soldering ....................................5 De-soldering..................................6 Section 2: Mechanical Assembly.............................7 Installing the feet..................................7 Mains Transformer, Choke, and Mains Installation ......................7 Configuring the Primary Winding for your World Region ....................9 Installing the IEC Socket (AC Socket) and Rocker Switch ....................12 Installing the Choke................................13 Installing the Mains Transformer............................13 Wiring up the Mains................................14...
Page 3 HT and Power Supply Ground Wiring..........................54 Electrical Test ..................................55 Section 8: RCA input, Selector and Noble Volume Pot......................57 Installing and wiring your first pair of RCA inputs ......................57 ELMA Switch Hook-up ...............................59 Volume Pot Installation ..............................60 Section 9: Audio Signal Test ..............................65 Section 10: Output Wiring..............................67 RCA Connections ................................67 Line Board Connections..............................67...
Page 4: Section1: Introduction
We recommend a rosin core flux solder, NOT acid core, such as “Kester 44”. An even higher recommendation is AUDIO NOTE corrosive-free silver solder, which you can purchase from Audio Note.
Page 5: Soldering
Thanks for purchasing this Audio Note kit. Our goal is to provide you with the highest quality Kit that you will build from scratch with these instructions. If you have any questions or comments during the build feel free to contact us and we would be happy to help out.
Page 6: De-Soldering
De-soldering Should you have to remove a component from the board, you will need to use either a solder ‘sucker’ or de-soldering braid. Removal is best achieved from the solder side of the board in either of the following ways: Solder Sucker - first ensure that the plunger is depressed on the tool;...
Page 7: Section 2: Mechanical Assembly
Section 2: Mechanical Assembly In this beginning section we will start by installing the 4 feet from the Fittings Bag then we will install the Mains transformer and Choke as shown in the pictures below. Installing the feet Insert 4 feet in the bottom of the chassis. Fix them each in place using an M4 nut and washer.
Page 8 Trim the wire to about __ inches. Strip about ¼” of insulation off the end of the green wire. Tin the bare wire by adding solder to the end. Copyright © 2007, 2008 AudioNote Kits Page 8 www.AudioNoteKits.com audionotekits@rogers.com...
Page 9: Configuring The Primary Winding For Your World Region
Add solder to secure the GND Lug to the end of the wire. Configuring the Primary Winding for your World Region Next step is to decide what world voltage you require – for example we have some of the most popular regions listed below: United States 120v...
Page 11 Now we must configure our Mains transformer for the World Voltage that we reside in. For this example we will show 120V Operation. Start by cutting two short pieces of wire approx 2” in length each, stripping the insulation off the ends and tinning the wire.
Page 12: Installing The Iec Socket (Ac Socket) And Rocker Switch
Here, the wires are soldered onto the top-most 0v and the bottom-most 120v for North American/Canadian 120v. Remember, we are wiring here for 120v - if your region is different then you will need to consult the regional wiring chart to determine how you inter-wire for your region. Installing the IEC Socket (AC Socket) and Rocker Switch The rocker switch simply snaps into pace in the chassis slot.
Page 13: Installing The Choke
Installing the Choke Since the Choke fits into a tight location we suggest you put the screws and washers into position through the holes in the choke covers – then lower the choke into position making sure that you align with the non painted hole - see opposite.
Page 14: Wiring Up The Mains
When installing the Mains transformer be sure to line it up with the unpainted hole in order to ensure a ground connection. Secure the transformer at all four corners. Wiring up the Mains Once the transformer is installed you can connect up the Blue and Brown Crimped wires from the Mains transformer directly to the Rocker Switch.
Page 15: Shield Positioning
Add the twisted wire (Cable #3) and the ground wire (Cable #4) as shown in the graphic opposite. Let’s add one final GROUND wire connection from the M4 screw in the chassis. Strip, tin and solder this wire to the 0 on the 400-300-0-300-400 side of the transformer SECONDARY –...
