[Elecraft] KX3: CM500 best price/use with

[john at kk9a.com]

I thought that the discussion was about the subject Yamaha CM500.  I do not
own this headset however I thought that it had an electret mic even though
it was advertised as dynamic.  Either way this was good information by
W3FPR.  I have a K3S and an electret mic so I keep my bias on.

John KK9A

-----Original Message-----
From: Bob McGraw K4TAX [mailto:rmcgraw at blomand.net] 
Sent: Saturday, November 11, 2017 5:33 PM
To: john at kk9a.com
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] KX3: CM500 best price/use with

I use the Koss SB-40 which has a dynamic mike. No bias needed. 

Bob, K4TAX


Sent from my iPhone

> On Nov 11, 2017, at 3:51 PM, <john at kk9a.com> <john at kk9a.com> wrote:
> 
> I was also confused by the posts that the CM500 works best with bias off.
> Thanks for explaining why this works only with the KX3/KX2.
> 
> John KK9A
> 
> 
> Don Wilhelm wrote: 
> Sat Nov 11 10:23:55 EST 2017
> 
> Yes, all electret microphones must have bias applied in some manner.
> I am not certain why you think this is a KX3 "problem".
> The tip and ring connected together is a characteristic of all 
> microphones intended primarily for computer use - and the Yamaha CM500 
> is one of those.  The ham microphones normally have a mono plug, and 
> do not apply, although with mono plugs, MIC BTN must be turned off in 
> the
> KX3/KX2 so that PTT is not activated when the mic plug is inserted 
> (the shell grounds the PTT ring).
> The normal computer jack applies bias to the ring, not the tip.
> In the KX3, there is residual voltage from the MIC BTN circuit applied 
> to the ring even with MIC BTN turned off - the combination of the tip 
> and ring connected together and the residual voltage from the mic 
> button circuit in the KX3/KX2 is why it works that way.
> 
> That is true of both the KX2 and KX3 - yes, it does not apply to the 
> K3/K3S which has no connection to the ring contact in the jack.
> 
> So not a "problem", it is just the way things work.
> 
> 73,
> Don W3FPR
> 
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