Amplimo Vanderveen UL40-S2 Instructions for use

STEP BY STEP
CONSTRUCTION MANUAL
FOR
THE
UL40-S2
VALVE AUDIO AMPLIFIER
By: Menno van der Veen and Amplimo BV
© Ir. buro Vanderveen; May 2006; 4th release

2
GENERAL INFORMATION
COPYRIGHT
The text, content, figures and circuit diagrams included in this construction manual are protected by and are
the property of Ir. buro Vanderveen. Copies of the content, or parts of it, in any material form, are prohibited
without the explicit written permission of Ir. buro Vanderveen. The electronic design of this kit: circuit
boards, diagrams, principles, and transformers also come fully under the copyright of Ir. buro Vanderveen.
SUPPLIER
Amplimo b.v. is the official supplier of the UL40-S2 kit in Europe. Amplimo b.v. also handles all contacts
with the customers and users of the UL40-S2.
CONSTUCTION MANUAL
This manual is not available in bookshops; it is only available with the UL40-S2 construction kit.
SERVICE
Service from Amplimo b.v. consists of two elements:
a) Answering of questions by telephone, fax or email.
b) Checking and adjustment of the buyer’s constructed amplifier for a charge of € 95 incl. VAT but excl.
shipping charges. Please ensure that the amplifier is well packed before sending it to: AMPLIMO b.v.;
Industrieweg 14; NL-7161 BX NEEDE, The Netherlands.
After inspection and repair, the amplifier will be returned, cash on delivery (shipping charges plus € 95.00)
or after a prepayment. Shipping is at risk of the customer. Inspection and repair will take a maximum of two
weeks. The customer will be notified if it takes longer.
GUARANTEE
1) Guarantee conditions and terms of delivery are defined in the “Algemene Voorwaarden voor de
Instrumentenbranche”.
2) The guarantee period is a total of 6 months from the date of purchase, (see below).
3) All elements of the construction kit fall under these guarantee conditions. The guarantee does not cover
destruction or damage by misuse. This is determined exclusively at the discretion of Amplimo b.v.
The following example clarifies this:
Every output transformer is checked completely before delivery. If it is found that the output transformer is
defective, Amplimo b.v. could conclude that the damage has been caused by misuse. For instance: by
shortening the leads of the output transformer (which you shouldn’t do) or damage due to a short circuit
through the transformer caused by the incorrect positioning of a valve in its socket. Because we are dealing
with a DIY construction kit, damage is possible if the construction directions are not followed in full. The
guarantee does not cover damage if it is due to faulty construction.
TERMS OF DELIVERY
1) The UL40-S2 amplifier is only sold as a complete construction kit, inclusive of the construction manual.
2) Individual components for the kit will only be supplied for the replacement of defective or incorrectly
supplied parts, to the original owners of the kit.
3) Delivery will only take place after the purchase price has been paid in cash, in advance into the
international bank account of Amplimo b.v. (IBAN NL 36 RABO 031311250), by cash on delivery or by
payment using VISA or MasterCard. If you want to personally collect the construction kit please contact
Amplimo b.v. first.
4) Acceptance by the buyer only takes places when the buyer has taken notice of the safety instructions on
the following page of this manual.
5) Amplimo b.v. and Ir. buro Vanderveen will not entertain any claim, under any circumstance, if it is the
result of not or only partially following the safety and building instructions.
6) In addition to the above, the General Terms of Delivery for the “Instrumentenbranche of the FHI” are
applicable
SAFETY INSTRUCTIONS
1) This construction kit employs high voltages (220/230 Volt 50 Hz AC and 380 Volt DC). These voltages
are potentially lethal if they come in contact with the human body. This is why you must take the
greatest care in avoiding accidents or damage of any kind.
2) Only work on the opened amplifier cabinet after the mains plug has been removed from the mains
socket AND after the amplifier’s high voltage supply has been discharged by first switching the
amplifier to the stand-by mode (power switch up and standby switch down) with the valves inserted
(although the filaments will glow, high voltage will be absent as the electrolytic capacitors would have
been discharged through the valves).

