Using a Shure 550L mic Drake "Twins" to 4 pin Kenwood TS 520S

Discussion in 'Microphones, Speakers & Audio Processing' started by KC0GXX, May 1, 2012.

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  1. KC0GXX

    KC0GXX Ham Member QRZ Page

    Hello everyone. I just got a new (old?) Kenwood TS 520s. I have used for years my old Drake "Twins" (R4A and TX-4) with a neat Shure 550L desk Mic.
    I want to use this mic with my 520s.
    Because I do NOT want to get rid of my Drakes, I want to be able to use the mic with both rigs.
    There is a compatibility problem with the inputs to the rigs.
    Drakes use a Switchcraft S230 plug, the 520s use the 4 pin plug.
    I am thinking about making a "relay box" so I can plug in the Shure to the box, and come out with a 4 pin plug to the 520s.
    This way, I think, I can use the mic/relay box for the Kenwood and not have to cut off and replace the plug, and just use the mic for the Drakes the way I always have.
    Does this sound like it will work?
    Vis a vis the output to the Kenwood rig, can I use the chassis ground and the mic ground together? (one ground to 3 and 4 pin)
    Please refer to picture for clarification.

  2. K0SPN

    K0SPN Ham Member QRZ Page

    If you read the manual, it will clearly say that you do not connect both grounds together.
    Everything I've seen says that you get hum on your signal when you do this.

    If you run new wire from the mic using 4 wire cable, you can easily make your switching box with a 4PDT switch/relay, tying the two grounds together for the Drake and leaving them single for the Kenwood.
  3. W9GB

    W9GB Ham Member QRZ Page

    Manual switch boxes have been used for this purpose for a number of yers.

    1. The Kenwood TS-520 and Drake TX-4 both use Hi-Z microphone inputs.
    2. When you use Hi-Z for audio, you desire to keep your audio connections SHORT in length.
    3. The Shure 550L is a 150 ohm (low-Z) output dynamic microphone. User Guide here:
    The Shure 550L has seperate ground leads for PTT and Audio. Make sure you properly wire 550L for UNBALANCED Audio input to the radios.
    4. Are you planning on impedance (Z) matching happening in this new switch box?
    Last edited: May 1, 2012
  4. KC0GXX

    KC0GXX Ham Member QRZ Page

    As I see, the Shure 550L mic actually has four wires from the mic-black, red, white and green. I think the green is for a balanced connection.

    Could you draw a diagram of the switching box as you have mentioned?

    I am a "visual " guy and I am NOT an electrical engineer (or even an "extra"), nor do I play one on TV.
  5. KC0GXX

    KC0GXX Ham Member QRZ Page

    Uh... No.
    Should I?
    How can I do that?
    Or should I just be thinking about getting another mic for my Kenwood.
    I have used this mic for years with my Drake, with no apparent problems. (Not that I KNOW of anyway :))

  6. K0SPN

    K0SPN Ham Member QRZ Page

    I can't draw well with a pencil, even worse on a computer.

    Looking at that user guide, your current mic/plug wiring should have the black (or maybe red), white, and shield connected to the sleeve; green on the ring; red (or maybe black) on the tip.
    If it's not, you'll have to figure out which wire goes where.

    Choose an input method, either wire into a box or get a plug. Plug would make it more versatile, but adds a bit of cost.
    One jack (female) for each type you need, i.e. 1 x TRS and 1 x 4 pin; plus cable and plugs to go from the switch box to the radios. Again, you could wire directly into the box but this limts you more.

                    4PDT Switch
           1 2 3 4  Pin
         | - - - -  One toggle side   |--Jack wired for Drake
    Mic--| - - - -  Input             |
         | - - - -  Other toggle side |--Jack wired for Kenwood
    Wire your mic input side to the input pins, one wire per pin.
    Wire each toggle side to it's jack, following the radio specific wiring diagrams from the manuals.
    Plug in your cables into the box and radio and away you go.

    Check the contacts on the switch you get to make sure that is the correct wiring.
    Hope that's visual enough.

    You would need a matching transformer on the Kenwood side to go from the low-Z to high-Z.
    Last edited: May 1, 2012
  7. W9GB

    W9GB Ham Member QRZ Page

    In amateur radio, as most technology and electronics ---
    it's 90% reading, learning, planning, assembling correct parts -- and 10% actual DIY Build or Assembly.

    Kenwood TS-520S User Manual

    Shure 550L Microphone User Guide

    The Kenwood TS-520S requires a 50 K ohm (Z) microphone input.
    A Lo-to-Hi (150 to 50K) audio transformer can be used. Heil Sound sells these (XT-1) as well as Mouser.

    Page 7 shows you the proper wiring for the 4-pin circular connector to Kenwood radio.
    Preference to keep PTT and audio grounds separate, when possible.
    Last edited: May 2, 2012
  8. KC0GXX

    KC0GXX Ham Member QRZ Page

    Thanks everyone for the ideas.
    Problems solved (via Ebay.)
    I got a new (old) Kenwood MC-50 mic. Put on a new 4 pin plug, and
    "Bob's yer Uncle!"
  9. K0SPN

    K0SPN Ham Member QRZ Page

    You probably bought the one I bid on, ya jerk.

    Actually, I did need one and watched the prices for the last couple weeks.
    I did bid on a couple, but this last week especially prices have been way over the top.
    But that's okay as I just bought one in very good, almost like new shape from the wanted ad I posted here a week ago.
    Even including shipping, it was cheaper than any of the final sale prices from eBay.

    Nice deal for me; thanks Phillip, K4ORC.
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