Page 1
1 meg
68k
39k
180k
.0047
68k
.033
0.1
330 pF
0.33
100 pF
25k lin
250k
log
250k lin
1M log
100k
4k7
250k log
1k5
2.2uF
2.2uF
1k5
15k
100k 100k
1M log
.022
470 pF
680k
470k
470k
470
pF
.033
1 meg
1 meg
100k
1k5
330 R
330 R
.033
.033
1k5
220k
250k lin
1M log
25k lin
220 pF
0.1
15k
43k
0.1
.033
1 nF
470k
25k
lin
1k5
1N4007
Relay 1B
N.C.
N.O.
N.O.
N.C.
Relay 1A
.033
2N5462
2N5462
To Effects Send
Sockets
5 Volt
supply
Pin 3 on
6-pin DIN
socket
Front panel
switch
Mute Send
Signal
Pin 2 on
6-pin DIN
socket
Low Current
Green LED
on Front
Panel
Low
Current
Red LED
on Front
Panel
5 Volt
supply
100k
0.1
100 pF
H.T. G
H.T. F
H.T. E
MK50II Pre-amp
Circuit design and
drawing by Martin
Kidd 25/01/11
100k
Page 2
Relay 2
N.C.
N.O.
Relay 3
N.O.
N.C.
Send 1
Send 2
Return 2
Return 1
1N4007
.033
Mute send signal
1 meg
1k5
220k
Mute point
5 Volts
Effects loop 1-2
footswitch
22k ¾-Watt
47uF
450V
.033
220k
1 meg
log
1 meg
log
Master 1
Master 2
5 Volts
1N4007
To Phase Splitter
1k5
Low Current
Green LED
Signal from
Relay 1B
Pin 2 on 6-pin
DIN socket
H.T. D
MK50II Effects
Loop
Circuit design and
drawing by Martin
Kidd 25/01/11
Page 3
Bias Supply
B+
91k 100k
1 meg
1 meg
470 R
10k
4k7
0.1
25k lin
0.1
.0047
47k
1 meg log
100uF 63V
1k 4W
1k 4W
220k
10k
10k
.022
.033
.033
100 pF
H.T. C
H.T.D
16 ohm
8 ohm
4 ohm
common
blue
brown
green
red
white
black
(yellow)
From
Master
Volumes
1 ohm 1-Watt
1 ohm 1-Watt
MK50II Output Stage
including Phase Splitter
Circuit design and
drawing by Martin
Kidd 25/01/11
Page 4
Centre tap
not used
3.15 Volts
a.c
3.15 Volts
a.c
To all
heaters
C.T.
Mains Switch
Standby Switch
47k
Fuse: T2A for 230V or
T4A for 115V
Short red line indicated series winding for
230V operation. Dotted Blue and Magenta
lines indicate parallel wiring for 115V
operation.
Mains inlet
socket
7805
2200 uF
25V
Brige rectifier
module
5 Volt supply
50+50uF
500V
50+50uF
500V
47uF
450V
47uF
450V
47uF
450V
100R
7W
10k 3W 10k 3W 10k 3W 10k ¾W
4x
1N4007
brown
white
black
blue
yellow
yellow
black
black
red
red
wh/bk
wh
B+ C D E F G
1N4007
10k
22k
220k
220k
100uF
63V
SPST Switch
for 6L6/EL34
Bias voltage
Front Panel Mains
Indicator
MK50II Power Supply
H.T. Fuse:
T500m.A
pink
Circuit design and
drawing by Martin
Kidd 25/01/11
Page 5
0.1 uF
2N5462MAC97
220k
Mute Send
Signal
Mute point on
effects loop
MK50II Mute Circuit
5 Volt
Circuit design and
drawing by Martin
Kidd 25/01/11
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