3
3) Never work with both hands placed in the amplifier at the same time when it is switched on, or when
there is still a high voltage present in the set. This situation is extremely dangerous, as leakage or
discharge currents may flow from hand to hand via the heart.
4) Only use the prescribed fuses.
5) Take care to ensure that all high voltage leads are insulated and positioned far away from metal parts.
6) DO NOT SHORTEN THE LEADS OF THE OUTPUT TRANSFORMERS as this will cause irreparable
damage to the transformers.
7) Do not insert conductive objects into the cabinet.
8) Thoroughly check that the electrolytic capacitors are mounted as instructed, take care not mistake the
negative pole with the positive pole, as this could cause acid to leak or for the capacitor to explode.
9) Thoroughly check that transformer leads are connected to the PCB and other parts in accordance with
their prescribed colour scheme.
10) Ensure that valve sockets (particular the Octal types) are mounted the right way round in accordance
with the diagram.
11) When switching on for the first time explicitly follow the “test procedure” given for the completed set.
12) On the following pages you will find the so called “EG-verklaring van overeenstemming” with
explanations. To meet the terms of this declaration, the constructor has to follow ALL directions and
conditions.
13) Make sure that there is sufficient room around the amplifier for ventilation; at least 3cm is required
each side and 10cm above. Take care to prevent any fluids from entering the amplifier. If this happens,
immediately disconnect the set from the mains supply and send the amplifier to Amplimo to be
checked. Also note that the cover situated above the valves will become very warm. Take care at all
times to prevent the cover from being touched (paying special attention to children). Again with children
in mind, position the amplifier so that it becomes impossible to poke metal objects into the cabinet.
14) This amplifier has to be earthed – ensure that the mains socket has an earth connection.
15) With soldered joints, hook the wire in place to form a mechanically stable joint before soldering. This
ensures that the wire cannot become loose to cause potential damage or to become a hazard. A piece
of heatshrink sleeving around this type of joint not only prevents you from touching the bare terminal,
but is also gives extra protection against the contact from working loose.
16) Where two or more wires are soldered in close proximity to each other on the PCB or for instance on
the volume control, they have to be secured in place by the use of a cable tie. This prevents the wires
from drifting about in the cabinet if they accidentally become unsoldered.
Amplimo b.v.
Industrieweg 14
NL-7161 BX NEEDE
The Netherlands
Tel: [phone]
Fax: [phone]
Email: [e-mail]
Internet: www.amplimo.nl
INTRODUCTION
Dear buyer,
Thank you for buying the UL40-S2 valve amplifier. This amplifier was born out of
the love for music, faithful music reproduction and exceptional spatial image. This amplifier
is based on many years of experience and study by the designer. The latest techniques
and knowledge are used in this design. Some of the details are outlined below:
The output transformer is designed according the latest techniques. Superior
insulation materials, grades of copper wire, core compositions and other materials are
used (the ultimate of transformers using superior silver/gold wire are now also available at
extra cost). All of this results in not only an extremely wide frequency range, but also in
excellent detailed reproduction. Each valve is carefully selected by using computerized
measuring equipment before finally being matched by hand. The electrical circuit excels by
simplicity, realising minimal distortion by using carefully selected components in the signal
paths. As negative feedback from the output to the input is not used the concept is
amplification straightforward. The printed circuit board uses an extraordinary structure

4
called “LEP = logistic earth patterns”. This means that the ground tracks are laid out in a
special way so that there is a minimal degradation of audio signals. Even the mains
ground is connected in a special way to one central point. Passive components such as
resistors and capacitors are selected with extreme care to contribute to an open and
detailed sound image. The amplifier can be operated in several modes (Triode, Ultra-
Linear and Pentode) making it possible to experiment with these well known valve
configurations. Fast electrolytic capacitors are used in the power supply to give the
amplifier a clear and clean high-frequency response. High frequency decoupling is used
for the filaments, providing low radiation from the PCB.
We could reveal further new facts and advantages, but much greater details are
given in previously written articles (publication in Radio Bulletin Elektronica, December
1994, publication in Radio Bulletin Elektronica July/August 1996, publication in “Het
Vanderveen BuizenBouwboek”, 4th and later releases, publication in the book “Modern
High End Valve Amplifiers with Toroidal Transformers”; all of which are available from
Amplimo b.v.). In these the details of this design are extensively explained. The UL40-S2
is a revamped version of the original UL40-S, to which several improvements have been
incorporated (including the option of quiescent current adjustment for the output valves to
keep them matched for longer and more extensive high-frequency decoupling of the
power supply) in addition to having a superior metal cabinet.
We hope that you will get lot of pleasure from building this UL40-S2 valve amplifier
together with a greater joy in listening to your favourite music using this amplifier. Should
you have any questions, please contact our customer support department.
Ir. buro Vanderveen and Amplimo b.v.
Menno van der Veen, Hans Braam

