[Elecraft] K3 Yamaha CM500 vs Koss SB40

[Dave Hachadorian]

The SB40 has a dynamic microphone, so the usual K3 settings for 
that are High Gain / No Bias.

If you are running the SB40 into a sound card, you need a card 
with 20dB boost on the microphone input.

One SB40 reviewer tried to replace the dynamic element with an 
electret, but he said there was insufficient lead length left 
after he removed the dynamic element.

As a last resort, you can tape pretty much any old electret 
element to the mic boom and run a separate mic line from the 
element.  Mouser has a good selection of electret elements, many 
under $5.  My CM500 microphone element failed, and I replaced it 
with an electret element out of an old toy that I found laying 
around the house.  It sounds fine.

The SB45 headset has an electret element, but it is not the same 
comfortable headphone arrangement as the CM-500.

Dave Hachadorian, K6LL
Yuma, AZ


-----Original Message----- 
From: cx7tt at 4email.net
Sent: Thursday, November 5, 2015 6:40 PM
To: Elecraft at mailman.qth.net
Subject: [Elecraft] K3 Yamaha CM500 vs Koss SB40


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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