MFJ hamproaudio MFJ-652 User manual

INSTRUCTION MANUAL
CAUTION: Read All Instructions Before Operating Equipment
MFJ ENTERPRISES, INC.
300 Industrial Park Road
Starkville, MS 39759 USA
Tel: [phone] Fax: [phone]
COPYRIGHT 2005 MFJ ENTERPRISES, INC.
C
Model MFJ-652
VERSION 1A

DISCLAIMER
Information in this manual is designed for user purposes only and is not
intended to supersede information contained in customer regulations, technical
manuals/documents, positional handbooks, or other official publications. The
copy of this manual provided to the customer will not be updated to reflect
current data.
Customers using this manual should report errors or omissions,
recommendations for improvements, or other comments to MFJ Enterprises, 300
Industrial Park Road, Starkville, MS 39759. Phone: [phone]; FAX: (662)
323-6551. Business hours: M-F 8-4:30 CST.

MFJ-652 hamProAudioTM Transmit Audio Equalizer Instruction & Technical Manual
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TABLE OF CONTENTS
TOPIC PAGE
1. TABLE OF CONTENTS 2
2. LIST OF FIGURES 2
3. INTRODUCTION AND FEATURES 3
4. TYPICAL SPECIFICATIONS 4
5. SYSTEM CONTROLS 5
a. FRONT PANEL JACKS AND CONTROLS 5
b. REAR PANEL JACKS AND CONTROLS 6
6. SYSTEM SETUP 7
a.INTERNALHEADERS 7
b.INTERNALJUMPERBLOCK 8
c.CABLES 10
d.POWER 10
e.HEADPHONES 10
f.RADIOAUDIO 10
7. THEORY OF OPERATION 11
8. MFJ-652 EASY-START INSTRUCTIONS 12
9. IN CASE OF DIFFICULTY 15
10.TECHNICAL ASSISTANCE 15
LIST OF FIGURES
Figure 1 Front Panel Jacks and Controls 5
Figure 2 Rear Panel Jacks and Controls 6
Figure 3 Internal Headers 7
Figure 4-10Internal Jumper Blocks 8-12
Figure 11 Functional Diagram 15
Figure 12 Schematic 20
LIST OF TABLES
Table 1 Microphone Pinout 13

MFJ-652 hamProAudioTM Transmit Audio Equalizer Instruction & Technical Manual
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INTRODUCTION & FEATURES
INTRODUCTION
The MFJ-652 hamProAudio Transmit Audio Equalizer is a quality microphone
audio equalizer. With 4 adjustable center frequencies you can adjust your
microphone audio for rich full audio for rag chewing. For serious DXing you can
increase the high and decrease the lows for a signal that really punches through
the pile-ups.
hamProAudio Quality: Designed with the serious ham in mind. Not just a
typical audio equalizer being used with an amateur station. Choice of
components and extensive RF filtering and bypassing allows for a unit that is
designed to be used in a RF environment.
Fully adjustable Gain Amplifiers: You have full control of the input level from
your microphone and output level to your radio. With MFJ’s LED monitoring you
set the output level once and then feel confident that you are driving your radio
with the perfect level no matter how much you increase or decrease the gain of
each section of the equalizer.
Audio Pass Through from your Radio: No need to switch the headphones
from the MFJ-652 to the radio. At the push of a button you can instantly switch
from normal operation to a test mode. This allows you to adjust the settings
without going on the air with the built in monitor amplifier.
By-pass Function: Switch the MFJ-652 in or out and you still have the received
audio in the headphones.
Multiple Outputs: The MFJ-652 has multiple audio outputs. Microphone audio
is fed out through the RJ-45 connector or through the 3.5 -mm Auxiliary Output
Jack.
Rugged Construction: Attractive all-metal cabinet, conservative component
selection, space age SMD Circuitry and extensive RF filtering ensure solid
performance for years to come. Fully covered by MFJ’s “No Matter What” one
year limited warranty.
Before attempting to operate your MFJ-652, please read the manual thoroughly.
It contains important details about setting up your unit to obtain the best
performance.

