WiMo W2IHY User manual

W2IHY
8 BAND
AUDIO EQUALIZER
AND
NOISE GATE
OPERATING MANUAL

W2IHY 8 BAND AUDIO
EQUALIZER AND
NOISE GATE
OPERATING MANUAL
October 2003
Julius D. Jones
19 Vanessa Lane
Staatsburg, N.Y. (12580)
[phone]
E-mail: [e-mail]
Home Page: http:// www.w2ihy.com
c 2000 W2IHY, ALL RIGHTS RESERVED
-2-
TECHNOLOGIES
W2IHY
MIC OUT & POWER CABLE WIRING
-27-
TEN TEC
DRAKE TR7
DRAKE T4XB
COLLINS 32S 1, 32S3
COLLINS KWM2A
COLLINS 32V2, 32V3
KWS-1
Hallicrafters
E.F. Johnson
HI-Z
HI-Z
Kenwood
TS520/TS530
TS820/TS830
+ Mic
+ Mic
+ Mic
+ Mic
- Mic
- Mic
- Mic
- Mic
- Mic
+ Mic
+ Mic
- Mic
PTT
PTT
PTT
PTT
PTT
PTT
GND
GND
GND
GND
GND
GND
4 Pin Mic Connector Pin 3
4 Pin Mic Connector Pin 2
4 Pin Mic Connector Pin 3
4 Pin Mic Connector Pin 2
4 Pin Mic Connector Pin 2
4 Pin Mic Connector Pin 3
4 Pin Mic Connector Pin 1
4 Pin Mic Connector Pin 3
4 Pin Mic Connector Pin 1
4 Pin Mic Connector Pin 1
2 Pin Mic Connector Pin 1
2 Pin Mic Connector Pin 2
2 Pin Mic Connector Spring/Case
4 Pin Mic Connector Pin 2
4 Pin Mic Connector Pin 1
4 Pin Mic Connector Pin 4
Equalizer / Noise Gate Mic Out to Xcvr cable wiring
Power GND
+ 7 to 14V dc
Shield of Cable
Shield of Cable
Shield of Cable
Shield of Cable
Shield of Cable
Shield of Cable
DIN connectors shown on the side to be soldered
DO NOT SOLDER TO SHIELD OF DIN

TABLE OF CONTENTS
Introduction ........................... 6
Front Panel Controls ..... 7-9
- Pictorial
-
- Power On LED
- Equalizer On/Off
- Equalizer Controls
- Noise Gate On/Off Switch
- Noise Gate LED
- Noise Gate Level
- Noise Gate Delay
- Mic Gain LED
Power On/Off / Phone Volume control
-3-
Rear Panel Controls..10,11
- Pictorial
- Mic Select
- Mic Input (8 pin)
- Mic Input (XLR)
- Mic Input (RCA)
- PTT Input (RCA)
- Mic Output Select
- Mic Output A
MIC OUT & POWER CABLE WIRING
-26-
Alinco DX77
Kenwood
TS130/140
TS430/440
TS850/TS870
TS930/940/950
SG2020
K2
Japan Radio
JST-135
JST-245
Yaesu
FT990/ft992
FT1000MP/M-V
+ Mic
PTT
GND
ICOM
735
745/746
756/756 PRO
775
781
KACHINA
Gnd
PTT
+ Mic
Gnd
Gnd
PTT
PTT
- Mic
- Mic
- Mic
- Mic
+ Mic
+ Mic
8 Pin Mic Connector Pin 8
8 Pin Mic Connector Pin 5
8 Pin Mic Connector Pin 3
8 Pin Mic Connector Pin 1
8 Pin Mic Connector Pin 1
8 Pin Mic Connector Pin 7
8 Pin Mic Connector Pin 5
8 Pin Mic Connector Pin 6
Shield of Cable
Shield of Cable
Shield of Cable
Shield of Cable
8 Pin Mic Connector Pin 2
8 Pin Mic Connector Pin 2
8 Pin Mic Connector Pin 6
8 Pin Mic Connector Pin 7
8 Pin Mic Connector Pin 7
8 Pin Mic Connector Pin 1
8 Pin Mic Connector Pin 8
+ Mic
PTT
GND
- Mic
8 Pin Mic Connector Pin 6
8 Pin Mic Connector Pin 7
Shield of Cable
8 Pin Mic Connector Pin 8
ICOM BALANCED
MODULATOR
746
756 / 756 PRO
775
781
910H
+ Mic
PTT
GND
- Mic
8 Pin DIN Connector Pin 3
8 Pin DIN Connector Pin 2
Shield of Cable
8 Pin DIN Connector Pin 4
DIN connectors shown on the side to be soldered
DO NOT SOLDER TO SHIELD OF DIN
Yaesu
FT102/107
FT707/747/757/767
FT847
FT1000/1000D