Page 16 Here correct installation of the shield – You will need to remove it later on when we wire up to the Mains transformer but for now you can leave it in and show off your wonderful work to your wife! This concludes the IEC Wiring section for the Mains Transformer.
Page 17: Section 3: M2 Power Supply
Section 3: M2 Power Supply In this section we will be assembling the M2 Power Supply Board PCB. Here is a view of the parts that you will find in the M2 Power Supply Kit Bag Most of the parts for this section can be found in the M2 Power Supply bag (although the filament wires may be located elsewhere).
Page 18: M2 Power Supply Board Parts List
M2 Power Supply Board Parts List The Complete Parts list for the M2 board is shown below. For resistor color code chart refer to the APPENDIX. You can also find an 'Interactive Resistor Color Code Calculator' on our website (available from the Links page). Category Quantity Part...
Page 19: M2 Power Supply Board Construction Steps
M2 Power Supply Board Construction Steps Installing the Valve Bases Lets start by installing the 8-pin valve base with correct orientation. The 8-pin (octal) valve base is shown opposite. It’s a fairly tight fit into the board so take you will need to take your time and make sure all the legs are individually positioned over the holes in the board.
Page 20 The next job is to solder the valve base into position – Once you have fitted the octal into position I suggest you use a cap or something to support the board so that it is nice and horizontal. The reason for this is so that the valve base will be soldered into the board nice and level –...
Page 21: Installing The Resistors
Installing the Resistors Resistors 100R R5, R6 100K R1 ,R10 150K 220K 470K If you have a voltmeter you can check the value of each resistor prior to soldering in OR you can refer to the color code chart in the above parts list. Identity the correct resistor and then install in the specified designator (R1 for example).
Page 22 Above shows the installation of the 100R resistor into the R8 position – Bend the legs slightly on the underside to keep the resistor in place. We suggest you install the spacers on the board at this point. Once you are feeling confident of your resistor installation it is time to solder on the underside of the board.
Page 23: Installing Resistors In The Ht Adjust Position
Once the joints have been made, give them a quick inspection and touch up any that look suspicious in any way. Next step is to clip the leads - you want to do this but be careful not to clip off too close to the board where you endanger the pad –...
Page 24: Zener Diode Installation
Bend one of the legs over and through the hole in the board as shown - solder into position from the top of the board. Take the leg of the other resistor and twist it around the leg of the other one as shown opposite. Here you can see the resistors in position –...
Page 25: Electrolytic Capacitor Installation
Here you can see the Zener diode installed in the correct orientation. Electrolytic Capacitor Installation Capacitors (Electrolytic) 2200uF 35V 22uF 450V C6 ,C7 Do not install C2 and C4 at this stage 68uF 450V C3, C5 We are now going to install the Electrolytic Capacitors into the power supply Board.
Page 26 Here we can see both 68uF capacitors (C3 and C5) correctly installed. Install the remaining electrolytic capacitors that are required at this stage (i.e. C9, C6, and C7). You can see these installed in the picture opposite. Copyright © 2007, 2008 AudioNote Kits Page 26 www.AudioNoteKits.com audionotekits@rogers.com...
Page 27: Installing The Bridge Rectifier
Installing the Bridge Rectifier Semiconductor Devices KBU6J6A Install the Bridge Rectifier into position in U1. Note the notch is located facing into the middle of the board - you will also see a corresponding notch stenciled on the PCB. Installing the Non-Polarized Capacitors Capacitors (Non-polarized) Disc 4700uF 3000v .22uf 600V...
Page 28: Wiring The M2 Power Supply Board
Wiring the M2 Power Supply Board Get your Bag #2 from the Wire Bag as we will be installing the “filament” wires onto the board. We are going to connect several wires to the M2 power supply board – this is easier to do at this stage. FILAMENT LESSON: In order for a tube to function it must be supplied with a Filament Voltage –...
Page 29 Now take the short wire from BAG #2 - we will be using this to hardwire from the 8-pin valve base to the 9-pin valve base. The graphic to the left shows the connections for the twisted wires. EXPLANATION: On the M2 Power Supply Board we will have 2 different tubes - a 6X5 and an ECL82.