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INTRODUCTION & FEATURES
TYPICAL SPECIFICATIONS
Input source……………………Dynamic or Electret mic low or high Z
Stereo or Monaural radio audio.
Sound card or Modem
Output ………………………….Adjustable signal level. RJ-45 or 3.5 –mm
Frequency Range……………..300, 600, 1200, 2400 Hz center
Overall Response……………..100-5000 Hz
Total harmonic distortion …….1% maximum, <0.2% typical

MFJ-652 hamProAudioTM Transmit Audio Equalizer Instruction & Technical Manual
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SYSTEM CONTROLS
MFJ-652 JACKS AND CONTROLS
2400 Hz1200 Hz600 Hz300 Hz
MFJ Voice Band Microphone EqualizerhamProAudio™
MFJ-652
+
-
MIC IN
ON
OFF/
BYPASS
MONITOR OUTPUT
+
-+ -
MaxMin MaxMin
INPUT LEVEL POWEROUTPUT LEVEL
+
-
EQUALIZER
0 0 0 0
Figure 1: MFJ-652 Front Panel Jacks and Controls
1. RJ-45 Microphone Input Jack: Accepts input from a Standard RJ-45
microphone.
8-Pin Microphone Input Jack: Accepts input from a standard 8 pin
microphone.
2. 300 Hz: Cuts or emphasizes lowest speech frequencies.
3. 600 Hz: Cuts or emphasizes mid-range speech frequencies.
4. 1200 Hz: Cuts or emphasizes upper-range speech frequencies.
5. 2400 Hz: Cuts or emphasizes syllabant sounds and adjacent channel
“chatter”.
6. Input Level LED: Allows for easy setting of the input level to the
equalizer. Never worry about overdriving the equalizer.
7. Monitor Output Level: Easily set the output monitor to a comfortable
level in the headphones.
8. Output Level LED: Set the output level trimpot one time and you will
have easy control of the signal sent to your radio.
9. Output Level Control: Adjusts the level sent to you radio.
10. Power LED: Visual indication whether the unit is in line or not.
11. On & Off/Bypass Switch: Allows you to use either your microphone
direct or through the MFJ-652.
1 2 3 45 6 7 9 810 11

MFJ-652 hamProAudioTM Transmit Audio Equalizer Instruction & Technical Manual
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SYSTEM CONTROLS
POWER
12VDC
OUTPUT
LED
LEVEL
EXTERNAL
PTT
SWITCH
AUX.
AUDIO
OUTPUT
AUX.
AUDIO
INPUT
INPUT
LED
LEVEL
MIC
OUT
RECEIVED
AUDIO
INPUT
MFJ ENTERPRISES, INC.
STARKVILLE, MS USA
FROM
MFJ-652
FROM
RADIO
OUT
HEADPHONE
AUDIO
Figure 2: MFJ-652 Rear Panel Jacks and Controls
1. Power: Accepts 2.1 –mm power plug to supply 12-15 volts to the unit.
2. Output LED Level adjust: Sets the level at which the output led
illuminates.
3. From Radio/From MFJ-652: This switch allows the audio to be fed from
the radio to the headphones or in the test mode for the audio from the
microphone to be fed to the headphones for setting the MFJ-652.
Additionally in the test mode the PTT is disabled allowing you to key the
microphone without keying the radio.
4. Headphones Out: Allows you to use a pair of ¼ stereo headphones.
5. External PTT Input: Accepts a ¼ inch plug from a remote hand switch or
foot switch
6. Auxiliary Output: Accept a 3.5 –mm plug for direct audio output. With
internal jumper set allows PTT also.
7. Input LED Level: Allows for adjustment of the input gain depending on
your microphone.
8. Auxiliary Input: This multifunction input allows for just about anything to
be used with the MFJ-652. Use a Heil boom mic, The MFJ-393 Boom Mic
Headset or even a computer microphone by setting the appropriate
internal jumper.
9. RJ-45 Mic Output: This is where the MFJ-5398 or MFJ-5397MX is
attached.
10.Received Audio Input: This jack allows either stereo or mono (if wired
properly) audio from your radio.
1 2 3 4 5 67 98 10