5
B1-b
V1
V1
B3
B2
VL V0
EL34
EL34
1/2 6922
(or 1/2 6N1P)
1/26922
(or1/2 6N1P)
Copyright: Ir.buro Vanderveen
1/4 W 1 W 5 W
125 V
125 V
..... V
275 V
275 V
365 V
59 mA
59 mA
26 V
= to
Beyschlag
; +/- 20 %
VDV6040PP
BLK (5 x)
BLU (5 x)
5 Ohm
30 Watt
YELLOW
VIO
RED
BRN
GREEN
Amplimo
T1
B1-a
- STEREO
Inputs ( 4 x)
100k
250k
UL40-S2 Version 5; 21-11- 2000
Design: Menno van der Veen
= Audio ground
= Case =Mains ground
P1 = Volume
P2 = Left - Right balance
P3 = AC-BalanceB2-B3
P4 = Quiescent BalanceB2 - B3
C:\UL40S2\UL40-2.cdr
P2
R3
C7
100nF
100V
220µF
25 V 100nF 100V
1000µF40V
180k
R10
150k
R11
P3
100k
C1 C2
C3
100nF
630V
C4 470nF
630V
C5 470nF
630V
R12
1k
R13
220k
R14 1
R15
1k
R16
4k7 220
R17
R18
1k
P4
1k R19
4k7
R20
220k
1
R21
R22
1k
C6
R23
1k
R24
1k
R25
10
S0
P1
ALPS
50k - AUDIO
4k7
R2 2k2 R4
R5
47k
680
R6
680
R7
47k
R8
1M
R9
to A other channel
A
S1
S1
AMPLIMO
6N536
T2
680k
280V
0.6A
6.3V
7A
115V
115V
2.2
2.2
traag
D1 D2
D3
D4
4 x 1N4007
Z2 1A
Z1 1A
I t >2
2
CONNECTOR
IEC MAINS-
CHASSIS
GROUND
C:\UL40S2\UL40-v-2.cdr
15k
15k
330µF
400 V 47µF
47µF
350 V
350 V
47
4 x 1N4007
D5 D6
D7D8
D9 Red D10 YEL
220µF
16-25 V
1k5
680
Tr-1
BC547B
or
equivalent
10k
150k
STAND-BY
D9 = power on
D10 = tubes on
VL = 26 V
f = 0 V
f = 6.3 V
V1R
V1L
= 235 V
= 235 V
V0 = 355 V
UL40-S2 Version 4; 27-10-2000
Power Supply Section
Design: Menno van der Veen
Copyright: Ir.buro Vanderveen
Drawing for 230 V 50 Hz
R30
R31
R32
R33
R34
R35
R36 R37
R38
R39
C10
C11 C12 C13
C14
C15 - C20
C22
10 nF
10 nF
1000 V
1000 V
100 nF
100 V
6 x
Power Switch
b
a
S2
B1
Y1
B2
Y2
RED
YEL
BLU
GRY
C23 10 nF
1000 V

