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Copyright © 2018 AudioNote Kits

www.AudioNoteKits.com

[email protected]

Page 33

Section 7

12AU7 Input Buffer PCB Installation

7.1 Overview

Next, we'll build the 12AU7 Input Buffer board. This is the board that will be mounted on the
front of the chassis.

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Summary of Contents for L4 EL34i

Page 1: ...L4 EL34i Integrated Amplifier Construction Manual Version 2 13 June 2019 audionotekits rogers com 1 613 822 7188 ...

Page 2: ...acitors 12 1 6 6 Diodes 12 1 6 7 Hardware Mechanical 13 1 6 8 Wire Stripping and Tinning 13 1 6 9 Wire Color 14 1 6 10 Optional Finishing Touches 14 1 7 Build Process 14 1 7 1 Some Good Rules of Thumb for Building Your Headphone Amplifier 14 1 7 2 Organization of this Manual 15 1 7 3 Electrical Safety Warning 17 Section 2 Feet IEC and Rocker Switch Installation 2 1 Overview 18 2 2 Feet Installatio...

Page 3: ...6 Section 8 ECF80 EL34 PCB Installation 8 1 Overview 37 8 2 Building the ECF80 EL34 PCB 37 8 2 1 Resistor Installation 39 8 2 2 Capacitor Installation 40 8 3 Final Assembly of the ECF80 EL34 PCB 41 Section 9 Speaker Posts Selector Switch RCA Jacks Installation 9 1 Speaker Posts RCA Jacks Installation 42 9 2 Installing and Wiring the Volume Pot PCB 44 9 2 1 Left Right Channel Orientation 47 9 2 2 T...

Page 4: ...nterwiring 63 11 7 LED Installation 64 11 8 Interwiring Chart 65 Section 12 Testing 12 1 Power On and Voltage Checks 66 12 1 1 Mains Fuse Installation 66 12 1 2 AC Voltage Checks 67 12 1 2 DC Voltage Checks 67 12 2 Install the Tubes 68 12 2 1 Checking Amplification 69 Section 13 Finishing Touches 13 1 Installing the Front Faceplate 70 13 2 Installing the Chassis Top 70 Section 14 Congratulations a...

Page 5: ...ath of audio superiority and we ve created this manual to guide you through each step of the assembly process with as much detail and clarity possible To facilitate the build process the manual has been divided into a number of sections each focusing on a separate aspect of the system follow through the sections in order and we guarantee not only a problem free experience but a pleasant time doing...

Page 6: ...earnest during the 2000s with development assisted by Audio Note UK engineering Audio Note UK parts were used throughout the kits depending on the various levels and budgets By 2013 ANK Audio Kits as it came to be called had developed a wide product range covering all areas of two channel audio a single ended 300B product line an EL34 classAB and single ended product line digital to analog convert...

Page 7: ...e way We tested a front end 12AU7 tube stage as a pre amplifier in the unit and were blown away by the results Today we have re architected the major PCB and enhanced the power supply The amplifier runs in class AB1 mode providing about 35W of pure EL34 power The new L4 EL34i Integrated Amplifier is born The amplifier has the detail of a single ended amplifier and the slam of push pull ideal for a...

Page 8: ...uide you through the complete build and test of the amplifier Please remember if you have any questions please don t hesitate to contact audionotekits rogers com Above you can see the general layout of the amplifier this includes starting from top right and moving clockwise the Mains transformer T 190 Choke CH 100W Power Supply PCB ECF80 EL34 PCB Output Transformers ...

Page 9: ...otekits rogers com Page 9 The other parts of the kit are shown in this picture 12AU7 Input Buffer PCB on front of chassis Volume Pot and PCB Extension kit for selector switch Before we begin let s familiarize ourselves with the basic operation of the amplifier ...

Page 10: ...nnect directly to the Output Transformers Primary Red and Black wires the Secondary or output of the Output Transformer connects to the speaker posts The ground and 8 Ohm of the speaker post connect back to the ECF80 EL34 PCB this is the feedback That is the complete audio path of the EL34 Integrated The power supply consists of the Mains transformer and Choke IEC IEC PCB and rocker switch the AC ...

Page 11: ...ld You should use lead free ONLY if you are experienced using it and confident Lead free solder requires a higher melting temperature and thus is more difficult to use We don t recommend lead free solder for first time builders We suggest that you practice your soldering before starting on the kit Feel free to request practice parts with your kit so that you can practice tinning wires and making n...

