Hello mario ,
Congratulations on your new purchase
Here is the building application guideline for the 300B stereo integrated amplifier
I have included an italian traduction but i cannot check it so i can only hope
that it is as accurate as possible .
Safety :
But first a word of caution , the voltages are lethal so respect safety instructions for working with High voltage devices ,
also be very diciplined when doing so as a mistake may result of being too careless
It is at your risk that you are building this high voltage amplifier , be warned .
A few safety tips :
Pull the power plug out of the mains when working in the amp
After you have powered up the amp ,give it a few minutes after you have pulled
the power plug To discharge the capacitors .
When you must measure the amp under working voltage , keep 1 hand in your pocket
( your left ) And only use one hand to
hold the probe to measure ( the other probe connect it to power ground = ground
of high voltage power supply )
Be sure that the bleeder resistors of the high voltage capacitors are mounted
,
And even after having disconnected the powerplug measure the high voltage line
until it drops to a safe level ( 60 to 80 volts )
before putting both your hands in the amp ,
Never work or touch lines that carry high voltage ( or even low voltage ) with wet hands , if you have washed your hands
give them time to dry properly .
Ok , i hope this was all common knowledge and nothing new .
Congratulations on purchasing this splendid amplifier , it is a stereo Single Ended pure class A amplifier using only triodes as
active amplifying devices .
All resistors in signal path are dale 1 watt , all signal capacitors are mkp
types
And all bypass small caps are either mpp or mkp types .
Bill of materials :
You should check that you have these in the box , mounting hardware
1 of each :
toroid power transformer
euro connectormale chassis 230 vac in
fuseholder plastic for 6,35mm fuse
panasonic pot stereo log 100K
commutator stereo 2x6 contacts
bridge 6A/800 volts
pcb 10x16 ( partially pre-mounted)
wooden chassis ( the finishing is up to you , paint or varnisch)
stainless steel top plate
aluminium bottom plate
2 of each :
transformer LL1623/90mA
transformer black housing
speaker terminals
krone VV300b tubes
ux4 300b tubesocket
rubber for ux4 tube socket
noval tube socket
2C51 Western Electric
chokes 20H/80mA
interuptor 10a/250v
56 ohm/25watt
pcb 140 mm long about 1 cm large strips
pcb for transformer model C
8 RCA female chassis sockets
5 rubber feet , plastic knob for pot & commutator
screws : ( length is estimated) inbus = allen key =hex inside
12 pcs M3x10 black inbus ( noval tube socket & pcb's)
16 pcs M4x10 black inbus (transformers & housings )
12 pcs M3x15 chrome inbus (speaker terminals &bridge &euroconnector
&rubber feet)
4 M4x20 black inbus (300B tube sockets )
1 pcs M8x80 black inbus ( for power transformer )
20 pcs selftreading 3,5x13mm ( for metal chassis top&bottom)
4 pcs selftreading 3,5x9,5mm ( for chokes )
4 metal shaft with screw 10 mm long ( for pcb powersupply)
4 metal shaft with screw 15 mm long ( for 140mm strip pcb)
all nuts & anti-slip & washers included
Bill of materials electronic parts
Capacitors :
5 pcs 470µF/450v panasonic
8 pcs 0,47µF/630v mpp ( brown-orange)
1 pc 0,47µF/400 mkp
3 pcs 2,7µF/400v mkp ( black-dark blue)
2 pcs 4,7µF/400 mkp
2 pcs 0,22µF/400v mkp
2 pcs 0,22µF/630v mpp
1 pc 10nF/630v mpp
4 pcs 3µF/385v japan
3 pcs 4700µF/16v xapcon
1 piece 22µF/500v illinois
3 pcs 1000µF/100v xapcon
1 pcs 470µF/100v xapcon
2 pcs 1µF/250v sink foil mkp
2 pcs 470µF/4v panasonic
2 pcs 33pF ( for hf suppression , not absolutely necessary )
Resistors : dale 1 watt unless otherwise specified
2 pcs 150K
7 pcs 390 ohm
2 pcs 82K
4 pcs 4k7
2 pcs 220K/2watt
1 piece 68K/5w
6 pcs 47k
2 pcs 4K7 5watt
2 pcs 270ohm
2 pcs 560 ohm
2 pcs 68K
2 pcs multiturn pot 50K
1 pot stereo 100K panasonic
2 pcs 22ohm/5watt
2 pcs 0,47ohm/5watt
cables :
shielded cable black signal 1 metre