Page 30 Here is the completed connection of the “parallel filament”. We are now going to install the 6X5 filament wire - this is the THICK black & white twisted wire that is located in Bag #1 of your WIRE BAG. This is the wire that will connect from the Mains transformer secondary to the 6X5 filament.
Page 31: Filament Component Section Of The M2 Power Supply Board
Now get out your BAG#3 from the wire bag and we will install the red and black wires that will be used as the B+ (High Voltage) and corresponding Ground wire. These pictures show the red and black wires installed in the B+ and GND holes on the M2 power supply board.
Page 32: Regulator Installation
The 1N4007 Diodes are polarized and therefore need to be installed correctly. In the picture above you will note the D3 & D6 designators which shows a bar – this bar lines up with the gray strip on the zener diode – Note how they are correctly installed.
Page 33: Installing The Led Harness
The pictures above and opposite show a successfully configured regulator. Once these components are in place you can then install the remaining two electrolytic capacitors (C2 and C4). Installing the LED Harness Take the LED Harness from your M2 PS bag and you can solder it onto the board as shown opposite.
Page 34: Installing The Heatsink
Then take the twisted thick RED wires and connect these to the 300V 300V on the PCB. The picture opposite is what your M2 Power supply board should now look like! Installing the Heatsink Feel free now to “place” (do not screw in) your newly assembled board into position in the chassis.
Page 35: Installing The Choke Wire
Installing the Choke Wire The Black CHOKE that is located at the rear of the chassis and has a red and black wire. you will want to twist these wires by hand and feed them along the shield towards the M2 PCB.
Page 36: Inter-Wiring To The Mains Transformer
Inter-wiring to the Mains Transformer I would suggest at this stage to REMOVE the black shield so that we can work on this side of the chassis. The following graphic shows the wiring between the M2 PCB and Mains Transformer. Note that the ‘second’ transformer is simply another view of the same mains transformer.
Page 37 We are now going to take the 3 pairs of twisted wires that are already connected to the M2 Power Supply Board and connect these directly to the SECONDARY of the Mains transformer. Start by taking the RED / RED twisted pair and trim to a good length and then solder to the ‘300’...
Page 38 The third pair of wires is the Red/Black twisted pair that is connected to the 13V6 on the M2 power supply board. Note that the 0 tap is not used here. The last wire for hookup in this section will be the long green wire with the GND lug on one end found in your IEC Kit Bag- Secure the GND lug end on the M4 screw in the chassis and trim and solder from the top of the board the green wire into the GND hole located near the 13V6 pads on the M2 power supply Board.
Page 39: Securing The Regulators To The Heatsink
Securing the Regulators to the Heatsink We are now going to secure the regulators to the Heat Sink that is installed in the chassis. The picture opposite shows the parts that are necessary to do this. EXPLANATION: It is ideal to electrically isolate the regulator from the ground on the chassis (i.e.
Page 40 That completes our assembly of the M2 Power Supply Board. Feel free to re install the shield back into position or you can wait until nearer the end of the kit build if you prefer. Copyright © 2007, 2008 AudioNote Kits Page 40 www.AudioNoteKits.com audionotekits@rogers.com...
Page 41: Section 4: M2 Power Supply Testing
Section 4: M2 Power Supply Testing Preparations Fitting the Mains Fuse In this section we are going to electrically test the power supply. Start by installing a 1A Slo Blo fuse (IEC BAG) into position as shown. Use a screwdriver or flat edge or your fingers pull the Fuse holder out - you will need to squeeze to completely remove it.
Page 42: Installing The Led Indicator
Installing the LED Indicator The LED on the M2 Power Supply Board will be the first indicator that we have power – I would suggest just taping the LED – make sure the metal leads of the LED are not touching any other circuitry or chassis –...