6
LIST OF COMPONENTS
CODE VALUE TYPE QUANTITY PRINTING
Resistors
R2 4,7kΩ 1W metal film 2 ye-vi-blk-br-br
R3 100kΩ 1W metal film 2 br–blk–blk–or–br
R4 2,2kΩ 1W metal film 2 rd–rd–blk–br–br
R5 47kΩ 1W metal film 2 ye–vi–blk–rd–br
R6 680Ω 1W metal film 2 blu–gry–blk–blk–br
R7 680Ω 1W metal film 2 blu–gry–blk–blk–br
R8 47kΩ 1W metal film 2 ye–vi–blk–rd–br
R9 1MΩ 1W metal film 2 br–blk–blk–ye–br
R10 180kΩ 1W metal film 2 br–gry–blk–or–br
R11 150kΩ 1W metal film 2 br–grn–blk–or–br
R12 1kΩ 1W metal film 2 br–blk–blk–br–br
R13 220kΩ 1W metal film 2 rd–rd–blk–or–br
R14 1Ω 1W metal film 2 br–blk–blk–sil–br
R15 1kΩ 1W metal film 2 br–blk–blk–br–br
R16 4,7kΩ 1W metal film 2 ye–vi–blk–br–br
R17 220Ω 7W Wire wound 2 220R 5% 7W
R18 1kΩ 1W metal film 2 br–blk–blk–br–br
R19 4,7kΩ 1W metal film 2 ye–vi–blk–br–br
R20 220kΩ 1W metal film 2 rd–rd–blk–or–br
R21 1Ω 1W metal film 2 br–blk–blk–sil–br
R22 1kΩ 1W metal film 2 br–blk–blk–br–br
R23 1kΩ 1W metal film 2 br–blk–blk–br–br
R24 1kΩ 1W metal film 2 br–blk–blk–br–br
R25 10Ω 1/4W carbon film 1 br–blk–blk–gld
R30 680kΩ 1/4W carbon film 1 blu–gry–ye–gld
R31 2,2Ω 1W metal film 1 rd–rd–blk–sil–br
R32 2,2Ω 1W metal film 1 rd–rd–blk–sil–br
R33 15kΩ 1W metal film 1 br–grn–blk–rd–br
R34 15kΩ 1W metal film 1 br–grn–blk–rd–br
R35 47Ω 1W metal film 1 ye–vi–blk–gld–br
R36 1,5kΩ 1/4W carbon film 1 br–grn–rd–gld
R37 680Ω 1/4W carbon film 1 blu–gry–br–gld
R38 10kΩ 1/4W carbon film 1 br–blk–or–gld
R39 150kΩ 1/4W carbon film 1 br–grn–ye–gld
Capacitors
C1 220µF / 25V electrolytic cap radial 2
C2 0,1µF / 100V capacitor radial MKT, MKH 2
C3 0,1µF / 630V capacitor radial MKP 2
C4 0,47µF / 630V capacitor radial MKP 2
C5 0,47µF / 630V capacitor radial MKP 2
C6 1000uF / 40V electrolytic cap axial 2
C7 0,1µF / 100V capacitor radial MKT, MKH 1
C10 10nF / 1200V capacitor radial MKP 1
C11 10nF / 1200V capacitor radial MKP 1
C12 330µF / 400V electrolytic cap radial 1
C13 47µF / 350V electrolytic cap axial 1
C14 47µF / 350V electrolytic cap axial 1
C15 0,1µF / 100V capacitor radial MKT, MKH 1
C16 0,1µF / 100V capacitor radial MKT, MKH 1
C17 0,1µF / 100V capacitor radial MKT, MKH 1
C18 0,1µF / 100V capacitor radial MKT, MKH 1
C19 0,1µF / 100V capacitor radial MKT, MKH 1
C20 0,1µF / 100V capacitor radial MKT, MKH 1
C22 220µF / 25V electrolytic cap radial 1
C23 10nF / 1200V capacitor radial MKP 1
Potentiometers
P1 50kΩ log stereo volume control ALPS 1
P2 250kΩ trimpot small horz. 1
P3 100kΩ trimpot small horz. 2
P4 1kΩ trimpot small horz. 2

