WORLD DESIGNS WDPre3 User manual

10
Holding the shaft of the switch in a small vice or mole grips,
cut the shaft of the input selector switch to 20mm length
measured from the end of the threaded portion. Sand the cut end
of the shaft smooth to fit the chrome knob.
Cut the six way cable from the Relay PCB to length and solder
the free ends to the terminals of the input selector switch as
follows:
Black -Inner Terminal A, Blue -Pin 2, Green -Pin 3,
Red -Pin 4, Yellow -Pin 5, White -Pin 6.
Check that the inner “locking”washer is set to position 6
(6-way) pass the switch through the hole in the chassis and
secure using the washer and nut from the provided.
WDPre3 Kit Assembly Instructions
FITTING THE INPUT SELECTOR SWITCH
Fit M3 x 12mm spacers to the COMPONENT side of the board. Use
fibre washers under M3 screws on the SOLDER side of the board to
avoid grounding the tracks.
Push the completed Relay Switch Board onto the phono sockets at
the inside rear of the case and secure using M3 x 6 bolts
through the rear panel into the spacers.
Solder the two (Ground) tinned copper wires from the input phono
socket solder tags to the GRD1 PCB terminal pin.
IMPORTANT: DO NOT SOLDER THE PHONO SOCKETS AT THIS STAGE.
FITTING THE RELAY SWITCH BOARD
Fig. 9 Input Selector Switch
Fig. 9
10
Holding the shaft of the switch in a small vice or mole grips,
cut the shaft of the input selector switch to 20mm length
measured from the end of the threaded portion. Sand the cut end
of the shaft smooth to fit the chrome knob.
Cut the six way cable from the Relay PCB to length and solder
the free ends to the terminals of the input selector switch as
follows:
Black -Inner Terminal A, Blue -Pin 2, Green -Pin 3,
Red -Pin 4, Yellow -Pin 5, White -Pin 6.
Check that the inner “locking”washer is set to position 6
(6-way) pass the switch through the hole in the chassis and
secure using the washer and nut from the provided.
WDPre3 Kit Assembly Instructions
FITTING THE INPUT SELECTOR SWITCH
Fit M3 x 12mm spacers to the COMPONENT side of the board. Use
fibre washers under M3 screws on the SOLDER side of the board to
avoid grounding the tracks.
Push the completed Relay Switch Board onto the phono sockets at
the inside rear of the case and secure using M3 x 6 bolts
through the rear panel into the spacers.
Solder the two (Ground) tinned copper wires from the input phono
socket solder tags to the GRD1 PCB terminal pin.
IMPORTANT: DO NOT SOLDER THE PHONO SOCKETS AT THIS STAGE.
FITTING THE RELAY SWITCH BOARD
Fig. 9 Input Selector Switch
Fig. 9