TABLE OF CONTENTS
-4-
Rear panel Controls ...........12
- Mic Output B
- Phones
- Power
Bottom Panel Controls ... 13
- Pictorial
- Mic In Gain
- Mic Output Level
- Mic input impedance
Schematics
- 8 band Mother Board...14, 15
- 8 Band EQ Pot Board … 16
Getting Started Tutorial.. 18,19
- Adjusting Mic In Level
- Adjusting Mic Out Level
- Adjusting Noise Gate Level
- Adjusting Noise Gate Delay
- Adjusting the Equalizer
Changing EQ Bandpass
Center Frequencies ........17
-25-
MIC OUT WIRING OPTIONS
MIC OUT A/B
5 Pin Male DIN
Din connectors shown
on side to be soldered Gnd
PTT
- Mic
+ Mic Balanced
Output
Hi-Z Output
Low Impedance Balanced Output to Low Impedance Radio
5 PIN DIN MIC OUTPUT CONNECTION
Low Impedance Unbalanced Output to Low Impedance Radio
Low Impedance Unbalanced Output to High Impedance Radio
High Impedance Unbalanced Output to High Impedance Radio
DO NOT CONNECT MIC WIRE SHIELD TO SHIELD OF DIN CONNECTOR
CONNECT ONLY AS SHOWN
MIC OUT A/B
5 Pin Male DIN
Din connectors shown
on side to be soldered Gnd (Mic cable shield)
PTT
- Mic
+ Mic Balanced
Output
MIC OUT A/B
5 Pin Male DIN
Din connectors shown
on side to be soldered Gnd (Mic cable shield)
PTT
+ Mic Unbalanced
Output
MIC OUT A/B
5 Pin Male DIN
1K Ohm
Din connectors shown
on side to be soldered Gnd (Mic cable shield)
PTT
+ Mic
MIC OUT A/B
5 Pin Male DIN
1K Ohm
Din connectors shown
on side to be soldered Gnd (Mic cable shield)
PTT
HI-Z

INTERNAL WIRING
-24- -5-
TABLE OF CONTENTS
PC Boards and Parts
- Mother Board ...................21
- 8 Band EQ Board .............22
- Rear Connector Board ....23
Internal wiring ........................ 24
Preliminary Equalizer Settings.. . 20
Mic Out and Power Cable Wiring
- Mic Out Wiring Options.... 25
- Mic Out and Pwr Cable Wiring 26, 27
MIC IN
Shortest
Lead
Shortest
Lead
Shortest
Lead
Shield
not
Connected
J16 C41- .01uf
J2
MIC IN
PIN 1
PIN 7
J9
PHONES
PIN 1
PIN 2
J1-3
J1-1
J1-15
J1-2
J1-16
J1-14
J1-13
10“
16-1/2“
10“
6“
10“
E17
Note that J1-X is the flat ribbon
cable shown on page 15
Shield
Shield
Shield
Shield
Shield
Shield
Shield
Shield
Shield

INTRODUCTION
W2IHY AUDIO EQUALIZER
AND
NOISE GATE
Analog and digital technology have for many years been used in the
audio industry to do audio equalization and noise reduction. Many
amateurs have purchased audio equalizers and other equipment with
the hope of improving their transmitted audio signal. The amateurs who
have succeeded have in many cases had to pay premium prices for
audio equipment that not only required modifying, to properly
interface with their amateur stations, but also had to be hardened to
tolerate R.F.
The W2IHY 8 Band Audio Equalizer and Noise Gate solves two basic
problems many hams experience. The Audio Equalizer allows the
user to change the transmitted audio frequency response without
changing microphones or microphone cartridges. Transmitted audio,
with substantial high frequency content, can be used to work DX or
communicate in band conditions where there is a significant amount
of noise. A balanced frequency response may be more desirable in
strong signal, full noise quieting environments. Many amateur operators
transmit audio in high ambient noise environments. Typical high noise
sources include linear amplifier fans, dehumidifiers, room air
conditioners, road and wind noise during mobile operation, etc..
The Noise Gate eliminates the aforementioned noise from being
transmitted. On the air tests in high ambient noise conditions have
shown the Noise Gate to be very effective. The removal of moderate
to very high levels of ambient noise, from the transmitted audio signal,
results in audio with increased clarity and presence.
Extensive testing was done of the Noise Gate and Equalizer. The unit
has been designed to work in high RF environments. We feel so
confident that you will be delighted with the unit
The W2IHY Audio
Equalizer and Noise Gate represents affordable audio technology
designed for amateur radio use.
we offer a 30 day
money back , no questions asked, guarantee.
-6- -23-
8 BAND EQ REAR CONNECTOR
PC BOARD LAYOUT AND PARTS
C41, C42 - .001 uf mylar
C40 - .01 mylar,
C7, C13, C37, C39 - .1 uF ceramic monolithic
C39 - 4.7 uf tantalum electrolytic
J2, J4, J5 - Male 5 Pin DIN
R33, R34 - 47K ohm ¼ watt 5% resistor
RFC2, RFC3 - 100 uh R.F. choke
RFC4, RFC5 - 470 uh R.F. choke
S4 - 4 pole 3 position rotary switch
S5 - 4PDT slide switch
T1 - 600 ohm: 600 ohm audio transformer