Page 43: Ohm Check
Ohm Check EXPLANATION: There are a number of terms that we will be using in this section that we should be familiar with – the HT or High Voltage or B+ is all the same thing – this is the HIGHEST DC voltage in the circuit typically and is the voltage that we will be supplying to the Tubes in our audio signal path.
Page 44 First measure from B+ to GND on the M2 PCB (use the ground point closest to the LED section). You should read approximately 260v DC. Now measure the filament voltages - these are the connections labeled +6V2- on top of the PCB. These should be approximately 12v DC.
Page 45: Voltage Check Summary
While in AC mode measure the 13V6 pads on the M2 PCB – We have 8 0 8 taps which should give us roughly 16V Voltage Check Summary DC Voltage Checks Location Approx Reading B+ to GND 260v DC +6V2- 12v DC +6V2- 12v DC...
Page 46: Section 5: Install The Screen
Section 5: Install the Screen The next step is to install the metal screen. It is important that a good electrical contact is maintained between the chassis and the screen itself. This picture shows the hole that will make that contact from the chassis –...
Page 47: Section 6: Line Board Assembly
Section 6: Line Board Assembly In this section we will be building the Line Stage for the L2 Pre-Amplifier, which consists of a pair of 12AU7’s. Copyright © 2007, 2008 AudioNote Kits Page 47 www.AudioNoteKits.com audionotekits@rogers.com...
Page 49: Line Board Parts List
Line Board Parts List Category Quantity Part Designator Capacitors (Electrolytic) 470uf 16v C36, C37 Capacitors (Non-polarized) .47uf .47uf, 600v C34, C35 Resistors 680R R42, R43 R39, R46, R47, R48, R51, R52 R40, R41, R44, R45 R37, R38, R49, R50 Valve Bases 9 pin gold Valve Bases Tubes ECC82/12AU7/5814...
Page 50: Resistor Installation
Once the valve base has been screwed into position then we can solder the legs as shown opposite. you will probably feed plenty of solder into the hole to secure into position. Resistor Installation Resistors 680R R42, R43 R39, R46, R47, R48, R51, R52 R40, R41, R44, R45 R37, R38, R49, R50...
Page 51: Capacitor Installation
Here we are installing the resistor into the correct reference designator R42. It’s a good idea to look at the schematic as you are populating the board as a good double check with the manual. Once the resistor is installed then you can bend the legs back slightly on an angle so that the resistor will stay in position.
Page 52 We will start by installing the two electrolytic capacitors. As you are aware, the stripe is the negative side. Note that the Board is not marked with a ‘+’ or a ‘-‘ so you will have to follow our instructions - You will see the stripe of the electrolytic capacitor is facing the input side of the board –...
Page 53: Section 7: Wiring Up The Line Stage
Section 7: Wiring Up the Line Stage Position the L2 Line Board into the chassis – Don’t screw into position but place it in the correct orientation. As you can see, the input side of the Line Board is closest to the front of the chassis –...
Page 54: Ht And Power Supply Ground Wiring
In order for the 12AU7 tubes on the line board to “light up” and function properly a filament voltage needs to be applied to pins 4 & 5 – In this case we are supplying approx 12V DC between these pins. The one filament supply from the M2 Power supply board will supply the two tubes on the L2 Line Board.
Page 55: Electrical Test
Locate the HT-R, HT-L and HTGND pads - These are the pads that we will be working with. The HT wire will connect to one of the HT pads and you will use some silver wire to short between the two HT pads.
Page 56 Check the voltage across any of the 36K resistors R40, R41, R44, and R45 – all of these resistors should have a 120 volt drop across them – These are the plate resistors. Then check the cathode resistors – R42 & R43 – measure the DC voltage across these resistors and we should see something in the 4.5V range.
Page 57: Section 8: Rca Input, Selector And Noble Volume Pot
Section 8: RCA input, Selector and Noble Volume Pot In this section we will be hooking up the first RCA input and testing for successful audio. Installing and wiring your first pair of RCA inputs Effectively, you will be repeating the same procedure for all six pairs to stereo inputs. Therefore, this section will go into the greatest detail when showing the first stereo pair.
