Audio Note Mono Block 300b/2A3 User manual

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age 1
Manual Version 3.5 (Mk3 Mains Tx) - July 2008

Copyright © 2007, 2008 AudioNote Kits
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age 2
Table of Contents
Section1: Introduction..............................................................................................................................................................3
Chassis Orientation..............................................................................................................................................................3
Hardware and Kit Bags ........................................................................................................................................................3
General Overview ................................................................................................................................................................4
Section 2: Mechanical Section ................................................................................................................................................5
Installing the Grommets .......................................................................................................................................................5
Installing the Tang Strips .....................................................................................................................................................6
Installing the Mains Transformer .........................................................................................................................................8
reparing the Secondary Wires...........................................................................................................................................9
Fitting the Hard-Wiring osts .............................................................................................................................................10
Installing the Choke ...........................................................................................................................................................11
Installing the Rear 8 in Valve Base .................................................................................................................................12
Fitting the Heat Sink...........................................................................................................................................................12
Fitting the Filament Board Support Screw .........................................................................................................................14
Installing the Output Transformer ......................................................................................................................................14
Installing the Interstage Transformer .................................................................................................................................15
Section 3: IEC Section...........................................................................................................................................................16
Installing the IEC Inlet lug and Mains Rocker Switch......................................................................................................16
Connecting IEC and Transformer Grounds .......................................................................................................................17
Connecting the Mains rimary to the Rocker Switch ........................................................................................................18
Finishing off the mains wiring ............................................................................................................................................19
Section 4: Completing the ower Supply ..............................................................................................................................20
ower Supply Hard-Wiring.................................................................................................................................................21
Additional Wiring for arallel Triode Operation ..............................................................................................................30
Section 5: Building and Installing the Filament Board...........................................................................................................31
Section 6: Front Insert late and Remaining Wiring .............................................................................................................38
300B Valve Base Orientation.............................................................................................................................................38
Wiring the Front late ........................................................................................................................................................41
Filament Wire Connections to 300B and 6SH7 .................................................................................................................46
Output Transformer rimary Connections .........................................................................................................................47
Interstage Transformer Wiring ...........................................................................................................................................48
Input Signal Earth Connection ...........................................................................................................................................53
Speaker ost Installation ...................................................................................................................................................53
Tidying Up ..........................................................................................................................................................................54
Section 7: Final Checks, Testing, and Finishing Off .............................................................................................................55
Mono Block Wiring Check List ...........................................................................................................................................55
MonoBlock Wiring List....................................................................................................................................................55
Checklist.........................................................................................................................................................................57
Resistance Checks.........................................................................................................................................................59
Switching On and Testing ..................................................................................................................................................60
Mono Block Testing Kit ......................................................................................................................................................61
AC Wall Voltage Checks and Adjustment..........................................................................................................................61
Fitting the Feet and Base late .........................................................................................................................................62
ower On Notes.................................................................................................................................................................62
Final Thoughts ...................................................................................................................................................................63
Appendix................................................................................................................................................................................64
Resistor Color Code Reference .........................................................................................................................................65
AC Wiring Guide (Mk3 Mains Transformer).......................................................................................................................66
Front late Wiring Diagram................................................................................................................................................67
ower Supply Schematic (Mk3 Mains Transformer) .........................................................................................................68
Signal ath Schematic (Single 300B)................................................................................................................................69
Signal ath Schematic ( arallel 300B)..............................................................................................................................70

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age 3
Se tion1: Introdu tion
Congratulations on your
choice to build the InterStage Mono Block from Audio Note.
Chassis Orientation
We have a Left and a Right chassis for your mono block
build.
As you can see the hassis’ are a mirror image of one
another – strictly for cosmetic appeal at the end of the
build.
We would suggest you start by building the Right channel
according to the manual and then it will be quite easy to
follow the manual again for the left channel – the only
difference will be the mechanical install of transformers!
Hardware and Kit Bags
We have provided you with a series of Kit Bags for your build. The first Bag is the Main Hardware Bag and inside are all
the little bags containing the hardware required for each section. Examine this bag and you will see it is fairly self
explanatory for which section these belong. We use basically two types of metric screws in the kit – the M4 which is the
bigger of the screws and the M3 type which is smaller – now each can have their own specific lengths and head types –
for example you could have an M3 an head and an M3 Countersunk or flat screw – all the screws are hilips end.