FRONT PANEL CONTROLS
This section describes each of the controls on the front panel. You
can read through this section now. Some of the descriptions
will be more meaningful after you first work through the getting
started tutorial.
This switch and potentiometer (Pot.) turns the unit's power on and
off and is also used to adust the audio level into the Phone jack (18)
This LED goes on when power is on in the unit.
This switch turns the equalizer on and off. When the equalizer is
off adjusting the equalizer's controls has no effect on the output
audio.
(1)
(2) Power on LED (LED3)
(3) Equalizer On/Off Switch (S3)
Power On/Off Switch (S1) / Phones (monitor) Volume Control (R29)
-7-
1
2
3
4
5
69
8
7
8 BAND EQ BOARD
PC BOARD LAYOUT AND PARTS
* Mounted on pin side of P.C. board
-22-
C15 - .1 uF mylar
C16 - .1 uF monolithic
C17 - .18 uF mylar
C18 - 19 - 4.7 uF Tantalum electrolytic
C20 - 100 uF electrolytic
R1 - 10 ohm ¼ watt 5% Res
R2 -R3 1K ohms ¼ watt 5% Res
R4 - 3.3k ohm 10 pin 9 RES SIP
R5-R6 - 3.3K ohm 10 Pin 5 Res SIP
R7 - 15.0K ohm ¼ watt 1% Res
R8 - 100K ohm 10 Pin 9 Res SIP
R9 - R10 10K ohm ¼ watt 5% Res
R11 - R18, R20 100 K ohm Slide Pots*
R19 5K ohm Slide Pot*
R21 - 1M ohm 10 Pin 9 Res SIP
R22 - R23 1m 10 Pin Res SIP
U1- U3 Tl074 or JRC2060 (14 Pin DIP)
J1 (16 Pin DIP)
C1 - 300pF mylar
C2 - 390 pF mylar
C3 - 560 pF mylar
C4 - .0012 uF mylar
C5 - .003 uF mylar
C6 - .0022 uF mylar
C7 - .0039 uF mylar
C8 - .0047 uF mylar
C9 - .0056 uF mylar
C10 - .01 uF mylar
C11 - .012 uF mylar
C12 - .018 uF mylar
C13 - .022 uF mylar
C14 - .047 pF mylar