11
Fit the main PCB to the case with the IP+and IP-terminals
closest to the front panel. Fit M3 x 12 bolts into 5mm spacers
under the PCB. Then offer up the PCB to the case and secure the
spacers with M3 serrated washers and nuts under the case.
Wire the Green cable from the Earth terminal to the GND2 pin on
the far end of the PCB. Solder a 180mm length of Green cable
from the terminal pin GNDL to the nearest screen tag on the rear
of the output transformer. Link all the screen terminals on both
output transformers from this tag with tinned copper wire and
Green cable.
IMPORTANT –Check with a multimeter switched to Resistance that
pins GNDL, GNDR and the screen tags of both transformers have
good continuity to the Earth Terminal.
Solder the red cable from the positive terminal of the power
supply capacitor to the HT terminal of the nearest (Left
Channel) transformer and, using a length of Red cable link this
with the HT terminal of the other (Right Channel) transformer.
Using short lengths of red cable link the HT terminals of both
transformers to their corresponding HT PCB pins –“HT”for the
Right Channel transformer and “HT1”for the Left.
WDPre3 Kit Assembly Instructions
FITTING THE PRE3 PCB
Fig. 10
Fig 10. Transformer Screen Links
Fig. 11
11
Fit the main PCB to the case with the IP+and IP-terminals
closest to the front panel. Fit M3 x 12 bolts into 5mm spacers
under the PCB. Then offer up the PCB to the case and secure the
spacers with M3 serrated washers and nuts under the case.
Wire the Green cable from the Earth terminal to the GND2 pin on
the far end of the PCB. Solder a 180mm length of Green cable
from the terminal pin GNDL to the nearest screen tag on the rear
of the output transformer. Link all the screen terminals on both
output transformers from this tag with tinned copper wire and
Green cable.
IMPORTANT –Check with a multimeter switched to Resistance that
pins GNDL, GNDR and the screen tags of both transformers have
good continuity to the Earth Terminal.
Solder the red cable from the positive terminal of the power
supply capacitor to the HT terminal of the nearest (Left
Channel) transformer and, using a length of Red cable link this
with the HT terminal of the other (Right Channel) transformer.
Using short lengths of red cable link the HT terminals of both
transformers to their corresponding HT PCB pins –“HT”for the
Right Channel transformer and “HT1”for the Left.
WDPre3 Kit Assembly Instructions
FITTING THE PRE3 PCB
Fig. 10
Fig 10. Transformer Screen Links
Fig. 11

12
WDPre3 Kit Assembly Instructions
Using a short length of red cable link the OP+terminal on the
PCB to the A terminal on the transformer. Similarly link the
OPL+terminal on the PCB to the A terminal on the other
transformer. If you use slightly longer lengths of wire than you
might think necessary, you will be able to “lift”the PCB,
without disconnecting it, should you need to access it at a
later date.
Prepare the heater link cables by twisting approx. 200mm of
Brown and Grey wire together. Solder this pair, along with the
Brown and Grey wires from the Power input AND the Relay Board,
to the HTRL+(Brown) and HTRL-(Grey) PCB pins, cutting to
length as appropriate. Connect the other end of the heater link
cables to HTR+(Brown) and HTR-(Grey).
Connect the 300mm Grey and Black wires from the Right Channel
phono plug to the transformer closest to the front panel. Cut
the wires to length and solder the Grey wire to terminal 7 of
the transformer. Solder the Black wire to the CT terminal if you
require a Gain of x6 (recommended), or to the Terminal 18 if you
need a high gain of x12 (for low output sources).
Repeat this process for the Left Channel, connecting the 200mm
wires to the transformer closest to the rear of the chassis.
Fig. 11
Fig. 11 HT Wiring
Fig. 12
Fig. 13
12
WDPre3 Kit Assembly Instructions
Using a short length of red cable link the OP+terminal on the
PCB to the A terminal on the transformer. Similarly link the
OPL+terminal on the PCB to the A terminal on the other
transformer. If you use slightly longer lengths of wire than you
might think necessary, you will be able to “lift”the PCB,
without disconnecting it, should you need to access it at a
later date.
Prepare the heater link cables by twisting approx. 200mm of
Brown and Grey wire together. Solder this pair, along with the
Brown and Grey wires from the Power input AND the Relay Board,
to the HTRL+(Brown) and HTRL-(Grey) PCB pins, cutting to
length as appropriate. Connect the other end of the heater link
cables to HTR+(Brown) and HTR-(Grey).
Connect the 300mm Grey and Black wires from the Right Channel
phono plug to the transformer closest to the front panel. Cut
the wires to length and solder the Grey wire to terminal 7 of
the transformer. Solder the Black wire to the CT terminal if you
require a Gain of x6 (recommended), or to the Terminal 18 if you
need a high gain of x12 (for low output sources).
Repeat this process for the Left Channel, connecting the 200mm
wires to the transformer closest to the rear of the chassis.
Fig. 11
Fig. 11 HT Wiring
Fig. 12
Fig. 13