twisted brown grey heaters 2 meters
silver signal cable 0,6mm2 signal 0,5metre
ofc 1,5mm2 speaker 0,5metre
orange or red high voltage 3 meters
black or blue ground 3 meters
purple negative bias 1 meter
solid core green with brown marks 2 meter
solid core copper 1,4mm2 1,5 meter
solder 1mm2 5 meter
Construction ( finally )
But first the what you need to complete this kit list :
Screwdriver allen key M3, M4
Pair of pliers for electronics
Pair of plier for electricity
Soldering iron 25 watts & wet sponge
Stripper for wire ( adjustable )
Electric voltage & ohm meter ( digital preferable)
Screwdriver philips
Patience (cannot be bought )
Cutter for electronics
A few construction tips : also see appendices (hand writing )
When you strip a wire , be sure not to have cut the conductor ( even not slightly as it might break later )
then twist the conductors ( if multi stranded ) then tin with a bit of solder
.
Solder should be used in an intelligent way : take 2 resistors twist them together
Keep 1 cm not twisted ( see appendices ) and use the solder to hold them together
Not for the electrical contact .
Also the way in which you solder is very important , the solder tip should be
wiped clean after every solder joint
(use a sponge thats moist = wet )
Let the solder flow from the soldering iron to the part , never blow ,too cool
solder joint.
If too hot use gloves . see appendices for help ( or burn fingers very slightly)
Please note that tube pin numbers are counted viewed from the solder side
And they are counted clockwise .
Step 1 Assembly : ( use the drawing of the top plate chassis
to guide )
Take the top plate , prepare all screws ect
Before mounting anything clean the topplate using aceton (you can purchase
anywhere)
Use a cotton cloth ( old T-shirt )
Mount the toroid use M8x80 + anti slip + nut , make sure the wires go through the big hole without getting stuck
between transformer housing and metal chassis , twist the wires from the power transformer that belong together , example blue & grey
Mount the lundahl output transformers , the pcb with the 16 wire ends to the
back side
Of the chassis ( the front has the tubes ) use M4 allen screws black
Mount the chokes , make sure to use the selftreading 3,5x9,5 mm screws &
make sure
There is no contact between the pins and the metal chassis
Mount the euro connector use white-chrome M3x15 mm
Mount the fuseholder , tighten firmly ( do not break )
Mount the 8 RCA chassis inputs , make sure to use the plastik washers so that
there is no electrical contact between them
Mount the noval tube sockets use m3 black allen screws
Mount the ux4 tube socket , use the rubber supplied to isolate from metal top
plate
Do not overtighten as the socket will break if you do so use m4x20 black allen
screws
Mount the screws with the metal shafts for the pcb holders ( 10mm for power pcb & 15 mm for the strips )
use m3 x 8 mm (or 10 mm or 6 mm) black allen screws
Mount the 2 dale 56 ohm / 25 watt resistors use m3 x 10 mm black allen screws
Mount the speaker terminals at the back with the chrome M3x15 mm
Mount the bridge ( rectifier black little device with 4 pins ) chrome M3x15
Make sure everything is nicely mounted , not to tight but tight enough use
the tube
Of glue supplied on every nut to make sure that nothing will come loose , you
can allways unscrew things .
This may or may not help to assemble ,(premount on wooden chassis)
Eventually screw onto wooden chassis using 3,5x13 mm
Step 2 : look at the wiring diagram hand drawn for clarification
When Preparing a cable , strip & pre tin patiently and cautiously ,
For the heaters & filaments use brown-grey twisted wire
For ground use blue or black wire ( signal & power ground)
For high voltage use red or orange wire
For signal use silver 0,6mm2 ( separate bag) or solid core (green-brown)
Also use shielded wire to get to the commutator from RCA sockets
Mount the PCB small with letter C on one side , make sure the loudspeaker terminals are on the outside.
