K3 Yamaha CM500 vs Koss SB40

[CX7TT]

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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[Dave Hachadorian-2]

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: [hidden email]
Sent: Thursday, November 5, 2015 6:40 PM
To: [hidden email]
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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[gm3sek]

Dave Hachadorian, K6LL, wrote:

>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.
>
Probably any half-decent electret element will sound fine too. If the
frequency response is reasonably level and the sensitivity is  about the
same as other electrets - in other words, if there's nothing "wrong" or
"unusual" about it - then the K3 will manage the rest.

Over the past 7 years I've had very good results with the Koss CS-100, a
lightweight on-ear computer headset with the usual electret microphone.
That headset was originally purchased for Skype but was found to work
very well indeed with the K3 - not only for my own voice but also for my
wife and for guest operators. As a result, these headsets have
proliferated around our household and also throughout the radio club.

Still preferring closed-cup headphones for my own use, about two years
ago I switched to the Koss CM-45. The electret microphone is essentially
identical to the CS-100, so operators can freely swap headsets without
needing to change any microphone or EQ settings.

>The SB45 headset has an electret element, but it is not the same
>comfortable headphone arrangement as the CM-500.
>
Headphone comfort is a very individual thing. I have used the Koss SB-45
for about two years now with no discomfort over many long hours; on the
other hand, Heil headphones hurt my ears within ten minutes. The CM-500
I have never tried, as it's not readily available in Europe.

So, in what way is the headphone arrangement "different" between the
SB45 and the CM-500?


73 from Ian GM3SEK

(Please excuse any delayed replies over the next few days - we're having
phone-line problems.)


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[Don Wilhelm-4]

Tom,

I do not have the specifications for the Koss SB40, but all the ad
statements say it has a dynamic microphone element.
What happens if you turn off the bias?  If you get no audio, then it is
an electret element, but if you do get audio out of it, it is dynamic.
Operating a dynamic microphone with bias turned on will create distortion.

73,
Don W3FPR

On 11/5/2015 8:40 PM, [hidden email] wrote:

>
> 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?
>
>

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[Bob McGraw - K4TAX]

As a general rule, if you measure the DC resistance at the connector on
the mike and it is less than 2K ohms, it is likely dynamic.  If it is
10K or more, it is likely an electret element.    If it is near infinity
then likely there is a DC blocking capacitor in the circuit.   The R
values have nothing to do with impedance, as they are just DC resistance
values.

The electret element requires bias.  They dynamic will likely distort
when bias is turned on.

73
Bob, K4TAX



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[KEN-3]

I have been very happy with the Koss SB-45 and get great audio reports
with it.  I have found the ear
phones comfortable.

Ken WA8JXM

On 11/5/15 9:41 PM, Dave Hachadorian wrote:
> The SB45 headset has an electret element, but it is not the same
> comfortable headphone arrangement as the CM-500.

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