[Elecraft] KX3: CM500 best price/use with

[Walter Underwood]

The Koss SB40 has a dynamic mic. The Koss SB45 has an electret mic. The SB45 is cheaper and has a better mic.

https://smile.amazon.com/Koss-sb45-SB-45-Communication-Stereophones/dp/B00081A2CW/

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Nov 11, 2017, at 2:32 PM, Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:
> 
> 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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> 
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