FRONT PANEL CONTROLS
(4) Equalizer CONTROLS (R11-R18)
(5) Noise Gate On / Off Switch (S2)
(6) Noise Gate LED (LED1)
These slide potentiometers work only when the Equalizer On/Off
Switch S3 is in the on position. The potentiometers control
the output of 8 bandpass filters. The center frequency of these
filters are 50 Hz, 100 Hz, 200 Hz, 400 Hz, 800 Hz, 1600 Hz,
2400 Hz and 3200 HZ. The scale, for setting these potentiometers,
is calibrated between -16 db. to + 16 dB. Pushing a potentiometer
forward (up) will increase the output of the equalizer within the
bandpass of the filter whose slide potentiometer is changed.
Pushing a potentiometer backward (down) will decrease the
output of the equalizer within the bandpass of the filter whose
slide potentiometer is changed. Setting all 8 potentiometers at the
zero marking will produce audio at about the same output level
as when the Equalizer On/Off Switch S3 (3) is in the off position.
Adjusting the equalizer 50 Hz, 100 Hz and 200 Hz slide pots
affects the heaviness / weight of the audio. Adjusting the equalizer
400 Hz and 800 Hz slide pots affects the warmth of the audio.
Adjusting the equalizer 1600 Hz, 2400 Hz and 3200 Hz slide
pots affects the clarity and presence of the audio.
This switch turns the noise gate on and off. When the noise
gate is off changing the gate delay or level controls has
no effect on the audio. When the noise gate is off audio is
always being passed (gated) through the noise gate to the output.
This LED is used to help properly adjust the noise gate level
control and to indicate when audio is being sent (gated) to the
output. The LED being on (green) indicates that audio is being
gated through the unit to the output. The LED being off indicates
that audio is not being passed (gated) through to the output.
When the Noise Gate On / Off Switch (5) is in the off position the
noise gate LED is on.
-8-
8 BAND EQ MOTHER BOARD
PC BOARD LAYOUT AND PARTS
-21-
* Parts mounted on pin side of P.S. Board
C1,C3, C4,C6,C14, C25-C28, C33 4.7 uF radial electrolytic
C7*, C13*, C16, C17, C32 .1 uF ceramic monolithic
C8 - 22 uF radial electrolytic
C9, C29 - 4.7 uF non polarized radial electrolytic
C10, C11, C12, C15, C31 - 100 uF radial electrolytic
C2, - 10 uF radial electrolytic
C4 - 1 uF radial electrolytic
C18 - C20 - .1 uF mylar
C5 - .033 uF mylar
C23 - C24 - 470 uF radial electrolytic
C21, C34 - .01 uF mylar
C36 - 120 pf ceramic
C22, C35 - .001 uF mylar
D1, D2 - 1N914
D3 - 1N4001
LED1 - Green LED; LED2 - Red LED; LED3 - Amber
Q1 - 2N3417
REG 1 - 7805 with heat sink
Rfc1 - 470 uH R.F. choke
R1, R2, R22 - 10K ohm 5 Resistor 10 pin SIP
R3 - 100 ohm 5 Resistor 10 pin SIP
R4 - 1K ohm 5 Resistor 10 Pin SIP
R5, R6, R27, R30 - 10 ohm ¼ watt 5% Resistor
R7, - 6.8K ohm ¼ watt 5% Resistor
R8, R9 - 5.6K ohm ¼ watt 5% Resistor
R10 - 10K ohm ¼ watt Resistor
R11 - 2.2K ohm ¼ watt Resistor
R12 - 100K ohm horizontal Pot mounted on PC board
R13 - 20K ohm horizontal Pot mounted on PC board
R19 - 33K ohm ¼ watt 5% Resistor
R14 - 75K ohm ¼ watt 5% Resistor
R15* - R17* - 25K ohm Slide Pot
R18* - 5K ohm Slide Pot
R21 - 680 ohm 5 Resistor 10 Pin SIP
R23 - 200 ohm ¼ watt 5% Resistor
R20, R24, R25, R33*. R34* - 47K ¼ watt 5% Resistor
R26 - 0 Ohms (Piece of wire)
R28 - 22K ohm 5 Resistor 10 pin SIP
R29* - 10K Pot with Switch (Used for volume control)
R31 - 1K ohm ¼ watt Resistor
R32 - 33K ohm ¼ watt 5% resistor
U1, U5 - Tl074 or JRC2060; U2 - 74HC00;
U3 - 74LS123;U4- 74HC4053; U6 - LM 386-1

FRONT PANEL CONTROLS
(7) Noise gate Level (R19)
(8) Noise Gate Delay (R20)
(9) Mic Gain LED (LED2)
This slide pot. works only when the noise gate is on. This pot.
sets the level at which background noise will be not gated to the
audio output. Pushing this control up will make the unit less
sensitive to higher background ambient noise. Pushing this
control down will make the unit, more sensitive to background
noise.
This control adjusts the length of time audio will be gated to the
output after the noise gate has automatically turned off (Noise gate
LED off). Pushing the delay slide pot. up increases the delay
(decay) time. Pushing the pot. down decreases the delay time.
This LED is used to help adjust the MIC In Gain pot. When the
LED goes on this indicates that the EQ is being overdriven.
This LED should never go on.
-9-
-20-
PRELIMINARY EQUALIZER SETTINGS