Solder it carefully on the lundahl transformers , (once mounted they are very though to get unmounted so i prefer to
cable this point to point but for the kit i supply the pcb )
Use the supplied 2 x 1,5 mm cable to hook up to the speaker terminals
Cable all tube heaters
Cable the 56 ohm resistors to the pcb , please notice there is a mod , instead of R2 you make a bridge ( so R2 is considered as 0 ohms )
only R1 is used but instead of being one 56 ohm resistor we will put the 2 resistors (56ohm)in series so we keep the 112 ohm value 50 watt ,
so the resistors are in series . ( do not mount the pcb yet , use red aor orange) they carry the full high voltage .
Connect the 6,3volt AC ( the blue and grey wires from the power transformer ) to the rectifier ( the 2 middle pins ) ,
mount the 3 4700µF/16v caps use the 0,47/5 watt resistors ( to drop the voltage ) and hook up the filament wires ( brown-grey)
make sure
The 300B gets its filament voltage after the resistors and the 5670W before
the resistors
Connect on only one 300B tube socket the 22ohm/5watt resistors (1 on every thick round hole = pin 1 and 4 )
Mount the 140mm pcb ( one above and one beneath the 2C51)
Or one above the 300B. use M3 black allen x10mm and metal bushing as spacer
15mm
Premount the bushings for the pcb , use 4 screws M3 black allen 10mm and 10mm bushing metal
Mount the 2 switches , tighten firmly
Connect the euro connector to the power switch use the white wire for this purpose
Connect the chassis ground to the middle pin of the euro connector ( white wire
)
Also connect the fuse in this way , hook up to the power transformer ( rose
wires )
The Pcb of the power supply :
It is allready partially pre mounted , but still needs carefull assembly
Note there is a change R2 is not used , just put a bridge so the resistor value
is 0 ohms
R1 = old R1 + old R2 so new R1 = 112 ohms 50 watts , the 2 resistors are simply
put in series . f
Cable the resisors with red or orange to the pcb ( the pcb is not yet mounted but make sure the cables are long enough to get
to the right spot on the pcb ) and use a short re wire to connect them in series , remember all red or orange wired components
carry the full high voltage .
1 side of the resistor goes to the pcb the other side goes to the stand by switch
, to the switch also add the 68K 5watt resistor
( see wiring diagram )
Look at the schematic :
The components that are numbered R2 C1 ect are all mounted on the PCB , select the components and solder to the PCB
The only exception is R4 , R4 is the 2 chokes in parallell , cable the 2 chokes with red or orange , the pins that are the closest
together are the ones used , check with the ohm meter if you are not sure . prepare the wires so that they are the right size to connect to the pcb .
The pcb is now ready , solder the red and yellow wires from the power transformer
To the pcb ( diodes D1 and diodes D3 ) and ( diodes D2 and D4 ) make sure that
they are on the right spot , the wires should
not have a direct connection to any of the capacitors .
Connect the white and black wire from the power transformer , 1 wire to the diodes D5 , D6 and the other to R7
Prepare the following 2 red cables to the power transformers they leave the
pcb from C5 or C6
Prepare 2 red cables for the Ub left and right connect to C10 & C14
Next step is very important :
Prepare black ( or blue ) 4 cables
2 you connect to the negative side of C5 or C6 they are for the power tubes
and goto the 22 ohm resistor
that is mounted on the 300B tube socket , on black wire to each .
the other 4 black wires are mounted to the negative side of C10 & C14 (
respect left & right channel ) they will be connected
to the node of 560 ohms ( ground ) and to the ground of the capacitors 4,7µF//0,22µF
also prepare one black wire for connecting the 10 ohm resistor to chassis ground
the 10 ohm resistor will be cabled next to the euroconnector .