Page 12: ...itors For those who have not built a piece of electronics before here is a little lesson on capacitors There are basically two types of capacitors that we use in the kits electrolytic and signal capacitors Of these electrolytic capacitors require special attention Electrolytic capacitors are polarized which means they have a POSITIVE and a NEGATIVE lead and typically have values like 100uf 450V 10...

Page 13: ... M3 size obviously which is a thinner shaft diameter than an M4 16mm is the length of the shaft and the head type is CSK which is a countersunk or flat head screw Once you have the screws mastered look at the matching nuts such as M4 nut or M3 nut and corresponding washers Standoffs are common in the kits again they are either M3 or M4 size with different lengths They are typically threaded so the...

Page 14: ...ders who want to incorporate some of these finishing touches should feel free to do so While we don t officially support or supply parts for these optional enhancements there s no reason why you couldn t or shouldn t do them if you want to and feel that you can handle them Without getting into the details you re on your own here what you ll want to get hold of are heatshrink to bundle wires cable ...

Page 15: ...tion 3 Mains Transformer installation Section 4 IEC PCB Installation Section 5 Choke installation Section 6 Power Supply PCB Installation Section 7 12AU7 Input Buffer PCB Installation Section 8 ECF80 EL34 PCB Installation Section 9 Speaker Posts Selector Switch RCA Jacks Installation Section 10 Output Transformers Installation Section 11 Interwiring Section 12 Testing Section 13 Finishing Touches ...

Page 16: ... audionotekits rogers com Page 16 Here s another way of looking at how the manual is organized and how the sections fit into the big picture the main sections are mapped so that they mirror how the components will be positioned in the amplifier chassis ...

Page 17: ... safety There are sufficient voltages in this kit to give you a very nasty and harmful shock so be careful when powering on debugging and probing around Please contact ANK Audio Kits via phone or email audionotekits rogers com to discuss any precautions necessary when building the kit if you feel unsure about what you are doing at any stage of the build ...

Page 18: ... Page 18 Section 2 Feet IEC and Rocker Switch Installation 2 1 Overview In this and the following three sections we will install the feet IEC socket and PCB rocker switch Mains Transformer and the Choke as well as make the important initial connections to the Mains transformer ...

Page 19: ...the chassis using the provided hardware in the Feet bag in the big Hardware bag Use an M4 screw along with the big washer on the outside of the foot and then a M4 nut and M4 black serrated washer against the chassis on the inside of the chassis Might be handy to use an M4 nut driver or something similar to tighten the nuts for the feet on the inside of the chassis Now you are ready to go ...

Page 20: ...s rogers com Page 20 2 3 IEC and Rocker Switch Installation Let s install the input AC receptacle IEC plug and rocker switch in the rear of the chassis Here you can see the correct installation of the IEC plug in the rear of the chassis along with the rocker switch ...

Page 21: ...w It uses 2 rubber strips to isolate it from the chassis Lay down the two rubber strips so that they are over the correct holes in the chassis these holes are about 100mm apart from each then place the Mains transformer carefully over top the Primary of the Mains transformer 2 Black 2 White 1 Green wire is placed towards the back of the chassis while the Secondary wires are placed towards the fron...

Page 22: ... rogers com Page 22 The provided hardware in the bag marked Mains transformer will be used to secure down the Mains transformer Prior to securing the transformer in place we will hook up the IEC section and PCB with the provided parts and cables found in the IEC bag ...

Page 23: ... 1 IEC PCB Wiring The IEC PCB makes wiring the Mains transformer for your world voltage a little easier it is mounted on the rear of the chassis in a horizontal position above and to the left of the IEC and rocker switch Let s wire it first and then we ll install it Before we begin note the position of the ground lug ...

Page 24: ...Copyright 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 24 Connect the four Primary wires as shown The wiring is the same for both 120V and 240V systems ...

Page 25: ...n Complete the wiring for the rocker switch IEC and grounds as shown Be sure to allow sufficient length for all wires it s a good idea to lay it all out first before cutting the wires to the appropriate length The ground lugs connection point is located on the chassis bottom between the Mains transformer and the back panel as shown ...

Page 26: ...Complete the wiring for the rocker switch IEC and grounds as shown Be sure to allow sufficient length for all wires it s a good idea to lay it all out first before cutting the wires to the appropriate length The ground lugs connection point is located on the chassis bottom between the Mains transformer and the back panel as shown ...