7
Semiconductors
D1 t/m D8 1N4007 diode 8
D9 LED red flat top 1
D10 LED yellow flat top 1
Tr1 BC547 transistor NPN 1
Other parts
Z Fuse holder PCB-mount 1
Z1,Z1’ T1A I²t min.15t Slow-blow fuse IEC127 5x20mm 2 for 230V use only
Z1,Z1’ T2A I²t min.40t Slow-blow fuse IEC 127 5x20mm 2 for 115V use only
Z2 T0,63A Slow-blow fuse 5x20mm 1
S0 switch Selector 1
S1, S2 switch Toggle 2
T1 PAT4002 Output transformer VDV6040PP 2
T2 6N536P Power transformer AMPLIMO 1
PRINT1 PCB main double sided 1
PRINT2 PCB input single sided 1
PRINT3 PCB alps single sided 1
B1 6922 Valve Electro Harmonix 2
B2, B3 EL34 Matched valve Svetlana 4
NOVAL noval Valve socket PCB mount 2
OCTAL octal Valve socket PCB mount 4
WBTR Speaker terminal WBT red 2
WBTW Speaker terminal WBT white 2
CINCH 2V stereo input cinch gold plate 2
MAINS INPUT Mains input 3-terminals 1
MAINS CORD Mains cord 1
SHAFT Extension shaft aluminium 1
SHAFTCOUPL. Shaft coupling 2
SHAFTSUPPORT Shaft support 1
KNOB Instrument knob aluminium black 2
BUSH Nylon spacer 7,5mm 1
FOOT incl. Mounting material 3
Assembly-parts
CABINET 1
COVER 1
BASE 1
FRONT 1
M4x10mm screw Pan head black 8 for base
M3x8 screw Counter sunk black 1 for mains input
M3x10 screw Counter sunk black 1 for mains input
ST2,9x6,3mm screw Pan head black 3 for cover
ST2,9x13mm screw Pan head black 2 for cinch inputs
M4x12mm screw Pan head black hex socket 4 for front
M3x10mm screw Pan head black 5 for PCB
M5x60mm screw Pan head black hex socket 1 for power transformer
M4 washer spring washer 8
M3 washer spring washer 3
M3 nut nut 2
M5 nut nut 1 for power transformer
M5 washer washer 1 for power transformer
SOLDER solder with silver SILTECH 30 grams
WIRE wire several colours 7 several lengths
ISOLATION SLEEVE several colours 2 several lengths
HEAT SHRINK 2 several lengths
TIE WRAPS Tie wraps 20
STICKER warning sticker 1 for base
SOLDER TERMINAL Solder terminal 6.3mm blade Faston 2
SOLDER TERMINAL Solder terminal small ceramic lug 32
SOLDER TERMINAL Solder tag M3 1 For mains-earth

8
CONSTRUCTION - general hints -
MOUNTING OF COMPONENTS ON THE PCB
Some examples for mounting axial components (= longitudinal leads) are drawn above.
Determine length “L” for these components by measuring the distance between the holes in the
circuit board. Then bend the leads to the right size using a pair of pliers. The components will
then fit neatly into the holes of the circuit board. To prevent the part falling out when turning the
PCB upside down, you can bend the leads slightly outwards.
SOLDERING
A good soldering technique is important for long term reliability and the correct functioning of the
set.
Bad solder connections (“dry joints”) are the main cause of poor electrical contact. These can
work loose after several cycles of warming up and cooling down.
Note the following:
1. Use a good soldering iron rated at a medium power (30-75 Watt).
2. Only use the high quality solder supplied in the kit. This contains silver and a resin core.
3. Briefly preheat the contact and the lead to be soldered by touching both parts at the same time
with the soldering iron.
4. Then introduce the solder letting it flow properly round the lead.
5. Use of the correct amount of solder is very important (see figure above).
6. Visually check the joint: a good joint is shiny, a bad one is dull.
7. Cut the leads close to the soldered joint to ensure that there are no long protruding leads.
Corona discharge from sharp points at high voltage can be prevented in this way.
8. Experts recommend against cutting the leads after soldering as this might deform the joint
causing bad contacts after a period of time. However cutting before soldering is not always
possible, therefore trim the lead back after soldering, and to guarantee good connections you
can reheat each joint with the soldering iron.
WIRING
We recommend cutting the various wires to length, and stripping the ends before you start to
build the amplifier. Neatly twist the stripped ends to strengthen them.
COLOUR LENGTH QUANTITY FUNCTION COLOUR LENGTH QUANTITY FUNCTION
blue 30 cm 2 mains input yellow 15 cm 1 + yellow LED
yellow/green 10 cm 1 earth yellow 25 cm 2 Stand-by switch
green 10 cm 2 power switch black 15 cm 2 - red and yellow LED
green 35 cm 2 input pcb black 35 cm 1 input pcb
green 7 cm 2 volume control black 7 cm 2 volume control
red 15 cm 1 + red LED black 30cm 1 speaker terminal R
black 20cm 1 speaker terminal L
jumper
¼ W resistor
5W resistor
Approx. 5mm from pcb
Amount of solder Good Too little Too much