-10-
(10) Mic Select (S4)
(11) Mic Input (J8)
This three position switch selects the ICOM, KENWOOD or
YAESU microphone plugged into the 8 pin Mic Input J8 (11).
8 Pin microphone male connector. Do not use this connector
when Mic in J6 (13) or Mic In J9 (12) are being used.
REAR PANEL CONTROLS
Icom Ken Yaesu
+Mic +Mic
+5V PTT +5V
PTT +5V
PTT
Gnd - Mic Gnd
Gnd +Mic
1
2
5
6
7
8
J8
Pin
PTT
PTT
Gnd
Gnd
11
14 16 19
13 17 18
15
10
12
The control sets the decay time of the trailing
edge of the Audio, when the noise gate turns off. This
circuitry exponentially reduces the audio output when there is no
audio present in the . (The delay circuitry helps to make the
transitions of gating and not gating of audio smooth and more
pleasing to the ear.) The duration of the exponential decay
is dependent on the setting of the control. The
delay control set at a minimum value (the slide pot all the way
down) will exponentially decay the audio in about 100 milliseconds.
The delay control set at a maximum value will allow the audio to
decay over a few seconds. On the air tests show the white bar part
of the Noise Gate Delay range gives very pleasing audio transitions.
(decay time of about .3 to .5 second). You can experiment on your
own to find the best setting for you.
If you have medium-to-high levels of ambient noise present when
you are transmitting, with the in the off
position, when you stop talking your power meter will indicate R.F.
still being transmitted. (set power meter on avg. power to do this
experiment). When the noise gate is turned on and properly
adjusted when you stop talking the power output will drop to the
bottom of the scale (no power output). People who listen to your
signal will be able to hear the difference and they will wonder where
the noise went.
Turn the on. Set all 8 equalizer slide
potentiometers to the 0 db point (marked on the case). Refer to the
Preliminary Equalizer Setting table on page 20. Use this table, as a
guide to determine initial starting points for equalizer settings. It is
suggested that the phones monitor be utilized to assist in adjusting
the equalizer. As you modify your equalizer settings (to determine what
the optimal setting is for you) it is recommended that you make
changes starting at the highest audio frequency (3200 Hz) first and
change the next lowest frequency (band) next until the lowest frequency
(50 hz) is adjusted. On the air experimentation will be required
to find the optimal settings based upon the users voice
characteristics and band conditions.
Noise Gate Delay
Mic Out
Mic In
Noise Gate Delay
Noise Gate Switch
Equalizer Switch
Adjusting The Audio Equalizer
-19-
GETTING STARTED TUTORIAL

REAR PANEL CONTROLS
-11-
(12) MIC Input (J9)
(13) Mic Input (J6)
This 3 pin XLR female connector works independent
of the mic select switch and may be used as another mic source.
Do not use this connector when Mic In J6 or J8 is being used.
This RCA female connector is used as an auxiliary
microphone input. This connector works independent of the mic
select switch and may be used for another audio source or
microphone. This input is also low impedance. Do not use if mic
is connected to J8 (11) or J9 (12).
(14) PTT INPUT (J7)
(15) MIC Out Select A/B (S4)
(16) Mic Output A (J5)
RCA female connector for auxiliary push to talk control. A foot
switch or other control may be connected to this connector.
Grounding the center jack of the connector grounds the push
to talk line on the Mic Out.
This two position slide switch directs audio to the 5 Pin DIN
Mic Out A (16) or the 5 Pin DIN Mic Out B (17).
5 Pin female DIN connector that has noise gate / equalizer
audio plus push to talk outputted. This connector is active
only when the Mic Out Slide Switch S4 (15) is in the
Mic Out Select A position.
XLR PIN Description.
1 gnd. / shield
2 + Mic
3 - Mic
-18-
Before plugging the power transformer into the wall preset the
following controls as indicated:
and switches all off.
to select microphone you will be using.
Connect your microphone into the rear connector. Plug the
power transformer (module) into the wall and into the
connector of the unit. Attach the microphone cable between your
transceiver/transmitter and the of the unit. If the microphone
being used is an electret mic (ICOM HM12, SM6,...) and requires
D.C. on the mic line plug the shorting jumper supplied onto the
pins at the bottom of the case otherwise leave it off. Turn
the switch on. The orange/yellow should go on.
, using a screwdriver, turn the
(located at the bottom of the unit) clockwise
until the just goes on. Now turn the Mic in Level control
counterclockwise such that when you
speak into the mic.
, using a screwdriver, turn the
control clockwise until the audio level, as shown by
your transceiver's/ transmitters metering is at the proper level. If
you are using push to talk on your transceiver you will have to
push the PTT switch on your microphone while making this
adjustment.
Turn the on. (Please note that when the
is off the should always go
on indicating audio is being sent / gated to the . When the
is turned on the may be on
or off depending on the position of the control
and the audio level.) Adjust the Noise Gate Level control until
the Noise Gate LED just goes off.
(If audio is coming from your
transceiver's/ receiver's speaker you should turn off the audio.)
When you now talk into your microphone the
should go on indicating audio is being sent to the When
you stop talking the should turn off indicating
that audio is not being sent and background noise is not being
sent / gated to the .
Power, Equalizer Noise Gate
Mic Select
Mic In
Power
Mic Out
MIC
Jumper
Power Power on LED
Mic In Level Control
Mic LED
Mic Out Level
Noise Gate Switch
Noise Gate Switch Noise Gate LED
Mic Out
Noise Gate Switch Noise Gate LED
Noise Gate Level
Mic In
Noise Gate LED
Mic Out.
Mic Out LED
Mic Out
Adjusting the Mic Levels
the LED never goes on
While talking into the microphone
While talking into the microphone
This adjustment should be made
with the level of ambient noise that will be present when you will
be talking into the microphone.
Noise Gate Adjustments
GETTING STARTED TUTORIAL

