Silicon Chip – April 2019

42 Silicon chip Australia’s electronics magazine siliconchip.com.au

GND

IN OUT

GND

IN OUT

l

l

+57V

+57V

0V

0V

–57V

–57V

CON3

3.3kW

5W

3.3kW

5W

LED1

LED2

4700 μF

63V

4700 μF

63V

4700 μF

63V

4700 μF

63V

4700 μF

63V

4700 μF

63V

A

K

A

K

TERM 1

TERM 2

TERM 3

BR1 35A/600V

~ ~

+

• S1 F1 5A

T1

POWER

A

N

E

2200 μF

25V

2200 μF

25V

100 μF

16V

100 μF

16V

+15V

30V

AC

+20V

–15V

0V

0V

CON4

CON1

CON2

CON5

D– 14 D: 1N 4004 CON6

REG1 7815

REG2 7915

A

K

A

K

A

K

A

K

40V

40V

0V

0V

15V

15V

0V

0V

T1: 240V TO 2x 40V/300VA,

2x 15V/7.5VA

A K

LEDS

A

K

OUT

GND

IN

IN

7591

GND OUT

GND

IN

7815

1N 4004

SC 2019 power AMPLIFIER & PREAMPLIFIER POWER SUPPLY

Fig.14: this amplifier power supply is based on a toroidal transformer (T1) with two 40V windings and two 15V windings,

but you could use two separate transformers if necessary. You can use a transformer with lower voltage main secondary

windings (ie, less than 40V) to achieve a lower amplifier supply voltage, without making any changes to the board.

Ultr

a-LD

(^) Mk
.2
Am
plifie
r Po
we
r Su
0110
1119

• 
  


• 
  

• 
  


• 
  

0

tput 1Ou

tput 2Ou

-IN

+IN

CT

AC15VCT~ 15 AC30V

-15V 0 +15V 0 +20V

4700 μF 63V

4700 μF 63V

4700 μF 63V

4700 μF 63V

4700 μF 63V

4700 μF 63V

CON1

CON2

TERM 1

TERM 2

TERM 3

220 μF

16V

220 μF

16V

REG1

7815

REG2

7915

A

A

A

A

K K

K K

LED2

LED1

Ultr

a-LD

Mk

.3^

Po

we

r Suppl

y

0110

(^1119)

• 
  

+

25V 25V

2200 μF^2200 μF

+

+

+

+

+

+

AMPLIFIER

POWER

OUTPUT 2

+57V0V–57V

• 57V0V+57V

CT

+IN

–IN

15V CT15V 30VAC

–15V 0 +15V 0 +20V

3.3kW5W

3.3kW5W

4004 4004

4004 4004 D3–D^6

COCON4N4 COCON5N5

COCON3N3 COCON6N6

DC

INPUT

FROM

BRIDGE

DC

INPUT

FROM

BRIDGE

15V AC INPUT

PREAMP DC OUTPUT

AMPLIFIER

POWER

OUTPUT 2

AMPLIFIER

POWER

OUTPUT 2

AMPLIFIER

POWER

OUTPUT 1

CON5 and CON3 with CON6 before
soldering them in place, with the wire
entry holes facing towards the nearest
edge of the board. Then you can mount

the two 5W resistors, with their bodies

a few millimetres above the PCB sur-

face to allow cooling air to circulate.

Next install the spade con-

nectors. If using the vertical type with

two pins, push these into the board

and solder them in place – you will

need a hot iron to do this. If us-

Fig.15: install the parts

on the power supply

board as shown here,

taking care to ensure

that all the electrolytic

capacitors are mounted

with the correct polarity.

Be sure also to use the

correct regulator at each

location. The two LEDs

indicate when power

is applied and remain

lit until the 4700μF

capacitors discharge

after switch-off.