9
STEP 1 – main circuit board -
Figure 1
SOLDER TERMINALS + FASTON CONNECTORS
1. The correct side for mounting the valve sockets is clearly marked on the circuit board (Dutch:
BOVENKANT=BUISVOETKANT). The side for mounting the other components is also marked
(Dutch: COMPONENTENKANT).
2. First push the 22 small solder terminals into their holes on the component side of the PCB
using a pair of pliers and align them as shown in figure 1. Solder them into place (to ensure
a nice flat surface first bend the pins aside with a knife before soldering. This mounting
method provides a strong connection as well as preventing corona discharge from the PCB
to the metal cabinet).
3. Now solder the two largest Faston spade connectors into place on the component-side.
These are for the 6.3V filament supply for the valves.
Scratch any oxide off with a knife until they are clean, the solder will flow better now.

10
STEP 2 – main circuit board –
Figure 2
NOVAL and OCTAL VALVE SOCKETS
1. First mount the two smaller ceramic Noval (9 pin) sockets on the socket side
(BUISVOETKANT), and solder them into place. Insert the 6922 valve into the socket prior to
soldering for the best results as the prongs will now be correctly aligned. After soldering, the
valve can be removed from the socket.
2. Note: do not bend the prongs of the Noval sockets over as this is not necessary to keep
them in place. If the sockets need replacing at a later date, it is almost impossible to do so
once the prongs have been bent. Bending also puts strain on the contacts.
3. Mount the four white ceramic Octal (8 pin) sockets on the socket side, but do not solder
them in place yet. Take note of the alignment of the slot in the middle hole of the socket.
Align this slot with the dash on the PCB between pins 1 and 8. (Please ignore the numbers
on the base of the socket as these might differ).
Now insert the circuit board from the bottom upwards into the cabinet, in such a way so that
the four octal-sockets protrude through the holes provided for them in the cabinet. Now turn
the cabinet (complete with the PCB) upside down and temporarily fasten the board in place
using the M3 screws. Check that the sockets correctly protrude through the cabinet before
soldering them in place.
4. Note: do not bend the prongs of the octal sockets for the same reasons as given for the
noval sockets. In this case it is unnecessary to insert the valves into the sockets prior to
soldering.

11
STEP 3 – main circuit board –
Figure 3
0.1 µF CAPACITORS
1. Components that have been mounted so far are coloured turquoise in figure 3, while the parts
which are to be mounted at this stage are coloured yellow. From now on this colour code will
be used as this makes it easier to recognise what is required for each construction step.
2. Capacitors C15-C20 (high frequency decoupling of the 6.3 V filament supply), capacitor C2
(high frequency bypass of the electrolytic capacitor C1) and C7 (high frequency decoupling of
the ground-connection), are all 0.1µF. Their positions are marked in figure 3.
3. Solder these into place and crop the leads.

12
STEP 4 – main circuit board -
Figure 4
¼ WATT RESISTORS
1. Resistors R25, R30, R36, R37, R38 and R39 are all ¼ Watt types. These resistors are clearly
recognisable because they are smaller then the pale blue 1 Watt metal film Beyschlag
resistors.
2. Values and colour codes are as follows:
R25 =
10 
brown black black +tolerance band
R30 =
680 k
blue grey yellow +tolerance band
R36 =
1k5=1500 
brown green red +tolerance band
R37 =
680 
blue grey brown +tolerance band
R38 =
10 k
brown black orange +tolerance band
R39 =
150 k
brown green yellow +tolerance band
3. Mount the resistors at the marked positions and solder them into place.
COLOURCODE-INDEX 1 for ¼ Watt resistors (3 bands in total)
COLOUR BAND 1 BAND 2 BAND 3
black bl 0 0 x 1
brown br 1 1 x 10
red rd 2 2 x 100
orange or 3 3 x 1K
yellow ye 4 4 x 10K
green grn 5 5 x 100K
blue bl 6 6 x 1M
violet vi 7 7 x 0.1
grey gry 8 8 x 0.01
white wt 9 9
TOLERANCES: brown 1%, red 2%, gold 5%
EXAMPLE: brown - green - yellow - gold = 150k/ 5%

