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ELEX K2 (Hohner Stringvox) (r3) K2-2 'Matrix' Board: Schematic
F1
F 1
G1
A 1
bass range
1
2
3
4
b a
b a
b a
b a
solder teminals for wires to K2-3
ⓐ 1
2
piano sustain (off = grounded)
1
3
+13
2
+1 5
4
1K0
5
PHB (bass) audio
3
–1
6
560R
7
GND
4
61 × K2-1
–26
5
socket pairs
8
NC
6
9
Strings (bass) audio
7
10
Strings (bass) decay
8
11
12
Cello (bass) decay
9
13
Cello (bass) audio
10
14
GND
11
15
ⓐ 16
GND
12
ⓑ solder terminals
+13
13
for wires to Bass
–15
14
Pedal connector
This board takes:
• audio signal inputs
from the OS-5 TOG
board, and divides
them producing 61
additional pitches,
• gates from the
K2-3 contact board
and optionally the
sustain pedal, and
• decay CV from
K2-14.
It routes all these to
the 61 K2-1 voicing
boards, which return
audio signals, which
are routed out to the
filter and amplifier
boards.
Terminal identifiers on
the board are as in the
copper, except:
ⓐ K2-1 socket pin
numbers (which
are as given on the
K2-1 schematic),
and
ⓑ notes for bass pedal
NC
7
connector wire
IC1
terminals.
8
Terminal descriptions
outside the board are
my additions.
P = Piano voice
H = Harpsichord voice
B = Bass voice
1m0
16V
A1
B 1
B1
C1
C 1
D1
E 1
E1
F2
F 2
G2
A 2
A2
B 2
B2
C2
C 2
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
C
C
D
D
E
E
E
E
F
F
F
F
G
G
A
A
A
A
B
B
B
B
C
C
NC
1
7
1
7
1
7
IC2
IC3
14
8
14
8
14
8
100n
100n
100n
D2
E 2
E2
F3
F 3
G3
A 3
A3
B 3
B3
C3
C 3
D3
E 3
E3
F4
F 4
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
1
7
1
7
1
IC4
IC5
IC6
14
8
14
8
14
100n
100n
100n
G4
A 4
A4
B 4
B4
C4
C 4
D4
E 4
E4
F5
F 5
G5
A 5
A5
B 5
B5
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
b a
7
1
7
1
7
1
IC7
IC8
IC9
(or AY-1-5050)
8
14
8
14
8
14
7-stage dividers
100n
100n
100n
designed c.1975 ELEX S.p.A. (Excelsior)
drawn 2024 electropict
C5
C 5
D5
E 5
E5
F6
treble range
56
57
58
59
60
61
b a
b a
b a
b a
b a
b a61
1 ⓐ
2
3W
0R56
3
4
5
BA130
15
PH (treble) audio
6
4
NC
7
6
GND
8
16
Strings (treble) audio
9
17
Strings (treble) decay
10
11
12
18
Cello (treble) decay
13
19
Cello (treble) audio
14
11
15
16 ⓐ
NC
20
GND
NC
21
pitch
NC
13
+13 to pitch trimmer
9 × TMS3438
OS-5
socket
+ acc.
–
F
G
G
A
A
B
C
C
D
D
E
F
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