Page 27: ...Peel off the paper covering on the plastic insulating board then using the IEC hardware mount the IEC PCB to the back of the amplifier as shown in the picture below use 2 standoffs then the PCB 2 more standoffs and finally the plastic insulating board If you are in any doubt as to the IEC wiring please contact audionotekits rogers com 4 3 Additional Mains Wire Preparation Twist the remaining Mains...

Page 28: ...Copyright 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 28 Time for a break ...

Page 29: ... rogers com Page 29 Section 5 Choke Installation 5 1 Choke Installation Install the large Choke called the CH 100W which you will see marked on the underside of the unit Note that the 2 black wires exit the Choke nearest the side panel of the chassis Here s a picture ...

Page 30: ... AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 30 Section 6 Power Supply PCB Installation 6 1 Overview In this section we ll be building the Power Supply board which is situated next to the Choke ...

Page 31: ...nual or on your disk Take your time and take a break from time to time While it s not necessary you can solder through hole resistors on the top as well as the bottom if you prefer But don t use to much solder you don t want create blobs just a good connection When you re done here s a way to double check your connections 1 Set your multimeter to the Ohm position 2 Touch one end to the lead of a r...

Page 32: ...Install the four standoffs onto the board from the hardware bags position it as shown in the Choke Installation section above and secure to the bottom of the chassis with M4 10mm screws If your kit is supplied with solid bottom feet you should omit the underside screw on the right front through the chassis to the standoff Don t worry the Power Supply PCB isn t going anywhere ...

Page 33: ...ts www AudioNoteKits com audionotekits rogers com Page 33 Section 7 12AU7 Input Buffer PCB Installation 7 1 Overview Next we ll build the 12AU7 Input Buffer board This is the board that will be mounted on the front of the chassis ...

Page 34: ...Copyright 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 34 This board is basically the pre amplifier section and it contains a single 12AU7 tube ...

Page 35: ...he board We suggest that you use just a little solder to secure each pin to the board perhaps just start with two pins which are opposite to each other to make sure the base stays level then you can add more solder to the pins In the end you can fill up the entire valve base hole Be very careful not to let any solder bridge to the next pin as this will cause a short We recommend you then touch the...

Page 36: ...7 Input Buffer PCB You can mount the 12AU7 Input Buffer PCB on the front of the amplifier you may later want to wire under the board but it is easy to unhook when this is necessary Use the countersunk screws on the front to that it is FLAT and then the PAN head screws on the inside of the chassis along with the 10mm standoffs ...

Page 37: ... This is the large PCB that we will start to populate and verify Quite a bit of work but we can take it one step at a time We will divide up the board into several sections and take our time 8 2 Building the ECF80 EL34 PCB The ECF80 EL34 PCB will be populated with the parts from the ECF80 EL34 bag Let s go through the parts one by one ...

Page 38: ... two 9 pin valve bases and four 8 pin CMC black valve bases The 9 pin valve bases only go in one way BUT the 8 pin valve bases have a key or slot on them that you must match up to the PCB for correct installation I suggest we not install the valve bases just yet let s install the resistors and then come back to the bases ...

Page 39: ...9 2 10R 3W 1 R20 470R 3W 4 R21 1 R21 2 R22 1 R22 2 220R 1 2W 1 R25 620R 1 4W 1 R26 22K 1W 2 R27 1 R27 2 220R 1W 2 R28 1 R28 2 220R 1W 1 R29 330K 2W 1 R30 47K 2W When you see R1 1 this means that R1 has a value of 470K for example and that there is a right and left channel which are designated as R1 1 470K R1 2 470K I suggest you use an Ohm meter to verify the values of the resistors that you are i...

Page 40: ...or for recognizing resistors in correct positions Once resistors are installed we would recommend you check high resolution images to make sure all is well 8 2 2 Capacitor Installation Electrolytic Capacitors The cap in middle of the board with no designation is C3 for the 100uf 450v cap Position it correctly QTY Designation Description 2 C1 1 C1 2 10uf 160V 1 C3 100uf 450V 1 C9 33uf 350V 2 C15 1 ...

Page 41: ...de foil 8 3 Final Assembly of the ECF80 EL34 PCB Now you can install the valve bases For the 8 pin sockets be sure to match the notch on the valve base with the PCB Take your time soldering on the underside of the board as they will require a fair bit of heat and solder to adhere them to the board Take your time No rushing Install the standoffs for the board you will note there are 9 standoffs use...