13
WDPre3 Kit Assembly Instructions
Fig. 12 Heater Wiring
Fig. 13 Output Wiring
13
WDPre3 Kit Assembly Instructions
Fig. 12 Heater Wiring
Fig. 13 Output Wiring

Take 275mm Blue twin core screened cable, cut back the outer
insulation AND the screen braid to approx 25mm and insulate to
avoid fraying. Solder the White/Clear inner core to the
potentiometer terminal L3 and the Blue inner core to the
terminal L1.
Repeat for the Right channel, soldering the White/Clear inner
core to terminal R3 and the Blue inner core to terminal R1.
Take 200mm Blue twin core screened cable and cut back the outer
insulation to approx 25mm. Cut back the Blue inner core
insulation to 25mm, unplait the braid, twist these wires
together, and insulate. Solder these wires to the potentiometer
terminal L1, and the White/Clear inner core to the potentiometer
terminal L2.
Repeat for the Right channel, this time using approx 75mm cable.
Fit the potentiometer to the front panel using the washer and
nut provided. If necessary, scrape some paint away from inside
the chassis to make sure that the potentiometer is grounded.
14
WDPre3 Kit Assembly Instructions
WIRING THE INPUTS AND VOLUME CONTROL
Fig. 14 Potentiometer Wiring
Fig. 14 Take 275mm Blue twin core screened cable, cut back the outer
insulation AND the screen braid to approx 25mm and insulate to
avoid fraying. Solder the White/Clear inner core to the
potentiometer terminal L3 and the Blue inner core to the
terminal L1.
Repeat for the Right channel, soldering the White/Clear inner
core to terminal R3 and the Blue inner core to terminal R1.
Take 200mm Blue twin core screened cable and cut back the outer
insulation to approx 25mm. Cut back the Blue inner core
insulation to 25mm, unplait the braid, twist these wires
together, and insulate. Solder these wires to the potentiometer
terminal L1, and the White/Clear inner core to the potentiometer
terminal L2.
Repeat for the Right channel, this time using approx 75mm cable.
Fit the potentiometer to the front panel using the washer and
nut provided. If necessary, scrape some paint away from inside
the chassis to make sure that the potentiometer is grounded.
14
WDPre3 Kit Assembly Instructions
WIRING THE INPUTS AND VOLUME CONTROL
Fig. 14 Potentiometer Wiring
Fig. 14

15
Taking the 60mm signal cable from the potentiometer, cut to
length and trim back the outer insulation AND the screen braid
to approx 25mm. Insulate to avoid fraying. Solder the White/
Clear inner core to the PCB pin IP+, and the Blue inner core to
the PCB pin IP-.
Repeat for the Left Channel (the 200mm length) and solder the
White/Clear inner core to the PCB pin IPL+and the Blue to IPL-.
Taking the 275mm cables from the potentiometer, cut to length
and trim back approx 25mm of the outer insulation, unplait and
twist the braid together and insulate if you wish. Solder the
wires for the Right channel to the pins on the Relay PCB as fol-
lows: the Screen braid to GRD3, the Blue inner core to OPGR and
the White/Clear inner core to OPR. While it is not strictly nec-
essary to separate the screen and the blue inner core, doing so
provides extra mechanical stability to the joints.
Repeat for the Left channel -the screen braid to GRD2, the Blue
inner core to OPGL and the White/Clear inner core to OPL.
WDPre3 Kit Assembly Instructions
Fig. 15 Signal Wiring and LED
Fig. 15
Solder 150 of Black wire to the short leg of the LED and 150mm
of Red wire to the long leg of the LED. Cover the joints with
heat-shrink sleeving and twist the wires together.
Solder the Red cable to the LED1 PCB pin and the Black cable to
the LED2 pin.
The LED can then be pushed through the hole in the front panel,
ready for fitting to the fascia.
Proceed to Constructing the Power Cables and Testing the Amplifier.
WIRING THE LED
15
Taking the 60mm signal cable from the potentiometer, cut to
length and trim back the outer insulation AND the screen braid
to approx 25mm. Insulate to avoid fraying. Solder the White/
Clear inner core to the PCB pin IP+, and the Blue inner core to
the PCB pin IP-.
Repeat for the Left Channel (the 200mm length) and solder the
White/Clear inner core to the PCB pin IPL+and the Blue to IPL-.
Taking the 275mm cables from the potentiometer, cut to length
and trim back approx 25mm of the outer insulation, unplait and
twist the braid together and insulate if you wish. Solder the
wires for the Right channel to the pins on the Relay PCB as fol-
lows: the Screen braid to GRD3, the Blue inner core to OPGR and
the White/Clear inner core to OPR. While it is not strictly nec-
essary to separate the screen and the blue inner core, doing so
provides extra mechanical stability to the joints.
Repeat for the Left channel -the screen braid to GRD2, the Blue
inner core to OPGL and the White/Clear inner core to OPL.
WDPre3 Kit Assembly Instructions
Fig. 15 Signal Wiring and LED
Fig. 15
Solder 150 of Black wire to the short leg of the LED and 150mm
of Red wire to the long leg of the LED. Cover the joints with
heat-shrink sleeving and twist the wires together.
Solder the Red cable to the LED1 PCB pin and the Black cable to
the LED2 pin.
The LED can then be pushed through the hole in the front panel,
ready for fitting to the fascia.
Proceed to Constructing the Power Cables and Testing the Amplifier.
WIRING THE LED