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In each kit bag is a parts list that you can check over – let us know if any parts are missing.
General Overview
The general order of the build is as follows:
• Install all the transformers on the kit (we will call this the mechanical section).
• The IEC section where we hook up the IEC inlet and rocker switch.
• Build the hard-wired power supply followed the filament board.
• Fit and wire the front insert plate where we will do most of the work out side the chassis.
• Install the front insert plate in the chassis and complete all of the final inter-wiring and checks.
Take your time on the kit build – savor the build experience and do not be in too much of a hurry to turn on your kit!
Feel free to contact us for any questions or even moral support! Best of luck
Regards
Brian Smith and Audio Note Engineering

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age 5
Se tion 2: Me hani al Se tion
NOTE: With your manual will be a CD with all the hi-resolution photos used in the manual so you can look in detail at the
pictures on your computer.
Installing the Grommets
Let’s start by installing the rubber grommets into the chassis.
The 2 larger grommets will be positioned in the top left portion of the chassis.
The other 4 grommets are installed in the chassis as
highlighted opposite.

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age 6
Installing the Tang Strips
We are now going to install the TANG strips – these are
secured to the chassis to hold up the front and rear
faceplates.
When looking at the TANG strip you will see that it has 6
holes in it – One row of three has ems (which means that
a screw will secure to the hole). The other row of three are
straight through holes.
When positioning the Tang into the chassis, make sure that
the 3 straight through holes go under the chassis and the 3
pemed holes are visible.
The flat surface is on top!
Once the Tang is in position use a 10mm Black CSK (flat) screw to secure into place – you will need an M3 nut on the
underside of the chassis.

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age 7
This picture on the left is showing the underside of the
chassis with the TANGS screwed into position.
Insert the tangs on both the front and rear insert plates using the black M3 screws provided.

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age 8
Installing the Mains Transformer
Installation of the Mains Transformer is next.
Use the rubber strips provided and lay the transformer
down in the orientation shown opposite.
The primaries go towards the back of the chassis and the
secondardies (with more wires) go towards the tang strips.
Feed the wires through the chassis as shown.
You might want a second pair of hands for the mechanical
install – if you are alone you can lie the transformer down.
A tip is to spray some WD40 oil on the grommets on the
secondary and the wires so that the wire will slide easily
through the grommet – look out for twists in the secondary
wires as this may make it more difficult to slide through.
Here you can see the wires have been successfully fed
through the chassis.

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age 9
Make sure that the Mains transformer sits on the rubber
strips provided!
To secure the Mains transformer you will use a M4 16mm
pan head screw with a fender washer on top of the chassis.
On the underside of the chassis you will want to put a
serrated M4 washer against the chassis and secure with an
M4 Nut.
Secure the nuts on the underside of the chassis with a nut
driver or wrench.
Preparing the Secondary ires
The following sequence shows that you will want to match the same colored wires in pairs on the secondaries and twist
them neatly. Then, it is a good idea to use the provided cable ties to tie the mains wire together and neatly store in the
chassis so that it is not in the way as we proceed with the mechanical build!

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age 10
Fitting the Hard- iring Posts
The next step is to install the 2 hardwiring posts for the
power supply – these will be installed in the countersunk
screws on the chassis.
The hardwiring posts will be installed with a Countersunk
M3 screw into the positions indicated by the blue arrows.
The dotted white lines show the orientation of each post.

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age 11
Here, you can see how they look from the underside.
You can see in this picture how the countersunk screws
that are securing the hardware tags under the chassis are
flush with the top of the chassis.
This is important so that we can fit a transformer on top!
Installing the Choke
Install the CHOKE -165 next.
Thread the wires through the grommet and secure onto the
chassis with an M4 nut and m4 washer on top and a m4
serrated and m4 nut underneath.

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age 12
Installing the Rear 8 Pin Valve Base
Install the 8 pin valve base with the M3 CSK 8mm screw and the m3 nut - You will want the notch facing in towards the
chassis!
The fitted 8-pin valve base - shown from the top and underside.
Fitting the Heat Sink
The next step is to install the flat screws that will hold in the Heat sink that we will be using later in the build – The reason
they need to be installed now is that they are situated under the Output transformer.

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age 13
You will use the Countersunk M4
screws in the two holes as shown in
these pictures.
This picture shows the screws protruding through the
chassis – the next step is to install the heat sink into
position.
The Heat sink is installed.
Note the position of the little holes towards the back of the
chassis.