prepare 2 purple wire to connect to components next to each power tube
hook up to C20 negative side
prepare 2 black wires from C20 positive side , they must be as long as the purple
wires
you may mount the pcb use M3 bolts and washers to tighten up
_____________________________________________________________________
connect the power transformer high voltage from the power supply
also go from the power transformer primary to the plate ( anode ) of the 300B
which is pin 2 ( check with the supplied lundahl datasheet )
300B pinning :
pin 1 = the first thicker pin then go clockwise till you get to the other thick
pin ( pin 4 )
prepare 4 pieces of stereo shielded wire 18 cm
prepare 4 pieces of stereo shielded wire 15 cm
strip them so that on every side you can twist the shield ( ground of signal
)
together and the signal together see appendices
the idea is to have a parallell conductor herebye doubling wire section .
solder the 18 cm to the rca input sockets far away , the shield to the outer side and the signal to the middle pin . cable all .
prepare 2 signal cables ( use silver 0,6 mm2 ) to go to each pre amp tube use
a knife to scratch of the teflon or lacquer that isolate it
prepare 2 copper 1,4mm2 solid core wires for the ground connection
hook the signals up to the commutator use pin 1 to 4 ( be logical left and
right channel symmetrie )
the cable that goes to the pre amp tube is hooked in the middle ( signal )
hook all the grounds together , ( left channel grounds with left channel and right channel with right channel )
preparations for point to point soldering :
this actually means joining everything together that belongs so , look at the
schematic
and you 'll understand , this description is only for 1 channel , so repeat
it for the other channel as well , see appendices for help
take the 150K resistor and 33 pF capacitor , twist together
take the 47K and 68K resistors and twist together
take the 4,7µF/400v mkp capacitor and the 0,22µF capacitor and twist
together
take the 39K and 47K resistor and twist together
take the 560 ohm resistor and the 220µF/6v capacitor and twist together
take the node 4K7 and 82K and 0,47µF/630v mkp and twist together at the
common point make sur to leave about 1,5 cm
to the body untwisted
solder on every beginning ( from the body of the component ) of twisting a bit
of solder , cut of 1cm further the excessive leads ,
see appendices for example
then right at the comutator you also solder the 150K resistor with the 33pF capacitor parallell on it ( see appendice )
the tube 5670W has the following pinning viewed from beneath , ( solder side
)
pin 1 = filament or heater
pin 2 = cathode 1
pin 3 = grid 1
pin 4 = anode or plate 1
pin 5 = screen connect to ground connect it to ground use a black wire
pin 6 = anode or plate 2
pin 7 = grid 2
pin 8 = cathode 2
pin 9 = filament or heater
prepare the pinnings , pre tin all pins of the tube sockets , especially the
300B ones ,
if you have a problem use the point of the soldering iron to scrub the surface
of the to tin part , after 3-4 seconds this works and
the solder gets grip on the surface
take the 390 ohm resistor and on one side cut off so that you still have max 1 cm ( less is better ) solder one resistor to each grid of the 5670W
take the 4K7 and do the same ( grid of 300B )
solder the 1µF/250v sink foil mkp to the 560 ohm resistor , bend the legs of the capacitor and use pliers to make hooks the squeeze
with plier to tighten hook and the add a drop of solder , ( i would like to remind you that the solder is used for mechanical strenght as
glue not as electric conductor in all possible cases )
take the cathode resitors of the 5670 and solder on to the cathodes , you should leave about 1,5 cm of wire on those
also solder the grouped anode or plate resistor solder to there respective
anodes
( res 68K//47K & 39K//47K ) make sure nothing touches anything else
4K7 connect to 39K//47K and to 68K//47K , if necessary use a wire to hook up
to either
one of the resistors
the same applies for the 4,7mkp//0,22µF cap , use a wire to hook up to the resistors , the ground side solder to the solder strip
the grounding technique is the following ,
principle 1 : signal follows ground
principle 2 : powersupply ground follows last powerssupply capacitor
principle 3 : use equal length ground wires for left and right
signal ground : read before starting so you can prepare wires and twist them together where 2 wires join on one solder point
at the audio switch , all grounds of the inputs join , there the 150K//33pF
are soldered
to the connected grounds ,
from there a wire you can use silver or the green with brown
solid core mixed alloy to continue the ground to the 270 ohm resistor ,
from that resistor also a black wire goes to the 4,7µF//0,22µF powersupply
cap ( if you didn't solder them together on a solder strip )
from that same capacitor comes a black wire from the pcb from C10 or C14 respect
left right .
