Elecraft MD2 "Heil Sound" Mic to Flex 1500

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  • Updated 3 years ago
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I have an old Elecraft MD2 Heil Sound desk Microphone and
would like to wire up an adaptor to work with Flex 1500. The only button on the mic is the PTT. My understanding is the resister was added on the MD2 to increase auido level so it might not be necessary when connected to the Flex 1500.

The Elecraft MD2 pin out is:            Flex 1500 pin out:

1=AF (5.6K resister to 5V)                      1=N.C.
2=PTT                                                            2=N.C.
3=N.C.                                                            3=5V
4=N.C.                                                            4=Mic(-) Mic ground?
5=N.C.                                                            5=Mic (+)
6=5V                                                               6=PTT
7=GND                                                           7=Chassis Ground (PTT GND)
8=GND (PTT GND)                                     8=N.C

Would the correct wiring be?

    MD2                                                   Flex

1=AF (5.6K resister to 5V)           5=Mic (+) 
2=PTT                                                6=PTT
6=5V                                                   3=5V
8=GND (PTT GND)                        7=Chassis Ground (PTT GND)
7=GND                                               4=Mic (-) Mic ground?

Im worried about the resister applying voltage to pin 5 on the Flex. 

I would appreciate any input.


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Robert Jones -KD7YDW

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Posted 3 years ago

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Tim - W4TME, Customer Experience Manager

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This is a condenser type mic so it needs the +5VDC bias on the mic+ line.  You do not need the mic bias resister (it is already installed in the 1500 along with a filter cap) and jumper blocks installed, so the mic will need to be configured for a K3 not a K2.  I think this will work, but no promises as I don't have one of these mics to try out.

Mic Connector to FLEX-1500

1 Mic audio, low-Z (~600 ohms)  -> 1500 pin 5 (mic+)
2 PTT -> 1500 pin 6
3 DOWN button 
4 UP button
5 FUNCTION button
6 8V (10 mA max) -> 1500 pin 5
7 Ground -> 1500 pin 4
8 Ground -> 1500 pin 7
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Robert Jones -KD7YDW

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You have mic pin 6 (8v) going to 1500 pin 5 (mic+).  Did you mean to have mic pin 6 (8v) going to 1500 pin 3 (5V)?