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 <[email protected]> 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, <[email protected]> <[email protected]> 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 >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
