CM-500 Headset blocking capacitor value

KD0RC

I just got a Yamaha CM-500 headset, and am building the little adapter to put the mic bias from my Flex 6400 to the right pin on the headset. No value is shown for the capacitor. I was told by a good friend (and engineer...) that a .1 uf would do it. That feels a little small for passing audio, or is it just me?

73 & thanks for any info,

Len, KD0RC

VE7ATJ_Don

That value should work ok, but i'd suggest a 1 or 5 uf to get more fidelity.

KD0RC

Thanks Don, I appreciate it. I may parallel 2 or 3 .1 uf and see what it sounds like. If it constricts my audio too much for the EQ to compensate, then I will order some bigger caps. I usually need to cut the lows on my transmitted audio anyway, so this might be fine.

73,

Len

VE7ATJ_Don

Len, i'd use the tx audio adjustments to 'tailor' out the lows, rather than the cap. It'll do a better job of giving you more punch in your audio signal, imho....

KD0RC

Hi Don, Yep, I just got done with that. I only had room in the plug housing for one .1 uf cap, so I started there. I was able to get it to sound just like the FHM-3 mic with only minor tweaking of the EQ. I use Ken, NM9P's method using Full Duplex and RXA for adjusting the mic audio. Got a good visual indication that I have it about right. I also record as I go so that I can hear the "off-the-air" signal to verify that it sounds good.

So far the CM500 headset seems good. With my Creative T-10 speakers, I had to pump up the 1k and 2k sliders on the RX EQ, but the CM500 doesn't seem to need that. It is as if the headset was designed for radio communications use.

One interesting thing... The packaging lists it as having a dynamic mic, but they include a 3 v bias battery box. I confirmed that it does not work without bias, showing that indeed, it is an electret mic.

Now to try it out on the air...

73,

Len

Tom OBoyle

Len and Don -

Thanks for publishing this. I put in a 1uf with my Yamaha and it drives the radio well.

73 de Tom, N9GUN

Tom OBoyle