BOTTOM PANEL CONTROLS
(20) Mic Jumper
(21) Mic In Gain (R12)
Microphone cartridges with
very low output (Like a Heil HC4 or Heil HC5) may require
the Mic In Gain Control to be adjusted to maximum gain.
(22) Mic Output Level (R13)
(23) Mic Input Impedance
Plugging the jumper (shorting block) puts +5V on the Mic In
line of the microphone's cartridge (11, 12 & 13). Required for mic's
such as ICOM’s Hm12, HM36 and Sm6 and the Heil Hmi and MH2
(made for the Elecraft radio’s) and other electret microphones.
This pot., when turned clockwise, increases the microphone
amplifier's gain. The gain should be changed while speaking
into microphone until Mic LED (10) just barely goes on Now
turn the pot counterclockwise, while speaking into the mic til
the LED NEVER goes on. (The LED going on indicates that
the EQ is being overdriven.)
Changes the unit's audio output. (Clockwise rotation increases
output.)
Insertion of one of these jumpers (shorting blocks) selects
200 or 600 ohm input impedance.
.
No jumpers connected selects
high impedance
-13-
20
23 21
22
8
Band
Equalizer
Pot
Board
with
Noise
Gate
Pot
s
Audio
IN
C7
-
.0039
uf
U3b
TL074
7
C2
390
p
f
C20 - 100 uf
C16 - .1 uf R1
10
R16
-
100
K
R8f
100
K
R17
-
100
K
R21g
1M
R23c
1M
R4g
3.3K
R6b
3.3K
R6c
3.3K
+5
V
U3c
TL074
+
10
9
8
-
+
R2
1K
R3
1K
R8G
100
K
R23b
1
M
8
8
8
1
6
5
2
3
1
5
6
1
7
1
4
3
1
4
3
C17
-.18uf
C15
-
.1uf
C14
-
.047uf
C13
-
.022uf
400
Hertz
C6
.0022uf
200
Hertz
100
Hertz
C10 - .01uf
C8 - .0047uf
R8a
100K
+5V
1
3
5
6
7
2
R7
14.3K
1%
R4b
3.3K
R5b
3.3K
R4c
3.3K
R5c
3.3K
R4d
3.3K
R14
-
100
K
R21d
1M
R22c
1M
R21c
1M
R8c
100K
R21A
1M
R22a
1M
R1
1
-
100
K
R12
-
100
K
R13
-
100
K
C12 - .018uf
U1a
TL074
U2a
TL074
U2b
TL074
U2c
TL074
+
+
+
13
12
+
10
9
8
-
-
-
C9
-
.0056
uf
C1
1
-
.012
uf
C5
-
.003
uf
2400
Hertz
3200
Hertz
1600
Hertz
800
Hertz
R9
10K
R10
10K
C19
4.7
uf
+5V
4
1
1
1
3
2
C18
4.7
uf
+
+
-
R8b
100K
R21B
1
M
R22b
1
M
R5a
3.3K
1
1
1
2
2
1
1
4
3
2
1
3
3
4
4
3
3
3
5
3
1
1
4
4
4
1
1
1
5
6
2
5
6
3
1
1
2
2
2
R8d
100K
R22d
1M
50
Hertz
U2d
TL074
U3a
TL074
+
14
+
3
2
1
+5V
+
6
5
-
-
-
C1
300
p
f
J1-7
J1-6
R15
-
100
K
R21e
1
M
R23a
1
M
R4e
3.3K
R6a
3.3K
R8e
100
K
R21h
1M
R23d
1M
R4f
3.3K
R6d
3.3K
J1-
12
J1-
4
J1-
5
J1- 9
R4h
3.3K
R18
-
100
K
R20 - 5K
R19 - 100 K
C3
560
p
f
C4
.0012
uf
U3d
TL074
14
13
12
+
-
Audio
Out
+
5V
GND
R8h
100
K
R21f
1
M
R5d
3.3K
R4a
3.3K
1
5
5
7
8
1
2
8
7
1
9
9
9
1
1
8
7
3
1
2
7
8
2
3
1
1
3
2
1
7
7
1
1
6
6
6
2
3
2
1
2
1
2
1
3
1
1
1
1
1
2
3
J1-10
J1-1
1
Noise
Gate
Delay
Control
Noise
Gate
Level
Control
Note:
Slide
Pot
sare
mounted
on
Pin
side
of
the
board
Julius
Jones
REV
1
6
-14-99
Note:
J1
goes
to
a
16
pin
DIP
socket