-12-
(18) Phones (J3)
(19) Power
1/4“ Stereo headphone connector used to monitor audio from
the equalizer. The output level of this connector is controlled by
phone volume control R29 (1)
(An inline adapter
should be used with headsets that do not use 1/4“ stereo
connectors. Stores like Radio Shack have audio plug adapters
available.)
5 Pin Din connector. 7 - 14 VDC input at 100 ma.
Headphones using other than
1/4“ stereo connectors may not operate properly when
plugged into stereo phones connector J3.
+7 to 14V
GND
Power
5 Pin Male DIN
Din connectors shown
on side to be soldered
(17) Mic Output B (J4)
5 Pin female DIN connector that has noise gate / equalizer
audio plus push to talk outputted. This connector is active
only when the Mic Out Slide Switch S4 (15) is in the Mic Out
select B position.
Gnd
PTT
- Mic
+ Mic Balanced
Output
Hi-Z Output
MIC OUT A/B
5 Pin Male DIN
Din connectors shown
on side to be soldered
REAR PANEL CONTROLS
-17-
C2 - .1uf
100 Hertz
C1 - .01uf
7
R1
3.3K R2
3.3K
R5 - 100 K
U2b
TL074
+
-
R6
100K
R3
1 M R4
1 M
Each EQ bandpass filter is very similar. The center frequencies, of each
bandpass filter is determined by the values of the capacitors and
resistors used. The equations below define what capacitor values are
required for a given center frequency. Below is a schematic of a
bandpass filter with a center frequency of 100 Hz.
C1= (.9046) / (Freq in Hz.) <=In uf => C2=C1 x 10
The above equations are valid for only the resistor values shown in the
schematic above.
The bandpass filter in the schematic has a center frequency at 100 hz.
example: The capacitor values required to obtain a bandpass filter center
frequency of 4800hz is calculated as follows:
C1=.9046/FREQ=.9046/4800=,0001885UF=188.5 PF
C2=C1 x 10= .0018858uf
The closest real value capacitors that can be purchased are as follows
- C1 calculates to be 188.5 pf. The closest real value that
can be purchased is 180 pf
- C2 calculates to be .001885 uf. The closest real value that
can be purchased is .0018uf
CHANGING EQ BANDPASS
FILTER CENTER FREQUENCIES

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 Pots
Audio IN
C7 - .0039 uf
U3b
TL074
7
C2
390 pf
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
16
5
2
315
6
1
71
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
35
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
R11 - 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
C11 - .012 uf
C5 - .003 uf
2400 Hertz
3200 Hertz
1600 Hertz
800 Hertz
R9
10K
R10 10K
C19
4.7 uf
+5V
4
111
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
53
1
1
4
4
4
1
1
1
5
6
2
56
31
1
2
2
2
R8d
100K
R22d
1M
50 Hertz
U2d
TL074
U3a
TL074
+14
+
3 21
+5V
+
6
5
-
--
C1
300 pf
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 pf
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
19
9
9
1
18
7
31
2
7
82
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
23
J1-10
J1-11
Noise Gate
Delay Control
Noise Gate
Level Control
Note: Slide Pots are mounted on Pin side of the board
Julius Jones REV 1 6 -14-99 Note: J1 goes to a 16 pin DIP socket