16
The power cables for the WDPre3 and WDPhono3 are assembled from
the cable, binder line sockets and binder line plugs provided
with each amplifier.
Use a sufficient length of the 4 core grey lead for each power
cable connection (bear in mind that users of the WDPhono3 with
MC transformers may need to place the WDPhono3 at a distance
from all power transformers to minimize hum pickup).
The 4 cores consist of 3 black leads with numbered printing
(though this can be difficult to see) and a green /yellow lead.
Use the green/yellow lead for the Ground connections to pin 3.
Check the continuity with your multimeter of the Black leads to
ensure correct labelling and use for pins 1, 2 and 4.
Always connect plug to socket using the same NUMBER pins e.g.
connect a Black lead between Pin 1 on the plug to Pin 1 on the
socket. Repeat for Pins 2 to Pins 4.
Assemble in this order:
1. Pass the rear plastic sleeve, rubber cable bush and socket
ring of the plug or socket over the cable.
2. Push the cable clamp carrier sleeve onto the cable.
3. Strip and solder the cable cores to the pins as outlined
above.
4. Using your multimeter check continuity between the pins using
the numbers as shown in the diagram above.
5. Slide the cable clamp carrier sleeve up to the plug/socket
insert and clip it into the insert.
6. Screw the metal cable clamp strap onto the carrier sleeve.
7. Clip the top cover onto the clamp carrier sleeve.
8. Slide the socket ring, rubber cable bushing and rear sleeve
up to the plug or socket body.
9. Fix the rear sleeve with the self tapping screw provided.
WDPre3 Kit Assembly Instructions
CONSTRUCTING THE POWER CABLES
1. Heater ––ve
2. HT
3. Green /Y-Ground
4. Heater +ve
Fig. 16 Power Plug and Socket Connections
Fig. 16
Fig. 17
16
The power cables for the WDPre3 and WDPhono3 are assembled from
the cable, binder line sockets and binder line plugs provided
with each amplifier.
Use a sufficient length of the 4 core grey lead for each power
cable connection (bear in mind that users of the WDPhono3 with
MC transformers may need to place the WDPhono3 at a distance
from all power transformers to minimize hum pickup).
The 4 cores consist of 3 black leads with numbered printing
(though this can be difficult to see) and a green /yellow lead.
Use the green/yellow lead for the Ground connections to pin 3.
Check the continuity with your multimeter of the Black leads to
ensure correct labelling and use for pins 1, 2 and 4.
Always connect plug to socket using the same NUMBER pins e.g.
connect a Black lead between Pin 1 on the plug to Pin 1 on the
socket. Repeat for Pins 2 to Pins 4.
Assemble in this order:
1. Pass the rear plastic sleeve, rubber cable bush and socket
ring of the plug or socket over the cable.
2. Push the cable clamp carrier sleeve onto the cable.
3. Strip and solder the cable cores to the pins as outlined
above.
4. Using your multimeter check continuity between the pins using
the numbers as shown in the diagram above.
5. Slide the cable clamp carrier sleeve up to the plug/socket
insert and clip it into the insert.
6. Screw the metal cable clamp strap onto the carrier sleeve.
7. Clip the top cover onto the clamp carrier sleeve.
8. Slide the socket ring, rubber cable bushing and rear sleeve
up to the plug or socket body.
9. Fix the rear sleeve with the self tapping screw provided.
WDPre3 Kit Assembly Instructions
CONSTRUCTING THE POWER CABLES
1. Heater ––ve
2. HT
3. Green /Y-Ground
4. Heater +ve
Fig. 16 Power Plug and Socket Connections
Fig. 16
Fig. 17