13
STEP 5 – main circuit board -
Figure 5
DIODES and TRANSISTOR
1. Diodes D1-4 and D5-8 each are all type 1N4007. These black diodes carry a clear white ring
marking the cathode. Each cathode is marked with a black line in figure 5.
2. Diodes D1-4, inserted with the correct cathode orientation, must be mounted 5mm above the
circuit board. This distance is necessary to prevent high voltage discharge from the diodes to
the printed circuit below. The diodes will also radiate heat better without discolouring the PCB.
3. Diodes D5-8, inserted with the correct cathode orientation, may be mounted close to the PCB.
These diodes are not at high voltage, they only rectify the 6.3V AC for the LED indication
circuit.
4. Transistor T1 has three terminals, the middle of which is the 'Base'. The case has a flat side,
which provides clear identification of the 'Collector' and 'Emitter' terminals. Mount the transistor
into the marked position and make sure the distance between the transistor and PCB is about
7mm. This keeps any mechanical strain to a minimum.
5. Solder the diodes and transistor into place.

14
STEP 6 – main circuit board -
Figure 6
TRIMPOTS
1. Trimpots P2 (1 piece), P3 (2 pieces) and P4 (2 pieces) are now inserted into the PCB.
2. The value of each is clearly printed on the side.
P2 = 250 k
P3 = 100 k
P4 = 1 k
3. Solder the trimpots into the marked positions and turn each indicator (marked by a little arrow)
into the mid position using a screwdriver (the arrow is to point to the middle of the round
section). The adjustment of each trimpot is almost right at this setting and will only need slight
adjustment.
4. The function of each trimpot is as follows:
P2 = balance between right and left channel (balance control)
P3 = one per channel: equal signal to both output valves (AC-balance)
P4 = one per channel: equal quiescent current through each output valve (DC-balance)
The function of P2 is straightforward. Left and right channels have to have the same volume
setting to obtain a correct balance in the sound image.
P3 provides the grids of the output valves with equal signal levels to ensure that the output
transformer is driven symmetrically. This prevents transformer hum and overshoot when a
100Hz squarewave is reproduced. In the adjustment procedure given at the end of this
manual, the correct adjustment of P3 is clearly described.
The quiescent-plate-current through both output valves can be adjusted by means of P4. The
output valves are supplied as matched pairs (matched for equal currents), however quiescent
current can drift as the valves age. This can be compensated for by adjusting P4. The
adjustment is very simple: position yourself close to the speaker and listen to the level of hum.
Adjust P4 until the hum is at a minimum.

15
STEP 7 – main circuit board -
Figure 7
1 Watt RESISTORS, audio part 1
1. Resistors R2 up to and including R11 are used for the preamplifier and the phase splitter of
the amplifier. They are all 1 Watt Beyschlag metal film resistors.
2. As they run hot mount resistors R5 and R8, 5mm above the PCB. The remaining resistors
may be mounted close to the PCB.
3. Values and colour codes are as follows (see table below)
R2 =
4k7 = 4700 
yellow violet black brown +tolerance band
R3 =
100 k
brown black black orange +tolerance band
R4 =
2k2 = 2200 
red red black brown +tolerance band
R5 =
47 k
yellow violet black red +tolerance band
R6 =
680 
blue grey black black +tolerance band
R7 =
680 
blue grey black black +tolerance band
R8 =
47 k
yellow violet black red +tolerance band
R9 =
1 M
brown black black yellow +tolerance band
R10 =
180 k
brown grey black orange +tolerance band
R11 =
150 k
brown green black orange +tolerance band
COLOUR CODE-INDEX 2 for 1 Watt
resistors (4 bands in total)
COLOUR BAND 1 BAND 2 BAND 3 BAND 4
black bla 0 0 0 x 1
brown bro 1 1 1 x 10
red red 2 2 2 x 100
orange ora 3 3 3 x 1K
yellow yel 4 4 4 x 10K
green grn 5 5 5 x 100K
blue blu 6 6 6 x 1M
violet vio 7 7 7 x 10M
grey gry 8 8 8
white wht 9 9 9
gold gld x 0.1
silver sil x 0.01
TOLERANCES:
brown 1%, red 2%, gold 5%
EXAMPLE:
yellow -violet -black -red -brown = 47 k /1 %