Page 58 Step 1: Install the first set of RCA connectors. Install the BLACK RCA (left) on the bottom of the chassis and RED RCA (right) on the top of the chassis. Install the Black RCA on the top and the red RCA on the bottom.
Page 59: Elma Switch Hook-Up
Repeat this for the other RCA and you should have two pairs of wires as shown to the left. ELMA Switch Hook-up The next step is to wire up the ELMA selector switch. You may want to add the knob to it with the little hex wrench so you can stand it up for easy soldering! The pictures opposite show that the...
Page 60: Volume Pot Installation
This diagram shows the pin layouts of the ELMA selector switch. The order that you wire your inputs is dictated by the order shown on the front panel: 1. PHONO 2. CD 3. DAC 4. AUX 5. TUNER 6. LINE Of source you may only wish to wire up the inputs that you will be using - the choice is yours.
Page 61 Install the Volume pot in the center hole. TIP: You may want to scrape off the Black paint on the Noble pot where the pot comes in contact with the chassis - this would be on the inside of the chassis - use a flat headed screw driver and just take off some of the black paint - this way the pot makes a...
Page 62 Here we can see the wire soldered to the Noble PCB. Now take the wire and solder to the ELMA selector – The red wire would go on the RIGHT side of the ELMA output and the black wire on the LEFT side of the ELMA output (see ELMA graphic).
Page 63 Now connect a ground wire – Black – from the NOBLE PCB Ground to either the LINGND or the RINGND (these are connected internally). That should do it! We now have a completed wiring for a single Line Stereo Input for your pre-amp! You can do a quick tie wrap to clean up some of the wiring.
Page 64 Step 3: Solder the twisted pair to the RCA connector. Next, tine the RCA post - applying a small amount of solder to the center area. Also, tine the ground lug. One the RCA has been tinned, heat the solder in the center section of the RCA.
Page 65: Section 9: Audio Signal Test
Section 9: Audio Signal Test I would suggest adding the knobs to the front panel with the ALLEN Key provided so that you can make adjustments. With the selector switch, turn the knob all the way to the LEFT or counter clockwise - Once it has reached this position then turn it ONE position to the RIGHT - This is the correct...
Page 66 By measuring the AC voltage at the output of the Line Board you will see an AC signal coming through - You will want to see a value of approximately 5mV at full volume - if you can adjust the volume control you should be able to see the audio signal larger or smaller - you can also try moving the selector switch and seeing the signal disappear and then reappear as you select.
Page 67: Section 10: Output Wiring
Section 10: Output Wiring If you are building the Phono Version of the L2 Pre-amplifier then it may be a good idea to now switch to the L2 Phono Board construction manual. If you choose, you could do that after wiring up the output - however, it may be more difficult because you would have to route the phono board and additional wiring under the output wiring! An AN-A (or AN-V), stereo paired wire has been supplied with your kit to connect the output of the line board to the output RCA connectors.
Page 68: Section 11: L2 Phono Board Build And Installation
Section 11: L2 Phono Board Build and Installation This section is only relevant to you if you are building the Phono version of the L2 Pre-amplifier. If you are not then you can skip this section and move onto the next. In this section we will build the L2 Phono PCB –...
Page 69: Phono Board Parts List
Phono Board Parts List The Complete Parts list for the Phono Board is shown below. Category Quantity Part Designator Capacitors (Electrolytic) 470uf 16v C9, C10 100uf 10v C1, C2 47uf 450v Capacitors (Non-polarized) .047uf C3, C4 .22uf C11, C12 2.7n C7, C8 8n2 (8200pf) C5, C6...
Page 70: Installing The Spacers And Valve Bases
Above we have a view of the top and underside of the board. Installing the Spacers and Valve Bases First install the M3 Hex spacers into position at the four corners of the board. Position the 9-pin valve bases onto the board –...
