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Inrad M629 Mic / PTT Adapter for 6000 Series

W4JBB Member ✭✭
I recently ordered the Flex 6400. I currently own an Inrad M629 mic with a foot-switch I use with my IC-7300. The mic cable is a 3-pin XLR to 1/8" mono (I think it's mono - it's inside the rack and a lot of trouble to disconnect/reconnect) plug. The foot switch plug is 1/4" mono (of that, I'm positive).

Do I just need a 1/8" mono-to-stereo adapter for the mic and 1/4" mono-to-RCA adapter for the foot switch to make the connections to the 6400?

Joel - W4JBB

Best Answer

  • Ken Wells
    Ken Wells Community Manager admin
    Answer ✓

    The 6400 and 6600 1/8" mic connector is a "Pseudo-Balanced" input.

    Be sure that you use a true balanced XLR-to-1/8" TRS cable. Be certain that the cable is balanced. There are a lot of cheap XLR 1/8 TRS that are designed to connect to computers and are NOT wired as balanced cables.


  • Erika - KØDD
    Erika - KØDD Member ✭✭✭

    Before you do anything, check inside the inside the M629... my brand new mic was wired completely incorrect inside compared to industry standard. I went right to an XLR cable into the back of my 6500 and had hum when touching the mic barrel. I did my first ssb contest with the new mic with hum... some time later I sorted it out and was disgusted after in desperation opened the mic itself... Shure sure knows how to wire a mic, Inrad not so much. I use mine on an OC White radio station boom. And use the foot switch religiously... direct to the ptt port on my 6500... it might not be in your best interest to mix ptt and balanced audio into the same connector due to rf... but I'm a purest when it comes to balanced audio. The m629 kludge to single ended in the mic is a bad idea 💡 DD

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    What did you Fing in the M629? I have one but used it only for Field Day

    Dave wo2x

  • W4JBB
    W4JBB Member ✭✭
    Mmm... Well, I *would* go to the balanced mic input if I could but, as far as I can tell from the manual, the 6400 doesn't have a balanced mic input.
  • John KB4DU
    John KB4DU Member ✭✭✭✭

    True, the 6400 doesn’t have a balanced input for the mic. Actually, I’m at a loss to see the value of balanced input in ham radio. The frequency response and signal level is the same for either balanced or unbalanced.

    Balanced mic lines can reduce hum/noise pickup on long mic lines, but not a factor for a 10 foot cord.

  • W4JBB
    W4JBB Member ✭✭
    Thanks, Ken. That answered my question.
  • n4frl
    n4frl Member
    I purchased a Inrad 629 mic about a month or so ago and have yet to be able to use it on the flex due to the hum and RF noise. I purchased the mic and the base along with 2 cables to be able to use it on my flex as well as my yaesu. I bought a adapter cable from our friends at flex from the store taking the 8 pin round foster to a Y arrangement one with a PTT and a 1/8 mic plug. Nothing but trouble. Contacted the folks over at Vibroplex and described the problem and it was all Flex cable issue and said he was not even aware that Flex was selling such a cable. I emailed him the link and thats where the road ended. If you can tell me a way out of this mess with some kind of mod I really would appreciate it.
  • W4JBB
    W4JBB Member ✭✭

    Hmm... I cannot picture how you're using that Foster connector with the Flex. Before I bought the Flex, I used my M629 with a Y adapter (unbalanced mic input-to-Foster / RCA-to-Foster) for my IC-7300 but, when I went to the Flex, I removed the Icom (Y) adapter. I suspect that Y adapter isn't balanced. If mine was, I didn't know it. It accepted an unbalanced mic cable from the M629. I'm not going to take it apart to confirm.

    Further up this thread, I was told I needed a true balanced mic cable. I found a similar cable at Flex but I have a sit/stand desk and the cable Flex sells is not long enough (my 6400 is in a rack on the floor under the desk).

    I go straight from my M629 to the 6400 with this cable:

    using this adapter (1/4" to 3.5 mm) for the back of the radio (I'm not sure, but I don't think this adapter is needed if you have the 6600):

    I had to buy the adapter because, no matter how I searched, I couldn't find a true balanced mic cable that was long enough with a 3.5 mm plug (other than the one at Flex which is too short).

    I have a foot switch for PTT and needed to buy this as well (Flex sells this):

    My foot switch goes straight to the back of the Flex into the PTT jack.

    I have no noise / hum and I am quite happy with the cost/performance ratio of the M629.

    Even though the plug shell needed tightening on the mic cable and I found a solder splatter on the cable near the XLR end (nothing big but, from a distance, it looked like a cut), I am happy with my purchase. The cable is "meaty." The info says the wire is 24 gauge so I suspect the "meatiness" is the jacket.I give the cable and 1/4-to-3.5 mm adapter a 4.5 out of 5.

    I have no affiliation with Sweetwater they're just the folks where I found all I needed in one place and who were not Amazon.


    Joel - W4JBB

  • W4JBB
    W4JBB Member ✭✭

    Mmmkay... Not sure where my comment went... I tried to edit it and it just disappeared...

    I cannot picture how you're using that Foster Y adapter with the Flex. I had (I still have it, I just don't use it) a Y adapter for my M629 that I purchased to use with my IC-7300. It goes from the Foster connector on the front to the M629 and a PTT foot switch.

    The Foster diagram for the IC-7300 does not show two mic inputs. I suspect the Yaesu Foster diagram only shows one input so it's not a balanced input.

    Further up this thread, I was told the Flex wanted a balanced mic input. I have a sit/stand desk with the Flex in a rack on the floor under my desk. The distance is about 13'. I bought this mic cable:

    ...and this adapter (if you have a 6600 [you didn't specify], I don't think you will need this adapter):

    ...because my searches could not find a balanced mic cable with a 3.5mm plug (other than the one Flex sells which is too short).

    For my PTT foot switch, I purchased (Flex has these):

    I have no affiliation with Sweetwater but they're the one place who had all I needed and who were not Amazon. They are sound guys and gals (not radio operators) though and may call and question why you're purchasing what you're purchasing. Not because they're being nosy but because they want to make sure you're getting what you need. My sales rep had a hard time reconciling why I needed what I needed until a phone call was made.

    Overall, I am happy with my purchase. I give the mic cable a 9 out of 10 - the shell at the TRS end needed slight tightening (I check all my cables) and there was a solder splatter at the XLR end. From a distance, the splatter looked like a cut. The cable is "meaty" but I suspect it's jacket "meatiness." The wire is 24 gauge. Everything else gets a 9.5 out of 10 (nothing's perfect).


    Joel - W4JBB

  • Ferrell
    Ferrell Member ✭✭
    Joel flex sales a y-cable that terminates in a male round foster connector. it has a RCA for ptt and a trs for mic input. As far as the Inrad mic base they sale the mic cord for yaesu which is the same as flex. It was a 4 pin xlr to run from the Inrad base to the round foster and provide the ptt and audio in the same cable.

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