[Elecraft] K3 Yamaha CM500 vs Koss SB40

[Walter Underwood]

The Koss SB40 has a dynamic mic instead of the electret in the Yamaha CM500. Koss does seem to make the CM500, mine says “Koss” on the plug. But the dynamic mic in the SB40 is a step down in quality from the electret in the CM500.

If you have mic bias on, you’ll need to turn that off for the SB40

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

> On Nov 5, 2015, at 5:40 PM, cx7tt at 4email.net wrote:
> 
> 
> My CM500 was looking kinda 'ratty' after 4 yrs with ear cushions
> starting to shed material. Saw where someone said that Koss actually
> makes the CM500 for Yamaha so ordered the SB40 as replacement.
> 
> First trial was CQ WW SSB a couple of weekends ago.  Rig had been
> sitting in the closet for several months so brought it out and coupled
> with Buddipole, 6ft out the window of 24th floor apartment here in HP.
> Audio reports were terrible including those from guys who knew my
> voice...I had to 'close talk' the SB40 with mic touching lips....using
> VOX as could not find the foot switch adaptor for the Heil footswitch.
> Vox had never been an issue as I have used VOX on the K3 for 7 years
> with no issues...best Vox I have ever experienced....audio was so bad,
> one guy suggested to turn down the drive on my amp....I was running
> barefoot K3/100 @ 90w.  Found CM500 in packing box and got it
> going....audio became the usual outstanding.
> 
> So, what is the difference between these two headsets and what can I do
> to properly use the SB40?
> 
> BTW, the Buddipole/CM500/K3 combo was great...due to proximity to
> building, could only use BP on 10 and 15m...worked over 600Qs in 3 hours
> on 10m on Sunday pm......great fun.
> 
> Suggestions for using the SB40 w/K3?
> 
> 73 Tom HP1/K6CT aka CX7TT
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