Wiring a Balanced Microphone
to the TS-590S Unbalanced Microphone Input
Using a balanced microphone with a transceiver's
unbalanced audio input in the presence of RF fields can be a
challenging setup unless you pay close attention to both ends of
the microphone cable. Obviously, start with good quality
connectors and microphone cable that is suitable for balanced
line work. I get my connectors and balanced line mic cable at Parts Express and
have had very good luck using this very durable cable with
braided shield:
I would avoid cables that use spiral wound shielding or
aluminum wrap shielding with a carrier wire as it’s easily
damaged and not always reliable in the presence of an RF field.
When connecting a balanced microphone to the unbalanced mic
input of the TS-590S keep in mind that the front panel
jack of the transceiver has two different grounds, one
specifically for audio, and another for establishing chassis
ground. With that in mind, when wiring up an 8 pin microphone
plug for use with a balanced microphone, observe the following:
Kenwood uses pin 7 as the MIC (-) that is terminated inside the
transceiver at the circuit board where the mic preamp is
located. Solder pin 7 of your 8 pin microphone plug to the
balanced lead you have selected for connection to Pin 3 of the
XLR connector on the other end of your cable that mates up with
your balanced microphone.
Kenwood connector pin 8 is the chassis ground of the TS-590S.
Solder the shield of the balanced line microphone cable to pin 8
(the center pin) of your microphone plug. At the other end of
your cable, the shield should be soldered to pin 1 of the XLR
connector that mates up with your balanced microphone.
Kenwood connector pin 1 is the MIC (+) audio lead so select the
remaining balanced lead and solder it to pin 1 of the 8 pin
connector. At the other end of the cable, solder the MIC (+)
audio lead to XLR connector pin 2.
The last step is the most important as far as keeping RF out of
your transmit audio. At the XLR connector, solder a bare wire
from XLR pin 1 to XLR pin 3, and then solder that to the XLR
ground tab so the metallic XLR body will be bonded to pins 1 and
3. Bonding these three connections together at this point will
keep the RF voltage potential on the various grounds at zero at
the mic and will also guarantee that the metallic microphone
body is at the same potential as the 590S chassis. The balanced
twisted leads inside the wire will reject hum and RF and will be
further protected by the coaxial shield that is connected to the
590S chassis with continuity right to the microphone’s metal
body.
The picture below is probably much clearer than all the wording
above. Note that this setup conforms to the industry standard
pin connections for XLR wiring.
To avoid adding another path for RF to enter the front mic
connector and also to keep things clean and simple, I elected to
use the PTT connection at the back panel REMOTE connector (pin
3) to control the TX/RX keying for voice operation. As long as
you have reasonable grounds at your station this should be
pretty much bullet-proof as far as keeping RF out of your
unbalanced transceiver’s microphone input.