17
WDPre3 Kit Assembly Instructions
Fig. 17 Binder Line Plug and Socket Construction
17
WDPre3 Kit Assembly Instructions
Fig. 17 Binder Line Plug and Socket Construction

18
Before connecting the power supply it is good practice to check all the
wiring, component positions on the PCB and follow the circuit diagrams
through the physical circuit to make sure everything is connected
correctly. Double checking all your connections and solder joints at this
stage will avoid a possible expensive mistake!
All readings were taken at 240V. Check your mains voltage before starting.
Use the OHM or RESISTANCE setting on your multimeter to check around the
circuit for continuity to ground. Attach one lead of your multimeter to
the Earth Terminal Ground and check that all ground points on the PCB
show close to zero Ohms. Check the cathodes of each valve base show the
correct resistance -Pin 3 U1/R3 1.2K, Pin 8 U1/R4 1k.
Before proceeding to test the amplifier, double-check that you have wired
the power cable correctly. Plug it into the rear of the PSU and referring
to Fig. 10 below, check that the voltage across pins 1 and 4 of the lead
binder socket is between 5.9 volts and 6.7 volts DC. Check that the
voltage across pins 2 and 3 of the lead binder sockets is between 380V
and 420V DC.
WDPre3 Kit Assembly Instructions
TESTING THE AMPLIFIER
Pin 1
Heater (-)
Pin 3
HT (-)
Pin 2
HT (+)
Pin 4
Heater (+)
380V to 420V DC
5.9V to 6.7V DC
Fig. 18 Power Socket Voltages
18
Before connecting the power supply it is good practice to check all the
wiring, component positions on the PCB and follow the circuit diagrams
through the physical circuit to make sure everything is connected
correctly. Double checking all your connections and solder joints at this
stage will avoid a possible expensive mistake!
All readings were taken at 240V. Check your mains voltage before starting.
Use the OHM or RESISTANCE setting on your multimeter to check around the
circuit for continuity to ground. Attach one lead of your multimeter to
the Earth Terminal Ground and check that all ground points on the PCB
show close to zero Ohms. Check the cathodes of each valve base show the
correct resistance -Pin 3 U1/R3 1.2K, Pin 8 U1/R4 1k.
Before proceeding to test the amplifier, double-check that you have wired
the power cable correctly. Plug it into the rear of the PSU and referring
to Fig. 10 below, check that the voltage across pins 1 and 4 of the lead
binder socket is between 5.9 volts and 6.7 volts DC. Check that the
voltage across pins 2 and 3 of the lead binder sockets is between 380V
and 420V DC.
WDPre3 Kit Assembly Instructions
TESTING THE AMPLIFIER
Pin 1
Heater (-)
Pin 3
HT (-)
Pin 2
HT (+)
Pin 4
Heater (+)
380V to 420V DC
5.9V to 6.7V DC
Fig. 18 Power Socket Voltages