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.
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
What did you Fing in the M629? I have one but used it only for Field Day
Dave wo2x
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.
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.
73,
Joel - W4JBB
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).
73,
Joel - W4JBB