MFJ-652 hamProAudioTM Transmit Audio Equalizer Instruction & Technical Manual
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SYSTEM SETUP
INTERNAL HEADERS
Figure 3: MFJ-652 Internal Headers
1. Header 1: This sets the input of the unit to your specific microphone.
Default 1-2 is set to 500-1000 ohms, the standard impedance setting for
most stock microphones. If you need low impedance then move the
jumper to positions 3-4. Remove for high impedance microphones.
2. Header 2: This allows the PTT line to be placed on the ring of the 3.5 –
mm auxiliary input jack. Default is off.
3. Header 3: This header allows phantom voltage to be fed to electret
microphones Default is 0 volts pins 1-2 shorted. Move this jumper to pins
3-4 for 1.5 volts, 5-6 for 5 volts or 7-8 for 8 volts.
4. Header 4: This header allows the phantom voltage set by header 4 to be
passed to the ring of the Auxiliary input jack. Default is off. If used with
standard computer microphone/headphones set to 5 volts.
5. Header 5: This header allows the PTT to be placed on the ring of the 3.5
-mm Auxiliary Output Jack.
6. Header 6: This header places phantom voltage on the microphone input
line and must be shorted for use with microphones that require phantom
voltage.

MFJ-652 hamProAudioTM Transmit Audio Equalizer Instruction & Technical Manual
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SYSTEM SETUP
INTERNAL JUMPER BLOCKS
Refer to Table 1 for common microphones. Consult your owners’ manual to
determine your specific microphone pinout.
Figure 4: MFJ-652 Internal Jumper Blocks
1. Jumper 1: Pass/Thru. This allows you to pass any other lines from the
microphone for feature such as up/down/fast. Normally all lines that are
not being used for the Mic Audio, Mic Ground and PTT line will be
jumpered.
2. Jumper 2: PTT to Radio. Place a jumper on the pin corresponding to the
pin that your radio requires for PTT
3. Jumper 3: Microphone Audio Ground to Radio. Place a jumper on the
pin that corresponds to the pin that your radio requires for the shielded
ground.
4. Jumper 4: Microphone Audio to Radio. Place a jumper on the pin that
corresponds to the pin on your radio that feeds microphone audio to the
radio.
5. Jumper 5: PTT from the Microphone. Place a jumper on the pin number
that corresponds to the pin of your microphone that supplies the PTT line
to the radio.
6. Jumper 6: Microphone Audio Ground. Place a jumper on the pin number
that corresponds to the pin that supplies the shielded ground from the
microphone.
7. Jumper 7: Microphone Audio Input. Place a jumper on the pin number
that corresponds to the pin that supplies microphone audio.

MFJ-652 hamProAudioTM Transmit Audio Equalizer Instruction & Technical Manual
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SYSTEM SETUP
INTERNAL JUMPER BLOCKS
The Jumper Installation diagrams within this instruction manual will help you in
setting up your MFJ-652 to match your radio. If your radio is not listed with the
diagram, it means that we have not verified your radio to use that diagram. You
can try to install jumpers as indicated. If that does not work, please refer to the
radio manual to identify the MIC pin assignment for you radio then follow the
instructions given at the end of this section in the MFJ-652 instruction manual to
install the jumpers.
Refer to this figure for the pin numbering 1-8 on the
internal jumper blocks. The RJ-45 connector is
numbered with the clip down. Note the position of the
key for the 8 pin round mic jack this could be rotated in
your particular unit.
ICOM 8-Pin Round Microphone Setup:
IC-255, 288, 28, 290, 38A, 375, 707, 718, 725, 726, 728, 729, 730, 735, 737, 745, 746,
746PRO, 751, IC-756, 756PRO, 756PROII, 775DSP, 761, 78, 781, 910H
This diagram may cover
some other radios in the
ICOM product line with 8-pin
round microphone jack.
If there are any Questions
concerning the information
provided, please refer to
your RADIO INSTRUCTION
MANUAL.
MFJ is neither liable nor
responsible for any mistakes
or errors in the information
provided.
Receive Audio is taken from
the Headphone Audio
Output.
Figure 5: ICOM 8-Pin Round Microphone Setup