Page 42: ...the rear of the chassis let s install the RCA jacks and speaker posts The RCAs install into the 6 holes in the center with the RED on top if you wish and the speaker posts install to the left and right with Red Black from top to bottom The picture below shows the way a single wire connects all the grounds together notice the insulation stripped where contact is made with the grounds on the RCAs ...

Page 43: ...th the RCAs jacks we recommend the following procedure Tin the RCA ground lead and put a puddle of solder in the center of the RCA Heat the solder puddle and slide the tinned signal lead to be connected into the center of the RCA Similarly hold the tinned Ground lead against the tinned Ground tab on the RCA and apply heat it will usually adhere immediately ...

Page 44: ...t 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 44 9 2 Installing and Wiring the Volume Pot PCB Once these are installed we are going to install the Volume Pot PCB and wire up the RCAs ...

Page 45: ...n position at the back of the chassis the selector switch and the ALPS volume pot these three sections are tied together as we will explain It s a good time to review our audio signal path so that you understand exactly what we are doing here and how it all makes sense Review the full page on the disk and read and understand how the audio signal travels from the RCAs into the selector switch and o...

Page 46: ...DF file on the disk to view these diagrams The following slides show how we will connect up the RCAs to the selector switch and then have the output of the selector switch go to the volume pot you will want to route these wires along the left side of the chassis and then across the front of the chassis and up to the volume pot ...

Page 47: ...ures associated make these designations as follows Looking from the front of the amplifier towards the front Left Channel Upper RCA jacks Left Output Transformer Right Channel Lower RCA jacks Right Output Transformer 9 2 2 The An A Shielded Cable Have a look at the yellow dual shielded cable One end has Red and White wires and a shield the other end just the Red and White wires The Red wire is the...

Page 48: ...Copyright 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 48 ...

Page 49: ...Copyright 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 49 ...

Page 50: ...Copyright 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 50 9 2 3 Mounting the Extension Kit and Selector Switch ...

Page 51: ...Copyright 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 51 You will want to mount the extension ...

Page 52: ...rs com Page 52 Using the bracket provided you will want to mount the selector switch into the bracket and screw it into position and then mount in the chassis in the 4 holes provided You can position the ECF80 EL34 PCB and then install the extension kit using the bushing ...

Page 53: ...Copyright 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 53 Section 10 Output Transformers Installation 10 1 Output Transformers Installation ...

Page 54: ...4 The IE core transformers install with the Red Black and Yellow wires facing the ECF80 EL34 PCB The build below positions is for the integrated amp but the transformer positioning is the same The unusual orientation of the transformers is not an issue you can position them either way ...

Page 55: ... one side you will see Red Black and Yellow dots and lugs On the other you will see Green larger Blue smaller in the middle and Purple larger Orient the transformers so that the Red Yellow and Black lugs face the center of the chassis If you have Red Black and Yellow leads attached to your transformers they will look like this ...

Page 56: ...hown in the diagram above Again don t worry Just be sure to connect the right points together and check the chart at the end of the Interwiring section and all will be well Using the wire from the OP Transformer bag prepare the following wires 2 Black wires of approximately 7 These MUST be long enough to reach from the Black speaker posts to the Green lugs on the Output Transformers 2 Black wires ...

Page 57: ...dle and upper Red speaker posts to the Blue and Purple lugs on the Output Transformers 2 Red wires of approximately 9 These MUST be long enough to reach from the upper Red speaker posts to the solder pads marked 8R on the ECF80 EL34 PCB Now make the following connections Solder two 7 lengths of Red wire to the two middle Red speaker posts one for each side Twist one end of the one of the remaining...

Page 58: ...mer Using the wire from the OP Transformer bag prepare the following wires 2 Red wires of approximately 7 These MUST be long enough to reach from the Red lugs of the Output Transformers to the A2 pads on the ECF80 EL34 PCB 2 Black wires of approximately 7 These MUST be long enough to reach from the Black lugs of the Output Transformers to the A1 pads on the ECF80 EL34 PCB For each transformer Sold...

Page 59: ...Copyright 2018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 59 Definitely time for another cup before we do the Interwiring ...

Page 60: ... of the kit build and we can now look at hooking everything up together this is considered the INTERWIRING STAGE This guide explains the interwiring best to look at the higher resolution version of these slides on disk to show the details The slide below shows the interwiring connections between the four boards EXAMINE it carefully and READ through this whole section first ...