16
STEP 8 – main circuit board –
Figure 8
1 Watt RESISTORS, audio part 2
1. Resistors R12, R14, R21, R22, R23 and R24 are also 1 Watt metal film resistors and are
situated around the output valves.
2. These resistors do not get warm and may be mounted close to the PCB.
3. Values and colour codes are:
R12
=
1 k
brown black black brown +tolerance band
R14 =
1 
brown black black silver +tolerance band
R21 =
1 
brown black black silver +tolerance band
R22 =
1 k
brown black black brown +tolerance band
R23 =
1 k
brown black black brown +tolerance band
R24 =
1 k
brown black black brown +tolerance band

17
STEP 9 – main circuit board –
Figure 9
1 Watt RESISTORS, quiescent current adjustment
1. Resistors R13, R15, R16, R18, R19 and R20 (together with trimpot P4) are part of the
quiescent current adjustment circuit for the output valves. They do not belong to the audio
circuit, but metal film resistors are used to guarantee long term stability.
2. None of these generate heat. They can be mounted close to the PCB.
3. Values and colour codes are:
R13
=
220 k
red red black orange +tolerance band
R15 =
1 k
brown black black brown +tolerance band
R16 =
4k7 
yellow violet black brown +tolerance band
R18 =
1 k
brown black black brown +tolerance band
R19 =
4k7 
yellow violet black brown +tolerance band
R20 =
220 k
red red black orange +tolerance band

18
STEP 10 – main circuit board –
Figure 10
Cathode and Supply Resistors
1. Resistor R17 is a 7 Watt resistor which has to be mounted 1cm above the PCB. This resistor
radiates a lot of heat, but at a distance of 1cm the PCB will not get damaged (otherwise
discolouration and even carbonization of the PCB will occur). The value of R17 is 220 ohm
and it is physically larger than the metal film resistors.
2. Resistors R31, R32, R33 and R34 are 1 Watt metal film resistors and all generate some heat.
Therefore they have to be mounted 5mm above the PCB.
However R35 does not get warm and may be mounted close to the PCB.
3. Values and colour codes are:
R31
=
2,2 
red red black silver +tolerance band
R32 =
2,2 
red red black silver +tolerance band
R33 =
15 k
brown green black red +tolerance band
R34 =
15 k
brown green black red +tolerance band
R35 =
47 
yellow violet black gold +tolerance band

19
STEP 11 – main circuit board –
Figure 11
CAPACITORS, signal and HF supply decoupling
1. Capacitors C4 and C5 (each 0.47µF / 630V, MKP = polypropylene) are used for the coupling
between the preamplifier stage and phase splitter to the output valves. Mount them close to
the PCB on the component side and SOLDER AT THE SOCKET SIDE.
2. Capacitor C3 (0.1µF / 630 V, MKP) provides the AC coupling of the audio signal to the grid of
the phase splitter.
Mount it close to the PCB and SOLDER AT THE SOCKET SIDE.
3. Capacitors C10 and C11 (each 10nF / 1200V, MKP) are used for high frequency decoupling
of the plate supply voltage from the power transformer. Together with resistors R31 and R32
they prevent all high frequency noise from the mains from reaching the audio part of the
amplifier via the power transformer. This RC filtering is very effective in this case and the
switching pulses of diodes D1-4 will also be suppressed.
Mount them close to the PCB and SOLDER AT THE SOCKET SIDE.
4. Capacitor C23 (10nF/1200V, MKP) is used for the suppression of the switching pulse
generated when switching from stand-by mode. Mount it close to the PCB and SOLDER AT
THE SOCKET SIDE.

20
STEP 12 – main circuit board –
Figure 12
CAPACITORS, audio electrolytic capacitors
1. Capacitor C1 (220µF, 25V) may be placed close to the PCB and soldered on the other side
(socket side). Carefully check that the negative terminal (marked by a thick line on the
capacitor) is in the correct position (see figure 12 pointing to the upperside)
2. Capacitors C6 (1000µF, 40 V) may also be mounted close to the PCB. Soldering is possible
on either side of the PCB; use whatever side is the easiest. The positive terminal of this
electrolytic capacitor is marked by a notch in the housing (see figure 12). Carefully check for
the correct polarization of these capacitors. To prevent C6 from becoming warm ensure that it
does not touch cathode resistor R17.