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age 14
Fitting the Filament Board Support Screw
The next step is to install the long M3 screw in the hole.
Secure with a nut.
Installing the Output Transformer
We are now going to install the Output transformer on the
top of the chassis.
Note that the side of the O/ transformer with the 2 wires
goes towards the rear of the chassis and the 3-wire side
goes to the front of the chassis.
Secure with M4 screws and fender washers.

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age 15
Installing the Interstage Transformer
The final mechanical installation is the Interstage
transformer – It can only go in one way with the wires
feeding into the grommet.
At this stage your mono block should similar to the following pictures:

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age 16
Se tion 3: IEC Se tion
IMPORTANT: You will need to look at the AC Wiring Guide in the Appendix to locate the wiring connections for your world
voltage (120, 240 etc.).
IMPORTANT: Many of the pictures in this manual regarding both the mains transformer’s primary and secondary lead
colors are taken from when we used to use the ‘old’ transformer. We have since moved onto a new transformer - referred
to here as the Mk2 mains transformer. We are currently in the process of updating the manual but you may find
inconsistencies. We have endeavored to update the instruction text and diagrams but the picture will take longer to
update.
Installing the IEC Inlet Plug and Mains Rocker Switch
In this section we are going to install the IEC (AC inlet plug)
and rocker switch.
With the chassis in the upside down position now where
you will be doing a lot of work, you can see the orientation
of the rocker switch and the IEC plug.
The rocker switch will snap into position while the IEC plug
will be held in place with M3 flat screws and M3 nuts.

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age 17
Connecting IEC and Transformer Grounds
Step 1 in the IEC section is to take the prepared Green wire and solder it to the GND post on the IEC plug (see graphic) –
You will want to strip and tin the end of the wire.
Step 2 is to take the long green/yellow wire from the Mains transformer with the GND lug already soldered to it – You will
probably want to shorten the wire and re attaché the GND lug to it and then secure to the GND log as shown.
Note that another wire will be connected to the GND lug shortly, so no need to tighten the nut all the way yet.

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age 18
Connecting the Mains Primary to the Rocker Switch
As stated earlier, it is important that you wire up the mains in accordance with your required mains voltage that varies in
different parts of the world. lease refer to the correct diagram in the AC Wiring Guide in the Appendix at the end of this
manual. The following instructions will be wiring for 120v (i.e. North America) if your voltage is different from this then you
will have to make the appropriate alterations to some of the instructions in the remainder of this section.
If you are living in North America with an AC wall voltage of
120V then you will want to select the two White wires and
twist them together.
If you're mains voltage is different then please refer to the
AC Wiring Guide in the Appendix for the correct
configuration.
Then cut to a desired length – twist the bare metal together
and tin all of the wire. You may also want to add some
solder to the rocker switch post and then solder to the post
through the little hole on the rocker switch post.
Connect to the rocker switch in the lower right hand position
(see graphic opposite) – and tie the ends together.
Now for the other side if the rocker.
For 120V operation you will want the
two Black wires – Twist them together,
then cut and twist the stripped ends
together – Tin the wire and solder to
the post in the bottom left view of the
rocker.
If you're mains voltage is different then
please refer to the AC Wiring Guide in
the Appendix for the correct
configuration.
Here you can see that we have connected the pairs of
wires to the Rocker switch.
Note: Lead colors are incorrect in this picture as this is
using a different mains transformer.

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age 19
Finishing off the mains wiring
Take the prepared twisted Brown/Blue wire now and
connect the rocker switch to the IEC plug as shown
opposite.
All the remaining wires on the rimary of the Mains
transformer can now be stowed away.
Cut off the exposed metal ends of these wires but keep
them to length.
You will want to heat shrink the ends so that they do not
come in contact with anything and tie wrap and tuck the
whole batch neatly away.

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age 20
Se tion 4: Completing the Power Supply
We are now going to make our first connections from the
secondary of the Mains transformers to the 8-pin valve
base.
Select the twisted pair of yellow wires from the secondary
as shown and we will be connecting these to the valve base
pins 2 & 8.
These wires are the filament supply for the 5Y3 (5U4G) that
carry 5 volts ac and cause the tube to light!
Now take the two Red wires from the Mains secondary for
300B operation and connect to pins 4 & 6 of the 8-pin valve
base.
These are the main high voltage wires that will be powering
the amplifier!
Note: or 2A3 operation you would use the two Orange
wires instead.