Fw: Non Amplified D104

[George & Jan]

I presently use a D104 that I modified using a rubber mounted Radio Shack
electret element. With bias on it works well. Reports on air are good.

Reports using the crystal element were poor.

George
AI4VZ

Anyone ever use the non amplified D104 mic? If you have, how does it perform
and what's it look like on the scope?  Does it sound good and natural
without sounding like you are talking in a trash can? How do you compare it
to other mics.

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[-.-. --.-N3TU -.-. --.-]

I tried a non amplified D104 and it  was not good at all. The audio was real low when the mike was at 60. It had a slight "fan noise" and I had no fans running. The mic was wired up right because when I put it back on my ADI radio it worked well. My ADI radio hand mic works on my K3. ADI and Kennwood wiring is the same. Now the non amplified D104  is a museum piece in the shack.

George & Jan wrote

I presently use a D104 that I modified using a rubber mounted Radio Shack
electret element. With bias on it works well. Reports on air are good.

Reports using the crystal element were poor.

George
AI4VZ

Anyone ever use the non amplified D104 mic? If you have, how does it perform
and what's it look like on the scope?  Does it sound good and natural
without sounding like you are talking in a trash can? How do you compare it
to other mics.

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[Ken Kopp-3]

The D104's are getting quite old and many / most have
elements that have "gone bad" with age.  There are many
elements that can be fitted into the space in the lollypop's
round head.  I -think- Heil makes a suitable cartridge.

73! Ken Kopp - K0PP
     [hidden email]
     http://tinyurl.com/7lm3m5

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[Don Wilhelm-4]

The non-amplified D-104 microphone is a great one for frequency response
*if* it is working into a very high impedance (50k to 2 megohms).
Unfortunately, the input impedance of the K3 and most other modern
transceivers is in the vicinityof 600 ohms, so the D-104 will  sound
very bad when used directly with those transceivers.

You could use a single FET stage behind the D-104 (it will easily fit
into the base) to match the impedances and it will sound good.  
Otherwise, it is a 'museum piece'.

Others have suggested a simple series resistor (something on the order
of 100k should do) to allow the stock D-104 to drive low impedance
transceivers - the crystal (or later ceramic) mic element produces lots
of voltage. I have not tried this technique, I am just passing along
information received.

73,
Don W3FPR

-.-. --.-N3TU -.-. --.- wrote:

> I tried a non amplified D104 and it  was not good at all. The audio was real
> low when the mike was at 60. It had a slight "fan noise" and I had no fans
> running. The mic was wired up right because when I put it back on my ADI
> radio it worked well. My ADI radio hand mic works on my K3. ADI and Kennwood
> wiring is the same. Now the non amplified D104  is a museum piece in the
> shack.
>
>
>
>
> George & Jan wrote:
>  
>> I presently use a D104 that I modified using a rubber mounted Radio Shack
>> electret element. With bias on it works well. Reports on air are good.
>>
>> Reports using the crystal element were poor.
>>
>> George
>> AI4VZ
>>
>> Anyone ever use the non amplified D104 mic? If you have, how does it
>> perform
>> and what's it look like on the scope?  Does it sound good and natural
>> without sounding like you are talking in a trash can? How do you compare
>> it
>> to other mics.
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>>    
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[AC7AC]

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[P.B. Christensen]

> Did you use the K3's MENU:MIC SEL option to choose high gain for the
> microphone input?

Good advice from Ron.  After checking that, and assuming the mic is
relatively old and its past quality-of-life unknown, I would consider
replacing the D-104's mic element with a similar crystal element from
Mouser:

http://www.mouser.com/catalog/specsheets/KT-400023.pdf

Price in small quantities is USD $4.77.

If you use a single-transistor FET buffer, be careful of the various designs
and mods seen on the web.  Some utilize unnecessary components at best, and
performance-degrading parts at worst.   If an existing 2-stage Astatic
buffer is used, one can place a resistor in series with the mic lead, > 1
megohm in value and make up the gain with the amp's level pot although it
may become unstable and certainly noisier than a well-designed single-stage
FET circuit.  Either circuit can be powered from the K3's mic connector
through a current-limiting resistor.

The existing input Z of the Astatic pre-amp calculates to ~ 470K-ohm and
although it may seem high, it's just not high enough for a crystal element
to achieve a reasonably flat response down to 80-90 Hz -- the first
fundamental of most male voices.  My D-104 achieves this with the K3 in ESSB
mode, although I'm not sure if all of the extended low-end can be captured
in the K3's default SSB Tx setting.

Paul, W9AC







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