Page 71 Fit the M3 screw from the top and secure with an M3 nut underneath. The next step is to solder the valve base into position by soldering each leg of the valve base – you can use plenty of solder to secure the valve base.
Page 72: Installing The Resistors
Installing the Resistors Resistors R3, R4, R15, R16 R5, R6 R18, R19 39K2 R11, R12 R1, R2 100K R9, R10 270K R7, R8 R19, R20 1M82 R13, R14 You can check out the color code chart for the resistors or use an ohmmeter to verify the value prior to insertion.
Page 73: Installing The Capacitors
On the underside of the board you can gently bend the legs back on an angle (not as far as 90 degrees!) so that the resistor will stay in position for later when we solder. Continue installing all the resistors – you will notice that we have the Beyschlag resistors for many of the values along with the red PNP precision resistors and the black HOLCO precision.
Page 74 Here are C7 and C8 installed on the board. Now go ahead and install the 8200p or 8N2 farad capacitors into positions C5 and C6. The remaining film capacitors will be dealt with later. Capacitors (Electrolytic) 470uf 16v C9, C10 100uf 10v C1, C2 47uf 450v...
Page 75 Here we are installing the electrolytic capacitor 470uf 16v in C10 – note the + stenciled on the board and the negative stripe of the capacitor on the opposite side – These value capacitors are used on the cathodes on the tubes. Go ahead and install C9 also;...
Page 76 Capacitors (Non-polarized) .047uf C3, C4 .22uf C11, C12 2.7n C7, C8 8n2 (8200pf) C5, C6 The .047uf caps are installed underneath the board as in the picture opposite. Look for the correct hole locations on the board and place capacitor into position. You will then need to clip the extra lead on the top side of the board –...
Page 77: Filament Wiring
Installing the Phono Section requires that we do the following things: Wire-up the valve filaments to the power supply. • Connect the output of the phono board to the • ELMA selector and Noble pot PCB as we did with the line inputs.
Page 78: Wiring The Output Of The Phono Stage Into The Elma Selector
Wiring the Output of the PHONO Stage into the ELMA selector Take the two 12” lengths of PTFE wire and connect the Signal and ground for the left and right output channels of the Phono Board. Then unwind about 6” of the color and black wires and then twist the black wires together.
Page 79: Connecting The Ht And Power Supply Ground
Connecting the HT and Power Supply Ground Now we are going to take the two lengths of PTFE wire for the HT and GND. Let’s begin by connecting one end of the red cable to one of the B+ pads on the M2 power supply board.
Page 80: Controlled Phono Input Test
We can now connect the input AN-A cable. The shielded AN-A cable has a red and white lead on one end – this is the end for the RCA’s. The other end has the red signal wire and the thicker ground wire - this is the side that connects to the PHONO board.
Page 81: Ground Post Installation
Play the PHONO Test track and take an AC voltage measurement on the output of the LINE Board - this is to ensure that the audio signal is passing through the phono stage - into the ELMA selector - then to the Volume PCB - then to the input of the Line stage - and to the Output of the LINE stage - it’s an almost complete Audio test path! If you are getting some voltage reading of a few volts - then...
Page 82: Section 11: Finishing Off
Section 11: Finishing Off Fitting the Faceplate Peel off the plastic and position and secure with the 4 x M4x10mm black CSK (countersunk or flat) screws Tighten these with care, as you do not want to let the screwdriver slip and mark the faceplate.
Page 83: Final Thoughts
Final Thoughts I think that is about it - you may now wish to fit the cover - I hope you enjoyed your experience with AudioNote Kits and your new L2 Pre-Amplifier Kit. Please send us an e-mail and tell us what you thought about the whole process – Send us a picture of your completed pre-amplifier if you can and also a little review or write-up would be useful.
Page 84: Appendix
Appendix The appendix contains auxiliary information. That is information that is either common to most project manuals or any last minute pieces of information that did not make it into the manual in time. It may also contain pull-out circuit diagrams that may be handy to have outside the manual etc.

Audio Note L2 Line Preamplifier Instruction Manual

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