the signal ground then continues from the 270 ohm resistor to the panasonic
pot , see appendices for connecting ,
from the pot you continue with signal ground to the 560 ohm node .
at this stage the amplifier is almost completed ,
it may look a mess but its electrical fully correct , and if soldered and stripped correctly this is build like a tank and should last an eternity .
rest a few details :
the negative power supply :
solder the pot 50K to the solder strip , use the 2 contacts beneath to solder
on 2 islands
it is difficult but just possible
see appendices for connection
connect the purple wire from powersupply to on terminal of the potentiometer
connect a purple wire from ( see appendices ) pot to 82K resistor
connect the black wire from powersupply to the unconnected last tab on the pot
if i didn't forget anything you are know finished .
put a fuse in the fuseholder 3,15A slow blow .
make sure no wires shortcircuit , make sure the pcb of the powersupply is mounted
tightly , make sure you checked all the high voltage
lines so that there are no shorts to ground
do not plug in the tubes yet .
connect the minus of your volt meter to the powersupply ground or any other
ground
put one hand in your pocket , your left prefarably , if you think that you are
not capable of doing this safe dont do it ,
hand it to someone who has experience because you are playing with your life , at your own risk .
power up , dont switch the high voltage on , ( standbye switch off )
check the high voltage red or orange wire , measure , if the standbye switch is correctly cabled voltage should rise slowly ,
but it will rise to full high voltage
know measure the 82K node ( connected to the 50K pot )
adjust until you have - 85 volts on that node . ( on both the sides )
at this stage remeasure high voltage , if its high its ok
switch off
wait a few minutes , remeasure high voltage
put the tubes in , be carefull when inserting the small tubes , do not break the pins or damage them use a plier if necessary to straighten them again ,
the trick is too use an old tube to open the new tube sockets a bit ( like a virgin )
power up , no high voltage , just stand bye , the tubes filaments should all
light slowly
up , measure the small tube filament voltage , you can measure either from the
bridge or straight from the tube socket pin 1 to pin 9
( do not tremble , use crocodile cables that you pre hook to the test points
if in difficulty )
this should read about 6,3volt +/- 15% tolerance
then measure the 300B filament voltage this should measure about 5V +/- 15%
if this is all ok , switch off , wait a few minutes
hook speakers up , hook cd on , turn volume to minimum
be carefull on the transformer the primary taps carry the high voltage
switch on , after 20 seconds switch the stand bye switch on ,
at this stage a very small hum should be noticeable depending on speaker sensibility and this means you can press play on the cd ,
slightly turn the volume up and turn the selector until you have the right channel , you should be listening to music know
if this is all ok , switch off , wait a few minutes
last things to do
mount transfomer black housing use M4 black allen screws use a bit of glue
mount on wooden chassis use 3,5x13 mm screws self threading
mount alu chassis with 5 rubber feet ( M3 white and round plates ) same screws
your amp is finished
a few notes , you can try different biasing for the 300B , depending on tube
it might sound better to you , with bias of -75 volt or bias from -75 volts
to -90 volts
the less negative you go , the harder the tube has to work .
last step let me know how this project is to you .
Addendum things i have forgotten but are important
Connection of the stand bye switch :
First take the 68K/5watt resistor and twist the 10nF/630v cap solder
Pre mount this on the switch
Connect one side of the 112 ohm 50 watt resistor ( from the 2 56 ohm resistor
in series )
And connect the other side of the switch to where the 112 ohm resistor was connected
to the pcb
Please note that according to the schematic there is a 22µF/500 volt
cap with 220K resistor
Included , ( first try without it ) to be mounted using MMP005 and plastik tie
next to the switch
The plus of the capacitor goes to the plus of the resistor which is hooked to
the plus of the diodes
The minus of the capacitor goes to the ground plane on the pcb