Page 61: ...e heat of the tubes and to improve the aesthetics of the build route the wires that connect to the ECF80 EL34 under the board You ll probably have to figure out which wiring order works best for you This is not an easy part of the build Take your time be careful and patient Take a break if you need to Looking at the slide on the previous page make the following connections from the ECF80 EL34 PCB ...

Page 62: ...Purple 6V3 3A AND LOOP OUT either lugs CT 6V3 Red Blue White 6V3 6A either Brown Black Green 6V3 6A either 11 4 Output Transformers Interwiring Looking at the slide at the beginning of this section make the following connections A1 left A2 left A1 right Black wire to OP 390 Left Red wire to OP 390 Left Black wire to OP 390 Right A2 right Red wire to OP 390 Right 11 5 Speaker Posts Interwiring Look...

Page 63: ... PCB Connect the Volume Pot PCB Left and Right OUTs to the Left and Right Inputs on the 12AU7 Input Buffer PCB Connect the GND on the Volume Pot PCB to the S GND on the 12AU7 Input Buffer PCB Make sure the solid core Black wire coming from the RCA Jacks is also connected to GND on the Volume Pot PCB Connect the signal leads from the AN A cable to the Volume Pot Left and Right INs Connect the tinne...

Page 64: ...ote Kits www AudioNoteKits com audionotekits rogers com Page 64 11 7 LED Installation The LED holder is attached to the front panel with a little adhesive Blu Tac or epoxy and the LED is wired to the EL34 LED PL either way ...

Page 65: ... PCB GND left side of slide ECF80 EL34 PCB B Red wire to PS PCB B as above GND beside B A1 left A2 left A1 right Green wire to PS PCB GND as above Black wire to OP 390 Left Red wire to OP 390 Left Black wire to OP 390 Right A2 right 8L LEFT 0L Red wire to OP 390 Right Purple to 8 Ohm speaker post Green to 0 Ohm speaker post 8R RIGHT Purple to 8 Ohm speaker post 12AU7 Input Buffer PCB 0R F F CH 2 O...

Page 66: ...ge With your voltmeter you can measure DC or AC and makes troubleshooting straightforward The other key tool on your meter is the Ohm meter you can take a resistor and measure the resistance in Ohms For example you pick up a resistor put a probe on each end and set your meter to Ohms and measure 1000 Ohms for example this is then a 1K resistor Just as important as resistance being able to measure ...

Page 67: ...heck for 6 3 6 7V AC Also on the ECF80 EL34 PCB check the 6V3 3A filaments on the side near the Power Supply PCB Check the Blue Yellow wires coming into the Power Supply PCB and you should see approximately 300V AC here 12 1 3 DC Voltage Checks Now some DC voltage checks On the Power Supply PCB you should have 375V DC between PS B and GND Also measure the B and GND on the ECF80 EL34 PCB it should ...

Page 68: ...own then you can check the Test points on the ECF80 EL34 PCB these are the cathodes of each EL34 and will tell us a few things ECF80 6BL8 Line Stage Tubes EL34 6CA7 Output Tubes If you measure approx 21 23V DC on each test point TP1 TP2 TP3 TP4 this tells us that all the tubes are operating correctly If they are very close in value to each other it means the tubes are well matched ...

Page 69: ... then power on the amp and play an audio CD test through the amp Adjust the volume to halfway and measure the AC voltage across the 8 Ohm resistors you should be able to adjust the volume and see the value change accordingly at zero volume you should see zero output signal As a final test I might suggest that you use an old pair of speakers to do a final test and let the amplifier run for an hour ...

Page 70: ...tion 13 Finishing Touches 13 1 Installing the Front Faceplate Remove the protective films from the front and back of the front faceplate Install the front faceplate using four Black M4 CSK flat head screws 13 3 Installing the Chassis Top Install the chassis top using the provided hardware ...

Page 71: ...u to tailor the sound to your specific preferences The 12AU7 ECC82 dual triode world is too extensive to go into here while the ECF80 triode pentode can be substituted by readily available NOS 6BL8 and E80CF 7643 tubes and there are many NOS and new production EL34 6CA7 types available 14 1 2 Thanks Thank you for investing in the ANKits L4 EL34i Integrated Amplifier and for working your way throug...

Page 72: ...ix 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 ...

Page 73: ...018 AudioNote Kits www AudioNoteKits com audionotekits rogers com Page 73 Resistor Color Code Reference You can also find an Interactive Resistor Color Code Calculator on our website available from the Links page ...

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